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Jones, R. A.

Publications and source records attributed to Jones, R. A..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Comparison of reacting and non-reacting shear layers at a high subsonic Mach number

The flow field in a hydrogen-fueled planar reacting shear layer was measured with an LDV system and is compared with a similar air to air case without combustion. Measurements were made with a speed ratio of 0.34 with the highspeed stream at Mach 0.71. They show that the shear layer with reaction grows faster than one without, and both cases are within the range of data scatter presented by the established database. The coupling between the streamwise and the cross-stream turbulence components inside the shear layer is slow, and reaction only increased it slightly. However, a more organized pattern of the Reynolds stress is present in the reacting shear layer, possibly as a result of larger scale structure formation in the layer associated with heat release.

Chang, C. T.↗
NASA NTRS1993

Comparison of reacting and non-reacting shear layers at a high subsonic Mach number

The flow field in a hydrogen-fueled planar reacting shear layer was measured with an LDV system and is compared with a similar air to air case without combustion. Measurements were made with a speed ratio of 0.34 with the highspeed stream at Mach 0.71. They show that the shear layer with reaction grows faster than one without, and both cases are within the range of data scatter presented by the established database. The coupling between the streamwise and the cross-stream turbulence components inside the shear layer is slow, and reaction only increased it slightly. However, a more organized pattern of the Reynolds stress is present in the reacting shear layer, possibly as a result of larger scale structure formation in the layer associated with heat release.

Chang, C. T.↗
NASA NTRS1991

Experimental investigation of a unique airbreathing pulsed laser propulsion concept

Investigations were conducted into unique methods of converting pulsed laser energy into propulsive thrust across a flat impulse surface under atmospheric conditions. The propulsion experiments were performed with a 1-micron neodymium-glass laser at the Space Plasma Branch of the Naval Research Laboratory. Laser-induced impulse was measured dynamically by ballistic pendulums and statically using piezoelectric pressure transducers on a stationary impulse surface. The principal goal was to explore methods for increasing the impulse coupling performance of airbreathing laser-propulsion engines. A magnetohydrodynamic thrust augmentation effect was discovered when a tesla-level magnetic field was applied perpendicular to the impulse surface. The impulse coupling coefficient performance doubled and continued to improve with increasing laser-pulse energies. The resultant performance of 180 to 200 N-s/MJ was found to be comparable to that of the earliest afterburning turbojets.

Myrabo, L. N.↗
NASA NTRS1985

Tolerance bounds for log gamma regression models

The present procedure for finding lower confidence bounds for the quantiles of Weibull populations, on the basis of the solution of a quadratic equation, is more accurate than current Monte Carlo tables and extends to any location-scale family. It is shown that this method is accurate for all members of the log gamma(K) family, where K = 1/2 to infinity, and works well for censored data, while also extending to regression data. An even more accurate procedure involving an approximation to the Lawless (1982) conditional procedure, with numerical integrations whose tables are independent of the data, is also presented. These methods are applied to the case of failure strengths of ceramic specimens from each of three billets of Si3N4, which have undergone flexural strength testing.

Jones, R. A.↗
NASA NTRS1978

Toward scramjet aircraft

The possibility for civil, military, and remotely-piloted aviation above Mach 5 is discussed with reference to the scramjet. Actively cooled aircraft structures of low weight are described, together with jet nozzle design and combustion parameters. The scramjet is seen as operating alone or in tandem with ramjet propulsion, which would power an aircraft up to scramjet speeds. Attention is given to the specific impulse of the scramjet engine, with hydrogen as the primary fuel. Applications include: advanced reconnaissance and interceptor aircraft, strategic cruise (both aircraft and missiles), highly-maneuverable interceptor missiles, transports, aircraft-type launch vehicles, first stages for Space Shuttle launching craft, and single-stage-to-orbit vehicles. Research has focused on increasing the propulsion power of the scramjet engine, while reducing drag on the accompanying airframe.

Jones, R. A.↗
NASA NTRS1978

Airframe-integrated propulsion system for hypersonic cruise vehicles

Research on a new, hydrogen burning, airbreathing engine concept which offers good potential for efficient hypersonic cruise vehicles is considered. Features of the engine which lead to good performance include; extensive engine-airframe integration, fixed geometry, low cooling, and the control of heat release in the supersonic combustor by mixed-modes of fuel injection from the combustor entrance. The engine concept is described along with results from inlet tests, direct-connect combustor tests, and tests of two subscale boiler-plate research engines presently underway at conditions which simulate flight at Mach 4 and 7.

Jones, R. A.↗
NASA NTRS1978

Airframe-integrated propulsion system for hypersonic cruise vehicles

The paper describes a new hydrogen-burning airframe-integrated scramjet concept which offers good potential for efficient hypersonic cruise vehicles. The characteristics of the engine which assure good performance are extensive engine-airframe integration, fixed geometry, low cooling, and control of heat release in the supersonic combustor by mixed modes of fuel injection from the combustor entrance. The present paper describes the concept and presents results from inlet tests, direct-connect combustor tests, and tests of two subscale boiler-plate research engines currently underway under conditions which simulate flight at Mach 4 and 7. It is concluded that this engine concept has the potential for high thrust and efficiency, low drag and weight, low cooling requirement, and application to a wide range of vehicle sizes.

Jones, R. A.↗
NASA NTRS1977

Apparatus for determining thermophysical properties of test specimens

Apparatus is described for directly measuring the quantity square root of pck of a test specimen such as a wind tunnel model where p is density, c is the specific heat and k is the thermal conductivity of the specimen. The test specimen and a reference specimen are simultaneously subjected to the heat from a heat source. A thermocouple is attached to the reference specimen for producing a first electrical analog signal proportional to the heat rate Q that the test specimen is subjected to and an infrared radiometer that is aimed at the test specimen produces a second electrical analog signal proportional to the surface temperature T of the test specimen. An analog-to-digital converter converts the first and second electrical analog signals to digital signals. These digital signals are applied to a computer for determining the quantity.

Creel, T. R., Jr.↗
NASA NTRS1977

Investigation of real-gas and viscous effects on the aerodynamic characteristics of a 40 deg half-cone with suggested correlations for the shuttle orbiter

Parameters were evaluated that might be used to correlate shuttle orbiter aerodynamic data to be used in extrapolating from wind-tunnel to flight conditions. Preliminary calculations indicate that the lee-side forces will have an insignificant influence on the aerodynamic characteristics of the orbiter for moderate angle-of-attack entries; therefore, this work is focused on phenomena which have an overriding influence on windward forces, namely, real-gas (equilibrium and nonequilibrium) and viscous-interaction effects. Analytically determined flow fields previously obtained on 40 deg blunted cones were used as a data source to evaluate various correlation parameters. Inviscid effects were found to be the dominant contributor to the aerodynamic coefficients in the altitude range of 64 to 76.2 km. The most suitable correlation of the aerodynamic forces on these cones is based on local dynamic pressure and local Mach number.

Hunt, J. L.↗
NASA NTRS1976

Effective thermal property improves phase change paint data

The phase-change coating technique presents itself as a valuable tool in determining the heat transfer rate over the surface of small complex wind tunnel models. A numerical technique is described which shows that an effective thermophysical property - the square root of the product of thermal conductivity, density, and specific heat - may significantly improve the accuracy of the phase-change coating technique with allowance for model inhomogeneity and temperature dependency in a transient environment. Results of the measured steady-state variation of the effective thermophysical property with temperature and the effect of surface heating rate on the effective thermophysical property are plotted for a representative homogeneous model material and for an extreme nonhomogeneous model material. The use of an effective thermophysical property to reduce phase-change paint data is recommended. The analysis also confirms that the apparatus described by Corwin and Kramer (1975) can be used to measure directly this effective thermophysical property for use in wind tunnel model heat-transfer measurements.

Drummond, J. P.↗
NASA NTRS1975

Propulsion concepts for high speed aircraft

A wide variety of potentially useful and effective airbreathing aircraft have been postulated to operate at speeds in excess of Mach 3.0 by NASA and the USAF. These systems include hydrogen-fueled transports of interest for very long ranges and airbreathing launch vehicles which are aircraft-type first stage candidates for future space shuttle systems. Other high speed airbreathing systems for possible future military applications include advanced reconnaissance and fighter/interceptor type aircraft and strategic systems. This paper presents (1) a chronology of Air Force technical activity on future propulsion concepts, (2) a status report on NASA research on scramjet technology for future systems which may require speeds above Mach 5, and (3) a description of a research vehicle by which advanced propulsion technology and other technologies related to high speed can be demonstrated.

Stull, F. D.↗
NASA NTRS1975

Automated electronic system for measuring thermophysical properties

Phase-charge coatings are used to measure surface temperature accurately under transient heating conditions. Coating melts when surface reaches calibrated phase-charge temperature. Temperature is monitored by infrared thermometer, and corresponding elapsed time is recorded by electronic data-handling system.

Creel, T. R., Jr.↗
NASA NTRS1975

Forward bearing reactor mechanism for Titan 3-E/Centaur D-1T space launch vehicle

System between the Titan/Centaur launch vehicle and its aerodynamic shroud is described. The system provides a precise spring constant and is capable of being inactivated during flight. Design requirements, design details, and the test program are discussed. The conventional English system of units was used during this development program for all principal measurements and calculations.

Jones, R. A.↗
NASA NTRS1975

Fail-safe system for activity cooled supersonic and hypersonic aircraft

A fail-safe-system concept was studied as an alternative to a redundant active cooling system for supersonic and hypersonic aircraft which use the heat sink of liquid-hydrogen fuel for cooling the aircraft structure. This concept consists of an abort maneuver by the aircraft and a passive thermal protection system (TPS) for the aircraft skin. The abort manuever provides a low-heat-load descent from normal cruise speed to a lower speed at which cooling is unnecessary, and the passive TPS allows the aircraft skin to absorb the abort heat load without exceeding critical skin temperature. On the basis of results obtained, it appears that this fail-safe-system concept warrants further consideration, inasmuch as a fail-safe system could possibly replace a redundant active cooling system with no increase in weight and would offer other potential advantages.

Jones, R. A.↗
NASA NTRS1974

Use of hexafluoroethane to simulate the inviscid real-gas effects on blunt entry vehicles

Results are presented of an experimental and theoretical investigation of the use of equilibrium hexafluoroethane C2F6 as an undissociated test gas in a wind tunnel to simulate the inviscid aerodynamic characteristics of blunt bodies in high-speed flight where dissociation occurs. The results indicate that the use of C2F6 as a test gas in wind tunnels is a practical and relatively simple and inexpensive method of obtaining test conditions with large normal-shock density ratios. Equations for the thermodynamic and transport properties of C2F6 are also included.

Hunt, J. L.↗
NASA NTRS1974

Effect of wall temperature spatial variations on aerodynamic heating to an actively cooled aircraft

The design of cooled skin panels, which requires consideration of many parameters such as heat load, skin thickness, panel size, tube spacing, tube size, temperature limits, coolant flow, etc., must minimize weight and thermal stresses. A design procedure for such panels has been developed by Bell Aerospace Company (Helenbrook and Anthony, 1971). This design procedure assumes a uniform heating rate to the panel, i.e., the variation of aerodynamic heating rate due to the cyclic wall temperature distribution, which results from the discrete coolant tube locations in such a panel, has been neglected. This study was made to determine if these variations were sufficiently large to cause variations in aerodynamic heating rate which would require coupling of boundary layer and conductive thermal analysis solutions.

Jones, R. A.↗
NASA NTRS1974

An exploratory investigation of a wake disruption technique for studying wake reestablishment time

An exploratory investigation was made of a wake disruption technique for studying the hypersonic-wake reestablishment time in a blowdown wind tunnel. In this technique, a highly underexpanded jet issuing from the base of a 10 deg half-angle cone totally disrupts and displaces the conventional wake. The jet was rapidly shut off by an explosively actuated valve and the time for wake reestablishment was measured. The tests were conducted in the Mach 6 high Reynolds number tunnel at a stagnation temperature of 506 K and stagnation pressure of 2.86 MPa. The model base jet stagnation pressure was 3.55 MPa at room temperature. High-speed schlieren motion pictures indicated that disappearance of the disrupting jet and reestablishment of the wake-recompression shock were probably occurring simultaneously and that the time disruptive-jet-air shutoff to wake recompression shock reestablishment was probably between 200 and 450 microseconds (flow lengths from 1.8 to 4.2). The values of flow lengths are about one-thord to one-half the values measured in impulse facilities in a previous study. This shorter time is believed to be largely due to difference in flow conditions between the jet disruption technique and impulse facilities.

Clark, L. E.↗