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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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Nonlinear least squares optimization program applied to atmospheric temperature sounding, solving for temperatures at various altitudes from simulated carbon dioxide intensity measurements
A precision pyrotechnic time delay initiator for missile staging was developed and tested. Incorporated in the assembly is a single bridgewire Apollo standard initiator (SBASI) for initiation, a through-bulkhead-initiator to provide isolation of the SBASI output from the delay, the pyrotechnic delay, and an output charge. An attempt was made to control both primary and secondary variables affecting functional performance of the delay initiator. Design and functional limit exploration was performed to establish tolerance levels on manufacturing and assembling operations. The test results demonstrate a 2% coefficient of variation at any one temperature and an overall 2.7% coefficient of variation throughout the temperature range of 30 to 120 F. Tests were conducted at simulated operational altitude from sea level to 200,000 feet.
A series of space simulation tests on FEP Teflon and other polymeric thermal control coatings was conducted using UV, electrons, protons and Lyman-alpha wavelength vacuum UV radiation. Interest was centered on simulating synchronous altitude radiation environment conditions. Physical changes in materials included loss of specularity and introduction of a high density of photographable tracking defects on a microscopic scale. An example shows the discharge of trapped electrons when dielectric strength is exceeded. This leaves a portion of the Teflon volume no longer clear, but diffusely transmitting and reflecting. Thermophysical changes included degradation of solar absorptance coefficients as much as five-fold. The situation that prevails for earth orbit contrasted with polymer performance in the solar wind. It is suggested that conductive overcoatings be developed for polymers and other flexible materials, comparable or superior to those available for fused silica SSMs.
Space shuttle base heating tests were conducted using a 0.040-scale model in the Plum Brook Space Power Facility of The NASA Lewis Research Center. The tests measured heat transfer rates, pressure distributions, and gas recovery temperatures on the orbiter vehicle 2A base configuration resulting from engine plume impingement. One hundred and sixty-eight hydrogen-oxygen engine firings were made at simulated flight altitudes ranging from 120,000 to 360,000 feet.
A mathematical model for the control of erythropoiesis was developed based on the balance between oxygen supply and demand at a renal oxygen detector which controls erythropoietin release and red cell production. Feedback regulation of tissue oxygen tension is accomplished by adjustments of hemoglobin levels resulting from the output of a renal-bone marrow controller. Special consideration was given to the determinants of tissue oxygenation including evaluation of the influence of blood flow, capillary diffusivity, oxygen uptake and oxygen-hemoglobin affinity. A theoretical analysis of the overall control system is presented. Computer simulations of altitude hypoxia, red cell infusion hyperoxia, and homolytic anemia demonstrate validity of the model for general human application in health and disease.
The Conservative Supra Characteristic Method (CSCM), an implicit upwind Navier-Stokes algorithm, is extended to the numerical simulation of flows in chemical equilibrium. The resulting computer code known as Chemistry and Gasdynamics Implicit - Version 2 (CAG12) is described. First-order accurate results are presented for inviscid and viscous Mach 20 flows of air past a hemisphere-cylinder. The solution procedure captures the bow shock in a chemically reacting gas, a technique that is needed for simulating high altitude, rarefied flows. In an initial effort to validate the code, the inviscid results are compared with published gasdynamic and chemistry solutions and satisfactorily agreement is obtained.
The capabilities and performance of various fault detection and accommodation (FDA) schemes in existing and projected engine control systems were investigated. Flight tests of the digital electronic engine control (DEEC) in an F-15 aircraft show discrepancies between flight results and predictions based on simulation and altitude testing. The FDA methodology and logic in the DEEC system, and the results of the flight failures which occurred to date are described.
A spaceborne lidar system is presently being constructed for flight aboard the U. S. Space Shuttle in early 1991. The experiment, Lidar In Space Technology Experiment (LITE), utilizes a neodymium:YAG laser and 0.85 meter effective diameter Cassegranian-configured telescope receiver for making elastic backscatter measurements. The laser will be frequency doubled and tripled simulataneously producing a 10 Hz rate of 200 mJ at 1064 nm, 400 mJ at 532 nm, and 150 mJ at 355 nm. The technological objectives of LITE are to evaluate lidar system operations in space, lidar techniques in space, and to provide a test bed for new lidar technologies in later flights. The measurement objectives include the determination of cloud top and planetary boundary layer heights, the measurement of tropospheric and stratospheric aerosols, and the measurement of temperature and density between 10 to 40 km altitude. Detailed simulations will be presented showing the errors associated with each of these measurement objectives. In addition, the experiment scenario will be described including measurement times, data flow, processing and archival, and initial plans for validation of the LITE data set with correlative measurements.
A piloted simulation study investigating handling qualities and flight characteristics required for helicopter air to air combat is presented. The Helicopter Air Combat system was used to investigate this role for Army rotorcraft. Experimental variables were the maneuver envelope size (load factor and sideslip), directional axis handling qualities, and pitch and roll control-response type. Over 450 simulated, low altitude, one-on-one engagements were conducted. Results from the experiment indicate that a well damped directional response, low sideforce caused by sideslip, and some effective dihedral are all desirable for weapon system performance, good handling qualities, and low pilot workload. An angular rate command system was favored over the attitude type pitch and roll response for most applications, and an enhanced maneuver envelope size over that of current generation aircraft was found to be advantageous. Pilot technique, background, and experience are additional factors which had a significant effect on performance in the air combat tasks investigated. The implication of these results on design requirements for future helicopters is presented.
The effect of perspective displays on flight performance is investigated using two simulation experiments. In the first, a perspective grid display was superimposed on computer-generated terrain and subjects attempted to maintain their initial attitude in a simulated hover using terrain and/or one of four grid patterns. Horizontal lines produced the best attitude control performance. In the second experiment, a square grid was studied in combination with various visual display configurations and grid attachment conditions. It was found that performance with the panel-mounted display was significantly worse than with the out-the-window or helmet-mounted displays. The results suggested that the partial grid attachment condition improved hovering performance with the panel-mounted display.
The design and construction of an altitude chamber, in which both pressure and temperature can be varied independently, was carried out by the NACA at the Langley Memorial Aeronautical Laboratory for the purpose of studying the effects of temperature and pressure on aeronautical research instruments. Temperatures from +20c to -50c are obtained by the expansion of CO2from standard containers. The chamber can be used for the calibration of research instruments under altitude conditions simulating those up to 45,000 feet. Results obtained with this chamber have a direct application in the design and calibration of instruments used in free flight research.
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A jet diffuser for simulating flight or ram conditions on a turbojet-engine static test stand was designed and investigated. The diffuser utilizes the kinetic energy of the jet from a turbojet engine to reduce the discharge pressure at the exhaust nozzle and thereby provides simulated ram-pressure ratios across the engine. The engine exhaust nozzle discharges into an exhaust chamber (flexibly sealed to the tail pipe), which is connected to a diffuser by a bell-shaped nozzle. The pressure in the exhaust chamber is controlled independently of engine speed by a variable-area shutter at the diffuser discharge. The jet diffuser simulated ram-pressure ratios from 0.95 to 2.2 at various simulated pressure altitudes for a range of engine speeds from 85 to 100 percent of maximum rpm. Agreement of data obtained with and without the jet diffuser for a ram-pressure ratio of 1.0 indicated that the presence of the diffuser did not interfere with the flow through the engine exhaust-nozzle outlet.
An investigation was conducted to determine the combustion response to rapid fuel-flow changes in a single tubular combustor at two simulated altitude-rotor speed conditions of 25,000 feet-70 percent rated engine speed and 50,000 feet-70 percent rated engine speed. Limiting rates of change of fuel flow (acceleration limits) were determined and the effects of certain combustion air flow variables on the transient combustion characteristics were studied with the aid of rapid-response instrumentation.
This manual describes the Propulsion Systems Laboratory (PSL) at NASA Lewis Research Center. The PSL complex supports two large engine test cells (PSL-3 and PSL-4) that are capable of providing flight simulation to altitudes of 70,000 ft. Facility variables at the engine or test-article inlet, such as pressure, temperature, and Mach number (up to 3.0 for PSL-3 and up to 6.0 planned for PSL-4), are discussed. Support systems such as the heated and cooled combustion air systems; the altitude exhaust system; the hydraulic system; the nitrogen, oxygen, and hydrogen systems; hydrogen burners; rotating screen assemblies; the engine exhaust gas-sampling system; the infrared imaging system; and single- and multiple-axis thrust stands are addressed. Facility safety procedures are also stated.
An investigation of the low-subsonic stability and control characteristics of a l/7-scale free-flying model modified to represent closely the North American X-15 airplane (configuration 3) has been made in the Langley full-scale tunnel. Flight conditions at a relatively low altitude were simulated with the center of gravity at 16.0 percent of the mean aerodynamic chord. The longitudinal stability and control were considered to be satisfactory for all flight conditions tested. The lateral flight behavior was generally satisfactory for angles of attack below about 20 deg. At higher angles, however, the model developed a tendency to fly in a side-slipped attitude because of static directional instability at small sideslip angles. Good roll control was maintained to the highest angles tested, but rudder effectiveness diminished with increasing angle of attack and became adverse for angles above 40 deg. Removal of the lower rudder had little effect on the lateral flight characteristics for angles of attack less than about 20 deg but caused the lateral flight behavior to become worse in the high angle-of-attack range. The addition of small fuselage forebody strakes improved the static directional stability and lateral flight behavior of both configurations.
The Federal Aviation Administration's Integrated Noise Model (INM) is one of the primary tools for land use planning around airports. The INM currently calculates airplane noise lateral attenuation using the methods contained in the Society of Automotive Engineer's Aerospace Information Report No. 1751 (SAE AIR 1751). Researchers have noted that improved lateral attenuation algorithms may improve airplane noise prediction. The authors of SAE AIR 1751 based existing methods on empirical data collected from flight tests using 1960s-technology airplanes with tail-mounted engines. To determine whether the SAE AIR 1751 methods are applicable for predicting the engine installation component of lateral attenuation for airplanes with wing-mounted engines, the National Aeronautics and Space Administration (NASA) sponsored a series of flight tests during September 2000 at their Wallops Flight Facility. Four airplanes, a Boeing 767-400, a Douglas DC-9, a Dassault Falcon 2000, and a Beech KingAir, were flown through a 20 microphone array. The airplanes were flown through the array at various power settings, flap settings, and altitudes to simulate take-off and arrival configurations. This paper presents the preliminary findings of this study.
The Oil-Free Turbomachinery research team at the NASA Glenn Research Center is conducting research to develop turbomachinery systems that utilize high-speed, high temperature foil (air) bearings that do not require an oil lubrication system. Such systems combine the most advanced foil bearings from industry with NASA-developed hightemperature solid-lubricant technology. New applications are being pursued, such as Oil- Free turbochargers, auxiliary power units, and turbine propulsion systems for aircraft. An Oil-Free business jet engine, for example, would be simpler, lighter, more reliable, and less costly to purchase and maintain than current engines. Another application is NASA's Prometheus mission, where gas bearings will be required for the closed-cycle turbine based power-conversion system of a nuclear power generator for deep space. To support these applications, Glenn's Oil-Free Turbomachinery research team developed the Ambient Pressure Test Rig. Using this facility, researchers can load and heat a bearing and evaluate its performance with reduced air pressure to simulate high altitude conditions. For the nuclear application, the test chamber can be purged with gases such as helium to study foil gas bearing operation in working fluids other than air.