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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

A State-of-the-Art Contamination Effects Research and Test Facility

In the ongoing effort to better understand various spacecraft contamination phenomena, a new state of the art contamination effects research and test facility was designed, and recently brought on-line at The Aerospace Corporation s Space Materials Laboratory. This high vacuum test chamber employs multiple in-situ analytical techniques, making it possible to study both the qualitative and quantitative aspects of contaminant film formation in the presence or absence of VUV radiation. Adsorption and desorption kinetics, "photo-fixing efficiency", transmission loss of uniform contaminant films, light scatter from non-uniform films, and film morphology have been studied in this facility. This paper describes this new capability in detail and presents data collected from several of the analytical instruments.

Olson, Keith R.↗
NASA NTRS1937

The Scale Effect in Towing Tests with Airplane-float Systems

The present report includes a description of the making of three-component measurements on a full-size float mounted on an actual airplane and the comparison of the results with those from two models of the same form but of different size which had been tested in the towing tank. The purpose of the comparison is to determine the effect of the Reynolds Number on the results of model tank tests. Following a brief discussion of previous tests intended to elucidate the problem of scale effect on float systems and a description of the testing equipment, the choice of the reference quantities to be used in the comparison is discussed. The selection of load, speed, and trim as a basis of comparison seems best suited to the practical operation of making this comparison. The quantities affected by scale are then: resistance, trimming moment, and their derivatives; planing number (resistance/weight on water); and position of center of pressure.

Schmidt, Rudolph↗
NASA NTRS1995

F-18 High Alpha Research Vehicle (HARV) parameter identification flight test maneuvers for optimal input design validation and lateral control effectiveness

Flight test maneuvers are specified for the F-18 High Alpha Research Vehicle (HARV). The maneuvers were designed for open loop parameter identification purposes, specifically for optimal input design validation at 5 degrees angle of attack, identification of individual strake effectiveness at 40 and 50 degrees angle of attack, and study of lateral dynamics and lateral control effectiveness at 40 and 50 degrees angle of attack. Each maneuver is to be realized by applying square wave inputs to specific control effectors using the On-Board Excitation System (OBES). Maneuver descriptions and complete specifications of the time/amplitude points define each input are included, along with plots of the input time histories.

Morelli, Eugene A.↗
NASA NTRS1944

Flight Tests of the Effect of Several Modifications on the Maximum Speed of the P-63A Airplane

Presented herein are the results of flight tests conducted to obtain the effect on maximum speed of several modifications to the P-63A airplane. These modifications made to the P-63A airplane as a result of previous flight and full-scale-tunnel tests increased the maximum speed of the airplane by 6 miles per hour. About one-half the increase is attributed to a reduction in drag and the remainder to increased ram at the carburetor entrance. The increase in ram of approximately 0.24 qc was obtained through modifications to the carburetor-scoop entrance and duct. The auxiliary supercharger is hydraulically coupled to the engine in such a way that the speed of the supercharger is regulated by absolute carburetor total pressure. This regulation is set so that full coupling is not reached until the airplane is well above full-throttle altitude. The action of the increased ram in reducing the speed of the auxiliary supercharger in the altitude range just above full-throttle altitude prevented a further speed increase of approximately 2 miles per hour from accompanying the increase in ram. Also, if the· auxiliary supercharger control could be rearranged to permit the maximum supercharger pressure ratio to be obtained at the full-throttle altitude, the speed in either the original or the modified configuration would be increased 5 miles per hour above that actually measured. The pressure recovery on the face of the prestone and oil radiators in the high-speed flight conditions was increased by an average of 14 percent of free-stream impact pressure as a result of the modifications made to the wing duct inlets.

Thomas J Voglewede↗
NASA NTRS1944

Whirling Arm Tests on the Effect of Ground Proximity to an Airplane Wing

This report gives the results of tests on a rectangular wing model with a 20% full spun split flap, conducted on the whirling arm at the Daniel Guggenheim Airship Institute in Akron, Ohio. The effect of a ground board on the lift and pitching moment was measured. The ground board consisted of an inclined ramp rising up in the test channel to a level floor extending for some distance parallel to the model path. The path of the wing model with respect to the ground board accordingly represented with comparative exactness an airplane coming in for a landing. The ground clearances over the level portion of the board varied from 0 6 to 1,6 chord lengths. Results are given in the standard dimensionless coefficients plotted versus angle of attack for a particular ground clearance. The effect of the ground board is to increase the lift coefficient for a given angle of attack all the way up the stall. The magnitude of the increase varies both with the ground clearance and the angle of attack. The effect on the pitching moment coefficient is not so readily apparent due to experimental difficulties but, in general, the diving moment increases over the ground board. This effect is apparent principally at the high angles of attack. An exception to this effect occurs with flaps deflected at the lowest ground clearance (0.6 chords). Here the diving moment decreases over the ground board.

Long, M. E.↗
NASA NTRS1987

Similarity rule for sidewall boundary-layer effects in airfoil testing

The simplified form of the similarity rule for sidewall boundary layer effects presented envisions the generation of changes in both airfoil thickness and freestream Mach number by the sidewall boundary layer. Within the small-disturbance approximation, this approach encompasses the methods of both Barnwell (1980) and Sewall (1982), and can accordingly be applied at speeds ranging from the lowest to transonic Mach numbers.

Murthy, A. V.↗
NASA NTRS1990

Thermal/vacuum vs. thermal atmospheric testing of space flight electronic assemblies

For space flight hardware, the thermal vacuum environmental test is the best test of a system's flight worthiness. Substituting an atmospheric pressure thermal test for a thermal/vacuum test can effectively reduce piece part temperatures by 20 C or more, even for low power density designs. Similar reductions in test effectiveness can also result from improper assembly level T/V test boundary conditions. The net result of these changes may reduce the effective test temperatures to the point where there is zero or negative margin over the flight thermal environment.

Gibbel, Mark↗
NASA NTRS1942

Preliminary Wind-Tunnel Tests of the Effect of Nacelles on the Characteristics of a Twin-Engine Bomber Model with Low-Drag Wing, Special Report

Tests were made in the NACA 19-foot pressure tunnel of a simplified twin-engine bomber model with an NACA low-drag wing primarily to obtain an indication of the effects of engine nacelles on the characteristics of the model both with and without simple split trailing-edge flaps. Nacelles with conventional-type cowlings representative of those used on an existing high-performance airplane and with NACA high-speed type E cowlings were tested. The tests were made without propeller slipstream. The aerodynamic effects of adding the nacelles to the low-drag wing were similar to the effects commonly obtained by adding similar nacelles to conventional wings. The maximum lift coefficient without flaps was slightly increased, but the increment in maximum lift due to deflecting the flaps was somewhat decreased. The stalling characteristics were improved by the presence of the nacelles. Addition of the nacelles had a destabilizing effect on the pitching moments, as is usual for nacelles that project forward of the wing. The drag increments due to the nacelles were of the usual order of magnitude, with the increment due to the nacelles with NACA type E cowlings approximately one-third less than that of the nacelles with conventional cowlings with built-in air scoops.

Wenzinger, Carl J.↗
NASA NTRS1987

Effect of aspect ratio on sidewall boundary-layer influence in two-dimensional airfoil testing

The effect of sidewall boundary layers in airfoil testing in two-dimensional wind tunnels is investigated. The non-linear crossflow velocity variation induced because of the changes in the sidewall boundary-layer thickness is represented by the flow between a wavy wall and straight wall. Using this flow model, a correction for the sidewall boundary-layer effects is derived in terms of the undisturbed sidewall boundary-layer properties, the test Mach number and the airfoil aspect ratio. Application of the proposed correction to available experimental data showed good correlation for the shock location and pressure.

Murthy, A. V.↗
NASA NTRS1986

Effect of aspect ratio on sidewall boundary-layer influence in two-dimensional airfoil testing

The effect of sidewall boundary layers in airfoil testing in two-dimensional wind tunnels is investigated. The non-linear crossflow velocity variation induced because of the changes in the sidewall boundary-layer thickness is represented by the flow between a wavy wall and a straight wall. Using this flow model, a correction for the sidewall boundary-layer effects is derived in terms of the undisturbed sidewall boundary-layer properties, the test Mach number and the airfoil aspect ratio. Application of the proposed correction to available experimental data showed good correlation for the shock location and pressure distribution on airfoils.

Murthy, A. V.↗
NASA NTRS2001

New Instrumentation, Patterns and Their Effects on TID Testing of Antifuse-Based FPGAs

TID-induced leakage currents for some families of antifuse-based Field Programmable Gate Array (FPGA) devices are significantly affected by the state of bias of a device's internal nodes; proper consideration of this effect is essential for proper testing of these devices and interpretation of test results. Variations in TID performance based on utilization of different internal logic modules for implementing identical circuits may be utilized by circuit designers for improvement in TID performance by tailoring the placement algorithm. Propagation delays are significantly affected by TID-induced damage for the devices of 54SX32S family.

Kleyner, Igor↗
NASA NTRS1952

An engineering method for estimating notch-size effect in fatigue tests on steel

Neuber's proposed method of calculating a practical factor of stress concentration for parts containing notches of arbitrary size depends on the knowledge of a "new material constant" which can be established only indirectly. In this paper, the new constant has been evaluated for a large variety of steels from fatigue tests reported in the literature, attention being confined to stresses near the endurance limit. Reasonably satisfactory results were obtained with the assumption that the constant depends only on the tensile strength of the steel. Even in cases where the notches were cracks of which only the depth was known, reasonably satisfactory agreement was found between calculated and experimental factors. It is also shown that the material constant can be used in an empirical formula to estimate the size effect on unnotched specimens tested in bending fatigue.

Kuhn, Paul↗
NASA NTRS1982

Design, production, and testing of field effect transistors

Cryogenic MOSFETS (CRYOFETS), specifically designed for low temperature preamplifier application with infrared extrinsic detectors were produced and comparatively tested with p-channel MOSFETs under matched conditions. The CRYOFETs exhibit lower voltage thresholds, high source-follower gains at lower bias voltage, and lower dc offset source voltage. The noise of the CRYOFET is found to be 2 to 4 times greater than the MOSFET with a correspondingly lower figure of merit (which is established for source-follower amplifiers). The device power dissipation at a gain of 0.98 is some two orders of magnitude lower than for the MOSFET. Further, CRYOFETs are free of low temperature I vs V character hysteresis and balky conduction turn-on effects and operate effectively in the 2.4 to 20 K range. These devices have promise for use on long term duration sensor missions and for on-focal-plane signal processing at low temperatures.

Sclar, N.↗