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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Laser Powered Launch Vehicle Performance Analyses

The purpose of this study is to establish the technical ground for modeling the physics of laser powered pulse detonation phenomenon. Laser powered propulsion systems involve complex fluid dynamics, thermodynamics and radiative transfer processes. Successful predictions of the performance of laser powered launch vehicle concepts depend on the sophisticate models that reflects the underlying flow physics including the laser ray tracing the focusing, inverse Bremsstrahlung (IB) effects, finite-rate air chemistry, thermal non-equilibrium, plasma radiation and detonation wave propagation, etc. The proposed work will extend the base-line numerical model to an efficient design analysis tool. The proposed model is suitable for 3-D analysis using parallel computing methods.

Chen, Yen-Sen↗
NASA NTRS1981

Powered-lift takeoff performance characteristics determined from flight test of the Quiet Short-haul Research Aircraft /QSRA/

A powered-lift, reduced thrust takeoff performance program utilizing quiet short-haul research aircraft has been conducted. It has been shown that the powered-lift upper surface blowing concept greatly enhances aircraft takeoff performance. The improvements include: (1) takeoff field lengths may be shortened by approximately 30%; (2) Air Force critical field lengths may be shortened by approximately 60%; (3) powered lift upper surface blowing aircraft have better handling and performance characteristics than comparable conventional aircraft; and (4) the low speeds associated with powered-lift takeoff enhance safety margins.

Riddle, D. W.↗
NASA NTRS1979

Cold-air performance of free power turbine designed for 112-kilowatt automotive gas-turbine engine. 2: Effects of variable stator-vane-chord setting angle on turbine performance

The cold-air performance of an axial-flow power turbine with a variable stator designed for a 112-kW automotive gas-turbine engine was determined at speeds from 30 to 110 percent of design and at pressure ratios from 1.11 to 2.67. Performance is presented in terms of equivalent mass flow, torque, power, and efficiency for stator-vane-chord setting angles of 26 degs, 30 degs, 35 degs (design), 40 degs, 45 degs, and 50 degs. Turbine braking performance at a nominal stator setting angle of 107 degs is also presented. Turbine efficiency increased with increasing stator setting angle. A 10-point efficiency increase was obtained by opening the stator from the design setting angle of 35 degs to a setting angle of 45 degs.

Mclallin, K. L.↗
NASA NTRS1972

ASDTIC - A feedback control innovation.

The ASDTIC (analog signal to discrete time interval converter) control subsystem provides precise output control of high performance aerospace power supplies. The key to ASDTIC operation is that it stably controls output by sensing output energy change as well as output magnitude. The ASDTIC control subsystem and control module were developed to improve power supply performance during static and dynamic input voltage and output load variations, to reduce output voltage or current regulation due to component variations or aging, to maintain a stable feedback control with variations in the loop gain or loop time constants, and to standardize the feedback control subsystem for power conditioning equipment.

Lalli, V. R.↗
NASA NTRS1972

ASDTIC: A feedback control innovation

The ASDTIC (Analog Signal to Discrete Time Interval Converter) control subsystem provides precise output control of high performance aerospace power supplies. The key to ASDTIC operation is that it stably controls output by sensing output energy change as well as output magnitude. The ASDTIC control subsystem and control module were developed to improve power supply performance during static and dynamic input voltage and output load variations, to reduce output voltage or current regulation due to component variations or aging, to maintain a stable feedback control with variations in the loop gain or loop time constants, and to standardize the feedback control subsystem for power conditioning equipment.

Lalli, V. R.↗
NASA NTRS2004

The Investigation Of Carbon Contamination And Sputtering Effects Of Xenon Ion Thrusters

The Electro-Physics Branch of the NASA Glenn Research Center investigates the effect of atomic oxygen, environmental durability of high performance power materials and surfaces, and low earth orbit. One of its current projects involves the analysis of ion thrusters. Ion thrusters are devices that initiate a beam of ions to a target area. The type of ion thruster that I have been working with this Summer of 2004 emits positively charged Xenon (Xe(+)) atoms through two grids, the screen grid and the accelerator grid, after it enters an ionization chamber. Insulators are used to mechanically hold and separate these two grids. A propellant isolator, an instrument that closely resembles insulators, is placed in front of the ionization chamber. Both the insulator and isolator are made with a ceramic compound and filled with insulating beads. The main difference between the two devices is that the propellant isolator allows gas to flow through, in this case, the gas is Xe(+) and the insulators do not. In order to avoid carbon deposits and other contaminating chemicals to settle on the insulators and propellant isolator, a metal shadow shield is placed around them. These shadow shields function as a protectant and can be shaped in numerous configurations. Part of my job responsibility this summer is to investigate the effectiveness of different shadow shields that are utilized on three different ion engines: the NSTAR (NASA Solar Electric Propulsion Technology Application Readiness), JIMO (Jupiter Icy Moons Orbiter), and NEXIS (Nuclear Electric Xenon Ion System). Using calculus and other mathematical tactics, I was asked to find the total flux of carbon contamination that was able to pass the protectant shadow shield. I familiarized myself with the software program, MathCad2004, to help perform some mathematical computations such as complex integration. Another method of studying the probability of contamination is by experimental simulation. After attaining the precise parameters of the actual shadow shields, I created replicas of three types of shadow shielding to be used to undergo testing. It will be placed in a machine that produces carbon atoms at a high temperature of 200 C. or beam is aimed at a targeted material. As a result of this collision, atoms and other particles are ejected out of the target surface. Another part of my internship consisted of research on sputter ejection, or the angle distribution of sputtered material. This research entailed finding the past results of sputter ejection investigation as well as creating another type of mock simulation. Other minor projects include calculating the path of Xe(+) gas through the insulating beads of the isolators and assisting my mentor in collecting data for his paper for the Joint Propulsion Conference & Exhibit to be held July 11-14,2004 in Fort Lauderdale, Florida.

Prak, Moline K.↗
NASA NTRS2006

Silicon-Based Optical Modulator with Ferroelectric Layer

According to a proposal, a silicon dioxide layer in a high-speed, low-power, silicon- based electro-optical modulator would be replaced by a layer of lead zirconate titanate or other ferroelectric oxide material. The purpose of this modification is to enhance the power performance and functionality of the modulator. In its unmodified form, the particular silicon- based electro-optical modulator is of an advanced design that overcomes the speed limitation of prior silicon-based electro- optical modulators. Whereas modulation frequencies of such devices had been limited to about 20 MHz, this modulator can operate at modulation frequencies as high as 1 GHz. This modulator can be characterized as a silicon-waveguide-based metal oxide/semiconductor (MOS) capacitor phase shifter in which modulation of the index of refraction in silicon is obtained by exploiting the free-charge-carrier-plasma dispersion effect. As shown in the figure, the modulator includes an n-doped crystalline silicon slab (the silicon layer of a silicon- on-insulator wafer) and a p-doped polycrystalline silicon rib with a gate oxide layer (the aforementioned silicon dioxide layer) sandwiched between them. Under accumulation conditions, the majority charge carriers in the silicon waveguide modify the index of refraction so that a phase shift is induced in the optical mode propagating in the waveguide. The advantage of using an MOS capacitor phase shifter is that it is possible to achieve high modulation speed because there are no slow carrier-generation or -recombination processes involved in the accumulation operation. The main advantage of the proposed substitution of a ferroelectric oxide layer for the silicon dioxide layer would arise from the spontaneous polarization effect of the ferroelectric layer: This spontaneous polarization would maintain accumulation conditions in the absence of applied voltage. Consequently, once the device had been switched to a given optical state, it would remain in that state, even in the absence of applied voltage (in other words, even with power turned off). A secondary advantage is that because the ferroelectric layer would have an index of refraction larger than that of silicon dioxide, there could be some reduction of optical losses attributable to fabrication of the modulator

Sheldon, Douglas↗
NASA NTRS1971

Measurements of plasma parameters in a simulated thermionic converter

Cesium-filled thermionic energy converters are examined as candidate electrical energy sources in spacecraft requiring tens to hundreds of kilowatts of electric power. The high operating temperatures necessary for a large specific power and high efficiency inevitably impose stringent constraints on the converter fabrication to achieve the desired reliability of the power system. The converter physics for reducing operating temperatures and cesium plasma losses are studied to achieve high reliability without sacrificing the power performance of the converters. Various cesium parameters which affect the converter performance are: (1) electron temperatures, (2) plasma ion densities, and (3) electric potential profiles. These were investigated using a Langmuir probe in a simulated converter. The parameters were measured in different cesium discharge modes.

Shimada, K.↗
NASA NTRS1972

Probe measurements of a cesium plasma in a simulated thermionic energy converter

Cesium-filled thermionic energy converters are considered as electrical energy sources in future spacecraft requiring tens to hundreds of kilowatts of electric power. The high operating temperatures necessary for a large specific power and high efficiency impose stringent constraints on the converter fabrication. The converter physics for reducing operating temperatures and cesium plasma losses are being studied to achieve high reliability without sacrificing the power performance of the converters. Various cesium parameters which affect the converter performance are: (1) electron temperatures, (2) plasma ion densities, and (3) electric potential profiles. These were investigated using a Langmuir probe in a simulated converter. The parameters were measured in different cesium discharge modes.

Shimada, K.↗
NASA NTRS1971

Simulation of ERTS RBV imagery.

Based on the signal-to-noise ratio, modulation transfer function (MTF), and light transfer characteristics of the return-beam vidicon (RBV) multispectral three-camera subsystem, developed for use on earth resources technology satellites (ERTS), an analytical prediction of the resolvability of ground targets was made as a function of target size, contrast, spectral distribution, and radiance level. To determine whether the analysis was correct, U.S. Air Force targets with various contrasts were utilized to simulate those contrasts and radiance levels that the RBV cameras would see in the actual ERTS scenes. Although the RBV camera used in this test had a somewhat lower signal-to-noise ratio than the flight cameras, the simulation still proved the validity of the theoretical analysis in predicting resolving power performance for any set of input parameters.

Weinstein, O.↗
NASA NTRS1972

High resolution multispectral camera system for ERTS A & B.

A very-high resolution multispectral television camera system is being developed for use on the earth resources technology satellite (ERTS) program. There are three cameras in the system, each viewing the same area but operating in the blue-green, red, and near-infrared spectral bands. In the laboratory the cameras' limiting resolution is 4500 TV lines over the 25 + 25-mm image format of the return beam vidicon (RBV). A model was developed to predict the resolving power performance of the RBV camera under realistic conditions. To verify the model, tests were conducted using the RBV camera, a laser-beam image reproducer and a series of AF tribar test patterns of known values of contrast. As a more graphic demonstration, simulated multispectral images were generated using color-IR photographs from Apollo 9. The measured signal-to-noise, resolution, and spectral characteristics of the ERTS Flight A and Flight B three-camera systems are presented in conclusion.

Miller, B. P.↗
NASA NTRS1973

High resolution multispectral camera system for ERTS A & B

A very high resolution multispectral television camera system has been developed for NASA for use on the Earth Resources Technology Satellite (ERTS) program. There are three cameras in the system, each viewing the same area but operating in the blue-green, red, and near-infrared spectral bands. In the laboratory the cameras' limiting resolution is 4500 TV lines over the 25 x 25-mm image format of the Return Beam Vidicon (RBV). Analysis of typical ERTS scenes shows that actual contrast ratios will be much lower than those of laboratory test targets. A model was developed to predict the resolving power performance of the RBV camera under realistic conditions. To verify the model, tests were conducted using the RBV camera, a laser-beam image reproducer and a series of AF tribar test patterns of known values of contrast. As a more graphic demonstration, simulated multispectral images were generated using color-IR photographs from Apollo 9. The measured signal-to-noise, resolution, and spectral characteristics of the ERTS Flight A and Flight B three-camera systems are presented in conclusion.

Miller, B. P.↗
NASA NTRS1975

Flight qualification of mortar-actuated parachute deployment systems

A brief discussion outlines background of mortar use in parachute deployment systems. A description of the system operation is presented. Effects of the environment on performance are discussed as well as the instrumentation needed to assess this performance. Power unit qualification and lot qualification for shear pins and cartridges is delineated. Functional mortar system tests are described. Finally, bridle deployment and parachute deployment are discussed.

Pleasants, J. E.↗
NASA NTRS1977

The 40 KW of Solar Cell Modules for the Large Scale Production Task a Low Cost Silicon Solar Array Project

Forty kilowatts of solar cell modules was produced in this program. This is equivalent to 4123 modules. The average power output per module was 9.7 watts at 16.5 volts, 60 C and 100 mW/sq cm. The peak production rate was 200 modules per week which is equal to 1.9 kW per week. This rate was sustained for over four and one-half months and is equivalent to 100 kW per year. This final report covers the solar cell module design, electrical and power performance, module preproduction environmental test results, production and shipping schedule, program summary, and delivery. A cost analysis section is written. Particular emphasis on the percentage of labor and material utilized in constructing a solar cell module is presented. Also included are cost reduction recommendations.

Jones, G. T.↗
NASA NTRS1980

Study of research and development requirements of small gas-turbine combustors

A survey is presented of the major small-engine manufacturers and governmental users. A consensus was undertaken regarding small-combustor requirements. The results presented are based on an evaluation of the information obtained in the course of the study. The current status of small-combustor technology is reviewed. The principal problems lie in liner cooling, fuel injection, part-power performance, and ignition. Projections of future engine requirements and their effect on the combustor are discussed. The major changes anticipated are significant increases in operating pressure and temperature levels and greater capability of using heavier alternative fuels. All aspects of combustor design are affected, but the principal impact is on liner durability. An R&D plan which addresses the critical combustor needs is described. The plan consists of 15 recommended programs for achieving necessary advances in the areas of liner thermal design, primary-zone performance, fuel injection, dilution, analytical modeling, and alternative-fuel utilization.

Demetri, E. P.↗
NASA NTRS1980

Advanced thermoelectric material development at JPL

A large number of planetary missions under consideration for the next two decades will be using radioisotope thermoelectric generators to provide the necessary spacecraft electrical power. Performance, reliability, lifetime and cost of these RTGs are expected to be more demanding and will require the development of advanced thermoelectric materials. An advanced thermoelectric materials development program is being conducted by JPL and is the subject of this paper. Under this program, alloys of rare earth chalcogenides have been synthesized and their thermoelectric properties evaluated. The selection of specific compounds on which the program is currently concentrating is influenced by criteria such as low thermal conductivity, reasonably high operating temperatures (not less than 1000 C) and stability of the compounds. The paper discusses the rationale, approach and current status of the program. In addition, the thermoelectric and thermophysical property measurement used to evaluate the materials are described. The preliminary results and analysis of these experimental data are also given.

Stapfer, G.↗