Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “environmental testing”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Evaluation of outer race tilt and lubrication on ball wear and SSME bearing life reductions

Several aspects of the SSME bearing operation were evaluated. The possibility of elastohydrodynamics (EHD) lubrication with a cryogenic fluid was analyzed. Films as thick as .61 microns were predicted with one theory which may be thick enough to provide hydrodynamic support. The film formation, however, is heavily dependent on good surface finish and a low bulk bearing temperature. Bearing dynamics to determine if the radial stiffness of a bearing which are dependent on bearing misalignment were analyzed. Four ball tests were conducted at several environmental conditions from an LN2 bath to 426 C in air. Surface coatings and ball materials are evaluated. Severe wear and high friction are measured for all ball materials except when the balls have surface lubricant coatings.

Kannel, J. W.↗
NASA NTRS1984

Flat-plate solar array progress and plans

The results of research into the technology of flat-plate solar arrays undertaken in the Flat-Plate Solar Array Project under the sponsorship of the U.S. Department of Energy are surveyed. Topics examined include Si refinement, ribbon-sheet substrate formation, module process sequences, environmental isolation, module engineering and testing, and photovoltaic-array economics.

Callaghan, W. T.↗
NASA NTRS1986

List of Preferred Electronic Parts

Components passed stringent qualification tests tabulated and described. Destructive and nondestructive qualification testing confirmed parts capable of withstanding spacecraft environments without excessive degradation and have stable characteristics during operating lives. Testing assessed effects of electrical, environmental, and mechanical stresses in various levels and time durations.

Covey, R. E.↗
NASA NTRS1987

Operation of an experimental algal gas exchanger for use in a CELSS

Concepts of a Closed Ecological Life Support System (CELSS) anticipate the use of photosynthetic organisms (higher plants and algae) for air revitalization. The rates of production and uptake of carbon dioxide and oxygen between the crew and the photosynthetic organisms are mismatched. An algal system used for gas exchange only will have the difficulty of an accumulation or depletion of these gases beyond physiologically tolerable limits (in a closed system the mismatch between assimilatory quotient (AQ) and respiratory quotient (RQ) is balanced by the operation of the waste processor). The results are given of a study designed to test the feasibility of using environmental manipulations to maintain physiologically appropriate atmospheres for algae and mice in a gas closed system. Specifically, the atmosphere behavior of this system is considered with algae grown on nitrate or urea and at different light intensities and optical densities. Manipulation of both allow operation of the system in a gas stable manner. Operation of such a system in a CELSS may be useful for reduction of buffer sizes, as a backup system for higher plant air revitalization and to supply extra oxygen to the waste processor or during crew changes.

Smernoff, David T.↗
NASA NTRS1987

Operation of an experimental algal gas exchanger for use in a CELSS

Concepts of a CELSS anticipate the use of photosynthetic organisms for air revitalization. The rates of production and uptake of carbon dioxide and oxygen between the crew and the photosynthetic organisms are mismatched. An algal system used for gas exchange only will have the difficulty of an accumulation or depletion of these gases beyond physiologically tolerable limits. The results of a study designed to test the feasibility of using environmental manipulations to maintain physiologically appropriate atmospheres for algae (Chlorella pyrenoidosa) and mice (Mus musculus strain DW/J) in a gas-closed system is reported. Specifically, the atmosphere behavior of this system with Chlorella grown on nitrate or urea and at different light intensities and optical densities is considered. Manipulation of both the photosynthetic rate and the assimilatory quotient of the alga has been found to reduce the mismatch of gas requirements and allow operation of the system in a gas-stable manner.

Smernoff, David T.↗
NASA NTRS1989

First year's results and field experience with the latest JILA absolute gravimeter

One of the six absolute gravity instruments developed and built by the Joint Institute for Laboratory Astrophysics (JILA) between 1982 and 1985 was tested under a variety of environmental conditions between May 1987 and 1988. Of the 30 sites visited during this period, 10 were occupied more than once. These reobservations indicate repeatability between 1 and 4 microgals.

Peter, G.↗
NASA NTRS1990

An adaptive array antenna for mobile satellite communications

The design of an adaptive array antenna for land vehicle operation and its performance in an operational satellite system is described. Linear and circularly polarized antenna designs are presented. The acquisition and tracking operation of a satellite is described and the effect on the communications signal is discussed. A number of system requirements are examined that have a major impact on the antenna design. The results of environmental, power handling, and RFI testing are presented and potential problems are identified.

Milne, Robert↗
NASA NTRS1992

Material selection and evaluation aimed at resolving deficiencies of a space technology material

NASA-Kennedy Space Center propellant handlers' visors are undergoing conversion from Plexiglass G to a Surlyn 8920-based material; various Surlyn compositions are here subjected to a battery of environmental and mechanical-properties tests under the relevant conditions. Specially-molded Surlyn samples have exhibited much higher impact strengths than either Plexiglass G or Lexan, and passed the ANSI weight-drop test. DSC results show that Surlyn and Plexiglass G exhibit strikingly different thermal transitions.

Ray, Asit K.↗
NASA NTRS1991

Focused technology: Nuclear propulsion

The topics presented are covered in viewgraph form and include: nuclear thermal propulsion (NTP), which challenges (1) high temperature fuel and materials, (2) hot hydrogen environment, (3) test facilities, (4) safety, (5) environmental impact compliance, and (6) concept development, and nuclear electric propulsion (NEP), which challenges (1) long operational lifetime, (2) high temperature reactors, turbines, and radiators, (3) high fuel burn-up reactor fuels, and designs, (4) efficient, high temperature power conditioning, (5) high efficiency, and long life thrusters, (6) safety, (7) environmental impact compliance, and (8) concept development.

Miller, Thomas J.↗
NASA NTRS1994

Microphysical modeling of cirrus. 2: Sensitivity studies

The one-dimensional cirrus model described in part 1 of this issue has been used to study the sensitivity of simulated cirrus microphysical and radiative properties to poorly known model parameters, poorly understood physical processes, and environmental conditions. Model parameters and physical processes investigated include nucleation rate, mode of nucleation (e.g., homogeneous freezing of aerosols and liquid droplets or heterogeneous deposition), ice crystal shape, and coagulation. These studies suggest that the leading sources of uncertainty in the model are the phase change (liquid-solid) energy barrier and the ice-water surface energy which dominate the homogeneous freezing nucleation rate and the coagulation sticking efficiency at low temperatures which controls the production of large ice crystals (radii greater than 100 mcirons). Environmental conditions considered in sensitivity tests were CN size distribution, vertical wind speed, and cloud height. We found that (unlike stratus clouds) variations in the total number of condensation nuclei (NC) have little effect on cirrus microphysical and radiative properties, since nucleation occurs only on the largest CN at the tail of the size distribution. The total number of ice crystals which nucleate has little or no relationship to the number of CN present and depends primarily on the temperature and the cooling rate. Stronger updrafts (more rapid cooling) generate higher ice number densities, ice water content, cloud optical depth, and net radiative forcing. Increasing the height of the clouds in the model leads to an increase in ice number density, a decrease in effective radius, and a decrease in ice water content. The most prominent effect of increasing cloud height was a rapid increase in the net cloud radiative forcing which can be attributed to the change in cloud temperature as well as change in cloud ice size distributions. It has long been recognized that changes in cloud height or cloud area have the greatest potential for causing feedbacks on climate change. Our results suggest that variations in vertical velocity or cloud microphysical changes associatd with cloud height changes may also be important.

Jensen, Eric J.↗
NASA NTRS1995

STS-69 Flight Day 6 Highlights

After being awakened by the Beatles song, 'A Hard Days Night', the flightcrew of the STS-69 mission, Cmdr. Dave Walker, Pilot Ken Cockrell, and Mission Specialists Jim Voss, Jim Newman, and Mike Gernhardt, began their sixth day in orbit by monitoring the free orbiting Wake Shield Facility (WSF). Later Cmdr. Walker conducted an interview with television reporters from Atlanta and Boston, answering questions about the mission and general questions about NASA's space program. The crew filmed a video for themselves performing daily routines (eating, shaving, exercising), as well as some of the physiological experiments, and shuttle equipment maintenance and checkout. One of the secondary experiments included the Commercial Generic Bioprocessing Apparatus-7 (CGBA-7), which served as an incubator and experiment station for a variety of tests (agricultural, pharmaceutical, biomedical, and environmental). Earth views included some cloud cover, the Gulf of Mexico, Texas, and the Atlantic Ocean.

Source record↗
NASA NTRS1999

Tensile, Compression, Open-Hole Compression and Double Cantilever Beam Fracture Toughness Testing of Multiple NASA Langley Research Center Composite Materials

The attached data summarizes the work performed by the Composite Materials Research Group at the University of Wyoming funded by the NASA LaRC Research Grant NAG-1-1294. The work consisted primarily of tension, compression, open-hole compression and double cantilever beam fracture toughness testing performed an a variety of NASA LaRC composite materials. Tests were performed at various environmental conditions and pre-conditioning requirements. The primary purpose of this work was to support the LaRC material development efforts. The data summaries are arranged in chronological order from oldest to newest.

Adams, Donald F.↗
NASA NTRS2002

Radiation Hardness Assurance for Space Systems

The space radiation environment can lead to extremely harsh operating conditions for on-board electronic box and systems. The characteristics of the radiation environment are highly dependent on the type of mission (date, duration and orbit). Radiation accelerates the aging of the electronic parts and material and can lead to a degradation of electrical performance; it can also create transient phenomena on parts. Such damage at the part level can induce damage or functional failure at electronic box, subsystem, and system levels. A rigorous methodology is needed to ensure that the radiation environment does not compromise the functionality and performance of the electronics during the system life. This methodology is called hardness assurance. It consists of those activities undertaken to ensure that the electronic piece parts placed in the space system perform to their design specifications after exposure to the space environment. It deals with system requirements, environmental definitions, part selection, part testing, shielding and radiation tolerant design. All these elements should play together in order to produce a system tolerant to.the radiation environment. An overview of the different steps of a space system hardness assurance program is given in section 2. In order to define the mission radiation specifications and compare these requirements to radiation test data, a detailed knowledge of the space environment and the corresponding electronic device failure mechanisms is required. The presentation by J. Mazur deals with the Earth space radiation environment as well as the internal environment of a spacecraft. The presentation by J. Schwank deals with ionization effects, and the presentation by T. Weatherford deals with Single particle Event Phenomena (SEP) in semiconductor devices and microcircuits. These three presentations provide more detailed background to complement the sections 3 and 4. Part selection and categorization are discussed in section 5. Section 6 presents the organization of the hardness assurance within a project. Section 7 discusses emerging radiation hardness assurance issues.

Poivey, Christian↗
NASA NTRS1982

Atmosphere Analyzer

California Measurements, Inc.'s model PC-2 Aerosol Particle Analyzer is produced in both airborne and ground-use versions. Originating from NASA technology, it is a quick and accurate method of detecting minute amounts of mass loadings on a quartz crystal -- offers utility as highly sensitive detector of fine particles suspended in air. When combined with suitable air delivery system, it provides immediate information on the size distribution and mass concentrations of aerosols. William Chiang, obtained a NASA license for multiple crystal oscillator technology, and initially developed a particle analyzer for NASA use with Langley Research Center assistance. Later his company produced the modified PC-2 for commercial applications Brunswick Corporation uses the device for atmospheric research and in studies of smoke particles in Fires. PC-2 is used by pharmaceutical and chemical companies in research on inhalation toxicology and environmental health. Also useful in testing various filters for safety masks and nuclear installations.

Source record↗
NASA NTRS2002

Temperature Dependence on the Strength and Stress Rupture Behavior of a Carbon-Fiber Reinforced Silicon Carbide (C/SiC) Composite

Tensile strengths and stress rupture lives of carbon-fiber reinforced silicon carbide (C/SiC) specimens were measured at 800 C and are compared to previously reported 1200 C data. All tests were conducted in an environmental chamber containing 1000 ppm of oxygen in argon. The average 800 C tensile strength of 610 MPa is 10% greater than at 1200 C. Average stress rupture lives at 800 C were 2.5 times longer than those obtained at 1200 C. The difference in the 800 and 1200 C lives is related to the oxidation rate of the reinforcing carbon fibers, which is the primary damage mode of C/SiC composites in oxygen-containing environments.

Verrilli, Michael J.↗
NASA NTRS2004

Ocean Carbon Flux, Transport, and Burial Within the Western and Eastern US Coastal Zones

This project has been to develop and apply a regional. eddy-resolving circulation and biogeochemistry model of both the western and eastern U.S. coastal regions, capable of simulating the processes that control the carbon cycle. Validation has been by statistical comparison with analyses from various satellite measurements, including those from EOS sensors, as well as from in situ measurements. Sensitivity studies were carried out to investigate how the coastal ecosystem and biogeochemical cycles respond to changes in climate, large-scale eutrophication from indus- trial pollution, and other anthropogenic induced changes. The research has been conducted in collaboration with research groups at UCLA. NASA/GSFC (Wallops), Rutgers, and SIO. Overall. the project was focused on several key modeling issues, each of which tie back into completing the primary task of developing a coastal carbon model for both the eastern and western US. coasts. Individual groups within the entire program are still collaborating to address these specific tasks. These include: implementation of the coupled circulation/biogeochemical model within the U.S. West Coast. including high-resolution, embedded subdomains for the Southern California Bight and Monterey Bay region; development of a biogeochemical model with resolved carbon, nitrogen and oxygen cycles; development of data assimilation techniques for use of satellite data sets; reconfiguration of the model domain to U.S. East Coast; development of coastal forcing fields: development of methods to compare the model against remotely sensed data; and, the test of model sensitivity to environmental conditions. Below, we present a summary of the progress made toward achieving these soak. Because this has been a multi-institutional, collaborative effort, we note the groups involved with particular activities.

McWilliams, James C.↗
NASA NTRS1997

Ultrasonic Studies of Composites Undergoing Thermal and Fatigue Loading

New composite materials possess attractive properties for use in advanced aircraft. A necessary requirement for their introduction into aeronautic use is an accurate understanding of their long term aging processes so that proper design criteria can be established. In order to understand those properties, these composites must be exposed to thermal and load cycles that are characteristic of flight conditions. Additionally, airline companies will require nondestructive evaluation (NDE) methods that can be used in the field to assess the condition of these new materials as they age. As part of an effort to obtain the required information about new composites for aviation use, we are performing ultrasonic measurements both in the NDE laboratory and in the materials testing laboratory at NASA. The materials testing laboratory is equipped with environmental chambers mounted on load frames so that composite samples can be exposed to thermal and loading cycles representative of flight protocols. Applying both temperature and load simultaneously will help to highlight temperature and load interactions during the aging of these composite materials. This study reports on our initial ultrasonic attenuation results from thermoset and thermoplastic composite samples. Ultrasonic attenuation measurements have been used reliably to assess the effects of material degradation. For example, recently, researchers have shown that by using frequencies of ultrasound on the order of 24 MHz, they could obtain adequate contrast in the evaluation of thermal degradation in these composites. This paper will present data that shows results at a lower frequency range. In addition, we report results on the frequency dependence of attenuation as the slope of attenuation with respect to frequency, beta = delta alpha (f) / delta f. The slope of attenuation is an attractive parameter since it is quantitative, yet does not require interface corrections like conventional quantitative attenuation measurements. This is a consequence of the assumption that interface correction terms are frequently independent. Uncertainty in those corrections terms compromises the value of conventional quantitative attenuation data.

Madaras, Eric I.↗
NASA NTRS1985

Automated Portable Test (APT) System: overview and prospects

The Automated Portable Test (APT) System is a notebook-sized, computer-based, human-performance and subjective-status assessment system. It is now being used in a wide range of environmental studies (e.g., simulator aftereffects, flight tests, drug effects, and hypoxia). Three questionnaires and 15 performance tests have been implemented, and the adaptation of 30 more tests is underway or is planned. The APT System is easily transportable, is inexpensive, and has the breadth of expansion options required for field and laboratory applications. The APT System is a powerful and expandable tool for human assessment in remote and unusual environments.

Aerospace Medicine/instrumentation↗