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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 667 records · Page 37

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NASA NTRS1980

Space Shuttle Orbiter nose cap and wing leading edge certification test program

A reinforced carbon-carbon thermal protection system is used on the space shuttle orbiter vehicle's nose cap and wing leading edge regions where temperatures reach 1538 C (2800 F). To verify the analyses used to certify reinforced carbon-carbon for the first flight and operational missions, a multi-environment incremental test program was developed and implemented through the combined efforts of Rockwell International and the National Aeronautics and Space Administration. Three separate facilities at the Johnson Space Center were used to subject full-scale nose cap and wing leading edge test articles to simulated critical launch, on-orbit, and atmospheric entry environments.

Suppanz, M. J.↗

NASA NTRS1980

Leading-edge 'Vortex Flaps' for enhanced subsonic aerodynamics of slender wings

The 'Vortex Flap' is a novel concept aimed at reducing the lift-dependent drag due to leading-edge flow separation on highly swept, slender wings at high angles of attack. The suction effect of coiled vortices generated via controlled separation over leading-edge flap surfaces is utilized to produce an aerodynamic thrust component. This principle was verified through wind-tunnel experiments on 74-deg and 60-deg delta wings and a supersonic-cruise slender wing aircraft configuration. Adaptation of the vortex-flap for augmentation of roll-control on the 74-deg delta at high angles of attack also was demonstrated. Selected results are presented in this paper to indicate the potential of the vortex flap concept to enhance the low-speed performance, stability and control of slender wing aircraft.

Rao, D. M.↗

NASA NTRS1981

The influence of leading-edge thrust on twisted and cambered wing design for supersonic cruise

A study of leading-edge thrust phenomena at supersonic speeds has shown that although these forces are not large, they can be a significant factor in the design of wings for supersonic cruise. It is seen that the rather severe twisted and cambered wing surfaces resulting from the application of present design methods, which ignore leading-edge thrust, can be replaced by more moderate surfaces with little or no loss in aerodynamic efficiency if realistic possibilities for the attainment of some fraction of the theoretical thrust are taken into account.

Carlson, H. W.↗

NASA NTRS1981

Mass loss of TEOS-coated RCC subjected to the environment at the shuttle wing leading edge

Coated, reinforced carbon-carbon (RCC) is used for the leading edges of the Space Shuttle. The mass loss characteristics of RCC specimens coated with tetra-ethyl-ortho-silicate (TEOS) were determined for conditions which simulated the entry environment expected at the stagnation area of the wing leading edge. Maximum specimen temperature was 1632 K. Specimens were exposed for up to 100 missions. Stress levels up to 8.274 MPa caused an average increase in oxidation of 6 percent over unstressed specimens. Experimentally determined mass losses were compared with those predicted by an existing empirical analysis.

Stroud, C. W.↗

NASA NTRS1981

Effect of positive pulse charge waveforms on the energy efficiency of lead-acid traction cells

The effects of four different charge methods on the energy conversion efficiency of 300 ampere hour lead acid traction cells were investigated. Three of the methods were positive pulse charge waveforms; the fourth, a constant current method, was used as a baseline of comparison. The positive pulse charge waveforms were: 120 Hz full wave rectified sinusoidal; 120 Hz silicon controlled rectified; and 1 kHz square wave. The constant current charger was set at the time average pulse current of each pulse waveform, which was 150 amps. The energy efficiency does not include charger losses. The lead acid traction cells were charged to 70 percent of rated ampere hour capacity in each case. The results of charging the cells using the three different pulse charge waveforms indicate there was no significant difference in energy conversion efficiency when compared to constant current charging at the time average pulse current value.

Smithrick, J. J.↗

NASA NTRS1982

Experimental study of delta wing leading-edge devices for drag reduction at high lift

The drag reduction devices selected for evaluation were the fence, slot, pylon-type vortex generator, and sharp leading-edge extension. These devices were tested on a 60 degree flatplate delta (with blunt leading edges) in the Langley Research Center 7- by 10-foot high-speed tunnel at low speed and to angles of attack of 28 degrees. Balance and static pressure measurements were taken. The results indicate that all the devices had significant drag reduction capability and improved longitudinal stability while a slight loss of lift and increased cruise drag occurred.

Johnson, T. D., Jr.↗

NASA NTRS1982

Space Shuttle Orbiter leading edge structural subsystem thermal performance

An extensive qualification test program and the STS-1 flight of the Space Shuttle Orbiter have provided the data necessary to verify the performance of the Orbiter thermal protection system. The reinforced carbon-carbon leading edge structural subsystem is used on areas of the orbiter where temperatures exceed 2300 F. The subsystem consists of the ROC nose cap and wing leading edge panels, metallic attachments, internal insulation, and interface tiles. Thermal response data from the qualification tests and the STS-1 flight, postflight inspection, and analytical predictions support the conclusion that the thermal performance of the subsystem verified the design.

Curry, D. M.↗

NASA NTRS1982

Wind-tunnel investigation of effects of wing-leading-edge modifications on the high angle-of-attack characteristics of a T-tail low-wing general-aviation aircraft

Exploratory tests have been conducted in the NASA-Langley Research Center's 12-Foot Low-Speed wind Tunnel to evaluate the application of wing-leading-edge devices on the stall-departure and spin resistance characteristics of a 1/6-scale model of a T-tail general-aviation aircraft. The model was force tested with an internal strain-gauge balance to obtain aerodynamic data on the complete configuration and with a separate wing balance to obtain aerodynamic data on the outer portion of the wing. The addition of the outboard leading-edge droop eliminated the abrupt stall of the windtip and maintained or increased the resultant-force coefficient up to about alpha = 32 degrees. This change in slope of the resultant-force coefficient curve with angle of attack has been shown to be important for eliminating autorotation and for providing spin resistance.

White, E. R.↗

NASA NTRS1983

Aeroelastic loads prediction for an arrow wing. Task 3: Evaluation of the Boeing three-dimensional leading-edge vortex code

Two separated flow computer programs and a semiempirical method for incorporating the experimentally measured separated flow effects into a linear aeroelastic analysis were evaluated. The three dimensional leading edge vortex (LEV) code is evaluated. This code is an improved panel method for three dimensional inviscid flow over a wing with leading edge vortex separation. The governing equations are the linear flow differential equation with nonlinear boundary conditions. The solution is iterative; the position as well as the strength of the vortex is determined. Cases for both full and partial span vortices were executed. The predicted pressures are good and adequately reflect changes in configuration.

Manro, M. E.↗

NASA NTRS1983

Joining lead wires to thin platinum alloy films

A two step process of joining a lead wire to .000002 m thick platinum alloy film which rests upon an equally thin alumina insulating layer which is adhered to a metal substrate is described. Typically the platinum alloy film forms part of a thermocouple for measuring the surface temperature of a gas turbine airfoil. In the first step the lead wire is deformed 30 to 60% at room temperature while the characteristic one million ohm resistance of the alumina insulating layer is monitored for degradation. In the second step the cold pressed assembly is heated at 865 to 1025 C for 4 to 75 hr in air. During the heating step any degradation of insulating layer resistance may be reversed, provided the resistance was not decreased below 100 ohm in the cold pressing.

Przybyszewski, J. S.↗

NASA NTRS1983

The evolution of Tollmien-Schlichting waves near a leading edge

The method of matched asymptotic expansions is used to study the generation of Tollmien-Schlichting waves by free-stream disturbances incident on a flat-plate boundary layer. Near the leading edge, the motion is governed by the unsteady boundary-layer equation, while farther downstream it is governed (to lowest order) by the Orr-Sommerfeld equation with slowly varying coefficients. It is shown that there is an overlap domain where the Tollmien-Schlichting wave solutions to the Orr-Sommerfeld equation and appropriate asymptotic solutions of the unsteady boundary-layer equation match, in the matched-asymptotic-expansion sense. The analysis explains how long-wavelength free-stream disturbances can generate Tollmien-Schlichting waves of much shorter wavelength. It also leads to a set of scaling laws for the asymptotic structure of the unsteady boundary layer.

Goldstein, M. E.↗

NASA NTRS1983

Lead isotope systematics of some igneous rocks from the Egyptian Shield

Lead isotope data on whole-rock samples and two feldspar separates for a variety of Pan-African (late Precambrian) igneous rocks for the Egyptian Shield are presented. It is pointed out that the eastern desert of Egypt is a Late Precambrian shield characterized by the widespread occurrence of granitic plutons. The lead isotope ratios may be used to delineate boundaries between Late Precambrian oceanic and continental environments in northeastern Africa. The samples belong to three groups. These groups are related to a younger plutonic sequence of granites and adamellites, a plutonic group consisting of older tonalites to granodiorites, and the Dokhan volcanic suite.

Gillespie, J. G.↗

NASA NTRS1985

Calculating Strain Relief in Electronic-Component Leads

Stress/strain formulas applicable to design of electronic-component leads compiled in report. Such things as factors of safety and whether or not lead is likely to fall in service determined in advance. Set of formulas is simple enough to be solved on programable hand-held calculator.

Snytsheuvel, H.↗

NASA NTRS1983

Space shuttle orbiter leading-edge flight performance compared to design goals

Thermo-structural performance of the Space Shuttle orbiter Columbia's leading-edge structural subsystem for the first five (5) flights is compared with the design goals. Lessons learned from thse initial flights of the first reusable manned spacecraft are discussed in order to assess design maturity, deficiencies, and modifications required to rectify the design deficiencies. Flight data and post-flight inspections support the conclusion that the leading-edge structural subsystem hardware performance was outstanding for the initial five (5) flights.

Curry, D. M.↗

NASA NTRS1984

Results of electric-vehicle propulsion system performance on three lead-acid battery systems

Three types of state of the art 6 V lead acid batteries were tested. The cycle life of lead acid batteries as a function of the electric vehicle propulsion system design was determined. Cycle life, degradation rate and failure modes with different battery types (baseline versus state of the art tubular and thin plate batteries were compared. The effects of testing strings of three versus six series connected batteries on overall performance were investigated. All three types do not seem to have an economically feasible battery system for the propulsion systems. The tubular plate batteries on the load leveled profile attained 235 cycles with no signs of degradation and minimal capacity loss.

Ewashinka, J. G.↗

NASA NTRS1984

Calculation of the 3-D viscous flow at the endwall leading edge region of an axial annular turbine cascade

A three-dimensional viscous computer code (VANS/MD) was employed to calculate the turbulent flow field at the end wall leading edge region of a 20 inch axial annular turbine cascade. The initial boundary layer roll-up and formation of the end wall vortices were computed at the vane leading edge. The calculated flow field was found to be periodic with a frequency of approximately 1600 Hz. The calculated size of the separation region for the hub endwall vortex compared favorably with measured endwall oil traces. In an effort to determine the effects of the turbulence model on the calculated unsteadiness, a laminar calculation was made. The periodic nature of the calculated flow field persisted with the frequency essentially unchanged.

Walitt, L.↗

NASA NTRS1984

Effect of an oscillating flow direction on leading edge heat transfer

An experimental investigation was conducted to examine the effect of a periodic variation in the angle of attack on heat transfer at the leading edge of a gas turbine blade. A circular cylinder was used as a large-scale model of the leading edge region. The cylinder was placed in a wind tunnel and was oscillated rotationally about its axis. The incident flow Reynolds number and the Strouhal number of oscillation were chosen to model an actual turbine condition. Incident turbulence levels up to 4.9 percent were produced by grids placed upstream of the cylinder. The transfer rate was measured using a mass transfer technique and heat transfer rates inferred from the results. A direct comparison of the unsteady and steady results indicate that the effect is dependent on the Strouhal number, turbulence level, and the turbulence length scale, but that the largest observed effect was only a 10 percent augmentation at the nominal stagnation position.

Marziale, M. L.↗

NASA NTRS1984

Engineering analysis of drooped leading-edge wings near stall

Numerical results obtained with a three-dimensional vortex panel computer program for the calculation of inviscid, incompressible (potential) flow over infinitely thin finite wings with camber are presented. The program, which is designed for wings with drooped leading edge discontinuities, is essentially a numerical representation of lifting surface theory, involving both spanwise and chordwise distributions of vorticity. The results also include two engineering approximations. First, the effect of the leading-edge discontinuities is modeled by assuming that the vortices emanating from the discontinuities aerodynamically divide the wing into three distinct sections of lower aspect ratio. Secondly, the effect of the separated flow at high angle of attack is modeled by applying rectangular vortex panels with a varying vortex strength over the portions of the wing with attached flow.

Anderson, J. D., Jr.↗