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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Optical and other property changes of M-50 bearing steel surfaces for different lubricants and additive prior to scuffing

An ester lubricant base oil containing one or more standard additives to protect against wear, corrosion, and oxidation was used in an experimental ball/plate elastohydrodynamic contact under load and speed conditions such as to induce scuffing failure in short times. Both the ball and the plate were of identically treated M-50 steel. After various periods of operating time the wear track on the plate was examined with an interference microscope of plus or minus 30 A depth resolution and sometimes also with a scanning ellipsometer and an Auger spectrometer. The optically deduced surface profiles varied with wavelength, indicating the presence of surface coatings, which were confirmed by the other instruments. As scuffing was approached, a thin (approximately A) oxide layer and a carbide layer formed in the wear track in particular when tricresylphosphate antiwear additive was present in the lubricant. The rates of the formation of these layers and their reactivity toward dilute alcholic HCl depended strongly on the lubricant and additives. Based on these results suggestions for improved formulations and a test method for bearing reliability could be proposed.

Lauer, J. L.↗
NASA NTRS1985

Dendritic web-type solar cell mini-modules

Twenty-five minimodules composed of dendritic web solar cells with nominal glass size of 12 by 40 cm were provided for study. The modules were identical with respect to design, materials, and manufacturing and assembly processes to full scale modules. The modules were also electrically functional. These minimodules were fabricated to provide test vehicle for environmental testing and to assess reliability of process and design procedures. The module design and performance are outlined.

Campbell, R. B.↗
NASA NTRS1986

Optical and other properties changes of M-50 bearing steel surfaces for different lubricants and additives prior to scuffing

An ester lubricant base oil containing one or more standard additives to protect against wear, corrosion, and oxidation was used in an experimental ball/plate elastohydrodynamic contact under load and speed conditions such as to induce scuffing failure in short times. Both the ball and the plate were of identically treated M-50 steel. After various periods of operating time the wear track on the plate was examined with an interference microscope of plus or minus 30 A depth resolution and sometimes also with a scanning ellipsometer and an Auger spectrometer. The optically deduced surface profiles varied with wavelength, indicating the presence of surface coatings, which were confirmed by the other instruments. As scuffing was approached, a thin (approximately A) oxide layer and a carbide layer formed in the wear track in particular when tricresylphosphate antiwear additive was present in the lubricant. The rates of the formation of these layers and their reactivity toward dilute alcoholic HCl depended strongly on the lubricant and additives. Based on these results suggestions for improved formulations and a test method for bearing reliability could be proposed.

Lauer, J. L.↗
NASA NTRS1986

Block 2 SRM conceptual design studies. Volume 1, Book 2: Preliminary development and verification plan

Activities that will be conducted in support of the development and verification of the Block 2 Solid Rocket Motor (SRM) are described. Development includes design, fabrication, processing, and testing activities in which the results are fed back into the project. Verification includes analytical and test activities which demonstrate SRM component/subassembly/assembly capability to perform its intended function. The management organization responsible for formulating and implementing the verification program is introduced. It also identifies the controls which will monitor and track the verification program. Integral with the design and certification of the SRM are other pieces of equipment used in transportation, handling, and testing which influence the reliability and maintainability of the SRM configuration. The certification of this equipment is also discussed.

Source record↗
NASA NTRS1987

Verification of flexible structures by ground test

The validation of math models of large space structures (LSS) by ground tests is attempted. Concepts for two types of LSS are presented: continuous type and linked subsystems. It was concluded that ground test which simulate space conditions are not entirely reliable, that there should be an integration of testing and analyses, which then should be validated with laboratory and flight experiments.

Wada, Ben K.↗
NASA NTRS1988

Lewis Structures Technology, 1988. Volume 1: Structural Dynamics

The specific purpose of the symposium was to familiarize the engineering structures community with the depth and range of research performed by the Structures Division of the Lewis Research Center and its academic and industrial partners. Sessions covered vibration control, fracture mechanics, ceramic component reliability, parallel computing, nondestructive testing, dynamical systems, fatigue and damage, wind turbines, hot section technology, structural mechanics codes, computational methods for dynamics, structural optimization, and applications of structural dynamics.

Source record↗
NASA NTRS1989

Measuring Mechanical Properties Of Optical Glasses

Report discusses mechanical tests measuring parameters of strength and fracture mechanics of optical glasses. To obtain required tables of mechanical properties of each glass of interest, both initial-strength and delayed-fracture techniques used. Modulus of rupture measured by well-known four-point bending method. Initial bending strength measured by lesser-known double-ring method, in which disk of glass supported on one face near edge by larger ring and pressed on its other face by smaller concentric ring. Method maximizes stress near center, making it more likely specimen fractures there, and thereby suppresses edge effects. Data from tests used to predict reliabilities and lifetimes of glass optical components of several proposed spaceborne instruments.

Tucker, Dennis S.↗
NASA NTRS1988

The effect of simulated weightlessness on performance and mood

The performance results of the bedrest study at Ames were not what were expected. The Air Combat Maneuvering performance test was tested to assure its reliability. However, the results from this study show a continued increase in performance. One would assume that scores would become constant if not decrease by the first days of bedrest because an inverted position would affect performance. It is also interesting to observe that while the subject's moods deteriorated, their performance improved. Although the performance results were surprising, the mood results were as expected.

Rosenberg, Bonnie↗
NASA NTRS1989

Environmental testing of a diode-laser-pumped Nd:YAG laser and a set of diode-laser-arrays

Results of the environmental test of a compact, rigid and lightweight diode-laser-pumped Nd:YAG laser module are discussed. All optical elements are bonded onto the module using space applicable epoxy, and two 200 mW diode laser arrays for pump sources are used to achieve 126 mW of CW output with about 7 percent electrical-to-optical conversion efficiency. This laser assembly and a set of 20 semiconductor diode laser arrays were environmentally tested by being subjected to vibrational and thermal conditions similar to those experienced during launch of the Space Shuttle, and both performed well. Nevertheless, some damage to the laser front facet in diode lasers was observed. Significant degradation was observed only on lasers which performed poorly in the life test. Improvements in the reliability of the Nd:YAG laser are suggested.

Hemmati, H.↗
NASA NTRS1991

The transition of ground-based space environmental effects testing to the space environment

The goal of the space flight program at the Center for Commercial Development of Space (CCDS)--Materials for Space Structures is to provide environmentally stable structural materials to support the continued humanization and commercialization of the space frontier. Information on environmental stability will be obtained through space exposure, evaluation, documentation, and subsequent return to the supplier of the candidate material for internal investigation. This program provides engineering and scientific service to space systems development firms and also exposes CCDS development candidate materials to space environments representative of in-flight conditions. The maintenance of a technological edge in space for NASA suggests the immediate search for space materials that maintain their structural integrity and remain environmentally stable. The materials being considered for long-lived space structures are complex, high strength/weight ratio composites. In order for these new candidate materials to qualify for use in space structures, they must undergo strenuous testing to determine their reliability and stability when subjected to the space environment. Ultraviolet radiation, atomic oxygen, debris/micrometeoroids, charged particles radiation, and thermal fatigue all influence the design of space structural materials. The investigation of these environmental interactions is the key purpose of this center. Some of the topics discussed with respect to the above information include: the Space Transportation System, mission planning, spaceborne experiments, and space flight payloads.

Zaat, Stephen V.↗
NASA NTRS1989

NASA-LaRc Flight-Critical Digital Systems Technology Workshop

The outcome is documented of a Flight-Critical Digital Systems Technology Workshop held at NASA-Langley December 13 to 15 1988. The purpose of the workshop was to elicit the aerospace industry's view of the issues which must be addressed for the practical realization of flight-critical digital systems. The workshop was divided into three parts: an overview session; three half-day meetings of seven working groups addressing aeronautical and space requirements, system design for validation, failure modes, system modeling, reliable software, and flight test; and a half-day summary of the research issues presented by the working group chairmen. Issues that generated the most consensus across the workshop were: (1) the lack of effective design and validation methods with support tools to enable engineering of highly-integrated, flight-critical digital systems, and (2) the lack of high quality laboratory and field data on system failures especially due to electromagnetic environment (EME).

Meissner, C. W., Jr.↗
NASA NTRS1990

Electronic assembly thermal testing - Dwell/duration/cycling

Testing of electronic assemblies varies throughout industry, NASA, and the military. Differences include test levels, atmospheric versus vacuum testing of assemblies, dwell durations at temperature extremes (especially high temperature), and thermal cycling versus dwell testing. Of particular interest are the different philosophies of thermal cycling versus single-cycle thermal dwell. An examination of the various failure physics for electronic assemblies has been initiated at JPL. The intent is to determine which failure modes are best revealed by thermal cycling testing and which are susceptible to high-temperature dwell physics. Preliminary results of this study are presented, along with discussions of testing goals, flight environments, reliability models, and the differences between industry and JPL design/test approaches.

Gibbel, Mark↗
NASA NTRS1991

Alkali metal propellants for MPD thrusters

Experiments performed in the United States in the 1960s and early 1970s and in the Soviet Union with alkali metal-fuelled MPD thrusters indicate performance levels substantially better than those achieved with gaseous propellants. Cathode wear appears to be less in engines with alkali metal propellants also. A critical review of the available data indicates that the data are consistent and reliable. An analysis of testing and systems-level considerations shows that pumping requirements for testing are substantially decreased and reductions in tankage fraction can be expected. In addition, while care must be exercised in handling the alkali metals, it is not prohibitively difficult or hazardous. The greatest disadvantage seems to be the potential for spacecraft contamination, but there appear to be viable strategies for minimizing the impact of propellant deposition on spacecraft surfaces. Renewed examination of alkali metal-fuelled MPD thrusters for ambitious SEI missions is recommended.

Polk, J. E.↗
NASA NTRS1992

Acoustic emission monitoring of low velocity impact damage in graphite/epoxy laminates during tensile loading

An acoustic emission (AE) system was set up in a linear location data acquisition mode to monitor the tensile loading of eight-ply quasi-isotropic graphite/epoxy specimens containing low velocity impact damage. The impact damage was induced using an instrumented drop weight tower. During impact, specimens were supported by either an aluminum plate or a membrane configuration. Cross-sectional examinations revealed that the aluminum plate configuration resulted in primarily matrix cracking and back surface fiber failure. The membrane support resulted in only matrix cracking and delamination damage. Penetrant enhanced radiography and immersion ultrasonics were used in order to assess the amount of impact damage in each tensile specimen. During tensile loading, AE reliably detected and located the damage sites which included fiber failure. All specimens with areas of fiber breakage ultimately failed at the impact site. AE did not reliably locate damage which consisted of only delaminations and matrix cracking. Specimens with this type of damage did not ultimately fail at the impact site. In summary, AE demonstrated the ability to increase the reliability of structural proof tests; however, the successful use of this technique requires extensive baseline testing.

Parker, Bradford H.↗
NASA NTRS1992

Study report recommendations for the next generation Range Safety System (RSS) Integrated Receiver/Decoder (IRD)

The Integrated Receiver/Decoder (IRD) currently used on the Space Shuttle was designed in the 1980 and prior time frame. Over the past 12 years, several parts have become obsolete or difficult to obtain. As directed by the Marshall Space Flight Center, a primary objective is to investigate updating the IRD design using the latest technology subsystems. To take advantage of experience with the current designs, an analysis of failures and a review of discrepancy reports, material review board actions, scrap, etc. are given. A recommended new design designated as the Advanced Receiver/Decoder (ARD) is presented. This design uses the latest technology components to simplify circuits, improve performance, reduce size and cost, and improve reliability. A self-test command is recommended that can improve and simplify operational procedures. Here, the new design is contrasted with the old. Possible simplification of the total Range Safety System is discussed, as is a single-step crypto technique that can improve and simplify operational procedures.

Crosby, Robert H.↗
NASA NTRS1928

Welding in airplane construction

The present article attempts to explain the principles for the production of a perfect weld and to throw light on the unexplained problems. Moreover, it is intended to elucidate the possibilities of testing the strength and reliability of welded parts.

WELDING↗
NASA NTRS1993

The Large Area Pulsed Solar Simulator (LAPSS)

A Large Area Pulsed Solar Simulator (LAPSS) has been installed at JPL. It is primarily intended to be used to illuminate and measure the electrical performance of photovoltaic devices. The simulator, originally manufactured by Spectrolab, Sylmar, California, occupies an area measuring about 3 meters wide by 12 meters long. The data acquisition and data processing subsystems have been modernized. Tests on the LAPSS performance resulted in better than +/- 2 percent uniformity of irradiance at the test plane and better than +/- 0.3 percent measurement repeatability after warm-up. Glass absorption filters are used to reduce the level of ultraviolet light emitted from the xenon flash lamps. This provides a close match to standard airmass zero and airmass 1.5 spectral irradiance distributions. The 2 millisecond light pulse prevents heating of the device under test, resulting in more reliable temperature measurements. Overall, excellent electrical performance measurements have been made of many different types and sizes of photovoltaic devices.

Mueller, R. L.↗
NASA NTRS1995

Fuel cell systems for First Lunar Outpost-reactant storage option

The office of Space, DOE, appointed a Lunar Surface Power Working Group to review candidate systems for the First Lunar Outpost habitat. The working group met for a total of five days in the fall of 1992 and concluded that the candidate involving a photovoltaic unit, a fuel cell, a regenerator to recycle the reactants, and storage of oxygen and hydrogen gases was the most attractive for this application. Most of the volume (97 percent) and weight (63 percent) are taken up by the reactants and their storage tanks. Therefore, in my work for the Group, and in this report, I have concentrated on finding ways to reduce these volumes and weights. Three options were considered: (1) the baseline case considered in the preliminary system design, that of separate high pressure (200 bar) storage tanks; (2) the use of two of the descent storage propellant tanks wrapped with graphite fibers to increase the pressure capability; and (3) the use of cryogenic storage of reactants in the propellant tanks. The first option results in high storage tank mass and volume. The second option saves 90 percent of the volume by making use of the propellant tanks, but it has little if any weight advantages; the weight saved by not providing extra tanks for reactant storage is nearly entirely added back by the weight of the additional material (graphite fibers) to strengthen the propellant tanks. Use of the descent storage propellant tanks for storage of the fuel cell reactants as cryogenic liquids requires a gas liquefaction system. The weight of this system is expected to be less than that of the storage tanks but it would require development and testing to prove its reliability. The solar array would have to be 40 percent larger and the heat projection range would be 170 percent larger than for storage of reactants as high pressure gases. For a high power system (greater than 20 kW) the larger energy storage requirement would probably favor the cryogenic storage option.

Nelson, P. A.↗