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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 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Development of a reaction wheel attitude control system for sounding rocket experiments and small Shuttle-based free flyers

A three-axis reaction wheel control system is currently under development. Initial emphasis is on a magnetic field reference, although the system is easily adaptable to other positional references, e.g., the gyroscopic. The system is housed in a skin section 17.25 inches in diameter and approximately 10 inches long. Current weight estimate is 75 pounds. An orthogonal triad of dc motors forms the basis of the system. Power is provided by silver-zinc cells and controlled by an 8-bit microprocessor. The control law is presented and the dynamical equations derived. Simulation results show that a payload with a roll MOI of 4.1 sl/sq ft and a transverse MOI of 20.3 sl/sq ft can typically be reoriented 90 degrees in 20-35 seconds, depending upon the initial body rates.

Ward, P. R.↗
NASA NTRS1986

High-efficiency GaAs solar concentrator cells for space and terrestrial applications

High-efficiency Al(x)Ga(1-x)As/GaAs heteroface solar concentrator cells have been developed for both space and terrestrial applications. The cells, which were grown using metalorganic chemical vapor deposition, have been fabricated in both the p-n and n-p configurations. Magnesium and zinc are used as p-type dopants, and Se is used as the n-type dopant. The space cells, which are designed for use in a Cassegrainian concentrator operating at 100 suns, AMO, have a circular illuminated area 4 mm in diameter on a 5 mm x 5 mm cell. These cells have exhibited flash-tested efficiencies as high as 23.6 percent at 28 C and 21.6 percent at 80 C. The terrestrial cells have a circular illuminated area 0.2 inches in diameter and are intended for use in a module which operates at 940 suns, AM1.5. These cells have shown a peak efficiency of 26 percent at 753 suns and over 25 percent at greater than 1000 suns.

Hamaker, H. C.↗
NASA NTRS1986

Infrared technology and applications; Proceedings of the Meeting, Cannes, France, November 26-29, 1985

The present conference on state-of-the-art IR systems and components technologies and their applications encompasses developments in IR systems design, production technologies, IR component testing, IR systems evaluations, laboratory and industrial applications, and aerospace ranging sensor and surveillance sensor applications. Attention is given to IR zoom lens telescopes, large zinc sulphide windows for airborne applications, thermal imaging system evaluation, minimum resolvable temperature difference measurement methods, industrial use of IR spectroscopy, platinum silicide sensor imagery, and recent developments in laser rangefinders.

Baker, Lionel R.↗
NASA NTRS1987

Use of gamma ray radiation to parallel the plates of a Fabry-Perot interferometer

The use of gamma radiation to parallel the plates of a Fabry-Perot etalon is examined. The method for determining the etalon parallelism, and the procedure for irradiating the posts are described. Changes in effective gap for the etalon over the surface are utilized to measure the parallelism of the Fabry-Perot etalon. An example in which this technique is applied to an etalon of fused silica plates, which are 132 mm in diameter and coded with zinc sulfide and cryolite, with Zerodur spaces 2 cm in length. The effect of the irradiation of the posts on the thermal performance of the etalon is investigated.

Skinner, Wilbert R.↗
NASA NTRS1987

Intrusions in the active layer of channeled-substrate-planar laser diodes

Channeled-substrate-planar laser diodes from various wafers were observed to develop a node or dark spot in their near-field patterns after failure during lifetesting. 'Node' devices from each wafer were angle-lapped and stained in an attempt to uncover a physical mechanism for this common failure symptom. Optical microscopic examination of the beveled cross sections revealed that an intrusion, in the form of a spike at the tip of the zinc diffusion front, had penetrated into the active layer of these diodes. The node observed in the near-field pattern appears to be in a position correspondig to the location of the spike in the active region. In addition, cathodoluminescence measurements on other 'node' diodes revealed a dark line region approximately 2-micron-wide running parallel to and in the middle of the 5-micron contact stripe. It is believed that this dark line region is representative of an area of nonradiative recombination which occurs in the portion of the active layer containing the intrusion.

Slavin, S. E.↗
NASA NTRS1987

The 250AH/90A active lithium-thionyl chloride cell for Centaur-G application

A high rate active Li/SOCl2 cell was designed for use in a 28 volt, 250 amp-hour space battery system. The lithium battery is being considered as a replacement of its heavier silver-zinc counterpart on board the Centaur-G booster rocket which is used to launch payloads from the Space Shuttle cargo bay into deep-space. Basically a feasibility study, this development effort is demonstrating the ability of the lithium cell to deliver up to 90 amps safely at power densities of approximately 25 watts per pound. Test data on 4 prototype units is showing an energy density of 85 watt-hours per pound and 9.0 watt-hours/cu in. The cells tested typically delivered 280 to 300 amp-hours under ambient temperature test conditions using alternating continuous loads of 90, 55, and 20 amperes throughout life. Data from four cells tested are presented to demonstrate the capability of Li/SOCl2 technology for a C/3 discharge rate in active and hermetic cell units.

Zolla, A. E.↗
NASA NTRS1987

Grace DAKASEP alkaline battery separator

The Grace DAKASEP separator was originally developed as a wicking layer for nickel-zinc alkaline batteries. The DAKASEP is a filled non-woven separator which is flexible and heat sealable. Through modification of formulation and processing variables, products with a variety of properties can be produced. Variations of DAKASEP were tested in Ni-H2, Ni-Zn, Ni-Cd, and primary alkaline batteries with good results. The properties of DAKASEP which are optimized for Hg-Zn primary batteries are shown in tabular form. This separator has high tensile strength, 12 micron average pore size, relatively low porosity at 46-48 percent, and consequently moderately high resistivity. Versions were produced with greater than 70 percent porosity and resistivities in 33 wt percent KOH as low as 3 ohm cm. Performance data for Hg-Zn E-1 size cells containing DAKASEP with the properties shown in tabular form, are more reproducible than data obtained with a competitive polypropylene non-woven separator. In addition, utilization of active material is in general considerably improved.

Giovannoni, R. T.↗
NASA NTRS1987

Ohmic contact formation in semi-insulating GaAs using shallow heavily doped p-type layers

The paper describes a simple, safe, and effective method for forming shallow zinc-doped p-type layers on chromium-doped semiinsulating GaAs, using an open-tube diffusion technique. The resulting peak dopant concentration for the 850-C diffusion was 10 to the 20th/cu cm. The contact resistance of ohmic contacts fabricated on these layers was found to be about 0.00005 ohm/sq cm. The variation of the contact resistance across the wafer reflected the variation of the doping concentration.

Bose, Amitava↗
NASA NTRS1988

An overview of cosmic ray research - Composition, acceleration and propagation

An overview of cosmic ray (CR) research and its relationship to other areas of high-energy astrophysics is presented. Research being conducted on the composition of cosmic rays (CRs) is examined, including the study of the solar system 'template' for CRs, CR abundances at earth, solar energetic particles, the CR elements beyond zinc, and the study of electrons, positrons, antinuclei, and of isotopic composition of CRs. Research on the CR energy spectrum and anisotropy is briefly reviewed. The study of acceleration processes, particle confinement, and propagation of CRs is addressed. Finally, the investigation of source abundances in CRs is discussed.

Wefel, John P.↗
NASA NTRS1988

Technologies for protection of the Space Station power system surfaces in atomic oxygen environment

Technologies for protecting Space Station surfaces from degradation caused by atomic oxygen are discussed, stressing protection of the power system surfaces. The Space Station power system is described and research concerning the solar array surfaces and radiator surfaces is examined. The possibility of coating the solar array sufaces with a sputter deposited thin film of silicon oxide containing small concentrations of polytetrafluoroethylene is presented. Hexamethyldisiloxane coating for these surfaces is also considered. For the radiator surfaces, possible coatings include silver teflon thermal coating and zinc orthotitanate.

Nahra, Henry K.↗
NASA NTRS1989

Making Durable Specimens For Electron Microscopy

Consistent metal-oxide cross sections prepared quickly. New process makes TEM/STEM cross sections of metal/oxide interfaces. After specimen bars oxidized, placed in specially designed mold. Following encapsulation in zinc alloy, 3-mm-diameter specimen bar sliced into disks suitable for further preparation steps. Technique used to prepare 3-mm-diameter specimens of cross sections of oxides of alloys intended for use at temperatures greater than approximately 600 degree C.

Doychak, Joseph↗
NASA NTRS1988

Acceleration ground test program to verify GAS payload No. 559 structure/support avionics and experiment structural integrity

Acceleration ground tests were conducted on the Get Away Special (GAS) payload 559 to verify the structural integrity of the structure/support avionics and two of the planned three flight experiments. The ITA (Integrated Test Area) Standardized Experiment Module (ISEM) structure was modified to accommodate the experiments for payload 559. The ISEM avionics consisted of a heavy duty sliver zinc power supply, three orthogonal-mounted low range microgravity accelerometers, a tri-axis high range accelerometer, a solid state recorder/programmer sequencer, and pressure and temperature sensors. The tests were conducted using the Gravitational Plant Physiology Laboratory Centrifuge of the University City Science Center in Philadelphia, PA. The launch-powered flight steady state acceleration profile of the shuttle was simulated from lift-off through jettison of the External Tank (3.0 g's). Additional tests were conducted at twice the nominal powered flight acceleration levels (6 g's) and an over-test condition of four times the powered flight loads to 12.6 g's. The present test program has demonstrated the value of conducting ground tests to verify GAS payload experiment integrity and operation before flying on the shuttle.

Cassanto, John M.↗
NASA NTRS1988

An electrochemical study of corrosion protection by primer-topcoat systems on 4130 steel with ac impedance and dc methods

To investigate metal surface corrosion and the breakdown of metal protective coatings, the ac impedance method is applied to six systems of primer coated and primer topcoated 4130 steel. Two primers were used: a zinc-rich epoxy primer and a red lead oxide epoxy primer. The epoxy-polyamine topcoat was used in four of the systems. The EG and G-PARC Model 368 ac impedance measurement system, along with dc measurements with the same system using the polarization resistance method, were used to monitor changing properties of coated 4230 steel disks immersed in 3.5 percent NaCl solutions buffered at pH 5.4 over periods of 40 to 60 days. The corrosion system can be represented by an electronic analog called an equivalent circuit consisting of resistors and capacitors in specific arrangements. This equivalent circuit parallels the impedance behavior of the corrosion system during a frequency scan. Values for the resistors and capacitors, that can be assigned in the equivalent circuit following a least-squares analysis of the data, describe changes that occur on the corroding metal surface and in the protective coatings. Two equivalent circuits have been determined that predict the correct Bode phase and magnitude of the experimental sample at different immersion times. The dc corrosion current density data are related to equivalent circuit element parameters. Methods for determining corrosion rate with ac impedance parameters are verified by the dc method.

Mendrek, M. J.↗
NASA NTRS1988

Pb-Zn liquid metal diffusion

The Lead-Zinc binary equilibrium system is currently being investigated. Ground based studies of this system were performed to examine the possibility of obtaining a couple which, after diffusion, could be examined continuously along the diffusion axis by quantitative metallography to determine the extent of diffusion. The specimens were analyzed by X-ray fluorescence in the scanning electron microscope to provide exact information on the chemical composition gradient. Two diffusion experiments were run simultaneously in the multipurpose furnace, each in its own isothermal cavity. Two flight samples, two flight backup samples, and two flight space samples were generated.

Pond, R. B., Sr.↗
NASA NTRS1989

Advances in lightweight nickel electrode technology

Studies are currently underway to further the development of lightweight nickel electrode technology. Work is focused primarily on the space nickel-hydrogen system and nickel-iron system but is also applicable to the nickel-cadmium and nickel-zinc systems. The goal is to reduce electrode weight while maintaining or improving performance thereby increasing electrode energy density. Two basic electrode structures are being investigated. The first is the traditional nickel sponge produced from sintered nickel-carbonyl powder and the second is a new material for this application which consists of a non-woven mat of nickel fiber. Electrodes are being manufactured, tested and evaluated at the electrode and cell level.

Coates, Dwaine↗
NASA NTRS1987

Development of a unique laboratory standard: Indium gallium arsenide detector for the 500-1700 nm spectral region

A planar (5 mm diameter) indium gallium arsenide detector having a high (greater than 50 pct) quantum efficiency from the visible into the infrared spectrum (500 to 1700 nm) was fabricated. Quantum efficiencies as high as 37 pct at 510 nm, 58 pct at 820 nm and 62 pct at 1300 nm and 1550 nm were measured. A planar InP/InGaAs detector structure was also fabricated using vapor phase epitaxy to grow device structures with 0, 0.2, 0.4 and 0.6 micrometer thick InP caps. Quantum efficiency was studied as a function of cap thickness. Conventional detector structures were also used by completely etching off the InP cap after zinc diffusion. Calibrated quantum efficiencies were measured. Best results were obtained with devices whose caps were completely removed by etching. Certain problems still remain with these detectors including non-uniform shunt resistance, reproducibility, contact resistance and narrow band anti-reflection coatings.

Source record↗
NASA NTRS1988

Raman determination of layer stresses and strains for heterostructures and its application to the cubic SiC/Si system

A set of formulas for a generalized axial stress in diamond and zinc-blende semiconductors under axial stress is derived to calculate stress-related Raman shifts. By analyzing known Raman data on cubic SiC under hydrostatic pressures, one of the Raman-stress coefficients was obtained, and the existing elastic stiffness constants of cubic SiC were optimized. A method for calculating the stress and strain in SiC films on (100) Si is proposed. It is suggested that the stress and strain expressions and the method of the stress and strain determinations in heterostructures are quite general and may be used for other systems.

Feng, Z. C.↗
NASA NTRS1988

Development of lithium-thionyl chloride batteries for Centaur

Lithium thionyl chloride (LiSOCl2) primary cells and batteries have received considerable attention over the last several years because of their high theoretical specific energy and energy density. The objective was to develop a 300 wh/kg cell capable of safe operation at C/2 rate and active storage life for 5 to 10 years. This technology would replace other primary cell technologies in NASA applications mainly the silver zinc (AgZn) batteries presently in use. The LiSOCl2 system exceeds the capabilities of the AgZn in terms of specific energy of 300 wh/kg (compared with 100 wh/kg for AgZn), active storage life of 10 to 20 times the 3 to 6 months active storage and has a significantly lower projected cost.

Halpert, Gerald↗