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At least 1,135 records · Page 63

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NASA NTRS1988

A rule-based systems approach to spacecraft communications configuration optimization

An experimental rule-based system for optimizing user spacecraft communications configurations was developed at NASA to support mission planning for spacecraft that obtain telecommunications services through NASA's Tracking and Data Relay Satellite System. Designated Expert for Communications Configuration Optimization (ECCO), and implemented in the OPS5 production system language, the system has shown the validity of a rule-based systems approach to this optimization problem. The development of ECCO and the incremental optimization method on which it is based are discussed. A test case using hypothetical mission data is included to demonstrate the optimization concept.

Rash, James L.↗

NASA NTRS1987

Multitasking for flows about multiple body configurations using the chimera grid scheme

The multitasking of a finite-difference scheme using multiple overset meshes is described. In this chimera, or multiple overset mesh approach, a multiple body configuration is mapped using a major grid about the main component of the configuration, with minor overset meshes used to map each additional component. This type of code is well suited to multitasking. Both steady and unsteady two dimensional computations are run on parallel processors on a CRAY-X/MP 48, usually with one mesh per processor. Flow field results are compared with single processor results to demonstrate the feasibility of running multiple mesh codes on parallel processors and to show the increase in efficiency.

Dougherty, F. C.↗

NASA NTRS1988

The sequential filter imaging radiometer (SFIR)- A new instrument configuration for earth observations

The sequential filter imaging radiometer (SFIR) concept is presented, contrasted with other sensor configurations, and its strengths and weaknesses discussed. In a pushbroom SFIR the optics images the scene onto a long, narrow area array. The length of the array defines the field of view. The spectral defining filters are sequentially placed over the full array, a sample of data for that band taken, and then the next filter is placed in front of the array. All filters are placed over the array in the time that it takes the image of the scene to advance the array width. Thus, the entire scene is observed in each band. Advantages of the SFIR are: spectral bands can be broad, narrow or overlap; it is easy to improve signal to noise ratio; and it is simple to make bands polarized. Its main disadvantage is that it requires more detectors than other instrument configurations.

Maxwell, Marvin S.↗

NASA NTRS1987

Flight test results for several light, canard-configured airplanes

Brief flight evaluations of two different, light, composite constructed, canard and winglet configured airplanes were performed to assess their handling qualities; one airplane was a single engine, pusher design and the other a twin engine, push-pull configuration. An emphasis was placed on the slow speed/high angle of attack region for both airplanes and on the engine-out regime for the twin. Mission suitability assessment included cockpit and control layout, ground and airborne handling qualities, and turbulence response. Very limited performance data was taken. Stall/spin tests and the effects of laminar flow loss on performance and handling qualities were assessed on an extended range, single engine pusher design.

Brown, Philip W.↗

NASA NTRS1987

Development of wing and tail configurations for low altitude unmanned research aircraft (LAURA)

The Low Altitude/Airspeed Unmanned Research Aircraft (LAURA) is being developed by the U.S. Navy for flight test research using low-Reynolds number airfoils. This vehicle consists of a standard modular fuselage designed to accept the installation of several wings/tails having low Reynolds number airfoils, and various planform shapes. Design constraints include shipboard storage, long flight endurance at very low airspeeds and sea-skimming cruise altitude. The stringent design constraints require the development of high-performance low Reynolds number (LRN) airfoils, suitable lifting surface configuration, and advanced airframe-propulsion systems. The present paper describes ongoing efforts to develop wing and tail configurations for LAURA using airfoils designed at NASA Langley Research Center.

Mangalam, S. M.↗

NASA NTRS1988

Civil applications of high speed rotorcraft and powered lift aircraft configurations

Advanced subsonic vertical and short takeoff and landing (V/STOL) aircraft configurations offer new transportation options for civil applications. Described is a range of vehicles from low-disk to high-disk loading aircraft, including high-speed rotorcraft, V/STOL aircraft, and short takeoff and landing (STOL) aircraft. The status and advantages of the various configurations are described. Some of these show promise for relieving congestion in high population-density regions and providing transportation opportunities for low population-density regions.

Albers, James A.↗

NASA NTRS1988

Adaptive p-version based finite element formulations for thermal modeling/analysis of structural configurations

Adaptive p-version based hierarchical finite element formulations in conjunction with a posteriori error estimation concepts are described with emphasis on applicability for thermal modeling/analysis of structural configurations. The basic concepts and formulations of hierarchical p-versiion finite element for thermal analysis are first described. A posteriori error estimation features are utililzed to steer the process of adaptive refinement. Several configurations comprised of one-dimensional structures are evaluated to validate the applicability of the proposed formulations and to demonstrate the potential of the p-version adaptive formulations for thermal modeling/analysis. The methodology offers potential and promises to be an attractive alternative to conventional finite element thermal modeling/analysis approaches.

Tamma, Kumar K.↗

NASA NTRS1988

Experimental and theoretical study of the effects of wing geometry on a supersonic multibody configuration

An experimental and theoretical investigation of planform effects on a low-fineness ratio multibody configuration was conducted in NASA-Langley Research Center's Unitary Plan Wind Tunnel at Mach number of 1.6, 1.8, 2.0 and 2.16. Experimental and theoretical values of lift, drag, and pitching moment as well as surface pressures were obtained on several configurations which varied in both outboard-wing panel and inboard-wing panel planforms. The three outboard-wing panels were a 65 -deg delta and two trapezoidal wing planforms. An unswept and a 60-deg swept inboard-wing panels were also tested. The purpose of the study was to determine the effect of wing planform on the supersonic aerodynamics. The large trapezoidal wing provided increased performance over the small trapezoidal wing primarily due to a reduction in the zero-lift drag coefficient. The swept inboard-wing panel planforms provided a slightly higher L/D than the unswept inboard-wing panel due to a minimal improvement in zero-lift drag. Linear-theory aerodynamic codes were used to analyze the effect of planform on the supersonic aerodynamics and were found to generally produce adequate results.

Bauer, Steven X. S.↗

NASA NTRS1987

The average configuration of the induced Venus magnetotail

The interaction of the solar-wind flow with Venus is discussed as well as the morphology of magnetic-field-line draping in the Venus magnetotail. Emphasis is placed on the importance of the interplanetary magnetic field X-component in controlling the configuration of field draping in this induced magnetotail. The average magnetic configuration of this magnetotail is studied. A connection is made between the derived consistent plasma flow speed and density and the observational energy/charge range and sensitivity of the Pioneer Venus Orbiter plasma analyzer.

Mccomas, D. J.↗

NASA NTRS1988

Application of the V(R) resistance curve method to fracture of various crack configurations

The fracture resistance curve method of Newman (1985), based on the crack-tip-opening displacement, V(R), for a 'stationary' crack, was applied to various crack configurations in 2024-T351 and 7075-T651 aluminum alloys tested at room temperature. Using a stationary crack solution, the crack-tip-displacement was calculated at the current crack length for the crack configurations which included compact, middle-crack, single-edge-crack, and three-hole-crack tension specimens. The results showed that the V(R) resistance curves are insensitive to crack length, specimen width, and specimen type up to maximum load. After the maximum load is reached, the V(R) remains nearly constant; this constant depends only on specimen type, specimen width, and crack length. The V(R) resistance curve method can be used with the strip-yield analyses to accurately predict stable crack growth and instability of cracked metallic materials.

Newman, J. C., Jr.↗

NASA NTRS1988

Summary of low-speed wind tunnel results of several high-speed counterrotation propeller configurations

The low speed aerodynamic performance characteristics of several advanced counterrotation pusher propeller configurations with cruise design Mach numbers of 0.72 and 0.80 were investigated in the NASA Low Speed Wind Tunnel. The tests were conducted at Mach numbers representative of the takeoff and landing flight regime. The investigation included: (1) the propeller performance characteristics over a range of blade angle settings and rotational speeds at a Mach number of 0.20; (2) the effect on the propeller performance of varying the axial rotor spacing and mismatching the power and rotational speeds on the propeller rotors; and (3) determining the reverse thrust performance characteristics at Mach numbers of 0.0, 0.10, 0.15 and 0.20. The results of the investigation indicated that the overall low speed performance of the counterrotation propeller configurations was reasonable.

Hughes, Christopher E.↗

NASA NTRS1988

The influence of subsonic mission segments on the use of variable-sweep wings for high speed civil transport configurations

A Mach-3.0, 250-passenger, 6500-n. mi. range SST configuration's alternative use of fixed-planform or variable-sweep wings is presently evaluated, with a view to effects on aerodynamics, mission performance, and sizing. After preliminary design, the fixed and variable-wing configurations were resized to perform missions incorporating subsonic cruise segments of as much as 4000 n. mi.; the effect of subsonic segment length on design gross weight and block time was then ascertained. Due to the reduced supersonic efficiency of the variable-sweep aircraft, over one-half of the 6500-n. mi. mission would have to be flown subsonically for its sizing to reach a lower ramp weight than that of its fixed-geometry counterpart.

Martin, Glenn L.↗

NASA NTRS1988

Configuration trade and code validation study on a conical hypersonic vehicle

A study has been conducted on a generic wing-cone transatmospheric vehicle at Mach numbers form 2.5 to 4.5. The objectives of the study were to experimentally define the aerodynamic characteristics of the vehicle and evaluate several computational aerodynamic prediction methods through comparison with the experimental results. The baseline wing-cone configuration fuselage consisted of a 5 deg half-angle cone forebody, cylindrical midbody, and 9 deg truncated cone afterbody. The 4-percent-thick diamond airfoil wing had an aspect ratio of 1. Several configuration variables were investigated to provide trade information on canard, wing-position and incidence, vertical tail, and nose bluntness effects. Results of the study show that wing-position and wing-incidence effects on the longitudinal aerodynamic characteristics can be significantly influenced by wing-body interference. The use of positive wing incidence to provide favorable forebody orientation for possible inlet performance improvement is accompanied by trim drag and lift-drag ratio penalties. The lateral-directional stability characteristics were strongly influenced by the location of the vertical tails. The higher-order full-potential method provided better estimates of the aerodynamic characteristics than either the linearized supersonic potential method or the tangent-cone/tangent-wedge/shock-expansion on method.

Covell, Peter F.↗

NASA NTRS1988

The characteristics of the ground vortex and its effect on the aerodynamics of the STOL configuration

The interaction of the free stream velocity on the wall jet formed by the impingement of deflected engine thrust results in a rolled up vortex which exerts sizable forces on a short takeoff (STOL) airplane configuration. Some data suggest that the boundary layer under the free stream ahead of the configuration may be important in determining the extent of the travel of the wall jet into the oncoming stream. Here, early studies of the ground vortex are examined, and those results are compared to some later data obtained with moving a model over a fixed ground board. The effect of the ground vortex on the aerodynamic characteristics are discussed.

Stewart, Vearle R.↗

NASA NTRS1988

Debris prevention analysis for DFI/OFI/OEI (STS-26 configuration only)

The first 3 shuttle flights to use the Redesigned Solid Rocket Motors (RSRMs) will utilize Development Flight Instrumentation (DFI), as well as Operational Flight Instrumentation (OFI), and Operational Environment Instrumentation (OEI). The OFI consists of high pressure transducers used on both RSRMs to monitor the igniter and motor chamber pressure. DFI consists of assorted strain gages, temperature sensors, accelerometers, girth gages, and low level pressure transducers. The latter are installed on the left hand booster to measure post-separation aerodynamic loading. OEI consistes of temperature sensors. After Flight 3, all DFI gages are to be deleted, and only OFI and OEI will be used for subsequent flights. This report deals specifically with debris prevention and hazards concernig the STS-26 flight DFI configuration only. Continued analysis is being done that will adequately address the debris hazards associated with the STS-27 and subsequent flight DFI configurations.

Richi, Glen A.↗

NASA NTRS1988

Robust model-based controller synthesis for the SCOLE configuration

The design of a robust compensator is considered for the SCOLE configuration using a frequency-response shaping technique based on the LQG/LTR algorithm. Results indicate that a tenth-order compensator can be used to meet stability-performance-robustness conditions for a 26th-order SCOLE model without destabilizing spillover effects. Since the SCOLE configuration is representative of many proposed spaceflight experiments, the results and design techniques employed potentially should be applicable to a wide range of large space structure control problems.

Armstrong, E. S.↗

NASA NTRS1989

The effects of magnetic nozzle configurations on plasma thrusters

Plasma thrusters have been operated at power levels from 10kW to 0.1MW. When these devices have had magnetic fields applied to them which form a nozzle configuration for the expanding plasma, they have shown marked increases in exhaust velocity which is in direct proportion to the magnitude of the applied field. Further, recent results have shown that electrode erosion may be influenced by applied magnetic fields. This research is directed to the experimental and computational study of the effects of applied magnetic field nozzles in the acceleration of plasma flows. Plasma source devices which eliminate the plasma interaction in normal thrusters are studied as most basic. Normal thruster configurations will be studied without applied fields and with applied magnetic nozzle fields. Unique computational studies will utilize existing codes which accurately include transport processes. Unique diagnostic studies will support the experimental studies to generate new data. Both computation and diagnostics will be combined to indicate the physical mechanisms and transport properties that are operative in order to allow scaling and accurate prediction of thruster performance.

York, Thomas M.↗

NASA NTRS1988

The Flying Diamond: A joined aircraft configuration design project, volume 1

The results of the analysis conducted on the Joined Wing Configuration study are presented. The joined wing configuration employs a conventional fuselage and incorporates two wings joined together near their tips to form a diamond shape in both plan view and front view. The arrangement of the lifting surfaces uses the rear wing as a horizontal tail and as a forward wing strut. The rear wing has its root at the tip of the vertical stabilizer and is structurally attached to the trailing edge of the forward wing. This arrangement of the two wings forms a truss structure which is inherently resistant to the aerodynamic bending loads generated during flight. This allows for a considerable reduction in the weight of the lifting surfaces. With smaller internal wing structures needed, the Joined Wing may employ thinner wings which are more suitable for supersonic and hypersonic flight, having less induced drag than conventional cantilever winged aircraft. Inherent in the Joined Wing is the capability of the generation of direct lift and side force which enhance the performance parameters.

Ball, Chris↗