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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Noise suppressor for turbo fan jet engines

A noise suppressor is disclosed for installation on the discharge or aft end of a turbo fan engine. Within the suppressor are fixed annular airfoils which are positioned to reduce the relative velocity between the high temperature fast moving jet exhaust and the low temperature slow moving air surrounding it. Within the suppressor nacelle is an exhaust jet nozzle which constrains the shape of the jet exhaust to a substantially uniform elongate shape irrespective of the power setting of the engine. Fixed ring airfoils within the suppressor nacelle therefore have the same salutary effects irrespective of the power setting at which the engine is operated.

Cheng, D. Y.↗
NASA NTRS1983

Body-surface pressure data on two monoplane-wing missile configurations with elliptical cross sections at Mach 2.50

Tabulated body surface pressure data for two monoplane-wing missile configurations are presented and analyzed. Body pressure data are presented for body-alone, body-tail, and body-wing-tail combinations. For the lost combination, data are presented for tail-fin deflection angles of 0 deg and 30 deg to simulate pitch, yaw, and roll control for both configurations. The data cover angles of attack from -5 deg to 25 deg and angles of roll from 0 deg to 90 deg at a Mach number of 2.50 and a Reynolds number of 6.56 x 1,000,000 per meter. Very consistent, systematic trends with angle of attack and angle of roll were observed in the data, and very good symmetry was found at a roll angle of 0 deg. Body pressures depended strongly on the local body cross-section shape, with very little dependence on the upstream shape. Undeflected fins had only a small influence on the pressures on the aft end of the body; however, tail-fin deflections caused large changes in the pressures.

Allen, J. M.↗
NASA NTRS1983

Evidence of erosive burning in shuttle solid rocket motor

Known models of Shuttle Solid Rocket Motor (SRM) performance have failed to produce pressure-time traces which accurately matched actual motor performance, especially during the first 5 seconds after ignition and during the last quarter of web burn time. Efforts to compensate for these differences in model reconstruction and actual performance resulted in resorting to the use of a Burning Anomaly Rate Function (BARF). It was suspected that propellant erosive burning was primarily responsible for the variation of model from actual results. The three dimensional Hercules Grain Design and Internal Ballistics Evaluation Program was made operational and slightly modified and an extensive trial and error effort was begun to test the hypothesis of erosive burning as an explanation of the burning anomaly. It was found that introduction of erosive burning (using Green's erosive burning equation) over portions of the aft segment grain and above a threshold gas Mach number did, in fact, give excellent agreement with the actual motor trace.

Martin, C. L.↗
NASA NTRS1983

Modeling of flexible structures for active control

If a flexible structure has a plane of symmetry, the equations of motion can be split into two uncoupled sets, one for symmetrical motions and one for anti-symmetric motions. If there are m controls, it is often convenient to assign the linear combinations of controls that enter into the m lowest frequency modes and new controls. As an example the feed-support structure of a spacecraft antenna is considered. It is modeled as a tetrahedron made up of flexible bars and connected to the spacecraft by six short flexible legs containing force actuators and displacement sensors. Due to the three-sided symmetry of this structure, both the symmetric and the anti-symmetric equations of motion can be decoupled into two subsystems. The resulting four subsystems are: (1) pitch/fore-aft motions with four degrees of freedom (DOF), two controls, and one output (the fore-aft motion of the feed); (2) vertical motions with three DOF, one control, and one output (the vertical motion of the feed); (3) roll/lateral motions with four DOF, two controls, and one output (the lateral motions of the feed); and (4) yaw motion with one DOF, one control, and no output (the feed does not move during yaw motion).

Bryson, A. E., Jr.↗
NASA NTRS1982

U.S. launch systems evolution

Shuttle improvements and Shuttle-derived vehicles which could answer projected launch system demands for the 1990s are explored. Traffic volume is suggested to be at levels exceeding the STS ability to deliver, thereby necessitating use of unmanned launch vehicles. Some payload delivery increase is possible using an Aft Cargo Carrier attached to the bottom of the external tank. This configuration would handle cargo with a diameter larger than the 15 ft allowable in the Orbiter bay. Various configurations of solid rocket booster cargo rockets are described, together with use of a module containing the Shuttle main engines and avionics as a recoverable part of a system able to place cargo 30 ft in diam and 90-100 ft tall in orbit. Using liquid reusable boosters would permit an increase of cargo capacity by the Shuttle of 50%, while a side-mount cargo vehicle (unmanned) offers a payload capacity of 165-200 klb. It is predicted that launch vehicles in the beginning of the 21st century will be of a fully reusable design.

Marshall, W. R.↗
NASA NTRS1983

Aerodynamic investigation of closely coupled lifting surfaces with positive and negative stagger for general aviation applications

Aerodynamic closely coupled lifting surfaces were investigated for both conventional tail aft configurations and canard configurations to determine whether positive stagger or negative stagger had more attractive aerodynamic characteristics. An inviscid multi-element vortex panel program was used in conjunction with a momentum integral boundary layer program to predict two-dimensional aerodynamic characteristics. A multi-element vortex lattice program was used for three-dimensional characteristics. Pressure distributions, transition location, momentum thickness, two- and three-dimensional drag, and boundary layer separation were compared for the positive and negative stagger case. For staggers less than six the results demonstrated that positive stagger configurations are aerodynamically superior.

Selberg, B. P.↗
NASA NTRS1983

Aerodynamic optimization, comparison, and trim design of canard and conventional high performance general aviation configurations

A design study has been conducted to optimize trim cruise flight of high performance general aviation canard aircraft which achieve minimum drag. In order to investigate the advantages and disadvantages of canard configured aircraft, corresponding conventional tail-aft 'baseline' aircraft were designed and used for comparison. Two-dimensional predictions were obtained by coupling inviscid results from a vortex panel multi-element program to a momentum integral boundary layer analysis. Using the results of the two-dimensional vortex panel analysis, a vortex lattice method was employed to predict the finite wing results. The analysis utilized a turbulent airfoil and a natural laminar airfoil which are two NASA state-of-the-art airfoil sections. The canard aircraft designs give quantitative results of wing and canard loadings, wing-to-canard moment arm ratios, and aspect ratio effects for trim cruise flight for a wide range of wing-to-canard area ratios. Both canard and baseline aircraft achieved a 25 to 30 percent improvement in performance over typical current technology aircraft, but high canard loading necessary for trim resulted in slightly poorer performance of the canard aircraft as compared to the baseline designs.

Keith, M. W.↗
NASA NTRS1983

Effects of various empennage parameters on the aerodynamic characteristics of a twin-engine afterbody model

An experimental investigation to determine the effects of various empennage parameters on aft-end drag and tail interference drag characteristics of a twin-engine, axisymmetric nozzle, afterbody model has been conducted in the Langley 16-Foot Transonic Tunnel. Model variables included: horizontal tail location; vertical tail location, toe angle, cant angle, configuration (single and twin) and airfoil (Symmetrical and cambered); and tail booms. Tests were conducted over a Mach number range from 0.6 to 1.2 and over an angle-of-attack range from -2 to 10 deg. Nozzle pressure ratio was varied from jet off to approximately 10.0.

Leavitt, L. D.↗
NASA NTRS1983

Propulsion installation characteristics for turbofan transports

Several investigations have been conducted in the Langley 8-Foot Transonic Pressure Tunnel and the Langley 16-Foot Transonic Tunnel to investigate propulsion integration characteristics for turbofan transport aircraft. These studies have focused on reducing the interference drag for conventional underwing, overwing, upper surface and wing aft-mounted engine nacelle installations. The experimental data presented in this paper will illustrate the difficulties associated with properly integrating nacelles and pylons with advanced supercritical wings. In addition guidelines for integrating the nacelle/pylons to eliminate adverse interference effects and possibly achieve favorable interference are discussed.

Henderson, W. P.↗
NASA NTRS1983

An experimental investigation of control surface effectiveness and real-gas simulation for biconics

Aerodynamic coefficients, pressure distributions, and oil-flow patterns measured on spherically blunted, 13 degrees/7 degrees on-axis and bent biconics at Mach 6 and 10 in air are compared. Angle of attack, referenced to the axis of the aft cone, was varied from zero to 40 degrees. The effect of deflection of base-mounted flaps on aerodynamic characteristics was examined at Mach 10. Real-gas effects on aerodynamic coefficients, pressure distributions and shock detachment distance were simulated by testing the biconic models in Mach 6 air and Mach 6 CF4 flows. (Density ratio equal to 5.3 for air and 12 for CF4.) The on-axis biconic is stable but cannot be trimmed at angles of attack above zero with the assumed center of gravity and flap configuration. Flaps on the bent biconic produced a stable and trim configuration for angles of attack from zero to 23 degrees. A significant effect of density ratio on aerodynamic coefficients, pressure distribution, and shock detachment distance was observed.

Miller, C. G.↗
NASA NTRS1983

Observations of optical emissions on STS-4

Following the discovery of intense vehicle glow of the Space Shuttle on the STS-3 mission, a new experiment to probe this phenomenon was developed and flown on the Shuttle STS-4 mission. A conventional camera was equipped with an objective transmission grating and several photographic exposures were taken of the Shuttle tail from the aft flight deck window. Vehicle glow surrounding Shuttle surfaces exposed to the ram direction was observed on a long (400 second) exposure. From analysis of the resulting spectral data it appears that the Shuttle glow has a diffuse spectral component in the region 6300 to 8000A. In addition, it has been possible to assess the spectral character of light emitted by the firing of a reaction control system thruster. Our data show that the light emitted from the thruster gases is confined to wavelengths shorter than 7200A.

Mende, S. B.↗
NASA NTRS1982

Graphite/polyimide technology overview and Space Shuttle Orbiter applications

The materials, production processes, testing procedures, and repair techniques for composite structures on the Orbiter are reviewed. The Orbiter currently features graphite/epoxy payload bay doors, as well as graphite/polyimide elevons, vertical tail, and aft body flap, which can withstand up to 600 F temperatures. Graphite/polyimide is also being considered for areas of the baseline aluminum structure and the thermal protection system in order to achieve a 20-30% weight reduction, i.e., over 7.5 tons. An analysis of the allowable stresses on FRC imide thermal protection system tiles bonded directly to the structure has shown satisfactory performances in high temperature and cryogenic conditions, although failure modes are yet to be determined. Ultrasonic emissions have been used for defect detection in nondestructive evaluations, together with tension, notch, shear, and compression tests. Field repairs have not been perfected, and require the evolution of high temperature adhesives that are curable under vacuum pressure and heat blankets.

Morita, W. H.↗
NASA NTRS1982

Fabrication of bonded graphite/polyimide structures for advanced aerospace applications

The tooling concepts and manufacturing techniques developed to produce subelements and full-scale bonded test articles for two of the NASA Composites for Advanced Transportation Systems are examined as part of the structural development of graphite/polyimide composite material systems for the Space Shuttle Orbiter and other space transportation systems. The subassembly and the assembly bonding of the test articles were accomplished using self-tooling and low-cost aluminum tooling concepts in order to eliminate the need for complex and expensive tools. Processing procedures and tooling approaches were developed which permit controlled pressure application on specific bonding planes. Two test articles were fabricated using these techniques, an acoustic panel and a quarter segment of the Space Shuttle aft body flap.

Frost, R. K.↗
NASA NTRS1983

The design, testing and analysis of aeroelastically tailored transonic flutter model wings

An investigation of both the static aeroelastic and flutter characteristics of an aft swept wing, aeroelastically tailored to washout in one design and to washin in another, has been performed using two one-fourth-scale cantilever models representing the two designs. The models have been designed using an MSC/NASTRAN finite element model to preserve the full-scale airplane washout and washin characteristics. Test results show that the effect of the skin-to-core adhesive on model stiffness must be considered in the design cycle. Flutter analyses correlate fairly well with test results. Consideration is also given to F-16 metal and washout wing flutter speeds and mass ratio effects.

Murphy, A. C.↗
NASA NTRS1983

A three degree-of-freedom, typical section flutter analysis using harmonic transonic air forces

Typical section flutter solutions are obtained using generalized air forces calculated with OPTRAN2, a program based on the transonic small perturbation potential equation, which uses potentials from a nonlinear solution to the steady flow to obtain linear unsteady air forces. Flutter results are calculated with a conventional, linear V-g type solution. Results are presented for a NACA 64A010 airfoil oscillating in plunge and pitch, and with a quarter-chord control surface in the Mach number range of 0.80 to 0.90. The flutter boundary shows a significant 'transonic' bucket, together with changes in flutter mode as, with increasing Mach numbers, a shock appears on the airfoil and then moves aft. Single degree-of-freedom instabilities associated with both the pitch and the control surface motions are identified.

Weatherill, W. H.↗
NASA NTRS1983

Exploratory low-speed wind-tunnel investigation of advanced commuter configurations including an over-the-wing propeller design

A recent low-speed wind-tunnel investigation of a three-surface regional transport configuration has shown large favorable power effects on longitudinal and lateral stability and marginal engine-out trim characteristics for some aft engine and empennage configurations. The present paper discusses these results in terms of static force test information obtained for power-off and power-on conditions. Also discussed in this paper are wind-tunnel results which indicate that mounting propellers over the wing can introduce large favorable slipstream interference effects which significantly reduce the wing drag at climb power conditions.

Johnson, J. L., Jr.↗
NASA NTRS1983

Test Report for MSFC Test No. 83-2: Pressure scaled water impact test of a 12.5 inch diameter model of the Space Shuttle solid rocket booster filament wound case and external TVC PCD

Water impact tests using a 12.5 inch diameter model representing a 8.56 percent scale of the Space Shuttle Solid Rocket Booster configuration were conducted. The two primary objectives of this SRB scale model water impact test program were: 1. Obtain cavity collapse applied pressure distributions for the 8.56 percent rigid body scale model FWC pressure magnitudes as a function of full-scale initial impact conditions at vertical velocities from 65 to 85 ft/sec, horizontal velocities from 0 to 45 ft/sec, and angles from -10 to +10 degrees. 2. Obtain rigid body applied pressures on the TVC pod and aft skirt internal stiffener rings at initial impact and cavity collapse loading events. In addition, nozzle loads were measured. Full scale vertical velocities of 65 to 85 ft/sec, horizontal velocities of 0 to 45 ft/sec, and impact angles from -10 to +10 degrees simulated.

Source record↗
NASA NTRS1983

Flight service evaluation of Kevlar-49 epoxy composite panels in wide-bodies commercial transport aircraft

Kevlar-49 fairing panels, installed as flight service components on three L-1011s, were inspected after 9 years of service. There are six Kevlar-49 panels on each aircraft: a left hand and right hand set of a wing body sandwich fairing; a solid laminate under wing fillet panel; and a 422 K (300 F) service aft engine fairing. The fairings have accumulated a total of 70,000 hours, with one ship set having over 24,000 hours service. The Kevlar-49 components were found to be performing satisfactorily in service with no major problems, or any condition requiring corrective action. The only defects noted were minor impact damage, a few minor disbonds and a minor degree of fastener hole fraying and elongation. These are for the most part comparable to damage noted on fiberglass fairings. The service history to date indicates that Kevlar-49 epoxy composite materials have satisfactory service characteristics for use in aircraft secondary structure.

Stone, R. H.↗