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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 1,315 records · Page 73

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NASA NTRS1980

Scientific objectives of the Solar Mesosphere Explorer mission

The paper describes the NASA Solar Mesosphere Explorer mission which will study mesospheric ozone and the processes which form and destroy it, measure the ozone density and its altitude distribution from 30 to 80 km, monitor incoming solar UV radiation, and provide a rigorous test of the photochemical equilibrium theory of the mesospheric oxygen-hydrogen system. Five instruments will be carried on the polar-orbiting spacecraft: UV ozone, IR airglow, and visible NO2 programmable Ebert-Fastie spectrometers, a four-channel IR radiometer, and a solar UV spectrometer. Atmospheric measurements will be made of the mesospheric and stratospheric ozone density distribution, water vapor density distribution, temperature profile, ozone photolysis rate, and NO2 density distribution. In addition, the solar UV monitor will measure both the 0.2-0.31 micron spectral region and the Lyman-alpha (0.1216 micron) contribution to the solar irradiance.

Thomas, G. E.↗

NASA NTRS1983

Development of a new integral solar cell protective cover

A unique polyimide polymer has been developed which shows promise as an encapsulant for interconnected solar cell modules. Such an integral cover offers important weight and cost advantages. The polymer has been characterized on silicon solar cells with respect to electrical output and spectral response. The response of the material-coated cells to electron, low-energy proton, and vacuum-ultraviolet radiation, thermal shock and humidity tests was determined.

Naselow, A. B.↗

NASA NTRS1987

Electromagnetic emission experiences using electric propulsion systems: A survey

As electric propulsion systems become ready to integrate with spacecraft systems, the impact of propulsion system radiated emissions are of significant interest. Radiated emissions from electromagnetic, electrostatic, and electrothermal systems have been characterized and results synopsized from the literature describing 21 space flight programs. Electromagnetic radiated emission results from ground tests and flight experiences are presented with particular attention paid to the performance of spacecraft subsystems and payloads during thruster operations. The impacts to transmission of radio frequency signals through plasma plumes are also reviewed.

Sovey, James S.↗

NASA NTRS1987

Electromagnetic emission experiences using electric propulsion systems - A survey

Sovey, James S.↗

NASA NTRS1987

Nuclear techniques in studies of condensed matter

Nuclear techniques have played an important role in the studies of materials over the past several decades. For example, X-ray diffraction, neutron diffraction, neutron activation, and particle- or photon-induced X-ray emission techniques have been used extensively for the elucidation of structural and compositional details of materials. Several new techniques have been developed recently. Four such techniques are briefly reviewed which have great potential in the study and development of new materials. Of these four, Mossbauer spectroscopy, muon spin rotation, and positron annihilation spectroscopy techniques exploit their great sensitivity to the local atomic environments in the test materials. Interest in synchrotron radiation, on the other hand, stems from its special properties, such as high intensity, high degree of polarization, and high monochromaticity. It is hoped that this brief review will stimulate interest in the exploitation of these newer techniques for the development of improved materials.

Singh, Jag J.↗

NASA NTRS1989

Liquid droplet generation

A pre-prototype segment of a droplet sheet generator for a liquid droplet radiator was designed, constructed and tested. The ability to achieve a uniform, non-diverging droplet sheet is limited by manufacturing tolerances on nozzle parallelism. For an array of 100, 100 micrometer diameters nozzles spaced 5 stream diameters apart, typical standard deviations in stream alignment were plus or minus 10 mrad. The drop to drop fractional speed variations of the drops in typical streams were similar and independent of position in the array. The absolute value of the speed dispersion depended on the amplitude of the disturbance applied to the stream. A second generation preliminary design of a 5200 stream segment of a droplet sheet generator was completed. The design is based on information developed during testing of the pre-prototype segment, along with the results of an acoustical analysis for the stagnation cavity pressure fluctuations used to break-up the streams into droplets.

Muntz, E. P.↗

NASA NTRS1988

Long-life/durable radiator coatings for Space Station

The anodic coatings developed by anodizing specific aluminum alloys show considerable promise as long-life/durable radiator coatings. These coatings, formed by the sulfuric acid anodizing process, were the best performers of a variety of candidate coatings subjected to ultraviolet radiation and temperature-cycling tests.

Jacobs, Steve↗

NASA NTRS1989

Solid propellant combustion response to oscillatory radiant heat flux

A progress report is given on a research project to use the microwave Doppler velocimeter technique to measure the combustion response to an oscillating thermal radiation source (CO2 laser). The test technique and supporting analyses are described, and the results are presented for an initial test series on the nonmetallized, composite propellant, Naval Weapons Center formulation A-13. It is concluded that in-depth transmission of radiant heat flux is not a factor at the CO2 laser wave length.

Strand, L. D.↗

NASA NTRS1989

The effect of electrode configuration on arcjet performance

A radiation cooled, segmented anode was tested in a low power (1 kW class) arcjet thruster in order to study the current distribution in the attachment region of the nozzle of the thruster. The nozzle was composed of five segments insulated from one another with boron nitride spacers and matched the critical dimensions of nozzles commonly used in previous testing. The anode was configured so that the current could be collected across any combination of the segments and the potential difference between the cathode and each of the segments was monitored during testing.

Curran, Frank M.↗

NASA NTRS1990

High Altitude Ozone Research Balloon

In order to create a mission model of the high altitude ozone research balloon (HAORB) several options for flight preparation, altitude control, flight termination, and payload recovery were considered. After the optimal launch date and location for two separate HAORB flights were calculated, a method for reducing the heat transfer from solar and infrared radiation was designed and analytically tested. This provided the most important advantage of the HAORB over conventional balloons, i.e., its improved flight duration. Comparisons of different parachute configurations were made, and a design best suited for the HAORB's needs was determined to provide for payload recovery after flight termination. In an effort to avoid possible payload damage, a landing system was also developed.

Cauthen, Timothy A.↗

NASA NTRS1990

X-ray thin foil filters at cryogenic temperatures

The X-Ray Spectrometer (XRS), which is being developed for one of the focal plane instruments of the Advanced X-Ray Astrophysics Facility, requires filters with high X-ray transmittance, high background rejection, and operation at cryogenic temperatures. Thin foil filters can provide high X-ray transmittance and the required rejection for low-energy radiation. The results of the test program demonstrate that these filters are fully successful at cryogenic temperatures and, therefore, can provide blocking filters for the XRS with the required performance.

Keski-Kuha, Ritva A. M.↗

NASA NTRS1990

Heat transfer in a compact tubular heat exchanger with helium gas at 3.5 MPa

A compact heat exchanger was constructed consisting of circular tubes in parallel brazed to a grooved base plate. This tube specimen heat exchanger was tested in an apparatus which radiatively heated the specimen on one side at a heat flux of up to 54 W/sq cm, and cooled the specimen with helium gas at 3.5 MPa and Reynolds numbers of 3000 to 35,000. The measured friction factor of the tube specimen was lower than that of a circular tube with fully developed turbulent flow, although the uncertainty was high due to entrance and exit losses. The measured Nusselt number, when modified to account for differences in fluid properties between the wall and the cooling fluid, agreed with past correlations for fully developed turbulent flow in circular tubes.

Olson, Douglas A.↗

NASA NTRS1991

From orbital debris capture systems through internal combustion engines on Mars

The investigation and conceptualization of an orbital debris collector was the primary area of design. In addition, an alternate structural design for Space Station Freedom and systems supporting resource utilization at Mars and the moon were studied. Hardware for production of oxygen from simulate Mars atmosphere was modified to permit more reliable operation at low pressures (down to 10 mb). An internal combustion engine was altered to study how Mars atmosphere could be used as a diluent to control combustion temperatures and avoid excess Mars propellant production requirements that would result from either methane-rich or oxygen-rich, methane-oxygen combustion. An elastic loop traction system that could be used for lunar construction vehicles was refined to permit testing. A parabolic heat rejection radiator system was designed and built to determine whether it was capable of increasing heat rejection rates during lunar daytime operation. In addition, an alternate space station truss design, utilizing a pre-integrated concept, was studied and found to reduce estimate extravehicular activity (EVA) time and increase the structural integrity when compared to the original Warren truss concept. An orbital-debris-capturing spacecraft design which could be mated with the Orbital Maneuvering Vehicle was studied. The design identified Soviet C-1B boosters as the best targets of opportunity in Earth orbits between an altitude of 900 km and 1100 km and at an inclination of 82.9 deg. A dual robot pallet, which could be spun to match the tumbling rate of the C-1B booster, was developed as the conceptual design.

Source record↗

NASA NTRS1993

Collapse and fragmentation of molecular cloud cores. I - Moderately centrally condensed cores

3D calculations of the collapse of moderately centrally condensed molecular cloud cores with varied thermal and rotational energies are presented. The calculations are carried out using a newly developed and tested second-order accurate radiative hydrodynamics code. Because of the use of a second-order accurate numerical scheme and initial clouds that resemble both observed prolate molecular cloud cores and magnetically supported clouds at the initiation of the dynamic collapse phase, the new models provide a superior estimate of the likelihood of fragmentation as a mechanism for binary star formation.

Boss, Alan P.↗

NASA NTRS1994

Analysis of space environment damage to solar cell assemblies from LDEF experiment A0171-GSFC test plate

The results of the postflight analysis of the solar cell assemblies from the LDEF (Long Duration Exposure facility) experiment A0171 is provided in this NASA sponsored research project. The following data on this research are provided as follows: (1) solar cell description, including, substrate composition and thickness, crystal orientation, anti-reflective coating composition and thickness; (2) preflight characteristics of the solar cell assemblies with respect to current and voltage; and (3) post-flight characteristics of the solar cell assemblies with respect to voltage and current. These solar cell assemblies are part of the Goddard Space Flight Center test plate which was designed to test the space environment effects (radiation, atomic oxygen, thermal cycling, meteoroid and debris) on conductively coated solar cell coversheets, various electrical bond materials, solar cell performance, and other material properties where feasible.

Hill, David C.↗

NASA NTRS1995

Photo-recovery of electron-irradiated GaAs solar cells

The first long-term (3000 hours) UV testing of unirradiated and 1 MeV electron-irradiated GaAs solar cells, with multilayer-coated coverslides to reduce solar array operating temperature, has produced some unexpected and important results. Two results, independent of the coverslide coatings, are of particular importance in terms of the predictability of GaAs solar-array lifetime in space: ( 1) The GaAs/Ge solar cells used for this series of tests displayed a much higher radiation degradation than that predicted based on JPL Solar Cell Radiation Handbook data. Covered cells degraded more in Isc than did bare cells. Short-term illumination at 60 C did not produce significant recovery (-1%) of the radiation damage. (2) However, electron radiation damage to these GaAs solar celIs anneals at 40 C when exposed to approximately 1 sun AM0 UV light sources for extended periods. The effect appears to be roughly linear with time (-1% of lsc per 1000 UVSH), is large (greater than or equal to 3%), and has not yet saturated (at 3000 hours). This photo-recovery of radiation damage to GaAs solar cells is a new effect and potentially important to the spacecraft community. The figure compares the effects of extended UV on irradiated and unirradiated GaAs solar cells with INTELSAT-6 Si cells. The effect and its generality, the extent of and conditions for photo-recovery, and the implications of such recovery for missions in radiation environments have not yet been determined.

Meulenberg, Andrew↗

NASA NTRS1996

Analytic Methods for Predicting Significant Multi-Quanta Effects in Collisional Molecular Energy Transfer

Collision-induced transitions can significantly affect molecular vibrational-rotational populations and energy transfer in atmospheres and gaseous systems. This, in turn. can strongly influence convective heat transfer through dissociation and recombination of diatomics. and radiative heat transfer due to strong vibrational coupling. It is necessary to know state-to-state rates to predict engine performance and aerothermodynamic behavior of hypersonic flows, to analyze diagnostic radiative data obtained from experimental test facilities, and to design heat shields and other thermal protective systems. Furthermore, transfer rates between vibrational and translational modes can strongly influence energy flow in various 'disturbed' environments, particularly where the vibrational and translational temperatures are not equilibrated.

Bieniek, Ronald J.↗

NASA NTRS1999

Testing of the Engineering Model Electrical Power Control Unit for the Fluids and Combustion Facility

The John H. Glenn Research Center at Lewis Field (GRC) in Cleveland, OH and the Sundstrand Corporation in Rockford, IL have designed and developed an Engineering Model (EM) Electrical Power Control Unit (EPCU) for the Fluids Combustion Facility, (FCF) experiments to be flown on the International Space Station (ISS). The EPCU will be used as the power interface to the ISS power distribution system for the FCF's space experiments'test and telemetry hardware. Furthermore. it is proposed to be the common power interface for all experiments. The EPCU is a three kilowatt 12OVdc-to-28Vdc converter utilizing three independent Power Converter Units (PCUs), each rated at 1kWe (36Adc @ 28Vdc) which are paralleled and synchronized. Each converter may be fed from one of two ISS power channels. The 28Vdc loads are connected to the EPCU output via 48 solid-state and current-limiting switches, rated at 4Adc each. These switches may be paralleled to supply any given load up to the 108Adc normal operational limit of the paralleled converters. The EPCU was designed in this manner to maximize allocated-power utilization. to shed loads autonomously, to provide fault tolerance. and to provide a flexible power converter and control module to meet various ISS load demands. Tests of the EPCU in the Power Systems Facility testbed at GRC reveal that the overall converted-power efficiency, is approximately 89% with a nominal-input voltage of 12OVdc and a total load in the range of 4O% to 110% rated 28Vdc load. (The PCUs alone have an efficiency of approximately 94.5%). Furthermore, the EM unit passed all flight-qualification level (and beyond) vibration tests, passed ISS EMI (conducted, radiated. and susceptibility) requirements. successfully operated for extended periods in a thermal/vacuum chamber, was integrated with a proto-flight experiment and passed all stability and functional requirements.

Kimnach, Greg L.↗