@TechReport{Dorsey??, authorkey = "DorseyJT DyessJW", author = "John T. Dorsey and James W. Dyess", title = "Structural Performance of Two Aerobrake Hexagonal Heat Shield Panel Concepts", institution = "NASA - Langley Research Centre", number = "NASA TM-4372", pages = "30", keywords = "Aerobrake Buckling Sandwich panel Isogrid panel Large space structures Spacecraft design", abstract = "Structural sizing and performance are presented for two structural concepts for an aerobrake hexagonal heat shield panel. One concept features a sandwich construction with an aluminum honeycomb core and thin quasi-isotropic graphite-epoxy face sheets. The other concept features a skin-rib isogrid construction with thin quasi-isotropic graphite-epoxy skins and graphite-epoxy ribs oriented at $0^\circ, +60^\circ, \rm and -\!60^\circ$ along the panel. Linear static, linear bifurcation buckling, and nonlinear static analyses were performed to compare the structural performance of the two panel concepts and assess their feasibility for a lunar transfer vehicle aerobrake application.", } @TechReport{Kwon??, authorkey = "KwonJH KimDH SchusterG LeeJH", author = "Jin Hyuk Kwon and Do Hoon Kim and Gregory Schuster and Ja H. Lee", title = "Phase Stability of Injection-Locked Beam of Semiconductor Lasers", institution = "NASA - Langley Research Centre", number = "NASA TT-10001", pages = "7", keywords = "Injection locked MOPA Laser diode", abstract = "An experiment on the phase stability of an injection-locked beam was done by using AlGaAs semiconductor lasers. The coherence of two beams from master and slave lasers was measured by interference between the beams in the Twymann-Green interferometer. The phase change of the output beam of the slave laser as a function of the driving current was measured in a Mach-Zehnder interferometer consisting of the master and slave lasers, and a value of 2.5 radians/mA was obtained.", } @TechReport{Blanchard??, authorkey = "BlanchardRC LarmanKT BarrettM", author = "Robert C. Blanchard and K. T. Larman and M. Barrett", title = "The High Resolution Accelerometer Package (Hi{RAP}) Flight Experiment Summary for the First 10 Flights", institution = "NASA - Langley Research Centre", number = "NASA RP-1267", pages = "316", keywords = "Rarefied-flow aerodynamics Accelerometer measurements Upper atmosphere", abstract = "The High Resolution Accelerometer Package (HiRAP) instrument is a triaxial, orthogonal system of gas-damped accelerometers with a resolution of \$110\^{}-6g\$ (1 \$$\backslash$mu$\backslash$!g\$). The purpose of HiRAP is to measure the low-frequency component of the total acceleration along the orbiter vehicle (OV) body axes while the OV descends through the rarefied-flow flight regime. Two HiRAP instruments have flown on a total of 10 Space Transportation System (STS) missions. The aerodynamic component of the acceleration measurements was separated from the total acceleration. Instrument bias and orbiter mechanical system acceleration effects were incorporated into one bulk bias. The bulk bias was subtracted from the acceleration measurements to produce aerodynamic descent data sets for all 10 flights. The aerodynamic acceleration data sets were input to an aerodynamic coefficient model. The aerodynamic acceleration data and coefficient model were used to estimate the atmospheric density for the altitude range of 140 to 60 km and a downrange distance of 600 km. For 8 of 10 flights results from this model agree with expected results. For the results that do not agree with expected results, a variety of error sources have been explored.", } @TechReport{Mcmaster??, authorkey = "McmasterLR ChuWP RowlandMW", author = "L. R. Mcmaster and W. P. Chu and M. W. Rowland", title = "{SAGE} {I} Data User's Guide", institution = "NASA - Langley Research Centre", number = "NASA RP-1275", pages = "26", keywords = "SAGE Aerosol Ozone Nitrogen dioxide", abstract = "This document is a guide for using the data products from the Stratospheric Aerosol and Gas Experiment I (SAGE I) for scientific investigations of stratospheric chemistry related to aerosol, ozone, nitrogen dioxide, dynamics, and climate change. Included is a detailed description of the aerosol profile tape, the ozone profile tape, and the nitrogen dioxide profile tape. These tapes are the SAGE I data products containing aerosol extinction data and ozone and nitrogen dioxide concentration data for use in the different scientific investigations. Also included are brief descriptions of the instrument operation; data collection, processing and validation; and some of the scientific analyses that have been conducted.", } @TechReport{Weaver??, authorkey = "WeaverWL BushKA DegnanKT HowertonCE TolsonCJ", author = "William L. Weaver and Kathryn A. Bush and Keith T. Degnan and Clayton E. Howerton and Carol J. Tolson", title = "Mission Description and In-Flight Operations of {ERBE} Instruments on {ERBS}, {NOAA} 9, and {NOAA} 10 Spacecraft February 1986 Through January 1987", institution = "NASA - Langley Research Centre", number = "NASA RP-1279", pages = "215", keywords = "ERBE ERBS Instrument operations Mission analysis Orbital environment", abstract = "Instruments of the Earth Radiation Budget Experiment (ERBE) are operating on three different Earth-orbiting spacecraft. The Earth Radiation Budget Satellite (ERBS) is operated by the National Aeronautics and Space Administration (NASA), and the NOAA 9 and NOAA 10 weather satellites are operated by the National Oceanic and Atmospheric Administration (NOAA). This paper is the second in a series that describes the ERBE mission, in-orbit environments, instrument design and operational features, and data processing and validation procedures. This paper decribes the spacecraft and instrument operations for the second full year of in-orbit operations, which extends from February 1986 through January 1987. Validation and archival of radiation measurements made by ERBE instruments during this second year of operation were completed in July 1991. This period includes the only time, November 1986 through January 1987, during which all ERBE instruments aboard the ERBS, NOAA 9, and NOAA 10 spacecraft were simultaneously operational. The paper covers normal and special operations of the spacecraft and instruments, operational anomalies, and the responses of the instruments to in-orbit and seasonal variations in the solar environment.", } @TechReport{Smith??, authorkey = "SmithGL RutanD BessTD", author = "G. Louis Smith and David Rutan and T. Dale Bess", title = "Atlas of Albedo and Absorbed Solar Radiation Derived From Nimbus 7 Earth Radiation Budget Data Set---November 1985 to October 1987", institution = "NASA - Langley Research Centre", number = "NASA RP-1281", pages = "55", keywords = "Earth radiation budget Albedo Nimbus 7 Wide-field-of-view radiometer Shortwave radiation Satellite radiation measurements", abstract = "An atlas of monthly mean global contour maps of albedo and absorbed solar radiation is presented for 21 months from November 1985 to October 1987. These data were retrieved from measurements made by the shortwave wide-field-of-view radiometer of the Earth Radiation Budget (ERB) instrument aboard the Nimbus 7 spacecraft. Profiles of zonal mean albedos and absorbed solar radiation were tabulated. These geographical distributions are provided as a resource for researchers studying the radiation budget of the Earth. The El Ni no/Southern Oscillation event of 1986--1987 is included in this data set. This atlas of albedo and absorbed solar radiation extends to 12 years the period covered by two similar atlases: NASA RP-1230 (July 1975 to October 1978) and NASA RP-1231 (November 1978 to October 1985). These three compilations complement the atlases of outgoing longwave radiation by Bess and Smith in NASA RP-1185, RP-1186, and RP-1261, which were also based on the Nimbus 6 and 7 ERB data.", } @TechReport{Carden??, authorkey = "CardenHD", author = "Huey D. Carden", title = "Effect of Crash Pulse Shape on Seat Stroke Requirements for Limiting Loads on Occupants of Aircraft", institution = "NASA - Langley Research Centre", number = "NASA TP-3126", pages = "21", keywords = "Crashworthiness Crash dynamics Human tolerance General aviation seats Seat testing", abstract = "An analytical study was made to (1) provide comparative information on various crash pulse shapes that potentially could be used to test seats under conditions included in Federal Regulations Part 23 $\backslash$S 23.562(b)(1) for dynamic testing of general aviation seats, (2) show the effects that crash pulse shape can have on the seat stroke requirements necessary to maintain a specified limit loading on the seat/occupant during crash pulse loadings, (3) compare results from certain analytical model pulses with approximations of actual crash pulses, and (4) compare analytical seat results with experimental airplane crash data. Structural and seat/occupant displacement equations in terms of the maximum deceleration, velocity change, limit seat pan load, and pulse time for five potentially useful pulse shapes were derived; from these, analytical seat stroke data were obtained for conditions as specified in Federal Regulations Part 23 $\backslash$S 23.562(b)(1) for dynamic testing of general aviation seats.", } @TechReport{Mukunda??, authorkey = "MukundaHS DrummondJP", author = "H. S. Mukunda and J. Philip Drummond", title = "Two-Dimensional Stability of Laminar Flames", institution = "NASA - Langley Research Centre", number = "NASA TP-3131", pages = "28", keywords = "Linear stability Premixed laminar flames Stability of flames", abstract = "This numerical study of the stability of laminar flames specifically addresses the dependence of stability on finite-rate chemistry with low activation energy and variable thermodynamic and transport properties. The calculations show that activation energy and details of chemistry play a minor role in altering the linear neutral stability results from asymptotic analysis. Variable specific heat makes a marginal change to the stability; variable transport properties, on the other hand, tend to substantially enhance the stability from a critical wave number of about 0.50 to 0.20. Also, the effects of variable properties tend to nullify the effects of nonunity Lewis number. When the Lewis number of a single species is different from unity, as is true in a hydrogen-air premixed flame, the stability results remain close to that of unity Lewis number.", } @TechReport{Mineck??, authorkey = "MineckRE", author = "Raymond E. Mineck", title = "Comparison of a Two-Dimensional Adaptive-Wall Technique With Analytical Wall Interference Correction Techniques", institution = "NASA - Langley Research Centre", number = "NASA TP-3132", pages = "70", keywords = "Adaptive-wall test section 2-D airfoil testing Wall interference", abstract = "A two-dimensional airfoil model has been tested in the adaptive-wall test section of the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel (TCT) and in the ventilated test section of the National Aeronautical Establishment Two-Dimensional High Reynolds Number Facility (HRNF). The primary goal of the tests was to compare different techniques to account for wall interference: adaptive test section walls and classical, analytical corrections. Tests were conducted over a Mach number range from 0.3 to 0.8 at chord Reynolds numbers of \$10 10\^{}6, 15 10\^{}6,\$ and \$20 10\^{}6\$. The angle of attack was varied from about \$-2\^{}$\backslash$circ\$ up to stall. Movement of the top and bottom test section walls was used to account for the wall interference in the 0.3-m TCT tests and a classical analytical correction technique was used to account for the wall interference in the HRNF tests. The test results are in good agreement.", } @TechReport{Raney??, authorkey = "RaneyDL LallmanFJ", author = "David L. Raney and Frederick J. Lallman", title = "Control Integration Concept for Hypersonic Cruise-Turn Maneuvers", institution = "NASA - Langley Research Centre", number = "NASA TP-3136", pages = "61", keywords = "Hypersonic maneuvers Automatic flight control Hypersonic vehicles Hypersonic flight Flight dynamics Angle of attack", abstract = "Piloting difficulties associated with conducting maneuvers in hypersonic flight are caused in part by the nonintuitive nature of the aircraft response and the stringent constraints anticipated on allowable angle-of-attack and dynamic pressure variations. This report documents an approach that provides precise, coordinated maneuver control during excursions from a hypersonic cruise flight path and observes the necessary flight condition constraints. The approach is to achieve specified guidance commands by resolving altitude and cross-range errors into a load factor and bank angle command by using a coordinate transformation that acts as an interface between outer- and inner-loop fight controls. This interface, referred to as a {"}resolver,{"} applies constraints on angle-of-attack and dynamic pressure perturbations while prioritizing altitude regulation over cross range. An unpiloted test simulation, in which the resolver was used to drive inner-loop flight controls, produced time histories of responses to guidance commands and atmospheric disturbances at Mach numbers of 6, 10, 15, and 20. Angle-of-attack and throttle perturbation constraints, combined with high-speed flight effects and the desire to maintain constant dynamic pressure, significantly impact the maneuver envelope for a hypersonic vehicle. Turn-rate, climb-rate, and descent-rate limits can be determined from these constraints. Density variation with altitude strongly influences climb- and descent-rate limits and throttle modulation if dynamic pressure is to be maintained during vertical transitions between cruise flight conditions.", } @TechReport{Shideler??, authorkey = "ShidelerJL FieldsRA ReardonLF GongL", author = "John L. Shideler and Roger A. Fields and Lawrence F. Reardon and Leslie Gong", title = "Thermal and Structural Tests of Rene 41 Honeycomb Integral-Tank Concept for Future Space Transportation Systems", institution = "NASA - Langley Research Centre", number = "NASA TP-3145", pages = "75", keywords = "Rene 41 honeycomb sandwich Space transportation systems Integral tank-and-fuselage Hot structures Combined thermal-structural tests", abstract = "Two flat 12- by 72-in. Rene 41 honeycomb sandwich panels were tested in a manner to produce combined thermal and mechanical longitudinal stresses that simulated those that would occur in a larger, more complex integral tank-and-fuselage structure of an Earth-to-orbit vehicle. Elastic strains measured at temperatures below 400\$\^{}$\backslash$circ\$F are compared with calculated values obtained from a linear elastic finite-element analysis to verify the analytical model and to establish confidence in the calculated strains. Elastic strains measured at higher temperatures (between about 600\$\^{}$\backslash$circ\$F and 1400\$\^{}$\backslash$circ\$F), where strain measurement is more difficult and less certain, are also compared with calculated strains. Agreement between measured and calculated strains for the lower temperatures is good, but agreement for the higher temperatures is poor because of unreliable strain measurements. Test results indicate that an ascent-and-entry life cycle of 500 is attainable under high combined thermal and mechanical elastic strains.", } @TechReport{Shinn??, authorkey = "ShinnJL WilsonJW", author = "Judy L. Shinn and John W. Wilson", title = "An Efficient {HZETRN} ({A} Galactic Cosmic Ray Transport Code)", institution = "NASA - Langley Research Centre", number = "NASA TP-3147", pages = "15", keywords = "Space radiation Numerical accuracy High-energy transport", abstract = "To meet the challenge of the future deep-space program, which involves extended manned space missions, an accurate and efficient engineering code for analyzing the shielding requirement against the high-energy galactic heavy ions is needed. The HZETRN is a deterministic code developed at Langley Research Center that is constantly under improvement both in physics and numerical computation and is targeted for such use. One problem area connected with the space-marching technique used in this code is the propagation of the local truncation error. By improving the numerical algorithms for interpolation, integration, and grid distribution formula, the efficiency of the code is increased by a factor of eight as the number of energy grid points is reduced. The numerical accuracy of better than 2 percent for a shield thickness of 150 g/cm\$\^{}2\$ is found when a 45-point energy grid is used. The propagating step size, which is related to the perturbation theory, is also reevaluated.", } @TechReport{Singh??, authorkey = "SinghJJ ShenCP SprinkleDR", author = "Jag J. Singh and Chih-Ping Shen and Danny R. Sprinkle", title = "Feasibility Study of a Low-Energy Gamma Ray System for Measuring Quantity and Flow Rate of Slush Hydrogen", institution = "NASA - Langley Research Centre", number = "NASA TP-3150", pages = "12", keywords = "Slush hydrogen Multiphase chemical systems Gamma rays Mass attenuation coefficient National Aero-Space Plane", abstract = "As part of a study to demonstrate the suitability of an X-ray or gamma ray probe for monitoring the quantity and flow rate of slush hydrogen, mass attenuation coefficients for Cd\$\^{}109\$ X- and gamma radiation in five chemical compounds have been measured. The Ag\$\^{}109\$ K X rays were used for water and acetic acid, whereas E3 transition from the first excited state at 87.7 keV in Ag\$\^{}109\$ provided the probe radiation for bromobenzene, \$$\backslash$alpha\^{}2\$-chloroisodurene, and cetyl bromide. Measurements were made for a single phase (gas, liquid, and solid) as well as mixed phases (liquid plus solid) in all cases. It has been shown that the mass attenuation coefficient for the selected radiations is independent of the phase of the test fluids or phase ratios in the case of mixed-phase fluids. This report describes the procedure and results for the five fluid systems investigated.", } @TechReport{Micol??, authorkey = "MicolJR", author = "John R. Micol", title = "Simulation of Real-Gas Effects on Pressure Distributions for Aeroassist Flight Experiment Vehicle and Comparison With Prediction", institution = "NASA - Langley Research Centre", number = "NASA TP-3157", pages = "68", keywords = "AFE Pressure distributions Real-gas simulation Hypersonic Blunt body", abstract = "Pressure distributions measured on a 60\$\^{}$\backslash$circ\$ half-angle elliptic cone, raked off at an angle of 73\$\^{}$\backslash$circ\$ from the cone centerline and having an ellipsoid nose (ellipticity equal to 2.0 in the symmetry plane), are presented for angles of attack from \$-10\^{}$\backslash$circ\$ to 10\$\^{}$\backslash$circ\$. The high normal shock density ratio aspect of a real gas was simulated by testing in Mach 6 air and CF\$\_4\$ (density ratio equal to 5.25 and 12.0, respectively). The effects of Reynolds number, angle of attack, and normal shock density ratio on these measurements are examined, and comparisons with a three-dimensional Euler code known as HALIS are made. A significant effect of density ratio on pressure distributions on the cone section of the configuration was observed; the magnitude of this effect decreased with increasing angle of attack. The effect of Reynolds number on pressure distributions was negligible for forebody pressure distributions, but a measurable effect was noted on base pressures. In general, the HALIS code accurately predicted the measured pressure distributions in air and CF\$\_4\$.", } @TechReport{Phan??, authorkey = "PhanMQ HortaLG JuangJN LongmanRW", author = "Minh Q. Phan and Lucas G. Horta and Jer-Nan Juang and Richard W. Longman", title = "Identification of Linear Systems by an Asymptotically Stable Observer", institution = "NASA - Langley Research Centre", number = "NASA TP-3164", pages = "67", keywords = "System identification Markov parameters Observer Markov parameters Observer pole placement System realization", abstract = "This paper presents a formulation for the identification of a linear multivariable system from single or multiple sets of input-output data. The system input-output relationship is expressed in terms of an observer, which is made asymptotically stable by an embedded eigenvalue assignment procedure. The prescribed eigenvalues for the observer may be real, complex, mixed real and complex, or zero. In this formulation, the Markov parameters of the observer are identified from input-output data. The Markov parameters of the actual system are then recovered from those of the observer and used to obtain a state space model of the system by standard realization techniques. The basic mathematical formulation is derived, and extensive numerical examples using simulated noise-free data are presented to illustrate the proposed method.", } @TechReport{Mccurdy??, authorkey = "MccurdyDA", author = "David A. Mccurdy", title = "Annoyance Caused by Aircraft En Route Noise", institution = "NASA - Langley Research Centre", number = "NASA TP-3165", pages = "38", keywords = "En route noise Advanced turboprop noise Propfan noise Propeller noise Subjective acoustics Psychoacoustics", abstract = "A laboratory experiment was conducted to quantify the annoyance response of people on the ground to en route noise generated by aircraft at cruise conditions. The en route noises were ground-level recordings of eight advanced turboprop aircraft flyovers and six conventional turbofan flyovers. The eight advanced turboprop en route noises represented the NASA Propfan Test Assessment aircraft operating at different combinations of altitude, aircraft Mach number, and propeller tip speed. The conventional turbofan en route noises represented six different commercial airliners. The overall durations of the en route noises varied from approximately 40 to 160 sec. In the experiment, 32 subjects judged the annoyance of the en route noises as well as recordings of both the takeoff and landing noises of each of 5 conventional turboprop and 5 conventional turbofan aircraft. Each of the noises was presented at three sound pressure levels to the subjects in an anechoic listening room. Analyses of the judgments found small differences in annoyance between three combinations of aircraft type and operation. Current tone and duration corrections did not significantly improve en route noise annoyance prediction. The optimum duration-correction magnitude for en route noise was approximately 1 dB per doubling of effective duration.", } @TechReport{Mcgowan??, authorkey = "McgowanDM CamardaCJ ScottiSJ", author = "David M. Mcgowan and Charles J. Camarda and Stephen J. Scotti", title = "A Simplified Method for Thermal Analysis of a Cowl Leading Edge Subject to Intense Local Shock-Wave-Interference Heating", institution = "NASA - Langley Research Centre", number = "NASA TP-3167", pages = "37", keywords = "Cowl leading edge Parameter study Shock-wave-interference heating Moving-pulse heat load Transient thermal analysis Analytical solution", abstract = "Type IV shock-wave-interference heating on a blunt body causes extremely intense heating over a very localized region of the body. This paper presents an analytical solution to a heat-transfer problem that approximates the shock-wave-interference heating of an engine cowl leading edge of the National Aero-Space Plane. The problem uses a simplified geometry to represent the leading edge. An analytical solution is developed that provides a means for approximating maximum temperature differences between the outer- and inner-surface temperatures of the leading edge. The solution is computationally efficient and, as a result, is well suited for conceptual and preliminary design or trade studies. Transient and steady-state analyses are conducted, and results obtained from the analytical solution are compared with results of two-dimensional thermal-finite-element analyses over a wide range of design parameters. Isotropic materials as well as laminated composite materials are studied. Results of parametric studies are presented to indicate the effects of the thickness of the cowl leading edge and the width of the region heated by the shock-wave interference on the thermal response of the leading edge. Finally, a nondimensional temperature parameter is developed that is useful in evaluating the effects of several design parameters on the thermal response of the leading edge.", } @TechReport{Barger??, authorkey = "BargerRL", author = "Raymond L. Barger", title = "Diffracted and Head Waves Associated With Waves on Nonseparable Surfaces", institution = "NASA - Langley Research Centre", number = "NASA TP-3169", pages = "15", keywords = "Diffraction Head waves Nonseparable surfaces Thin shell resonance", abstract = "A theory is presented for computing waves radiated from waves on a smooth surface. With the assumption that attenuation of the surface wave is due only to radiation and not to dissipation in the surface material, the radiation coefficient is derived in terms of the attenuation factor. The excitation coefficient is determined by the reciprocity condition. Formulas for the shape and the spreading of the radiated wave are derived, and some sample calculations are presented. An investigation of resonant phase matching for nonseparable surfaces is presented with a sample calculation. A discussion of how such calculations might be related to resonant frequencies of nonseparable thin shell structures is included. A description is given of nonseparable surfaces that can be modeled in the vector form that facilitates use of the appropriate formulas of differential geometry.", } @TechReport{Sydow??, authorkey = "SydowPD ShuartMJ", author = "P. Daniel Sydow and Mark J. Shuart", title = "Experimental Behavior of Graphite-Epoxy {Y}-Stiffened Specimens Loaded in Compression", institution = "NASA - Langley Research Centre", number = "NASA TP-3171", pages = "18", keywords = "Compression Composite materials Stiffened plates Impact damage Crippling Failure", abstract = "An experimental investigation of the behavior of graphite-epoxy Y-stiffened specimens loaded in compression is presented. Experimental results are presented for element specimens with a single stiffener and for panel specimens with three stiffeners. Response and failure characteristics of the specimens are described. Effects of impact damage on structural response for both specimen configurations are also presented. Experimental results indicate that impact location may significantly affect the residual strength of the Y-stiffened specimens. The failure results indicate that the critical failure mode is buckling of the stiffener webs for Y-stiffened element specimens and buckling of the stiffener webs and the stiffener blades for the Y-stiffened panel specimens.", } @TechReport{Barger??a, authorkey = "BargerRL MelsonND", author = "Raymond L. Barger and N. Duane Melson", title = "Comparison of Jet Plume Shape Predictions and Plume Influence on Sonic Boom Signature", institution = "NASA - Langley Research Centre", number = "NASA TP-3172", pages = "21", keywords = "Jet plume shape Sonic boom Signature", abstract = "An Euler shock-fitting marching code yields good agreement with semiempirically determined plume shapes, although the agreement decreases somewhat with increasing nozzle angle and the attendant increase in the nonisentropic nature of the flow. Some calculations for a low-boom configuration with a sample engine indicated that, for flight at altitudes above 60000 ft, the plume effect is dominant. This negates the advantages of a low-boom design. At lower altitudes, plume effects are significant but of the order that can be incorporated into the low-boom design process.", } @TechReport{Hill??, authorkey = "HillGF SachseGW YoungDC WadeLO BurneyLG", author = "Gerald F. Hill and Glen W. Sachse and Douglas C. Young and Larry O. Wade and Lewis G. Burney", title = "Venturi Air-Jet Vacuum Ejectors for High-Volume Atmospheric Sampling on Aircraft Platforms", institution = "NASA - Langley Research Centre", number = "NASA TP-3183", pages = "36", keywords = "Venturi Vacuum pump Ejectors Atmospheric sampling", abstract = "This report provides documentation of the installation and use of venturi air-jet vacuum ejectors for high-volume atmospheric sampling on aircraft platforms. It contains information on the types of venturis that are useful for meeting the pumping requirements of atmospheric-sampling experiments. A description of the configuration and installation of the venturi system vacuum line is included with details on the modifications that were made to adapt a venturi to the NASA Electra aircraft at Goddard Space Flight Center, Wallops Flight Facility. Flight test results are given for several venturis with emphasis on applications to the Differential Absorption Carbon Monoxide Measurement (DACOM) system at Langley Research Center. This report is a source document for atmospheric scientists interested in using the venturi systems installed on the NASA Electra or adapting the technology to other aircraft.", } @TechReport{Bezos??, authorkey = "BezosGM DunhamJRE GentryJGL MelsonJWE", author = "Gaudy M. Bezos and Jr. R. Earl Dunham and Jr. Garl L. Gentry and Jr. W. Edward Melson", title = "Wind Tunnel Aerodynamic Characteristics of a Transport-Type Airfoil in a Simulated Heavy Rain Environment", institution = "NASA - Langley Research Centre", number = "NASA TP-3184", pages = "66", keywords = "Heavy rain effects Transport-type airfoil Aerodynamic performance degradation Small-scale wind tunnel results", abstract = "The effects of simulated heavy rain on the aerodynamic characteristics of an NACA 64-210 airfoil section equipped with leading- and trailing-edge high-lift devices were investigated in the Langley 14- by 22-Foot Subsonic Tunnel. The model had a chord of 2.5 ft, a span of 8 ft, and was mounted on the tunnel centerline between two large endplates. Aerodynamic measurements in and out of the simulated rain environment were obtained for dynamic pressures of 30 and 50 psf and an angle-of-attack range of \$0\^{}$\backslash$circ\$ to \$20\^{}$\backslash$circ\$ for the cruise configuration and \$4\^{}$\backslash$circ\$ to \$20\^{}$\backslash$circ\$ for the landing configuration. The rain intensity was varied to produce liquid water contents ranging from 16 to 46 g/m\$\^{}3\$. The results obtained for various rain intensity levels and tunnel speeds showed significant losses in maximum lift capability and increases in drag for a given lift as the liquid water content was increased. The results obtained on the landing configuration also indicate a progressive decrease in the angle of attack at which maximum lift occurred and an increase in the slope of the pitching-moment curve as the liquid water content was increased. The sensitivity of test results to the effects of the water surface tension was also investigated. A chemical was introduced into the rain environment that reduced the surface tension of water by a factor of 2. The reduction in the surface tension of water did not significantly alter the level of performance losses for the landing configuration.", } @TechReport{Wilson??, authorkey = "WilsonJW CucinottaFA ShinnJL", author = "John W. Wilson and Francis A. Cucinotta and Judy L. Shinn", title = "Multiple Lesion Track Structure Model", institution = "NASA - Langley Research Centre", number = "NASA TP-3185", pages = "11", keywords = "Radiation Cells Nuclear Kinetics", abstract = "A multilesion cell kinetic model is derived, and radiation kinetic coefficients are related to the Katz track structure model. The repair-related coefficients are determined from the delayed plating experiments of Yang et al. for the C3H10T12 cell system. The model agrees well with the X-ray and heavy ion experiments of Yang et al. for the immediate plating, delaying plating, and fractionated exposure protocols employed by Yang. A study is made of the effects of target fragments in energetic proton exposures and of the repair-deficient target-fragment-induced lesions.", } @TechReport{Mukunda??a, authorkey = "MukundaHS SekarB CarpenterMH DrummondJP KumarA", author = "H. S. Mukunda and B. Sekar and M. H. Carpenter and J. Philip Drummond and Ajay Kumar", title = "Direct Simulation of High-Speed Mixing Layers", institution = "NASA - Langley Research Centre", number = "NASA TP-3186", pages = "61", keywords = "High-speed mixing-layer transition High-order finite difference Shear layer", abstract = "A computational study of a nonreacting high-speed mixing layer is performed. A higher order algorithm with sufficient grid points is used to resolve all relevant scales. In all cases, a temporal free-stream disturbance is introduced. The resulting flow is time-sampled to generate a statistical cross section of the flow properties. The studies are conducted at two convective Mach numbers, three free-stream turbulence intensities, three Reynolds numbers, and two types of initial profiles---hyperbolic tangent (tanh) and boundary layer. The boundary-layer profile leads to more realistic predictions of the transition processes. The predicted transition Reynolds number of \$0.1810\^{}6\$ compares well with experimental data. Normalized vortex spacings for the boundary-layer case are about 3.5 and compare favorably with the 1.5 to 2.5 found in experimental measurements. The tanh profile produces spacings of about 10. The growth rate of the layer is shown to be moderately affected by the initial disturbance field, but comparison with the experimental data of Papamoschou shows moderate agreement. For the boundary-layer case, it is shown that noise at the Strouhal number of 0.007 is selectively amplified and shows little Reynolds number dependence.", } @TechReport{Protzel??, authorkey = "ProtzelPW PalumboDL ArrasMK", author = "Peter W. Protzel and Daniel L. Palumbo and Michael K. Arras", title = "Fault Tolerance of Artificial Neural Networks With Applications in Critical Systems", institution = "NASA - Langley Research Centre", number = "NASA TP-3187", pages = "49", keywords = "Artificial neural networks Fault tolerance Performance measure", abstract = "One of the key benefits of future hardware implementations of certain artificial neural networks (ANN's) is their apparently {"}built-in{"} fault tolerance which makes them potential candidates for critical tasks with high reliability requirements. This paper investigates the fault-tolerance characteristics of time-continuous, recurrent ANN's that can be used to solve optimization problems. The principle of operation and the performance of these networks are first illustrated by using well-known model problems like the traveling salesman problem and the assignment problem. The ANN's are then subjected to up to 13 simultaneous {"}stuck-at-1{"} or {"}stuck-at-0{"} faults for network sizes of up to 900 {"}neurons.{"} The effect of these faults on the performance is demonstrated and the cause for the observed fault tolerance is discussed. An application is presented in which a network performs a critical task for a real-time distributed processing system by generating new task allocations during the reconfiguration of the system. The performance degradation of the ANN under the presence of faults is investigated by large-scale simulations, and the potential benefits of delegating a critical task to a fault-tolerant network are discussed.", } @TechReport{Wing??, authorkey = "WingDJ AsburySC", author = "David J. Wing and Scott C. Asbury", title = "Static Performance of a Cruciform Nozzle With Multiaxis Thrust-Vectoring and Reverse-Thrust Capabilities", institution = "NASA - Langley Research Centre", number = "NASA TP-3188", pages = "80", keywords = "Multiaxis thrust vectoring Multifunction nozzles Thrust vectoring Nozzles Reverse-thrust capabilities", abstract = "A multiaxis thrust-vectoring nozzle designed to have equal flow-turning capability in pitch and yaw was conceived and experimentally tested for internal, static performance. The cruciform-shaped convergent-divergent nozzle turned the flow for thrust vectoring by deflecting the divergent surfaces of the nozzle, called flaps. Methods for eliminating physical interference between pitch and yaw flaps at the larger multiaxis deflection angles were studied. These methods included restricting the pitch flaps from the path of the yaw flaps and shifting the flow path at the throat off the nozzle centerline to permit larger pitch-flap deflections without interfering with the operation of the yaw flaps. Two flap widths were tested at both dry and afterburning power settings. Vertical- and reverse-thrust configurations at dry power were also tested. Comparison with two-dimensional convergent-divergent nozzles showed lower but still competitive thrust performance and thrust-vectoring capability.", } @TechReport{Parrott??, authorkey = "ParrottTL JonesMG ThurlowEM", author = "Tony L. Parrott and Michael G. Jones and Ernie M. Thurlow", title = "Unsteady Pressure Loads in a Generic High-Speed Engine Model", institution = "NASA - Langley Research Centre", number = "NASA TP-3189", pages = "75", keywords = "Scramjet Unsteady loads Combustion noise Unstarts", abstract = "Unsteady pressure loads were measured along the top interior wall of a generic high-speed engine (GHSE) model undergoing performance tests in the Combustion-Heated Scramjet Test Facility at the Langley Research Center. Flow to the model inlet was simulated at 72 000 ft and a flight Mach number of 4. The inlet Mach number was 3.5 with a total temperature and pressure of 1640\$\^{}$\backslash$circ\$R and 92 psia. The unsteady pressure loads were measured with 5 piezoresistive gages, recessed into the wall 4 to 12 gage diameters to reduce incident heat flux to the diaphragms, and distributed from the inlet to the combustor. Contributors to the unsteady pressure loads included boundary layer turbulence, combustion noise, and transients generated by unstart loads. Typical turbulent boundary layer rms pressures in the inlet ranged from 133 dB in the inlet to 181 dB in the combustor over the frequency range from 0 to 5 kHz. Downstream of the inlet exit, combustion noise was shown to dominate boundary layer turbulence noise at increased heat release rates. Noise levels in the isolator section increased by 15 dB when the fuel-air ratio was increased from 0.37 to 0.57 of the stoichiometric ratio. Transient pressure disturbances associated with engine unstarts were measured in the inlet and have an upstream propagation speed of about 7 ft/sec and pressure jumps of at least 3 psia.", } @TechReport{Shivakumar??, authorkey = "ShivakumarKN NewmanJJC", author = "K. N. Shivakumar and Jr. J. C. Newman", title = "Stress Concentrations for Straight-Shank and Countersunk Holes in Plates Subjected to Tension, Bending, and Pin Loading", institution = "NASA - Langley Research Centre", number = "NASA TP-3192", pages = "34", keywords = "Countersunk holes 3-D stress-concentration analysis Finite-element analysis Countersink angle Isoparametric elements", abstract = "A three-dimensional stress-concentration analysis was conducted on straight-shank and countersunk (rivet) holes in a large plate subjected to various loading conditions. Three-dimensional finite-element analyses were performed with 20-node isoparametric elements. The plate material was assumed to be linear elastic and isotropic, with a Poisson's ratio of 0.3. Stress concentrations along the bore of the hole were computed for several ratios of hole radius to plate thickness (0.1 to 2.5) and ratios of countersink depth to plate thickness (0.25 to 1). The countersink angle was varied from", } @TechReport{Wood??, authorkey = "WoodRM BauerSXS", author = "Richard M. Wood and Steven X. S. Bauer", title = "The Natural Flow Wing-Design Concept", institution = "NASA - Langley Research Centre", number = "NASA TP-3193", pages = "43", keywords = "Supersonic Wing design Computational fluid dynamics Drag reduction", abstract = "A wing-design study has been conducted on a 65\$\^{}$\backslash$circ\$ swept leading-edge delta wing in which the wing geometry was modified to take advantage of the naturally occurring flow that forms over a slender wing in a supersonic flow field. Three-dimensional nonlinear analysis methods were used in the study which was divided into three parts---preliminary design, initial design, and final design. In the preliminary design, the wing planform, the design conditions, and the near-conical wing-design concept were derived, and a baseline standard wing (conventional airfoil distribution) and a baseline near-conical wing were chosen. During the initial analysis, a full-potential flow solver was employed to determine the aerodynamic characteristics of the baseline standard delta wing and to investigate modifications of the airfoil thickness, leading-edge radius, airfoil maximum-thickness position, and wing upper to lower surface asymmetry on the baseline near-conical wing. The final design employed an Euler solver to analyze the best wing configurations found in the initial design and to extend the study of wing asymmetry to develop a more refined wing. Benefits resulting from each modification are discussed, and a final ``natural flow'' wing geometry has been designed that provides an improvement in aerodynamic performance compared with that of a baseline conventional uncambered wing, linear-theory cambered wing, and near-conical wing.", } @TechReport{Jordan??, authorkey = "JordanJFL HahneDE", author = "Jr. Frank L. Jordan and David E. Hahne", title = "Wind-Tunnel Static and Free-Flight Investigation of High-Angle-of-Attack Stability and Control Characteristics of a Model of the {EA}-6{B} Airplane", institution = "NASA - Langley Research Centre", number = "NASA TP-3194", pages = "58", keywords = "Stability and control Dynamic stability High angle of attack Free flight", abstract = "An investigation was conducted in the Langley 30- by 60-Foot Tunnel and the Langley 12-Foot Low-Speed Tunnel to identify factors contributing to a directional divergence at high angles of attack for the EA-6B airplane. The study consisted of static wind-tunnel tests, smoke and tuft flow-visualization tests, and free-flight tests of a 1/8.5-scale model of the airplane. The results of the investigation indicate that the directional divergence of the airplane is brought about by a loss of directional stability and effective dihedral at high angles of attack. Several modifications were tested that significantly alleviate the stability problem. The results of the free-flight study show that the modified configuration exhibits good dynamic stability characteristics and could be flown at angles of attack significantly higher than those of the unmodified configuration.", } @TechReport{Nemeth??, authorkey = "NemethMP", author = "Michael P. Nemeth", title = "Buckling Behavior of Long Symmetrically Laminated Plates Subjected to Combined Loadings", institution = "NASA - Langley Research Centre", number = "NASA TP-3195", pages = "29", keywords = "Buckling Combined loads Anisotropy", abstract = "A parametric study is presented of the buckling behavior of infinitely long, symmetrically laminated anisotropic plates subjected to combined loadings. The loading conditions considered are axial tension and compression, transverse tension and compression, and shear. Results obtained using a special-purpose analysis, well-suited for parametric studies, are presented for clamped and simply supported plates. Moreover, results are presented for some common laminate constructions, and generic buckling design charts are presented for a wide range of parameters. The generic design charts are presented in terms of useful nondimensional parameters, and the dependence of the nondimensional parameters on laminate fiber orientation, stacking sequence, and material properties is discussed. An important finding of the study is that the effects of anisotropy are much more pronounced in shear-loaded plates than in compression-loaded plates. In addition, the effects of anisotropy on plates subjected to combined loadings are generally manifested as a phase shift of self-similar buckling interaction curves. A practical application of this phase shift is that the buckling resistance of long plates can be improved by applying a shear loading with a specific orientation. In all cases considered in the study, the buckling coefficients of infinitely long plates are found to be independent of the bending stiffness ratio \$$\backslash$left(D\_11/D\_22$\backslash$right)\^{}1/4\$.", } @TechReport{Jegley??, authorkey = "JegleyDC", author = "Dawn C. Jegley", title = "Effect of Low-Speed Impact Damage and Damage Location on Behavior of Composite Panels", institution = "NASA - Langley Research Centre", number = "NASA TP-3196", pages = "26", keywords = "Impact damage Graphite-epoxy Postbuckling", abstract = "The effect of low-speed impact damage on the compression and tension strength of thin and moderately thick composite specimens was investigated. Impact speeds ranged from 50 to 550 ft/sec, with corresponding impact energies from 0.25 to 30.7 ft-lb. Impact locations were at the center of the specimen or near a lateral unloaded edge. In this study, thin specimens with only 90\$\^{}$\backslash$circ\$ and \$$\backslash$pm45\^{}$\backslash$circ\$ plies that were impacted away from the unloaded edge suffered less reduction in maximum load-carrying capability because of impact damage than the same specimens impacted near the unloaded edge. Failure loads of thicker compression-loaded specimens with a similar stacking sequence were independent of impact location. Failure loads of thin tension-loaded specimens with 0\$\^{}$\backslash$circ\$ plies were independent of impact location, whereas failure loads of thicker compression-loaded specimens with 0\$\^{}$\backslash$circ\$ plies were dependent upon impact location. A finite-element analysis indicated that high axial strains occurred near the unloaded edges of postbuckled panels. Thus, impacts near the unloaded edge would significantly affect the behavior of the postbuckled panel.", } @TechReport{Howlett??, authorkey = "HowlettJT", author = "James T. Howlett", title = "Calculation of Unsteady Transonic Flows With Mild Separation by Viscous-Inviscid Interaction", institution = "NASA - Langley Research Centre", number = "NASA TP-3197", pages = "37", keywords = "Viscous-inviscid interaction Transonic unsteady aerodynamics Aileron buzz Boundary layer", abstract = "This paper presents a method for calculating viscous effects in two- and three-dimensional unsteady transonic flow fields. An integral boundary-layer method for turbulent viscous flow is coupled with the transonic small-disturbance potential equation in a quasi-steady manner. The viscous effects are modeled with Green's lag-entrainment equations for attached flow and an inverse boundary-layer method for flows that involve mild separation. The boundary-layer method is used stripwise to approximate three-dimensional effects. Applications are given for two-dimensional airfoils, aileron buzz, and a wing planform. Comparisons with inviscid calculations, other viscous calculation methods, and experimental data are presented. The results demonstrate that the present technique can economically and accurately calculate unsteady transonic flow fields that have viscous-inviscid interactions with mild flow separation.", } @TechReport{Herstrom??, authorkey = "HerstromCL GranthamC AllenCL DoggettWR WillRW", author = "Catherine L. Herstrom and Carolyn Grantham and Cheryl L. Allen and William R. Doggett and Ralph W. Will", title = "Software Design for Automated Assembly of Truss Structures", institution = "NASA - Langley Research Centre", number = "NASA TP-3198", pages = "45", keywords = "Robotic Assembly of truss structures Automated assembly Software design", abstract = "Concern over limited extravehicular and intravehicular activitiy time has increased the interest in performing in-space assembly and construction operations with automated robotic systems. A technique being considered at Langley Research Center is a supervised-autonomy approach, which can be monitored by an Earth-based supervisor that intervenes only when the automated system encounters a problem. A test-bed to support evaluation of the hardware and software requirements for supervised-autonomy assembly methods has been developed. This report describes the design of the software system necessary to support the assembly process. The system is implemented and successfully assembles and disassembles a planar tetrahedral truss structure. The software is hierarchical and supports both automated assembly operations and supervisor error-recovery procedures, including the capability to pause and reverse any operation. The software design serves as a model for the development of software for more sophisticated automated systems and as a test-bed for evaluation of new concepts and hardware components.", } @TechReport{Carlson??, authorkey = "CarlsonHW MannMJ", author = "Harry W. Carlson and Michael J. Mann", title = "Survey and Analysis of Research on Supersonic Drag-Due-to-Lift Minimization With Recommendations for Wing Design", institution = "NASA - Langley Research Centre", number = "NASA TP-3202", pages = "156", keywords = "Supersonic drag due to lift Supersonic wing design", abstract = "A survey of research on drag-due-to-lift minimization at supersonic speeds, including a study of the effectiveness of current design and analysis methods, has been conducted. The results show that a linearized theory analysis with estimated attainable thrust and vortex force effects can predict with reasonable accuracy the lifting efficiency of flat wings. Significantly better wing performance can be achieved through the use of twist and camber. Although linearized theory methods tend to overestimate the amount of twist and camber required for a given application and provide an overly optimistic performance prediction, these deficiencies can be overcome by implementation of recently developed empirical corrections. Numerous examples of the correlation of experiment and theory are presented to demonstrate the applicability and limitations of linearized theory methods with and without empirical corrections. The use of an Euler code for the estimation of aerodynamic characteristics of a twisted and cambered wing and its application to design by iteration are discussed.", } @TechReport{Joslin??, authorkey = "JoslinRD StreettCL ChangCL", author = "Ronald D. Joslin and Craig L. Streett and Chau-Lyan Chang", title = "Validation of Three-Dimensional Incompressible Spatial Direct Numerical Simulation Code", institution = "NASA - Langley Research Centre", number = "NASA TP-3205", pages = "47", keywords = "Direct numerical simulation Boundary-layer transition Boundary-layer stability Nonlinear boundary-layer stability PSE theory", abstract = "Spatially evolving instabilities in a boundary layer on a flat plate are computed by direct numerical simulation (DNS) of the incompressible Navier-Stokes equations. In a truncated physical domain, a nonstaggered mesh is used for the grid. A Chebyshev-collocation method is used normal to the wall; finite-difference and compact-difference methods are used in the streamwise direction; and a Fourier series is used in the spanwise direction. For time stepping, implicit Crank-Nicolson and explicit Runge-Kutta schemes are used for the time-splitting method. The influence-matrix technique is used to solve the pressure equation. At the outflow boundary, the buffer-domain technique is used to prevent convective wave reflection or upstream propagation of information from the boundary. Results of the DNS are compared with those from both linear stability theory (LST) and parabolized stability equation (PSE) theory. Computed disturbance amplitudes and phases are in very good agreement with those of LST (for small inflow disturbance amplitudes). A measure of the sensitivity of the inflow condition is demonstrated with both LST and PSE theory used to approximate inflows. Although the DNS numerics are very different than those of PSE theory, the results are in good agreement. A small discrepancy in the results that does occur is likely a result of the variation in PSE boundary condition treatment in the far field. Finally, a small-amplitude wave triad is forced at the inflow, and simulation results are compared with those of LST. Again, very good agreement is found between DNS and LST results for the 3-D simulations, the implication being that the disturbance amplitudes are sufficiently small that nonlinear interactions are negligible.", } @TechReport{Gupta??, authorkey = "GuptaRN JonesJJ RochelleWC", author = "Roop N. Gupta and Jim J. Jones and William C. Rochelle", title = "Stagnation-Point Heat-Transfer Rate Predictions at Aeroassist Flight Conditions", institution = "NASA - Langley Research Centre", number = "NASA TP-3208", pages = "19", keywords = "Hypersonic flow Stagnation-point heat transfer Low- and High-altitude flight conditions Navier-Stokes Viscous shock layer Boundary-layer methods Aeroassist Flight Experiment", abstract = "Results are presented for the stagnation-point heat-transfer rates used in the design process of the Aeroassist Flight Experiment (AFE) vehicle over its entire aeropass trajectory. The prediction methods used in this investigation demonstrate the application of computational fluid dynamics (CFD) techniques to a wide range of flight conditions and their usefulness in a design process. The heating rates were computed by a viscous-shock-layer (VSL) code at the lower altitudes and by a Navier-Stokes (N-S) code for the higher altitude cases. For both these methods, finite-rate chemically reacting gas was considered, and a temperature-dependent wall-catalysis model was used. The wall temperature for each case was assumed to be radiative equilibrium temperature, based on total (radiative plus convective) heating. The radiative heating was estimated by using a correlation equation. Wall slip was included in the N-S calculation method, and this method implicitly accounts for shock slip. The N-S/VSL combination of prediction methods was established by comparison with the published results of the benchmark flow-field code LAURA at lower altitudes and comparison with the direct simulation Monte Carlo results for the higher altitude cases of this study. For the purpose of obtaining the design heating rates over the entire forward face of the vehicle, a boundary-layer method (BLIMP code) that employs reacting chemistry and surface catalysis was used. The ratio of the VSL or N-S method prediction to that obtained from the boundary-layer method at the stagnation point is used to define an adjustment factor, which accounts for the errors involved in using the boundary-layer method.", } @TechReport{Palumbo??, authorkey = "PalumboDL GrahamRL", author = "Daniel L. Palumbo and R. Lynn Graham", title = "Experimental Validation of Clock Synchronization Algorithms", institution = "NASA - Langley Research Centre", number = "NASA TP-3209", pages = "22", keywords = "Clock synchronization Formal methods Verification Validation", abstract = "The objective of this work is to validate mathematically derived clock synchronization theories and their associated algorithms through experiment. Two theories are considered, the Interactive Convergence Clock Synchronization Algorithm and the Midpoint Algorithm. Special clock circuitry was designed and built so that several operating conditions and failure modes (including malicious failures) could be tested. Both theories are shown to predict conservative upper bounds (i.e., measured values of clock skew were always less than the theory prediction). Insight gained during experimentation led to alternative derivations of the theories. These new theories accurately predict the behavior of the clock system. It is found that a 100-percent penalty is paid to tolerate worst-case failures. It is also shown that under optimal conditions (with minimum error and no failures) the clock skew can be as much as three clock ticks. Clock skew grows to six clock ticks when failures are present. Finally, it is concluded that one cannot rely solely on test procedures or theoretical analysis to predict worst-case conditions.", } @TechReport{Lake??, authorkey = "LakeMS", author = "Mark S. Lake", title = "Stiffness and Strength Tailoring in Uniform Space-Filling Truss Structures", institution = "NASA - Langley Research Centre", number = "NASA TP-3210", pages = "28", keywords = "Truss Geometric symmetry Stiffness tailoring Strength tailoring Equivalent continuum analogy Crystallography", abstract = "This paper presents a deterministic procedure for tailoring the continuum stiffness and strength of uniform space-filling truss structures through the appropriate selection of truss geometry and member sizes (i.e., flexural and axial stiffnesses and length). The trusses considered herein are generated by uniform replication of a characteristic truss cell. The repeating cells are categorized by one of a set of possible geometric symmetry groups derived using crystallographic techniques. The elastic symmetry associated with each geometric symmetry group is identified to help select an appropriate truss geometry for a given application. Stiffness and strength tailoring of a given truss geometry is enabled through explicit expressions relating the continuum stiffnesses and failure stresses of the truss to the stiffnesses and failure loads of its members. These expressions are derived using an existing equivalent continuum analysis technique and a newly developed analytical failure theory for trusses. Several examples are presented to illustrate the application of these techniques and to demonstrate the usefulness of the information gained from this analysis.", } @TechReport{Nealy??, authorkey = "NealyJE StriepeSA SimonsenLC", author = "John E. Nealy and Scott A. Striepe and Lisa C. Simonsen", title = "{MIRACAL}: {A} Mission Radiation Calculation Program for Analysis of Lunar and Interplanetary Missions", institution = "NASA - Langley Research Centre", number = "NASA TP-3211", pages = "15", keywords = "Computational radiation data base Deep-space exploration", abstract = "A computational procedure and data base are developed for manned space exploration missions for which estimates are made for the energetic particle fluences encountered and the resulting dose equivalent incurred. The data base includes the following options: statistical or continuum model for ordinary solar proton events, selection of up to six observed large proton flare spectra, and galactic cosmic ray fluxes for elemental nuclei of charge numbers 1 through 92. The program requires as input trajectory definition information and specification of optional parameters, which include desired spectral data and nominal shield thickness. The procedure may be implemented as an independent program or as a subroutine in trajectory codes. This code should be most useful in mission optimization and selection studies for which radiation exposure is of special importance.", } @TechReport{Mcmillin??, authorkey = "McmillinSN BauerSXS HowellDT", author = "S. Naomi Mcmillin and Steven X. S. Bauer and Dorothy T. Howell", title = "Effect of Planform and Body on Supersonic Aerodynamics of Multibody Configurations", institution = "NASA - Langley Research Centre", number = "NASA TP-3212", pages = "282", keywords = "Multiple fuselage Supersonic Zero-lift drag Linear theory Planform shaping Aerodynamics Flight aircraft Longitudinal aerodynamics", abstract = "An experimental and theoretical investigation on the effect of the wing planform and bodies on the supersonic aerodynamics of a low-fineness-ratio, multibody configuration has been conducted in the Langley Unitary Plan Wind Tunnel at Mach numbers of 1.60, 1.80, 2.00, and 2.16. Force and moment data, flow-visualization data, and surface-pressure data were obtained on eight low-fineness-ratio, twin-body configurations. These configurations varied in inboard wing planform shape, outboard wing planform shape, outboard wing planform size, and presence of the bodies. The force and moment data showed that increasing the ratio of outboard wing area to total wing area or increasing the leading-edge sweep of the inboard wing influenced the aerodynamic characteristics. The flow-visualization data showed a complex flow-field system of shocks, shock-induced separation, and body vortex systems occurring between the side bodies. This flow field was substantially affected by the inboard wing planform shape but minimally affected by the outboard wing planform shape. The flow-visualization and surface-pressure data showed that the flow over the outboard wing developed as expected with changes in angle of attack and Mach number and was affected by the leading-edge sweep of the inboard wing and the presence of the bodies. Evaluation of the linear-theory prediction methods revealed their general inability to consistently predict the characteristics of these multibody configurations.", } @TechReport{Waller??, authorkey = "WallerMC", author = "Marvin C. Waller", title = "Flight Deck Benefits of Integrated Data Link Communication", institution = "NASA - Langley Research Centre", number = "NASA TP-3219", pages = "47", keywords = "Data link ATC Data link message exchange Flight deck integration Digital ATC communication Flight deck data link interfaces Mode-S data link", abstract = "A fixed-base, piloted simulation study was conducted to determine the operational benefits that result when air traffic control (ATC) instructions are transmitted to the flight deck of a transport airplane over a digital data link. The ATC instructions included altitude, airspeed, heading, radio frequency, and route assignment data. The interface between the flight deck and the data link was integrated with other subsystems of the airplane to facilitate data management. Data from the ATC instructions were distributed to the flight guidance and control system, the navigation system, and an automatically tuned communication radio. The copilot initiated the automation-assisted data distribution process. Digital communication and automated data distribution were compared with conventional voice radio communication and manual input of data into other subsystems of the simulated aircraft. Less time was required in the combined communication and data management process when data link ATC communication was integrated with the other subsystems. The test subjects, commercial airline pilots, provided favorable evaluations of both the digital communication and data management processes.", } @TechReport{Carlson??a, authorkey = "CarlsonJR", author = "John R. Carlson", title = "A Nozzle Internal Performance Prediction Method", institution = "NASA - Langley Research Centre", number = "NASA TP-3221", pages = "48", keywords = "Nozzles Nozzle performance Computational fluid dynamics Performance prediction", abstract = "A prediction method has been written and incorporated into a three-dimensional Navier-Stokes code (PAB3D) for the calculation of nozzle internal performance. The quantities calculated are discharge coefficient; normal, side, and axial thrust ratios; rolling, pitching, and yawing moments; and effective pitch and yaw vector angles. Four different case studies are presented to confirm the applicability of the methodology. Internal and, in most situations, external flow-field regions are required to be modeled. The computed nozzle discharge coefficient matches both the level and the trend of the experimental data within quoted experimental data accuracy (0.5 percent). Moment and force ratios are generally within 1 to 2 percent of the absolute level of experimental data, with the trends of data matched accurately.", } @TechReport{Jachimowski??, authorkey = "JachimowskiCJ", author = "Casimir J. Jachimowski", title = "An Analysis of Combustion Studies in Shock Expansion Tunnels and Reflected Shock Tunnels", institution = "NASA - Langley Research Centre", number = "NASA TP-3224", pages = "10", keywords = "Supersonic combustion Shock expansion tunnels Reflected shock tunnel Combustion modeling", abstract = "The effect of initial nonequilibrium dissociated air constituents on the combustion of hydrogen in high-speed flows for a simulated Mach 17 flight condition was investigated by analyzing the results of comparative combustion experiments performed in a reflected shock tunnel test gas and in a shock expansion tunnel test gas. The results were analyzed and interpreted with a one-dimensional quasi-three-stream combustor code that includes finite rate combustion chemistry. The results of this study indicate that the combustion process is kinetically controlled in the experiments in both tunnels and that the presence of the nonequilibrium partially dissociated oxygen in the reflected shock tunnel enhances the combustion. Methods of compensating for the effect of dissociated oxygen are discussed.", } @TechReport{Lach??, authorkey = "LachCL", author = "Cynthia L. Lach", title = "Effect of Temperature and Gap Opening Rate on the Resiliency of Candidate Solid Rocket Booster {O}-Ring Materials", institution = "NASA - Langley Research Centre", number = "NASA TP-3226", pages = "12", keywords = "O-ring Seal Resiliency Viton Elastomers", abstract = "As a part of the redesign of the Space Shuttle solid rocket motor following the Challenger accident, the field and nozzle-to-case joints were designed to minimize gap opening caused by internal motor pressurization during ignition. The O-ring seals and glands for these joints were designed both to accommodate structural deflections and to promote pressure-assisted sealing. The resiliency behavior of several candidate O-ring materials was evaluated for the effects of temperature and gap opening rates. The performance of three of the elastomeric materials was tested under the specific redesign gap opening requirement. Dynamic flexure conditions unique to launch produce low-frequency vibrations in the gap opening. The effect of these vibrations on the ability of the O-ring to maintain contact with the sealing surface was also addressed. The resiliency of the O-ring materials was found to be extremely sensitive to variations in temperature and gap opening rate. The top three elastomeric materials tracked the simulated solid rocket booster (SRB) field joint deflection at 75\$\^{}$\backslash$circ\$F and 120\$\^{}$\backslash$circ\$F. The external tank/SRB attach strut load vibrations had a negligible effect on the ability of the O-ring to track the simulated SRB field joint deflection.", } @TechReport{Schroeder??, authorkey = "SchroederLC BaileyMC MitchellJL", author = "Lyle C. Schroeder and M. C. Bailey and John L. Mitchell", title = "Deployable Reflector Antenna Performance Optimization Using Automated Surface Correction and Array-Feed Compensation", institution = "NASA - Langley Research Centre", number = "NASA TP-3228", pages = "68", keywords = "Large space deployable antenna Surface adjustment Array-feed antenna compensation", abstract = "Methods for increasing the electromagnetic (EM) performance of reflectors with rough surfaces were tested and evaluated. First one quadrant of the 15-meter hoop-column antenna was retrofitted with computer-driven and controlled motors to allow automated adjustment of the reflector surface. The surface errors, measured with metric photogrammetry, were used in a previously verified computer code to calculate control motor adjustments. With this system, a rough antenna surface (rms of \$$\backslash$approx\$0.180 inch) was corrected in two iterations to approximately the structural surface smoothness limit of 0.060 inch rms. The antenna pattern and gain improved significantly as a result of these surface adjustments. The EM performance was evaluated with a computer program for distorted reflector antennas which had been previously verified with experimental data. Next, the effects of the surface distortions were compensated for in computer simulations by superimposing excitation from an array feed to maximize antenna performance relative to an undistorted reflector. Results showed that a 61-element array could produce EM performance improvements equal to surface adjustments. When both mechanical surface adjustment and feed compensation techniques were applied, the equivalent operating frequency increased from approximately 6 to 18 GHz.", } @TechReport{Groom??, authorkey = "GroomNJ BritcherCP", author = "Nelson J. Groom and Colin P. Britcher", title = "Open-Loop Characteristics of Magnetic Suspension Systems Using Electromagnets Mounted in a Planar Array", institution = "NASA - Langley Research Centre", number = "NASA TP-3229", pages = "33", keywords = "Magnetic suspension Large-Gap Magnetic Suspension Magnetic levitation Magnetic suspension model Planar array suspension coils", abstract = "The open-loop characteristics of a Large-Gap Magnetic Suspension System (LGMSS) were investigated and numerical results are presented. The LGMSS considered provides five-degree-of-freedom control. The suspended element is a cylinder that contains a core composed of permanent magnet material. The magnetic actuators are air core electromagnets mounted in a planar array. Configurations utilizing five, six, seven, and eight electromagnets were investigated and all configurations were found to be controllable from coil currents and observable from suspended-element positions. Results indicate that increasing the number of coils has an insignificant effect on mode shapes and frequencies.", } @TechReport{Costen??, authorkey = "CostenRC StockLV", author = "Robert C. Costen and Larry V. Stock", title = "Inertial Oscillation of a Vertical Rotating Draft With Application to a Supercell Storm", institution = "NASA - Langley Research Centre", number = "NASA TP-3230", pages = "47", keywords = "Supercell thunderstorm Inertial oscillation", abstract = "An analytic model (``vertical rotating draft''), which includes the gross features of a supercell storm on an \$f\$-plane, undergoes an inertial oscillation that appears to have been overlooked in previous analytic and numerical models. The oscillation is nonlinear and consists of a long quiescent phase and a short intense phase. During the intense phase, the rotating draft has the following features of a supercell: the diameter of the core contracts as it spins up and expands as it spins down; if vertical wind shear is included, the track of the rotating draft turns to the right (an anticyclonic rotating draft turns to the left); this turning point is followed by a predominantly upward flow; and the horizontal pressure gradient is very small (a property of most tornadoless supercells). The rapid spin-up during the intense phase and the high Rossby numbers obtainable establish the ability of the Coriolis force to spin up single cyclonic or anticyclonic supercells by means of this inertial oscillation. This surprising result has implications for numerical supercell simulations, which generally do not rely on the Coriolis force as a source of rotation. The physics and mathematics of the inertial oscillation are given, and the solution is applied to a documented supercell.", } @TechReport{Dawicke??, authorkey = "DawickeDS NewmanJJC", author = "D. S. Dawicke and Jr. J. C. Newman", title = "Analysis and Prediction of Multiple-Site Damage ({MSD}) Fatigue Crack Growth", institution = "NASA - Langley Research Centre", number = "NASA TP-3231", pages = "16", keywords = "Multiple-site damage Stress intensity factor Fatigue Life prediction Indirect boundary element", abstract = "A technique was developed to calculate the stress intensity factor for multiple interacting cracks. The analysis was verified through comparison with accepted methods of calculating stress intensity factors. The technique was incorporated into a fatigue crack growth prediction model and used to predict the fatigue crack growth life for multiple-site damage (MSD). The analysis was verified through comparison with experiments conducted on uniaxially loaded flat panels with multiple cracks. Configurations with nearly equal and unequal crack distributions were examined. The fatigue crack growth predictions agreed within 20 percent of the experimental lives for all crack configurations considered.", } @TechReport{Barger??b, authorkey = "BargerRL", author = "Raymond L. Barger", title = "Trajectory Fitting in Function Space With Application to Analytic Modeling of Surfaces", institution = "NASA - Langley Research Centre", number = "NASA TP-3232", pages = "13", keywords = "Geometry modeling Analytic modeling Surface grid generation", abstract = "A theory for representing a parameter-dependent function as a function trajectory is described, along with the theory for determining a piecewise analytic fit to the trajectory. An example is given that illustrates the application of the theory to generating a smooth surface through a discrete set of input cross-section shapes. A simple procedure for smoothing in the parameter direction is presented, along with a computed example. Application of the theory to aerodynamic surface modeling is demonstrated by applying it to a blended wing-fuselage surface.", } @TechReport{Kelley??, authorkey = "KelleyHL CrowellCA WilsonJC", author = "Henry L. Kelley and Cynthia A. Crowell and John C. Wilson", title = "Two-Dimensional Aerodynamic Characteristics of Several Polygon-Shaped Cross-Sectional Models Applicable to Helicopter Fuselages", institution = "NASA - Langley Research Centre", number = "PR1L236003D313 NASA TP-3233 AVSCOM TR-92-B-002", pages = "28", keywords = "Helicopter Fuselage Tail boom Blunt bodies Aerodynamics", abstract = "A wind-tunnel investigation was conducted to determine two-dimensional aerodynamic characteristics of nine polygon-shaped models applicable to helicopter fuselages. The models varied from 12 to 15 scale and were nominally triangular, diamond, and rectangular in shape. Side force and normal force were obtained at increments of angle of flow incidence from \$-45\^{}$\backslash$circ\$ to 90\$\^{}$\backslash$circ\$. The data were compared with results from a baseline UH-60 tail-boom cross-sectional model. The results indicate that the overall shapes of the plots of normal force and side force were similar to the characteristic shape of the baseline data; however, there were important differences in magnitude. At a flow incidence of 0\$\^{}$\backslash$circ\$, larger values of normal force for the polygon models indicate an increase in fuselage down load of 1 to 2.5 percent of main-rotor thrust compared with the baseline value. Also, potential was indicated among some of the configurations to produce high fuselage side forces and yawing moments compared with the baseline model.", } @TechReport{Smith??a, authorkey = "SmithLA CampbellRL", author = "Leigh Ann Smith and Richard L. Campbell", title = "Applications of a Direct/Iterative Design Method to Complex Transonic Configurations", institution = "NASA - Langley Research Centre", number = "NASA TP-3234", pages = "34", keywords = "Aircraft design Drag reduction Transport aircraft Nacelle interference", abstract = "The current study explores the use of an automated direct/iterative design method for the reduction of drag for transport configurations, including configurations with engine nacelles. The method requires the user to choose a proper target-pressure distribution and then develops a corresponding airfoil section. The method can be applied to two-dimensional airfoil sections or to three-dimensional wings. The three cases that are presented show successful application of the method for reducing drag from various sources. The first two cases demonstrate the use of the method to reduce induced drag by designing to an elliptic span-load distribution and to reduce wave drag by decreasing the shock strength for a given lift. In the second case, a body-mounted nacelle is added and the method is successfully used to eliminate increases in wing drag associated with the nacelle addition by designing to an arbitrary pressure distribution that has an elliptic span-load distribution with reduced shock strength. The third case does not show a large drag decrease, but does demonstrate the elimination of nacelle influence on the original pressure distribution as a result of the redesigning of a wing in combination with a given underwing nacelle to clean-wing, target-pressure distributions. These cases illustrate several possible uses of the method for reducing different types of drag. The magnitude of the obtainable drag reduction varies with the constraints of the problem and the configuration to be modified.", } @TechReport{Katz??, authorkey = "KatzR CucinottaFA WilsonJW ShinnJL NgoDM", author = "Robert Katz and Francis A. Cucinotta and John W. Wilson and Judy L. Shinn and Duc M. Ngo", title = "Track Structure Model of Cell Damage in Space Flight", institution = "NASA - Langley Research Centre", number = "NASA TP-3235", pages = "30", keywords = "Radiation injury Track structure Nuclear fragmentation Relative biological effectiveness", abstract = "The phenomenological track-structure model of cell damage is discussed. A description of the application of the track-structure model with the NASA Langley transport code for laboratory and space radiation is given. Comparisons to experimental results for cell survival during exposure to monoenergetic, heavy-ion beams are made. The model is also applied to predict cell damage rates and relative biological effectiveness for deep-space exposures.", } @TechReport{Bangert??, authorkey = "BangertLS CarsonJGT", author = "Linda S. Bangert and Jr. George T. Carson", title = "Effect of Afterbody Geometry on Aerodynamic Characteristics of Isolated Nonaxisymmetric Afterbodies at Transonic Mach Numbers", institution = "NASA - Langley Research Centre", number = "NASA TP-3236", pages = "263", keywords = "Nonaxisymmetric afterbodies Afterbody drag Boattail drag", abstract = "A parametric study has been conducted in the Langley 16-Foot Transonic Tunnel on an isolated nonaxisymmetric fuselage model that simulates a twin-engine fighter. The effects of aft-end closure distribution (top/bottom nozzle-flap boattail angle versus nozzle-sidewall boattail angle) and afterbody and nozzle corner treatment (sharp or radius) were investigated. Four different closure distributions with three different corner radii were tested. Tests were conducted over a range of Mach numbers from 0.40 to 1.25 and over a range of angles of attack from \$-3\^{}$\backslash$circ\$ to 9\$\^{}$\backslash$circ\$. Solid plume simulators were used to simulate the jet exhaust. For a given closure distribution in the range of Mach numbers tested, the sharp-corner nozzles generally had the highest drag and the 2-in.\ corner-radius nozzles generally had the lowest drag. The effect of closure distribution on afterbody drag was highly dependent on configuration and flight condition.", } @TechReport{Simonsen??, authorkey = "SimonsenLC AtwellW NealyJE CucinottaF", author = "Lisa C. Simonsen and William Atwell and John E. Nealy and Francis Cucinotta", title = "Radiation Dose to Critical Body Organs for October 1989 Proton Event", institution = "NASA - Langley Research Centre", number = "NASA TP-3237", pages = "33", keywords = "Computerized anatomical models October 1989 solar proton event Radiation shielding Dose rates Cancer risk", abstract = "The Geostationary Operational Environmental Satellite (GOES-7) provides high-quality environmental data about the temporal development and energy characteristics of the protons emitted during a solar particle event. The GOES-7 time history of the hourly averaged integral proton flux for various particle kinetic energies are analyzed for the solar proton event occurring October 19--29, 1989. This event is similar to the August 1972 event that has been widely studied to estimate free-space and planetary radiation-protection requirements. By analyzing the time-history data, the dose rates, which can vary over many orders of magnitude in the early phases of the flare, can be estimated as well as the cumulative dose as a function of time. When basic transport results are coupled with detailed body organ thickness distributions calculated with the Computerized Anatomical Man and Computerized Anatomical Female models, the dose rates and cumulative doses to specific organs can be predicted. With these results, the risks of cancer incidence and mortality are estimated for astronauts in free space protected by various water shield thicknesses.", } @TechReport{Capone??, authorkey = "CaponeFJ ReRJ BareEA", author = "Francis J. Capone and Richard J. Re and E. Ann Bare", title = "Parametric Investigation of Single-Expansion-Ramp Nozzles at Mach Numbers From 0.60 to 1.20", institution = "NASA - Langley Research Centre", number = "NASA TP-3240", pages = "274", keywords = "Nonaxisymmetric nozzles Aeropropulsive performance Single-expansion-ramp nozzle Internal performance", abstract = "An investigation has been conducted in the Langley 16-Foot Transonic Tunnel to determine the effects of varying six nozzle geometric parameters on the internal and aeropropulsive performance characteristics of single-expansion-ramp nozzles. This investigation was conducted at Mach numbers from 0.60 to 1.20, nozzle pressure ratios from 1.5 to 12, and angles of attack of 0\$\^{}$\backslash$circ\$ and \$$\backslash$pm 6\^{}$\backslash$circ\$. Maximum aeropropulsive performance at a particular Mach number was highly dependent on the operating nozzle pressure ratio. For example, as the nozzle upper ramp length or angle increased, some nozzles had higher performance at a Mach number of 0.90 because the nozzle design pressure was the same as the operating pressure ratio. Thus, selection of the various nozzle geometric parameters should be based on the mission requirements of the aircraft. A combination of large upper ramp and large lower flap boattail angles produced greater nozzle drag coefficients at Mach numbers greater than 0.80, primarily from shock-induced separation on the lower flap of the nozzle. At static conditions, the convergent nozzle had high and nearly constant values of resultant thrust ratio over the entire range of nozzle pressure ratios tested. However, these nozzles had much lower aeropropulsive performance than the convergent-divergent nozzle at Mach numbers greater than 0.60.", } @TechReport{Shinn??a, authorkey = "ShinnJL JohnS TripathiRK WilsonJW TownsendLW NorburyJW", author = "Judy L. Shinn and Sarah John and Ram K. Tripathi and John W. Wilson and Lawrence W. Townsend and John W. Norbury", title = "Fully Energy-Dependent {HZETRN} ({A} Galactic Cosmic-Ray Transport Code)", institution = "NASA - Langley Research Centre", number = "NASA TP-3243", pages = "16", keywords = "Galactic cosmic radiation Fragmentation Linear energy transfer spectra", abstract = "For extended manned space missions, the radiation shielding design requires efficient and accurate cosmic-ray transport codes that can handle the physics processes in detail. The Langley Research Center galactic cosmic-ray transport code (HZETRN) is currently under development for such design use. The cross sections for the production of secondary nucleons in the existing HZETRN code are energy dependent only for nucleon collisions. The approximation of energy-independent, heavy-ion fragmentation cross section is now removed by implementing a mathematically simplified energy-dependent stepping formalism for heavy ions. The cross section at each computational grid is obtained by linear interpolation from a few tabulated data to minimize computing time. Test runs were made for galactic cosmic-ray transport through a liquid hydrogen shield and a water shield at solar minimum. The results show no appreciable change in total fluxes or computing time compared with energy-independent calculations. Differences in high LET (linear energy transfer) spectra are noted, however, because of the large variation in cross sections at low-energy region. The high LET components are significantly higher in the new code and have important implications on biological risk estimates for heavy-ion exposure.", } @TechReport{Parrish??, authorkey = "ParrishRV HoldenA WilliamsSP", author = "Russell V. Parrish and Anthony Holden and Steven P. Williams", title = "Correction Techniques for Depth Errors With Stereo Three-Dimensional Graphic Displays", institution = "NASA - Langley Research Centre", number = "PR 1L161102AH45 NASA TP-3244 ATCOM TR-92-B-011", pages = "17", keywords = "Stereo displays Stereopsis cueing Head movement Depth cues", abstract = "Three-dimensional (3-D), ``real-world'' pictorial displays that incorporate ``true'' depth cues via stereopsis techniques have proved effective for displaying complex information in a natural way to enhance situational awareness and to improve pilot/vehicle performance. In such displays, the display designer must map the depths in the real world to the depths available with the stereo display system. However, empirical data have shown that the human subject does not perceive the information at exactly the depth at which it is mathematically placed. Head movements can also seriously distort the depth information that is embedded in stereo 3-D displays because the transformations used in mapping the visual scene to the depth-viewing volume (DVV) depend intrinsically on the viewer location. The goal of this research has been to provide two correction techniques; the first technique corrects the original visual scene to the DDV mapping based on human perception errors, and the second (which is based on head-positioning sensor input data) corrects for errors induced by head movements. Empirical data are presented to validate both correction techniques. A combination of the two correction techniques effectively eliminates the distortions of depth information embedded in stereo 3-D displays.", } @TechReport{Heard??, authorkey = "HeardJWL WatsonJJ LakeMS BushHG JensenJK WallsomRE PhelpsJE", author = "Jr. Walter L. Heard and Judith J. Watson and Mark S. Lake and Harold G. Bush and J. Kermit Jensen and Richard E. Wallsom and James E. Phelps", title = "Tests of an Alternate Mobile Transporter and Extravehicular Activity Assembly Procedure for the Space Station Freedom Truss", institution = "NASA - Langley Research Centre", number = "NASA TP-3245", pages = "32", keywords = "EVA assembly Truss structure Space station assembly Erectable structures Mobile transporter Large space structures", abstract = "Results are presented from a ground test program of an alternate mobile transporter (MT) concept and extravehicular activity (EVA) assembly procedure for the Space Station Freedom (SSF) truss keel. A three-bay orthogonal tetrahedral truss beam consisting of 44 2-in-diameter struts and 16 nodes was assembled repeatedly in neutral buoyancy by pairs of pressure-suited test subjects working from astronaut positioning devices (APD's) on the MT. The truss bays were cubic with edges 15 ft long. All the truss joint hardware was found to be EVA compatible. The average unit assembly time for a single pair of experienced test subjects was 27.6 sec/strut, which is about half the time derived from other SSF truss assembly tests. A concept for integration of utility trays during truss assembly is introduced and demonstrated in the assembly tests. The concept, which requires minimal EVA handling of the trays, is shown to have little impact on overall assembly time. The results of these tests indicate that by using an MT equipped with APD's, rapid EVA assembly of space station-size truss structure can be expected.", } @TechReport{Heard??a, authorkey = "HeardJWL LakeMS BushHG JensenJK PhelpsJE WallsomRE", author = "Jr. Walter L. Heard and Mark S. Lake and Harold G. Bush and J. Kermit Jensen and James E. Phelps and Richard E. Wallsom", title = "Extravehicular Activity Compatibility Evaluation of Developmental", institution = "NASA - Langley Research Centre", number = "NASA TP-3246", pages = "60", keywords = "EVA compatibility Precision reflectors Tetrahedral truss Truss assembly Simulated EVA assembly", abstract = "This report presents results of tests performed in neutral buoyancy by two pressure-suited test subjects to simulate EVA tasks associated with the on-orbit construction and repair of a precision reflector spacecraft. Two complete neutral buoyancy assemblies of the test article (tetrahedral truss with three attached reflector panels) were performed. Truss joint hardware, two different panel attachment hardware concepts, and a panel replacement tool were evaluated. The test subjects found the operation and size of the truss joint hardware to be acceptable. Both panel attachment concepts were found to be EVA compatible, although one concept was judged by the test subjects to be considerably easier to operate. The average time to install a panel from a position within arm's reach of the test subjects was 1 min 14 sec. The panel replacement tool was used successfully to demonstrate the removal and replacement of a damaged reflector panel in 10 min 25 sec.", } @TechReport{Erickson??, authorkey = "EricksonGE RogersLW", author = "Gary E. Erickson and Lawrence W. Rogers", title = "Effects of Forebody Strakes and Mach Number on Overall Aerodynamic Characteristics of Configuration With \$55\^{}$\backslash$circ\$ Cropped Delta Wing", institution = "NASA - Langley Research Centre", number = "NASA TP-3253", pages = "170", keywords = "Vortex flows Subsonic flow Transonic flow Flow visualization Vortex breakdown Forebody strakes Delta wings Shock waves Aerodynamics Longitudinal stability Lateral stability Directional stability", abstract = "A wind tunnel data base was established for the effects of chine-like forebody strakes and Mach number on the longitudinal and lateral-directional characteristics of a generalized \$55\^{}$\backslash$circ\$ cropped delta wing--fuselage--centerline vertical tail configuration. The testing was conducted in the 7- by 10-Foot Transonic Tunnel at the David Taylor Research Center at free-stream Mach numbers of 0.40 to 1.10 and Reynolds numbers based on the wing mean aerodynamic chord of \$1.6010\^{}6\$ to \$2.5910\^{}6\$. The test matrix included angles of attack from \$0\^{}$\backslash$circ\$ to a maximum of \$28\^{}$\backslash$circ\$, angles of sideslip of \$0\^{}$\backslash$circ\$, \$+5\^{}$\backslash$circ\$, and \$-5\^{}$\backslash$circ\$, and wing leading-edge flap deflection angles of \$0\^{}$\backslash$circ\$ and \$30\^{}$\backslash$circ\$. Key flow phenomena at subsonic and transonic conditions were identified by measuring the model six-component forces and moments and wing upper surface static pressures and by conducting off-body flow visualization with a laser screen technique. These phenomena included coexisting and interacting vortex flows and shock waves, vortex breakdown, vortex flow interactions with the vertical tail, and vortices induced by flow separation from the hinge line of the deflected wing flap. The flow mechanisms were correlated with the longitudinal and lateral-directional aerodynamic data trends.", } @TechReport{Cano??, authorkey = "CanoRJ DowMB", author = "Roberto J. Cano and Marvin B. Dow", title = "Properties of Five Toughened Matrix Composite Materials", institution = "NASA - Langley Research Centre", number = "NASA TP-3254", pages = "58", keywords = "Graphite/toughened matrix composite materials Compression after impact Compression strength Tension strength Damage tolerance", abstract = "The use of toughened matrix composite materials offers an attractive solution to the problem of poor damage tolerance associated with advanced composite materials. In this study, the unidirectional laminate strengths and moduli, notched (open-hole) and unnotched tension and compression properties of quasi-isotropic laminates, and compression-after-impact strengths of five carbon fiber/toughened matrix composites, IM7/E7T1-2, IM7/X1845, G40-800X/5255-3, IM7/5255-3, and IM7/5260, have been evaluated. The compression-after-impact (CAI) strengths were determined primarily by impacting quasi-isotropic laminates with the NASA Langley air gun. A few CAI tests were also made with a drop-weight impactor. For a given impact energy, compression-after-impact strengths were determined to be dependent on impactor velocity. Properties and strengths for the five materials tested are compared with NASA data on other toughened matrix materials (IM7/8551-7, IM6/1808I, IM7/977-2, IM7/F655, and T800/F3900). This investigation found that all five materials were stronger and more impact damage tolerant than more brittle carbon/epoxy composite materials currently used in aircraft structures.", } @TechReport{Desai??, authorkey = "DesaiPN BraunRD PowellRW", author = "Prasun N. Desai and Robert D. Braun and Richard W. Powell", title = "Aspects of Parking Orbit Selection in a Manned Mars Mission", institution = "NASA - Langley Research Centre", number = "NASA TP-3256", pages = "27", keywords = "Mars parking orbits Manned mars mission Nonspherical gravitational effects", abstract = "For any round-trip Mars mission, the selection of a parking orbit at Mars must consider the precession caused by the oblateness of the planet. This precession will affect the departure condition for Earth return and, therefore, the initial mass required in low Earth orbit (LEO). In this investigation, which considers precession effects, minimum initial LEO masses were obtained for parking orbits characterized by having near-equatorial inclinations, high eccentricities, and three-dimensional departure burns (i.e., a burn with an in-plane and an out-of-plane velocity increment component). However, because near-equatorial inclination orbits have poor planetary coverage characteristics, they are not desirable from a science viewpoint. To enhance the potential for satisfying science requirements along with landing site accessibility, a penalty in the initial LEO mass is required. This study shows that there are a set of orbits characterized by low to moderate eccentricities (\$e=0.2\$ to 0.5) and nonequatorial inclinations (\$i=70\^{}$\backslash$circ\$ to \$140\^{}$\backslash$circ\$) that reduce this initial LEO mass penalty. Therefore, careful selection of a parking orbit at Mars can enhance the potential for satisfying science requirements with minimal mass penalties.", } @TechReport{Campbell??, authorkey = "CampbellRL", author = "Richard L. Campbell", title = "An Approach to Constrained Aerodynamic Design With Application to Airfoils", institution = "NASA - Langley Research Centre", number = "NASA TP-3260", pages = "22", keywords = "Airfoil design Design method", abstract = "An approach has been developed for incorporating flow and geometric constraints into the Direct Iterative Surface Curvature (DISC) design method. In this approach, an initial target pressure distribution is developed using a set of control points. The chordwise locations and pressure levels of these points are initially estimated either from empirical relationships and observed characteristics of pressure distributions for a given class of airfoils or by fitting the points to an existing pressure distribution. These values are then automatically adjusted during the design process to satisfy the flow and geometric constraints. The flow constraints currently available are lift, wave drag, pitching moment, pressure gradient, and local pressure levels. The geometric constraint options include maximum thickness, local thickness, leading-edge radius, and a ``glove{"} constraint involving inner and outer bounding surfaces. This design method has also been extended to include the successive constraint release (SCR) approach to constrained minimization.", } @TechReport{Barger??c, authorkey = "BargerRL", author = "Raymond L. Barger", title = "A Method for Designing Blended Wing-Body Configurations for Low Wave Drag", institution = "NASA - Langley Research Centre", number = "NASA TP-3261", pages = "17", keywords = "Supersonic aircraft design Blended wing-body Low-drag design", abstract = "A procedure for tailoring a blended wing-body configuration to reduce its computed wave drag is described. The method utilizes an iterative algorithm within the framework of first-order linear theory. Four computed examples are included. In each case, the zero-lift wave drag was reduced without an increase in drag due to lift.", } @TechReport{Jegley??a, authorkey = "JegleyDC", author = "Dawn C. Jegley", title = "Study of Compression-Loaded and Impact-Damaged Structurally Efficient Graphite-Thermoplastic Trapezoidal-Corrugation Sandwich and Semisandwich Panel", institution = "NASA - Langley Research Centre", number = "NASA TP-3264", pages = "29", keywords = "Graphite-thermoplastic Corrugation Thermoforming Sandwich Semisandwich Structural efficiency", abstract = "The structural efficiency of compression-loaded trapezoidal-corrugation sandwich and semisandwich composite panels is studied to determine their weight savings potential. Sandwich panels with two identical face sheets and a trapezoidal corrugated core between them and semisandwich panels with a corrugation attached to a single skin are considered. An optimization code is used to find the minimum weight designs for critical compressive load levels ranging from 3000 to 24 000 lb/in. Graphite-thermoplastic panels based on the optimal minimum weight designs were fabricated and tested. A finite-element analysis of several test specimens was also conducted. The results of the optimization study, the finite-element analysis, and the experiments are presented. The results of testing impact-damaged panels are also discussed.", } @TechReport{Leatherwood??, authorkey = "LeatherwoodJD SullivanBM", author = "Jack D. Leatherwood and Brenda M. Sullivan", title = "Laboratory Study of Effects of Sonic Boom Shaping on Subjective Loudness and Acceptability", institution = "NASA - Langley Research Centre", number = "NASA TP-3269", pages = "26", keywords = "Sonic boom Subjective loudness Acceptability Sonic boom simulator Signature shaping", abstract = "A laboratory study was conducted to determine the effects of sonic boom signature shaping on subjective loudness and acceptability. The study utilized the sonic boom simulator at the Langley Research Center. A wide range of symmetrical, front-shock-minimized signature shapes were investigated together with a limited number of asymmetrical signatures. Subjective loudness judgments were obtained from 60 test subjects by using an 11-point numerical category scale. Acceptability judgments were obtained using the method of constant stimuli. Results were used to assess the relative predictive ability of several noise metrics, determine the loudness benefits of detailed boom shaping, and derive laboratory sonic boom acceptability criteria. These results indicated that the A-weighted sound exposure level, the Stevens Mark VII Perceived Level, and the Zwicker Loudness Level metrics all performed well. Significant reductions in loudness were obtained by increasing front-shock rise time and/or decreasing front-shock overpressure of the front-shock-minimized signatures. In addition, the asymmetrical signatures were rated to be slightly quieter than the symmetrical front-shock-minimized signatures of equal A-weighted sound exposure level. However, this result was based on a limited number of asymmetric signatures. The comparison of laboratory acceptability results with acceptability data obtained in more realistic situations also indicated good agreement.", } @TechReport{Hamilton??, authorkey = "HamiltonHH MillmanDR GreendykeRB", author = "H. Harris {Hamilton, Ii} and Daniel R. Millman and Robert B. Greendyke", title = "Finite-Difference Solution for Laminar or Turbulent Boundary Layer Flow Over Axisymmetric Bodies With Ideal Gas, {CF}\$\_4\$, or Equilibrium Air Chemistry", institution = "NASA - Langley Research Centre", number = "NASA TP-3271", pages = "21", keywords = "Boundary layer Finite difference Heat transfer", abstract = "A computer code has been developed that uses an implicit finite-difference technique to solve nonsimilar, axisymmetric boundary layer equations for both laminar and turbulent flow. The code can treat ideal gases, air in chemical equilibrium, and carbon tetrafluoride (CF\$\_4\$), which is a useful test gas for hypersonic blunt-body simulations. This is the only known boundary layer code that can treat CF\$\_4\$. Comparisons with experimental data have demonstrated that accurate solutions are obtained. The method should prove useful as an analysis tool for comparing calculations with wind tunnel experiments and for making calculations about flight vehicles where equilibrium air chemistry assumptions are valid.", } @TechReport{Farley??, authorkey = "FarleyGL", author = "Gary L. Farley", title = "Relationship Between Mechanical-Property and Energy-Absorption Trends for Composite Tubes", institution = "NASA - Langley Research Centre", number = "WU 505-63-50-08 NASA TP-3284 ARL-TR-29", pages = "14", keywords = "Energy absorption Composite tubes Crushing mechanisms Carbon-epoxy Glass-epoxy Kevlar-epoxy", abstract = "U.S. Army helicopters are designed to dissipate prescribed levels of crash impact kinetic energy without compromising the integrity of the fuselage. Because of the complexity of the energy-absorption process, it is imperative for designers of energy-absorbing structures to develop an in-depth understanding of how and why composite structures absorb energy. A description of the crushing modes and mechanisms of energy absorption for composite tubes and beams is presented. Three primary crushing modes of composite structure including transverse shearing, lamina bending, and local buckling are described. The experimental data presented show that fiber and matrix mechanical properties and laminate stiffness and strength mechanical properties cannot reliably predict the energy-absorption response of composite tubes.", } @TechReport{Shively??, authorkey = "ShivelyDG DeshpandeMD CockrellCR", author = "David G. Shively and Manohar D. Deshpande and Capers R. Cockrell", title = "Scattering From Arbitrarily Shaped Microstrip Patch Antennas", institution = "NASA - Langley Research Centre", number = "WU 505-64-52-60 NASA TP-3291 CECOM TR-92-E-5", pages = "33", keywords = "Antennas Scattering Microstrip Moment method", abstract = "The scattering properties of arbitrarily shaped microstrip patch antennas are examined. The electric field integral equation for a current element on a grounded dielectric slab is developed for a rectangular geometry based on Galerkin's technique with subdomain rooftop basis functions. A shape function is introduced that allows a rectangular grid approximation to the arbitrarily shaped patch. The incident field on the patch is expressed as a function of incidence angle \$$\backslash$theta\^{}i, $\backslash$phi\^{}i\$. The resulting system of equations is then solved for the unknown current modes on the patch, and the electromagnetic scattering is calculated for a given angle. Comparisons are made with other calculated results as well as with measurements.", } @TechReport{Dorsey??, authorkey = "DorseyJT SutterTR WuKC", author = "John T. Dorsey and Thomas R. Sutter and K. Chauncey Wu", title = "Structurally Adaptive Space Crane Concept for Assembling Space Systems on Orbit", institution = "NASA - Langley Research Centre", number = "NASA TP-3307", pages = "19", keywords = "Space structures Space crane On-orbit assembly Truss structures Adaptive structures", abstract = "Many future human space exploration missions will probably require large vehicles that must be assembled on orbit. Thus, a device that can move, position, and assemble large and massive spacecraft components on orbit becomes essential for these missions. This paper describes a concept for such a device---a space crane concept that uses erectable truss hardware to achieve high-stiffness and low-mass booms and uses articulating-truss joints that can be assembled on orbit. The hardware has been tested and shown to have linear load-deflection response and to be structurally predictable. The hardware also permits the crane to be reconfigured into different geometries to satisfy future assembly requirements. A number of articulating and rotary joint concepts have been sized and analyzed, and the results are discussed in this paper. Two strategies have been proposed to suppress motion-induced vibration: placing viscous dampers in selected truss struts and preshaping motion commands. Preliminary analyses indicate that these techniques have the potential to greatly enhance structural damping.", } @TechReport{Reaves??, authorkey = "ReavesMC BelvinWK BaileyJP", author = "Mercedes C. Reaves and W. Keith Belvin and James P. Bailey", title = "Finite-Element-Analysis Model and Preliminary Ground Testing of Controls-Structures Interaction Evolutionary Model Reflector", institution = "NASA - Langley Research Centre", number = "NASA TM-4293", pages = "50", keywords = "Nonlinear finite-element analysis Cable-stiffened structures Ribbed antenna Prestressed structures", abstract = "Results of two different nonlinear finite-element analyses and preliminary static test results for the final design of the Controls-Structures Interaction Evolutionary Model reflector are presented. Load-deflection data bases are generated from analysis and testing of the 16-ft diameter, dish-shaped reflector, and natural frequencies and mode shapes are obtained from vibrational analysis. Experimental and analytical results show similar trends; however, future test hardware modifications and finite-element model refinement would be necessary to obtain better correlation. The two nonlinear analysis approaches are both adequate techniques for the analysis of prestressed structures with complex geometry.", } @TechReport{Anderson??, authorkey = "AndersonWK", author = "W. Kyle Anderson", title = "Grid Generation and Flow Solution Method for Euler Equations on Unstructured Grids", institution = "NASA - Langley Research Centre", number = "NASA TM-4295", pages = "18", keywords = "Unstructured grids Grid generation Implicit schemes", abstract = "A grid generation and flow solution algorithm for the Euler equations on unstructured grids is presented. The grid generation scheme, which utilizes Delaunay triangulation, generates the field points for the mesh based on cell aspect ratios and allows clustering of grid points near solid surfaces. The flow solution method is an implicit algorithm in which the linear set of equations arising at each time step is solved using a Gauss-Seidel procedure that is completely vectorizable. In addition, a study is conducted to examine the number of subiterations required for good convergence of the overall algorithm. Grid generation results are shown in two dimensions for an NACA 0012 airfoil as well as a two-element configuration. Flow solution results are shown for a two-dimensional flow over the NACA 0012 airfoil and for a two-element configuration in which the solution has been obtained through an adaptation procedure and compared with an exact solution. Preliminary three-dimensional results also are shown in which the subsonic flow over a business jet is computed.", } @TechReport{Bare??, authorkey = "BareEA ReubushDE HaddadRC", author = "E. Ann Bare and David E. Reubush and Raymond C. Haddad", title = "Flow Field Over the Wing of a Delta-Wing Fighter Model With Vortex Control Devices at Mach 0.6 to 1.2", institution = "NASA - Langley Research Centre", number = "NASA TM-4296", pages = "124", keywords = "Flow-field data Cone probes Delta wing Fighter aircraft Vortex control", abstract = "As part of a cooperative research program between NASA, McDonnell Douglas Corporation, and Wright Research and Development Center, a flow-field investigation was conducted on a 7.52-percent-scale wind tunnel model of an advanced fighter aircraft design. The investigation was conducted in the Langley 16-Foot Transonic Tunnel at Mach numbers of 0.6, 0.9, and 1.2. Angle of attack was varied from \$-4\^{}$\backslash$circ\$ to 30\$\^{}$\backslash$circ\$ and the model was tested at angles of sideslip of 0\$\^{}$\backslash$circ\$, 5\$\^{}$\backslash$circ\$, and \$-5\^{}$\backslash$circ\$. Data for over-the-wing flow field were obtained at four axial survey stations by the use of six 5-hole conical probes mounted on a survey mechanism. The wing leading-edge primary vortex exerted the greatest influence in terms of total pressure loss on the over-the-wing flow field in the area surveyed. A number of vortex control devices were also investigated. They included two different apex flaps, wing leading-edge vortex flaps, and small and large wing fences. The vortex flap and both apex flaps were beneficial in controlling the wing leading-edge primary vortex.", } @TechReport{Jackson??, authorkey = "JacksonEB CruzCI", author = "E. Bruce Jackson and Christopher I. Cruz", title = "Preliminary Subsonic Aerodynamic Model for Simulation Studies of the {HL}-20 Lifting Body", institution = "NASA - Langley Research Centre", number = "NASA TM-4302", pages = "66", keywords = "Lifting body Flight control Landing and approach Lift-to-drag ratio Flight dynamics", abstract = "A nonlinear, six-degree-of-freedom aerodynamic model for an early version of the HL-20 lifting body is described and compared with wind tunnel data upon which it is based. Polynomial functions describing most of the aerodynamic parameters are given and tables of these functions are presented. Techniques used to arrive at these functions are described. Basic aerodynamic coefficients were modeled as functions of angles of attack and sideslip. Vehicle lateral symmetry was assumed. Compressibility (Mach) effects were ignored. Control-surface effectiveness was assumed to vary linearly with angle of deflection and was assumed to be invariant with angle of sideslip. Dynamic derivatives were obtained from predictive aerodynamic codes. Landing-gear and ground effects were scaled from Space Shuttle data. The model described is provided to support pilot-in-the-loop simulation studies of the HL-20. By providing the data in tabular format, the model is suitable for the data interpolation architecture of many existing engineering simulation facilities. Because of the preliminary nature of the data, however, this model is not recommended for study of absolute performance of the HL-20.", } @TechReport{Pappa??, authorkey = "PappaRS SchenkA NollC", author = "Richard S. Pappa and Axel Schenk and Christopher Noll", title = "Eigensystem Realization Algorithm Modal Identification Experiences With Mini-Mast", institution = "NASA - Langley Research Centre", number = "NASA TM-4307", pages = "41", keywords = "Modal identification Large space structures Dynamic testing", abstract = "This paper summarizes work performed under a collaborative research effort between the National Aeronautics and Space Administration (NASA) and the German Aerospace Research Establishment (DLR, Deutsche Forschungsanstalt fur Luft- und Raumfahrt). The objective is to develop and demonstrate system identification technology for future large space structures. Recent experiences using the Eigensystem Realization Algorithm (ERA) for modal identification of Mini-Mast are reported. Mini-Mast is a 20-m-long deployable space truss used for structural dynamics and active-vibration-control research at the Langley Research Center. A comprehensive analysis of 306 frequency response functions (3 excitation forces and 102 displacement responses) was performed. Emphasis is placed on two topics of current research: (1) gaining an improved understanding of ERA performance characteristics in theory versus practice and (2) developing reliable techniques to improve identification results for complex experimental data. Because of nonlinearities and numerous local modes, modal identification of Mini-Mast proved to be surprisingly difficult. Methods available with ERA for obtaining detailed, high-confidence results are illustrated.", } @TechReport{Harris??, authorkey = "HarrisCD BrooksJCW ClukeyPG StackJP", author = "Charles D. Harris and Jr. Cuyler W. Brooks and Patricia G. Clukey and John P. Stack", title = "The {NASA} Langley Laminar-Flow-Control Experiment on a Swept, Supercritical Airfoil Evaluation of Initial Perforated Configuration", institution = "NASA - Langley Research Centre", number = "NASA TM-4309", pages = "123", keywords = "Laminar-flow control Contoured wind tunnel Transonic aerodynamics Supercritical swept wing", abstract = "This report documents, in a chronological manner, the initial evaluation of a large-chord, swept, supercritical airfoil incorporating an active laminar-flow-control (LFC) suction system with a perforated upper surface and describes deficiencies in the suction capability of the perforated panels as designed. The experiment was conducted in the Langley 8-Foot Transonic Pressure Tunnel. Also included is an evaluation of the influence of the proximity of the tunnel liner to the upper surface of the airfoil on the airfoil pressure distribution.", } @TechReport{Cucinotta??, authorkey = "CucinottaFA TownsendLW WilsonJW", author = "Francis A. Cucinotta and Lawrence W. Townsend and John W. Wilson", title = "Target Correlation Effects on Neutron-Nucleus Total, Absorption, and Abrasion Cross Sections", institution = "NASA - Langley Research Centre", number = "NASA TM-4314", pages = "18", keywords = "Heavy ions Fragmentation Correlation effects", abstract = "Second-order optical model solutions to the elastic scattering amplitude were used to evaluate total, absorption, and abrasion cross sections for neutron-nucleus scattering. Improved agreement with experimental data for total and absorption cross sections is found when compared with first-order (coherent approximation) solutions, especially below several hundred MeV. At higher energies, the first- and second-order solutions are similar. There are also large differences in abrasion cross-section calculations; these differences indicate a crucial role for cluster knockout in the abrasion step.", } @TechReport{Bavuso??, authorkey = "BavusoSJ KoppenSV HaleyPJ", author = "Salvatore J. Bavuso and Sandra V. Koppen and Pamela J. Haley", title = "Graphical Workstation Capability for Reliability Modeling", institution = "NASA - Langley Research Centre", number = "NASA TM-4317", pages = "11", keywords = "HARP Reliability Graphics Fault tree PC Markov Workstation Fault tolerance", abstract = "In addition to computational capabilities, software tools for estimating the reliability of fault-tolerant digital computer systems must also provide a means of interfacing with the user. This paper describes the new graphical interface capability of the hybrid automated reliability predictor (HARP), a software package that implements advanced reliability modeling techniques. The graphics oriented (GO) module provides the user with a graphical language for modeling system failure modes through the selection of various fault-tree gates, including sequence-dependency gates, or by a Markov chain. By using this graphical input language, a fault tree becomes a convenient notation for describing a system. In accounting for any sequence dependencies, HARP converts the fault-tree notation to a complex stochastic process that is reduced to a Markov chain, which it can then solve for system reliability. The graphics capability is available for use on an IBM-compatible PC, a Sun, and a VAX workstation. The GO module is written in the C programming language and uses the graphical kernel system (GKS) standard for graphics implementation. The PC, VAX, and Sun versions of the HARP GO module are currently in beta-testing stages.", } @TechReport{Teichman??, authorkey = "TeichmanLA SlempWS WitteJWG", author = "Louis A. Teichman and Wayne S. Slemp and Jr. William G. Witte", title = "Evaluation of Selected Thermal Control Coatings for Long-Life Space Structures", institution = "NASA - Langley Research Centre", number = "NASA TM-4319", pages = "14", keywords = "Passive thermal control, Solar absorptance, Thermal emittance, Graphite-reinforced resin matrix composites, Protective coatings, Anodization of aluminum, Sputtering of aluminum", abstract = "Graphite-reinforced resin matrix composites are being considered for spacecraft structural applications because of their light weight, high stiffness, and lower thermal expansion. Thin protective coatings with stable optical properties and the proper ratio of solar absorptance \$($\backslash$alpha\_s)\$ to thermal emittance \$($\backslash$varepsilon)\$ minimize orbital thermal extremes and protect these materials against space environmental degradation. Sputtered coatings applied directly to graphite/epoxy composite surfaces and anodized coatings applied to thin aluminum foil were studied for use both as an atomic oxygen barrier and as thermal control coatings. Additional effort was made to develop nickel-based coatings which could be applied directly to composites. These coating systems were selected because their inherent tenacity made them potentially more reliable than commercial white paints for long-life space missions. Results indicate that anodized aluminum foil coatings are suitable for tubular and flat composite structures on large platforms in low Earth orbit. Anodized foil provides protection against some elements of the natural space environment---atomic oxygen, ultraviolet, and particulate radiation---and offers a broad range of tailored \$$\backslash$alpha\_s/$\backslash$varepsilon\$. The foil is readily available and can be produced in large quantities, while the anodizing process is a routine commercial technique.", } @TechReport{Singh??a, authorkey = "SinghJJ EftekhariA HinkleyJA ClairTLS JensenBJ", author = "Jag J. Singh and Abe Eftekhari and Jeffrey A. Hinkley and Terry L. St. Clair and Brian J. Jensen", title = "Free Volume Variation With Molecular Weight of Polymers", institution = "NASA - Langley Research Centre", number = "NASA TM-4326", pages = "8", keywords = "Linear polymers Positron lifetime spectroscopy Free volume cell size Free volume model Molecular weight Rheology of polymers Mark-Houwink equation", abstract = "Free volume measurements have been made in several molecular weight fractions of two different geometries of poly(arylene ether ketone)s. Free volumes were measured using positron lifetime spectroscopy. It has been observed that the free volume cell size \$V\_f\$ varies with the molecular weight \$M\$ of the test samples according to an equation of the form \$V\_f=AM\^{}B\$, where \$A\$ and \$B\$ are constants. The molecular weights computed from the free volume cell sizes are in good agreement with the values measured by gel permeation chromatography.", } @TechReport{Manuel??, authorkey = "ManuelGS MolloyJK BarnaPS", author = "G. S. Manuel and John K. Molloy and P. S. Barna", title = "Effect of Collector Configuration on Test-Section Turbulence Levels in an Open-Jet Wind Tunnel", institution = "NASA - Langley Research Centre", number = "NASA TM-4333", pages = "20", keywords = "Open-jet configuration Airflow disturbance Collector configuration Turbulence levels.", abstract = "Flow quality studies in the Langley 14- by 22-Foot Subsonic Tunnel indicated periodic flow pulsations at discrete frequencies in the test section when the tunnel operated in an open-jet configuration. To alleviate this problem, experiments were conducted in a 1/24-scale model of the full-scale tunnel to evaluate the turbulence reduction potential of six collector configurations. As a result of these studies, the original bell-mouth collector of the 14- by 22-Foot Subsonic Tunnel was replaced with a collector with straight walls, and a slot was incorporated between the trailing edge of the collector and the entrance of the diffuser.", } @TechReport{Wilson??a, authorkey = "WilsonJC", author = "John C. Wilson", title = "Experimental Evaluation of a Flat Wake Theory for Predicting Rotor Inflow-Wake Velocities", institution = "NASA - Langley Research Centre", number = "NASA TM-4334 AVSCOM TR-92-B-004", pages = "51", keywords = "Rotor Inflow Wake Helicopter", abstract = "The theory for predicting helicopter inflow-wake velocities called flat wake theory was correlated with several sets of experimental data. The theory was developed by V. E. Baskin of the USSR, and a computer code known as DOWN was developed at Princeton University to implement the theory. The theory treats the wake geometry as rigid without interaction between induced velocities and wake structure. The wake structure is assumed to be a flat sheet of vorticity composed of trailing elements whose strength depends on the azimuthal and radial distributions of circulation on a rotor blade. The code predicts the three orthogonal components of flow velocity in the field surrounding the rotor. The predictions can be utilized in rotor performance and helicopter real-time flight-path simulation. The predictive capability of the coded version of the theory was correlated with flow velocity data from several sources. In general, the coded version of flat wake theory provides vertical inflow patterns similar to experimental patterns.", } @TechReport{Covell??, authorkey = "CovellPF WalkerIJ HowellDT", author = "Peter F. Covell and Ira J. Walker and Dorothy T. Howell", title = "Longitudinal and Lateral-Directional Aerodynamic Characteristics of a Wing-Cone Configuration at Mach Numbers From 2.5 to 4.5", institution = "NASA - Langley Research Centre", number = "NASA TM-4337", pages = "174", keywords = "Supersonic aerodynamics Lateral-directional aerodynamics Conical forebody Longitudinal aerodynamics", abstract = "An investigation has been conducted to determine the longitudinal and lateral-directional aerodynamic characteristics of a generic wing-cone configuration at supersonic speeds. The fuselage had a 5\$\^{}$\backslash$circ\$ half-angle cone forebody, cylindrical midbody, and a 9\$\^{}$\backslash$circ\$ truncated cone afterbody. The delta wing (aspect ratio 1.0) had a 4-percent-thick diamond airfoil section. The tests were made in the Langley Unitary Plan Wind Tunnel at Mach numbers from 2.50 to 4.50. Angle of attack was varied from \$-4\^{}$\backslash$circ\$ to \$28\^{}$\backslash$circ\$, and angle of sideslip varied from \$-8\^{}$\backslash$circ\$ to \$8\^{}$\backslash$circ\$. Several configurations were studied to determine the effects of variations in wing longitudinal position, wing incidence, vertical-tail configuration, canard shape, and nose bluntness. Typical effects of Reynolds number and Mach number on the longitudinal characteristics were observed. The incremental effects of the confiuration variables were generally unaffected by Mach number. The directional-stability characteristics of the large and small centerline-mounted vertical-tail configurations were significantly degraded with increasing angle of attack and Mach number.", } @TechReport{Adams??, authorkey = "AdamsJWM ChristhilfDM WaszakMR MukhopadhyayV SrinathkumarS", author = "Jr. William M. Adams and David M. Christhilf and Martin R. Waszak and Vivek Mukhopadhyay and S. Srinathkumar", title = "Design, Test, and Evaluation of Three Active Flutter Suppression Controllers", institution = "NASA - Langley Research Centre", number = "NASA TM-4338", pages = "39", keywords = "Flutter suppression Wind-tunnel test Active flexible wing Classical, frequency domain multi-input/multi-output constrained optimization Modified linear quadratic Gaussian/loop transfer recovery Robustness", abstract = "Three control law design techniques for flutter suppression are presented. Each technique uses multiple control surfaces and/or sensors. The first method uses traditional tools (such as pole/zero loci and Nyquist diagrams) for producing a controller that has minimal complexity and which is sufficiently robust to handle plant uncertainty. The second procedure uses linear combinations of several accelerometer signals and dynamic compensation to synthesize the modal rate of the critical mode for feedback to the distributed control surfaces. The third technique starts with a minimum-energy linear quadratic Gaussian controller, iteratively modifies intensity matrices corresponding to input and output noise, and applies controller order reduction to achieve a low-order, robust controller. The resulting designs have been implemented digitally and tested subsonically on the active flexible wing wind-tunnel model in the Langley Transonic Dynamics Tunnel. Only the traditional pole/zero loci design was sufficiently robust to errors in the nominal plant to successfully suppress flutter during the test. The traditional pole/zero loci design provided simultaneous suppression of symmetric and antisymmetric flutter with a 24-percent increase in attainable dynamic pressure. Posttest analyses are shown which illustrate the problems encountered with the other laws.", } @TechReport{Noonan??, authorkey = "NoonanKW AlthoffSL SamakDK GreenMD", author = "Kevin W. Noonan and Susan L. Althoff and Dhananjay K. Samak and Michael D. Green", title = "Effect of Blade Planform Variation on the Forward-Flight Performance of Small-Scale Rotors", institution = "NASA - Langley Research Centre", number = "WU 505-59-87-54 NASA TM-4345 AVSCOM TR-92-B-005", pages = "83", keywords = "Rotor performance Helicopter rotor Helicopter Blade planform geometry", abstract = "An investigation was conducted in the Glenn L. Martin Wind Tunnel to determine the effects of blade planform variation on the forward-flight performance of four small-scale rotors. The rotors were 5.417 ft in diameter and differed only in blade planform geometry. The four planforms were (1) rectangular, (2) 3:1 linear taper starting at 94 percent radius, (3) 3:1 linear taper starting at 75 percent radius, and (4) 3:1 linear taper starting at 50 percent radius. Each planform had a thrust-weighted solidity of 0.098. The investigation included forward-flight simulation at advance ratios from 0.14 to 0.43 for a range of rotor lift and drag coefficients. Among the four rotors, the rectangular rotor required the highest torque for the entire range of rotor drag coefficients attained at advance ratios greater than 0.14 for rotor lift coefficients \$C\_L\$ from 0.004 to 0.007. Among the rotors with tapered blades and for \$C\_L=0.004\$ to 0.007, either the 75-percent tapered rotor or the 50-percent tapered rotor required the least amount of torque for the full range of rotor drag coefficients attained at each advance ratio. The performance of the 94-percent tapered rotor was generally between that of the rectangular rotor and the 75- and 50-percent tapered rotors at each advance ratio for this range of rotor lift coefficients.", } @TechReport{Banks??, authorkey = "BanksDW GatlinGM PaulsonJJW", author = "Daniel W. Banks and Gregory M. Gatlin and Jr. John W. Paulson", title = "Low-Speed Longitudinal and Lateral-Directional Aerodynamic Characteristics of the {X}-31 Configuration", institution = "NASA - Langley Research Centre", number = "NASA TM-4351", pages = "339", keywords = "High angle of attack X-31 Configuration aerodynamics", abstract = "An experimental investigation of a 19-percent-scale model of the X-31 configuration was completed in the Langley 14- by 22-Foot Subsonic Tunnel. This investigation was performed to determine the static low-speed aerodynamic characteristics of the basic configuration over a large range of angle of attack and sideslip and to study the effects of strakes, leading-edge extensions (wing-body strakes), nose booms, speed-brake deployment, and inlet configurations. The ultimate purpose of this study was to optimize the configuration for high-angle-of-attack and maneuvering-flight conditions. The model was tested at angles of attack from \$-5\^{}$\backslash$circ\$ to \$67\^{}$\backslash$circ\$ and at sideslip angles from \$-16\^{}$\backslash$circ\$ to \$16\^{}$\backslash$circ\$ for speeds up to 190 knots (dynamic pressure of 120 psf).", } @TechReport{Mason??, authorkey = "MasonML CaponeFJ AsburySC", author = "Mary L. Mason and Francis J. Capone and Scott C. Asbury", title = "A Static Investigation of the Thrust Vectoring System of the {F}/{A}-18 High-Alpha Research Vehicle", institution = "NASA - Langley Research Centre", number = "NASA TM-4359", pages = "163", keywords = "Nozzle internal performance Multiaxis thrust vectoring Axisymmetric nozzle Thrust vectoring vanes", abstract = "A static (wind-off) test was conducted in the static test facility of the Langley 16-Foot Transonic Tunnel to evaluate the vectoring capability and isolated nozzle performance of the proposed thrust vectoring system of the F/A-18 high-alpha research vehicle (HARV). The thrust vectoring system consisted of three asymmetrically spaced vanes installed externally on a single test nozzle. Two nozzle configurations were tested: a maximum afterburner-power nozzle and a military-power nozzle. Vane size and vane actuation geometry were investigated, and an extensive matrix of vane deflection angles was tested. The nozzle pressure ratio ranged from 2 to 6. The results indicate that the three-vane system can successfully generate multiaxis (pitch and yaw) thrust vectoring. However, large resultant vector angles incurred large thrust losses. Resultant vector angles were always lower than the vane deflection angles. The maximum thrust vectoring angles achieved for the military-power nozzle were larger than the angles achieved for the maximum afterburner-power nozzle.", } @TechReport{Monta??, authorkey = "MontaWJ", author = "William J. Monta", title = "Pitot Survey of Exhaust Flow Field of a 2-{D} Scramjet Nozzle at Mach 6 With Air or Freon and Argon Used for Exhaust Simulation", institution = "NASA - Langley Research Centre", number = "NASA TM-4361", pages = "32", keywords = "Flow-field survey Hypersonic speed Scramjet exhaust simulation Nozzle exhaust flow", abstract = "A pitot-rake survey of the simulated exhaust of a half-span scramjet nozzle model was conducted in the Langley 20-Inch Mach 6 Tunnel to provide an additional data set for computational fluid dynamics (CFD) code comparisons. A wind-tunnel model was tested with a 26-tube pitot rake that could be manually positioned along the mid-semispan plane of the model. The model configuration had an external expansion surface of \$20\^{}$\backslash$circ\$ and an internal cowl expansion of 12\$\^{}$\backslash$circ\$; tests were also performed with a flow fence. Tests were conducted at a free-stream Reynolds number of approximately \$6.510\^{}6\$ per foot and a model angle of attack of \$-0.75\^{}$\backslash$circ\$. The two exhaust gas mediums that were tested were air and a Freon 12-argon mixture. Each medium was tested at two jet total pressures at approximately 28 and 14 psia. This document presents the flow-field survey results in graphical as well as tabular form, and several observations concerning the results are discussed. The surveys reveal the major expected flow-field characteristics for each test configuration. For a 50-percent Freon 12 and 50-percent argon mixture by volume (Fr-Ar), the exhaust jet pitot pressures were slightly higher than those for air. The addition of a flow fence slightly raised the pitot pressures for the Fr-Ar mixture, but it produced little change for air. For the Fr-Ar exhaust, the plume was larger and the region between the shock wave and plume was smaller.", } @TechReport{Cucinotta??a, authorkey = "CucinottaFA TownsendLW WilsonJW", author = "Francis A. Cucinotta and Lawrence W. Townsend and John W. Wilson", title = "Quasi-Elastic Nuclear Scattering at High Energies", institution = "NASA - Langley Research Centre", number = "NASA TM-4362", pages = "21", keywords = "Nuclear reactions Optical model Inclusive reactions Response functions", abstract = "The quasi-elastic scattering of two nuclei is considered in the high-energy optical model. Energy loss and momentum transfer spectra for projectile ions are evaluated in terms of an inelastic multiple-scattering series corresponding to multiple knockout of target nucleons. The leading-order correction to the coherent projectile approximation is evaluated. Calculations are compared with experiments.", } @TechReport{Tracy??, authorkey = "TracyMB PlentovichEB ChuJ", author = "M. B. Tracy and E. B. Plentovich and Julio Chu", title = "Measurements of Fluctuating Pressure in a Rectangular Cavity in Transonic Flow at High Reynolds Numbers", institution = "NASA - Langley Research Centre", number = "NASA TM-4363", pages = "30", keywords = "Cavity acoustics High Reynolds numbers Transonic speeds Unsteady flow", abstract = "An experiment was performed in the Langley 0.3-Meter Transonic Cryogenic Tunnel to study the internal acoustic field generated by rectangular cavities in transonic and subsonic flows and to determine the effect of Reynolds number and angle of yaw on the field. The cavity in this study was 11.25 in. long and 2.50 in. wide. The cavity depth was varied to obtain length-to-height \$(l/h)\$ ratios of 4.40, 6.70, 12.67, and 20.00. Data were obtained for a free-stream Mach number \$(M\_$\backslash$infty)\$ range from 0.20 to 0.90, a Reynolds number range from \$2 10\^{}6\$ to \$100 10\^{}6\$ per foot with a nearly constant boundary-layer thickness, and for two angles of yaw of 0\$\^{}$\backslash$circ\$ and 15\$\^{}$\backslash$circ\$. Results show that Reynolds number has little effect on the acoustic field in rectangular cavities at an angle of yaw of 0\$\^{}$\backslash$circ\$. Cavities with \$l/h = 4.40\$ and 6.70 generated tones at transonic speeds, whereas those with \$l/h = 20.00\$ did not. This trend agrees with data obtained previously at supersonic speeds. As \$M\_$\backslash$infty\$ decreased, the amplitude and bandwidth of the tones changed. No tones appeared for \$M\_$\backslash$infty = 0.20.\$ For a cavity with \$l/h = 12.67,\$ tones appeared at \$M\_$\backslash$infty = 0.60,\$ indicating a possible change in flow-field type. Changes in acoustic spectra with angle of yaw varied with Reynolds number, \$M\_$\backslash$infty\$, \$l/h\$ ratios, and acoustic mode number.", } @TechReport{Sydow??a, authorkey = "SydowPD CooperEG", author = "P. Daniel Sydow and Eric G. Cooper", title = "Development of a Machine Vision System for Automated Structural Assembly", institution = "NASA - Langley Research Centre", number = "NASA TM-4366", pages = "28", keywords = "Space trusses Machine vision Robotics Automated assembly Space structures", abstract = "Research is being conducted at the NASA Langley Research Center to develop a telerobotic assembly system designed to construct large space truss structures. This research program has been initiated within the past several years, and a ground-based test-bed has been developed to evaluate and expand the state of the art. Test-bed operations currently use predetermined (``taught{"}) points for truss structural assembly. Total dependence on the use of taught points for joint receptacle capture and strut installation is neither robust nor reliable enough for space operations. Therefore, a machine vision sensor guidance system is being developed to locate and guide the robot to a passive target mounted on the truss joint receptacle. The vision system hardware includes a miniature video camera, passive targets mounted on the joint receptacles, target illumination hardware, and an image processing system. Discrimination of the target from background clutter is accomplished through standard digital processing techniques. Once the target is identified, a pose estimation algorithm is invoked to determine the location, in three-dimensional space, of the target relative to the robots end-effector. Preliminary test results of the vision system in the Automated Structural Assembly Laboratory with a range of lighting and background conditions indicate that it is fully capable of successfully identifying joint receptacle targets throughout the required operational range. Controlled optical bench test results indicate that the system can also provide the pose estimation accuracy required to define the target position.", } @TechReport{Sutter??, authorkey = "SutterTR WuKC RiutortKT LauferJB PhelpsJE", author = "Thomas R. Sutter and K. Chauncey Wu and Kevin T. Riutort and Joseph B. Laufer and James E. Phelps", title = "Structural Characterization of a First-Generation Articulated-Truss Joint for Space Crane Application", institution = "NASA - Langley Research Centre", number = "NASA TM-4371", pages = "22", keywords = "Space crane In-space assembly Experimental testing Articulated-truss joints Static analysis Normal modes analysis", abstract = "A first-generation space crane articulated-truss joint was statically and dynamically characterized in a configuration that approximated an operational environment. The articulated-truss joint was integrated into a test-bed for structural characterization. Static characterization was performed by applying known loads and measuring the corresponding deflections to obtain load-deflection curves. Dynamic characterization was performed using modal testing to experimentally determine the first six mode shapes, frequencies, and modal damping values. Static and dynamic characteristics were also determined for a reference truss that served as a characterization baseline. Load-deflection curves and experimental frequency response functions are presented for the reference truss and the articulated-truss joint mounted in the test-bed. The static and dynamic experimental results are compared with analytical predictions obtained from finite element analyses. Load-deflection response is also presented for one of the linear actuators used in the articulated-truss joint. Finally, an assessment is presented for the predictability of the truss hardware used in the reference truss and articulated-truss joint based upon hardware stiffness properties that were previously obtained during the Precision Segmented Reflector (PSR) Technology Development Program.", } @TechReport{Wu??, authorkey = "WuKC SutterTR", author = "K. Chauncey Wu and Thomas R. Sutter", title = "Structural Analysis of Three Space Crane Articulated-Truss Joint Concepts", institution = "NASA - Langley Research Centre", number = "NASA TM-4373", pages = "30", keywords = "In-space construction Space crane Articulated-truss joint Linear actuators", abstract = "Three space crane articulated-truss joint concepts are studied to evaluate their static structural performance over a range of geometric design parameters. Emphasis is placed on maintaining the four-longeron reference truss performance across the joint while allowing large-angle articulation. A maximum positive articulation angle and the actuator length ratio required to reach that angle are computed for each concept as the design parameters are varied. Configurations with a maximum articulation angle less than 120\$\^{}$\backslash$circ\$ or actuators requiring a length ratio over 2 are not considered. Tip rotation and lateral deflections of a truss beam with an articulated-truss joint at the midspan are used to select a point design (with fixed values of the design parameters) for each concept. Deflections for one point design are up to 40 percent higher than for the other two designs. Dynamic performance (natural frequencies, mode shapes, and maximum allowable velocity for an emergency stop scenario) of the three point designs is computed as a function of joint articulation angle. The two lowest frequencies of each point design are relatively insensitive to large variations in joint articulation angle. One point design has a higher maximum tip velocity for the emergency stop than the other designs.", } @TechReport{Venkateswaran??, authorkey = "VenkateswaranS HuntLR PrabhuRK", author = "S. Venkateswaran and L. Roane Hunt and Ramadas K. Prabhu", title = "Computational Method To Predict Thermodynamic, Transport, and Flow Properties for the Modified Langley 8-Foot High-Temperature Tunnel", institution = "NASA - Langley Research Centre", number = "NASA TM-4374", pages = "35", keywords = "Air-methane-oxygen combustion Hypersonic Equilibrium chemically reacting Thermodynamic and transport High-temperature tunnel", abstract = "The Langley 8-Foot High-Temperature Tunnel (8-ft HTT) is used to test components of hypersonic vehicles for aerothermal loads definition and structural component verification. The test medium of the 8-ft HTT is obtained by burning a mixture of methane-air under high pressure; the combustion products are expanded through an axisymmetric conical-contoured nozzle to simulate atmospheric flight at Mach 7. This facility has been modified to raise the oxygen content of the test medium to match that of air and to include Mach 4 and Mach 5 capabilities. These modifications will facilitate the testing of hypersonic air-breathing propulsion systems for a wide range of flight conditions. A computational method to predict the thermodynamic, transport, and flow properties of the equilibrium chemically reacting oxygen-enriched methane-air combustion products has been implemented in a computer code. This code calculates the fuel, air, and oxygen mass flow rates and test section flow properties for Mach 7, Mach 5, and Mach 4 nozzle configurations for given combustor and mixer conditions. Salient features of the 8-ft HTT are described, and some of the predicted tunnel operational characteristics are presented in the carpet plots to assist users in preparing test plans.", } @TechReport{Williams??, authorkey = "WilliamsMD", author = "M. D. Williams", title = "Analysis and Development of Dynamic Selection of Laser Array Elements", institution = "NASA - Langley Research Centre", number = "NASA TM-4375", pages = "9", keywords = "Phased arrays Laser diodes", abstract = "The transmission of large amounts of power in space by laser beam (diode lasers, in particular) requires an array of lasers to increase total power. Concentration of the beam requires some degree of coherence. Temporal coherence can be obtained by locking amplifiers to a master oscillator. However, spatial coherence is not so easily created or maintained. Many mechanical, thermal, and electrical factors oppose it continually. A very simple method is described for creating and maintaining a degree of spatial coherence by simply turning selected diodes ON or OFF. The degree of coherence can be chosen; the greater the coherence, the larger is the number of lasers required for a given power and the longer the lifetime of the array. An experiment for analyzing performance, verifying theory, and evaluating critical parameters is also proposed.", } @TechReport{Williams??a, authorkey = "WilliamsRL", author = "Robert L. {Williams, Ii}", title = "Kinematic Equations for Control of the Redundant Eight-Degree-of-Freedom Advanced Research Manipulator {II}", institution = "NASA - Langley Research Centre", number = "NASA TM-4377", pages = "26", keywords = "Manipulator Redundant Kinematics Resolved rate control Telerobotics", abstract = "This paper presents the forward position and velocity kinematics for the redundant eight-degree-of-freedom Advanced Research Manipulator II (ARMII). Inverse position and velocity kinematic solutions are also presented. The approach in this paper is to specify two of the unknowns and solve for the remaining six unknowns. Two unknowns can be specified with two restrictions. First, the elbow joint angle and rate cannot be specified because they are known from the end-effector position and velocity. Second, one unknown must be specified from the four-jointed wrist, and the second from joints that translate the wrist, elbow joint excluded. There are eight solutions to the inverse position problem. The inverse velocity solution is unique, assuming the Jacobian matrix is not singular. A discussion of singularities is based on specifying two joint rates and analyzing the reduced Jacobian matrix. When this matrix is singular, the generalized inverse may be used as an alternate solution. Computer simulations were developed to verify the equations. Examples demonstrate agreement between forward and inverse solutions.", } @TechReport{Williams??b, authorkey = "WilliamsSP ParrishRV", author = "Steven P. Williams and Russell V. Parrish", title = "Computational Algorithms for Increased Control of Depth-Viewing Volume for Stereo Three-Dimensional Graphic Displays", institution = "NASA - Langley Research Centre", number = "NASA TM-4379 AVSCOM TR-92-E-002", pages = "24", keywords = "Stereo displays Transformation metrics Field of view Stereopsis cuing Computer graphics Viewing transformations Clipping algorithms Depth-viewing volume", abstract = "Three-dimensional pictorial displays incorporating depth cues by means of stereopsis offer a potential means of presenting information in a natural way to enhance situational awareness and improve operator performance. Conventional computational techniques rely on asymptotic projection transformations and symmetric clipping to produce the stereo display. Implementation of two new computational techniques, an asymmetric clipping algorithm and piecewise linear projection transformation, provides the display designer with more control and better utilization of the effective depth-viewing volume to allow full exploitation of stereopsis cuing. Asymmetric clipping increases the perceived field of view (FOV) for the stereopsis region. The total horizontal FOV provided by the asymmetric clipping algorithm is greater throughout the scene viewing envelope than that of the symmetric algorithm. The new piecewise linear projection transformation allows the designer to creatively partition the depth-viewing volume, with freedom to place depth cuing at the various scene distances at which emphasis is desired.", } @TechReport{Young??, authorkey = "YoungSD", author = "Steven D. Young", title = "Generalized Hypercube Structures and Hyperswitch Communication Network", institution = "NASA - Langley Research Centre", number = "NASA TM-4380", pages = "13", keywords = "Hypercube Hyperswitch, Integer partitions Adaptive routing", abstract = "One of the Grand Challenges of the Federal High Performance Computing and Communications (HPCC) Program is in remote exploration and experimentation (REE). The goal of the REE Project is to develop a space-borne computing technology base that will enable the next generation of missions to explore the Earth and the Solar System. This paper discusses an ongoing study that uses a recent development in communication control technology to implement hybrid hypercube structures. These architectures are similar to binary hypercubes, but they also provide added connectivity between the processors. This added connectivity increases communication reliability while decreasing the latency of interprocessor message passing. Because these factors directly determine the speed that can be obtained by multiprocessor systems, these architectures are attractive for applications such as REE, where high performance and ultrareliability are required. This paper describes and enumerates these architectures and discusses how they can be implemented with a modified version of the hyperswitch communication network (HCN). The HCN is analyzed because it has three attractive features that enable these architectures to be effective: speed, fault tolerance, and the ability to pass multiple messages simultaneously through the same hyperswitch controller.", } @TechReport{Waszak??, authorkey = "WaszakMR SrinathkumarS", author = "Martin R. Waszak and S. Srinathkumar", title = "Design and Experimental Validation of a Flutter Suppression Controller for the Active Flexible Wing", institution = "NASA - Langley Research Centre", number = "NASA TM-4381", pages = "17", keywords = "Flutter suppression Active control Active flexible wing", abstract = "The synthesis and experimental validation of an active flutter suppression controller for the Active Flexible Wing wind-tunnel model is presented. The design is accomplished with traditional root locus and Nyquist methods using interactive computer graphics tools and extensive simulation-based analysis. The design approach uses a fundamental understanding of the flutter mechanism to formulate a simple controller structure to meet stringent design specifications. Experimentally, the flutter suppression controller succeeded in simultaneous suppression of two flutter modes, significantly increasing the flutter dynamic pressure despite modeling errors in predicted flutter dynamic pressure and flutter frequency. The flutter suppression controller was also successfully operated in combination with another controller to perform flutter suppression during rapid rolling maneuvers.", } @TechReport{Belton??, authorkey = "BeltonPS CampbellRL", author = "Pamela S. Belton and Richard L. Campbell", title = "Experimental Study of a Generic High-Speed Civil Transport", institution = "NASA - Langley Research Centre", number = "NASA TM-4382", pages = "113", keywords = "High-speed civil transport Transonic wind tunnel test", abstract = "An experimental study of a generic high-speed civil transport has been conducted in the NASA Langley 8-Foot Transonic Pressure Tunnel. The data base was obtained for the purpose of assessing the accuracy of various levels of computational analysis. Two models differing only in wingtip geometry were tested with and without flow-through nacelles. The baseline model has a curved or crescent wingtip shape, while the second model has a more conventional straight wingtip shape. The study was conducted at Mach numbers from 0.30 to 1.19. Force data were obtained on both the straight wingtip model and the curved wingtip model. Only the curved wingtip model was instrumented for measuring pressures. Selected longitudinal, lateral, and directional data are presented for both models. Selected pressure distributions for the curved wingtip model are also presented.", } @TechReport{Cucinotta??b, authorkey = "CucinottaFA WilsonJW KatzR BadhwarG", author = "Francis A. Cucinotta and John W. Wilson and Robert Katz and Gautam Badhwar", title = "Katz Model Prediction of Caenorhabditis elegans Mutagenesis on {STS}-42", institution = "NASA - Langley Research Centre", number = "NASA TM-4383", pages = "7", keywords = "Radiation mutagenesis Track structure International Microgravity Laboratory Cosmic rays", abstract = "Response parameters that describe the production of recessive lethal mutations in C. elegans from ionizing radiation are obtained with the Katz track structure model. The authors used models of the space radiation environment and radiation transport to predict and discuss mutation rates for C. elegans on the IML-1 experiment aboard STS-42.", } @TechReport{Davidson??, authorkey = "DavidsonJB SchmidtDK", author = "John B. Davidson and David K. Schmidt", title = "Modified Optimal Control Pilot Model for Computer-Aided Design and Analysis", institution = "NASA - Langley Research Centre", number = "NASA TM-4384", pages = "27", keywords = "Manual vehicular control Pilot modelling Flying qualities", abstract = "This paper presents the theoretical development of a modified optimal control pilot model based upon the optimal control model (OCM) of the human operator developed by Kleinman, Baron, and Levison. This model is input compatible with the OCM and retains other key aspects of the OCM, such as a linear quadratic solution for the pilot gains with inclusion of control rate in the cost function, a Kalman estimator, and the ability to account for attention allocation and perception threshold effects. An algorithm designed for easy implementation in current dynamic systems analysis and design software is presented. Example results based upon the analysis of a tracking task using three basic dynamic systems are compared with measured results and with similar analyses performed with the OCM and two previously proposed simplified optimal pilot models. The pilot frequency responses and error statistics obtained with this modified optimal control model are shown to compare more favorably to the measured experimental results than the other previously proposed simplified models evaluated.", } @TechReport{Holloway??, authorkey = "HollowayCM", author = "C. Michael Holloway", title = "The Syntax of {DRAGOON}: Evaluation and Recommendations", institution = "NASA - Langley Research Centre", number = "NASA TM-4385", pages = "16", keywords = "Ada Programming languages DRAGOON Syntax", abstract = "Several different ways to add linguistic support for object-oriented programming to the Ada programming language have been proposed and developed in recent years. DRAGOON is one such Ada extension. This paper describes the DRAGOON syntax for classes, objects, and inheritance, and it evaluates the syntax against the following five criteria: readability, writeability, lack of ambiguity, ease of translation, and consistency with existing Ada syntax. The evaluation reveals several deficiencies in the notation. The paper concludes with a proposal for a revised syntax that corrects these deficiencies.", } @TechReport{Townsend??, authorkey = "TownsendLW CucinottaFA ShinnJL WilsonJW", author = "Lawrence W. Townsend and Francis A. Cucinotta and Judy L. Shinn and John W. Wilson", title = "Effects of Fragmentation Parameter Variations on Estimates of Galactic Cosmic Ray Exposure Dose Sensitivity Studies for Aluminum Shields", institution = "NASA - Langley Research Centre", number = "NASA TM-4386", pages = "8", keywords = "Galactic cosmic radiation Fragmentation Dose sensitivity studies", abstract = "Initial studies of the sensitivities of estimates of particle fluence, absorbed dose, and dose equivalent to fragmentation parameter variations are undertaken by using the Langley Research Center galactic cosmic ray transport code (HZETRN). The new results, presented as a function of aluminum shield thickness, include upper and lower bounds on dose/dose equivalent corresponding to the physically realistic extremes of the fragmentation process and the percentage of variation of the dose/dose equivalent as a function of fragmentation parameter variation.", } @TechReport{Singh??b, authorkey = "SinghJJ EftekhariA ShultzWJ ClairTLS", author = "Jag J. Singh and Abe Eftekhari and William J. Shultz and Terry L. St. Clair", title = "Free-Volume Characteristics of Epoxies", institution = "NASA - Langley Research Centre", number = "NASA TM-4390", pages = "11", keywords = "Cross-linked polymers Fluorene resins Positron lifetime spectroscopy Doppler broadening Free-volume cell size Bimodal free-volume cell size distribution Free-volume model", abstract = "Positron annihilation spectroscopy has been used to measure free-volume characteristics of selected epoxies. Fluorene resins, a new family of high-temperature thermosetting resins, were selected as the test medium. Experimental results indicate that the free-volume cell size \$V\_f\$ varies with the molecular weight between the cross-links \$M\_c\$ according to an equation of the form \$V\_f = AM\_c\^{}B\$, where \$A\$ and \$B\$ are structural constants. In two of the samples, the concentration of bulky fluorene groups was increased in the network backbone by replacement of some of the conventional bisphenol A epoxy resin with fluorene-derived epoxy resin. This resulted in an increase in their glass transition temperature for a given level of cross-linking. It has been found that in these samples, the Doppler broadening of the annihilation peak decreases with the increasing fluorene content, presumably due to enhanced damping of the chain motions.", } @TechReport{Belcastro??, authorkey = "BelcastroCM FischlR KamM", author = "Celeste M. Belcastro and Robert Fischl and Moshe Kam", title = "A Monitor for the Laboratory Evaluation of Control Integrity in Digital Control Systems Operating in Harsh Electromagnetic Environments", institution = "NASA - Langley Research Centre", number = "NASA TM-4402", pages = "21", keywords = "Fault detection Kalman filtering Statistical decision theory Electromagnetic disturbances Digital controllers", abstract = "This paper presents a strategy for dynamically monitoring digital controllers in the laboratory for susceptibility to electromagnetic disturbances that compromise control integrity. The integrity of digital control systems operating in harsh electromagnetic environments can be compromised by upsets caused by induced transient electrical signals. Digital system upset is a functional error mode that involves no component damage, can occur simultaneously in all channels of a redundant control computer, and is software dependent. The motivation for this work is the need to develop tools and techniques that can be used in the laboratory to validate and/or certify critical aircraft controllers operating in electromagnetically adverse environments that result from lightning, high-intensity radiated fields (HIRF), and nuclear electromagnetic pulses (NEMP). The detection strategy presented in this paper provides dynamic monitoring of a given control computer for degraded functional integrity resulting from redundancy management errors, control calculation errors, and control correctness/effectiveness errors. In particular, this paper discusses the use of Kalman filtering, data fusion, and statistical decision theory in monitoring a given digital controller for control calculation errors.", } @TechReport{Wilson??b, authorkey = "WilsonJW BadaviFF", author = "John W. Wilson and Francis F. Badavi", title = "A Study of the Generation of Linear Energy Transfer Spectra for Space Radiations", institution = "NASA - Langley Research Centre", number = "NASA TM-4410", pages = "7", keywords = "Particle spectra Linear energy transfer (LET) Stopping power", abstract = "The conversion of particle-energy spectra into a linear energy transfer (LET) distribution is a guide in assessing biologically significant components. The mapping of LET to energy is triple valued and can be defined only on open subintervals. A well-defined numerical procedure is found to allow generation of LET spectra on the open subintervals that are integrable in spite of their singular nature.", }