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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Characterization of polymer decomposition products by laser desorption mass spectrometry

Laser desorption mass spectrometry has been used to characterize the ash-like substances formed on the surfaces of polymer matrix composites (PMC's) during exposure on LDEF. In an effort to minimize fragmentation, material was removed from the sample surfaces by laser desorption and desorbed neutrals were ionized by electron impact. Ions were detected in a time-of-flight mass analyzer which allows the entire mass spectrum to be collected for each laser shot. The method is ideal for these studies because only a small amount of ash is available for analysis. Three sets of samples were studied including C/polysulfone, C/polyimide and C/phenolic. Each set contains leading and trailing edge LDEF samples and their respective controls. In each case, the mass spectrum of the ash shows a number of high mass peaks which can be assigned to fragments of the associated polymer. These high mass peaks are not observed in the spectra of the control samples. In general, the results indicate that the ash is formed from decomposition of the polymer matrix.

Pallix, Joan B.↗
NASA NTRS1974

Stability regions for quasiperiodic motion in the restricted problem of three bodies

Surfaces of section, plotted in configuration space, have been computed for the motion of the massless particle in the restricted problem of three bodies. Nine mass ratios and a wide variety of Jacobi constants were investigated; over four thousand orbits were computed, about half of which were finally used. The plots of surface of section have been reduced to plots of stability regions, following a method due to Henon (1965a, 1965b, 1966b, 1969). Sample surfaces of section are also given. The complete set of 276 surfaces of section has been published as a report (Jefferys, 1971) and is available upon request from the author.

Jefferys, W. H.↗
NASA NTRS1974

Nondestructive activation analysis of sample of lunar surface material returned by Luna 16 automatic station

The composition of a sample of lunar surface material returned by the Luna 16 automatic station from the Sea of Fertility was studied, using nondestructive activation analysis. The structure of the returned surface material is inhomogeneous; the surficial material is thin, quite homogeneous, and the granularity increases with depth. Based on grain size, the sample was separated into five zones. The activation analysis was conducted on a sample taken from the friable surficial layer, zone A. The content of Al, Mn, Na, Cr, Co, Fe, and Sc was determined by nondestructive activation analysis of the sample. In determining Cr, Co, Fe, and Sc, the sample was irradiated for 24 hours and cooled for 10 days. Gamma spectra of the samples were recorded with a semiconductor Ge(Li)-detector and a multichannel analyzer, and measurement data were processed with an electronic computer.

Chayko, M.↗
NASA NTRS1990

International cooperation for Mars exploration and sample return

The National Research Council's Space Studies Board has previously recommended that the next major phase of Mars exploration for the United States involve detailed in situ investigations of the surface of Mars and the return to earth for laboratory analysis of selected Martian surface samples. More recently, the European space science community has expressed general interest in the concept of cooperative Mars exploration and sample return. The USSR has now announced plans for a program of Mars exploration incorporating international cooperation. If the opportunity becomes available to participate in Mars exploration, interest is likely to emerge on the part of a number of other countries, such as Japan and Canada. The Space Studies Board's Committee on Cooperative Mars Exploration and Sample Return was asked by the National Aeronautics and Space Administration (NASA) to examine and report on the question of how Mars sample return missions might best be structured for effective implementation by NASA along with international partners. The committee examined alternatives ranging from scientific missions in which the United States would take a substantial lead, with international participation playing only an ancillary role, to missions in which international cooperation would be a basic part of the approach, with the international partners taking on comparably large mission responsibilities. On the basis of scientific strategies developed earlier by the Space Studies Board, the committee considered the scientific and technical basis of such collaboration and the most mutually beneficial arrangements for constructing successful cooperative missions, particularly with the USSR.

Levy, Eugene H.↗
NASA NTRS1972

Examination of the Surveyor 3 surface sampler scoop

The operation and external appearance of the surface sampling scoop are discussed. An attempt was made to measure the magnitude of the existing adhesion between the lunar soil and the various surfaces of the scoop.

Scott, R. F.↗
NASA NTRS1993

Physical properties of glasses exposed to Earth-facing and trailing-side environments on LDEF

The exposure of 108 glass samples and 12 glass-ceramic samples to Earth-orbit environments permitted measurements which establish the effects of each environment. Examination of five glass types and one glass ceramic located on both the Earth-facing side and the trailing edge revealed no reduction in strength within experimental limits. Strength measurements subjected less than 5 percent of the sample surface area to stresses above 90 percent of the glass's failure strength. Seven micrometeorite or space debris impacts occurred on trailing edge samples. One of those impacts occurred in a location which was subjected to 50 percent of the applied stress at failure. Micrometeorite or space debris impacts were not observed on Earth-facing samples. The physical shape and structure of the impact sites were carefully examined using stereographic scanning electron microscopy. These impacts induce a stress concentration at the damaged region which influences mechanical strength. The flaw size produced by such damage was examined to determine the magnitude of strength degradation in micrometeorite or space-debris impacted glasses. Scanning electron microscopy revealed topographical details of impact sites which included central melt zones and glass fiber production. The overall crater structure is similar to much larger impacts of large meteorite on the Moon in that the melt crater is surrounded by shocked regions of material which fracture zones and spall areas. Residual stresses arising from shock compression and cooling of the fused zone cannot currently be included in fracture mechanics analyses based on simple flaw size examination.

Wiedlocher, David E.↗
NASA NTRS2018

Remote Recession Measurements of Wire-Seeded PICA Samples in an Arc-Jet Flow

Various methods for remote recession sensing of PICA have been developed and several seeding methods have been tested. The most recent method involved seeding the ablator with wires fed to the sample from the backside with a defined amount of PICA left towards the upstream front of the sample. This seed method mimics the installation of in-depth thermocouples as they are frequently used in ground testing and flight. Arc-jet tests were conducted in the NASA Langley HYMETS facility at a heat flux of 320 W/sq.cm. The emission of the post-shock layer was observed in spectral resolution from the side along an optical axis perpendicular to the arc-jet flow and from the front, looking at the sample surface from an upstream position. Various metallic seed materials with different melting points were used. In addition to the emission spectroscopy measurements, the samples were monitored during the tests through pyrometry and videography. The time resolved response of the seeded material is described and compared to earlier tests with different seeding methods. The combination of seed materials was found to be critical for the selection of emission signatures characteristic for the material recession which can be isolated in the final emission spectra.

Winter, Michael↗
NASA NTRS1976

Real Time Dust Fall Monitor (RTDFM)

A prototype ultraviolet optical instrument designed and developed to monitor 300 level surface cleanliness is described. Size, weight, sensitivity, and simplicity design parameters were satisfied. Tests were conducted with various configurations of the detector array and sample surfaces. Circuit schematics are included. It is shown that output drift is due to effective lamp intensity variations. The instrument is intended to be a part of the integrated environmental contamination monitor of the space shuttle.

Claysmith, C. R.↗
NASA NTRS2005

Effects of Bedrock Landsliding on Cosmogenically Determined Erosion Rates

The successful quantification of long-term erosion rates underpins our understanding of landscape. formation, the topographic evolution of mountain ranges, and the mass balance within active orogens. The measurement of in situ-produced cosmogenic radionuclides (CRNs) in fluvial and alluvial sediments is perhaps the method with the greatest ability to provide such long-term erosion rates. In active orogens, however, deep-seated bedrock landsliding is an important erosional process, the effect of which on CRN-derived erosion rates is largely unquantified. We present a numerical simulation of cosmogenic nuclide production and distribution in landslide-dominated catchments to address the effect of bedrock landsliding on cosmogenic erosion rates in actively eroding landscapes. Results of the simulation indicate that the temporal stability of erosion rates determined from CRN concentrations in sediment decreases with increased ratios of landsliding to sediment detachment rates within a given catchment area, and that larger catchment areas must be sampled with increased frequency of landsliding in order to accurately evaluate long-term erosion rates. In addition, results of this simulation suggest that sediment sampling for CRNs is the appropriate method for determining long-term erosion rates in regions dominated by mass-wasting processes, while bedrock surface sampling for CRNs is generally an ineffective means of determining long-term erosion rates. Response times of CRN concentrations to changes in erosion rate indicate that climatically driven cycles of erosion may be detected relatively quickly after such changes occur, but that complete equilibration of CRN concentrations to new erosional conditions may take tens of thousands of years. Simulation results of CRN erosion rates are compared with a new, rich dataset of CRN concentrations from the Nepalese Himalaya, supporting conclusions drawn from the simulation.

Niemi, Nathan↗
NASA NTRS2015

Buoyant Effects on the Flammability of Silicone Samples Planned for the Spacecraft Fire Experiment (Saffire)

Flammability experiments on silicone samples were conducted in anticipation of the Spacecraft Fire Experiment (Saffire). The sample geometry was chosen to match the NASA 6001 Test 1 specification, namely 5 cm wide by 30 cm tall. Four thicknesses of silicone (0.25, 0.36, 0.61 and 1.00 mm) were examined. Tests included traditional upward buoyant flame spread using Test 1 procedures, downward opposed flow flame spread, horizontal and angled flame spread, forced flow upward and downward flame spread. In addition to these configurations, upward and downward tests were also conducted in a chamber with varying oxygen concentrations. In the upward buoyant flame spread tests, the flame generally did not burn the entire sample. As thickness was increased, the flame spread distance decreased before flame extinguishment. For the thickest sample, ignition could not be achieved. In the downward tests, the two thinnest samples permitted the flame to burn the entire sample, but the spread rate was lower compared to the corresponding upward values. The other two thicknesses could not be ignited in the downward configuration. The increased flammability for downward spreading flames relative to upward ones is uncommon. The two thinnest samples also burned completely in the horizontal configuration, as well as at angles up to 75 degrees from the horizontal. The upward and downward flammability behavior was compared in atmospheres of varying oxygen concentration to determine a maximum oxygen concentration for each configuration. Upward tests in air with an added forced flow were more flammable. Complementary analyses using SEM and TGA techniques suggest the importance of the silica layer formed on the burned sample surface. As silicone burns upward, silica deposits downstream •If the silicone is ignited in the downward configuration, it burns the entire length of the sample •Burning upward at an angle increases the burn length in some cases possibly due to less silica deposition •Forced flow in the upward burning case increases flammability, likely due to an increase in convective flow preventing silica from depositing •Samples in upward configuration burning under forced flow self extinguish after forced flow is removed

Flammability↗
NASA NTRS2017

OSIRIS-REx Asterod Sample Return Mission

OSIRIS-REx is NASA's third New Frontiers Program mission, following New Horizons that completed a flyby of Pluto in 2015 and the Juno mission to Jupiter that has just begun science operations. The OSIRIS-REx mission's primary objective is to collect pristine surface samples of a carbonaceous asteroid and return to Earth for analysis. Carbonaceous asteroids and comets are 'primitive' bodies that preserved remnants of the Solar System starting materials and through their study scientists can learn about the origin and the earliest evolution of the Solar System. The OSIRIS-REx spacecraft was successfully launched on September 8, 2016, beginning its seven year journey to asteroid 101955 Bennu. The robotic arm will collect 60-2000 grams of material from the surface of Bennu and will return to Earth in 2023 for worldwide distribution by the Astromaterials Curation Facility at NASA Johnson Space Center. The name OSIRIS-REx embodies the mission objectives (1) Origins: Return and analyze a sample of a carbonaceous asteroid, (2) Spectral Interpretation: Provide ground-truth for remote observation of asteroids, (3) Resource Identification: Determine the mineral and chemical makeup of a near-Earth asteroid (4) Security: Measure the non-gravitational that changes asteroidal orbits and (5) Regolith Explorer: Determine the properties of the material covering an asteroid surface. Asteroid Bennu may preserve remnants of stardust, interstellar materials and the first solids to form in the Solar System and the molecular precursors to the origin of life and the Earth's oceans. Bennu is a potentially hazardous asteroid, with an approximately 1 in 2700 chance of impacting the Earth late in the 22nd century. OSIRIS-REx collects from Bennu will help formulate the types of operations and identify mission activities that astronauts will perform during their expeditions. Such information is crucial in preparing for humanity's next steps beyond low Earthy orbit and on to deep space destinations.

Nakamura-Messinger, Keiki↗
NASA NTRS1992

Mechanical properties of glasses impacted by debris or micrometeorites

Mechanical strength measurements on five glasses and one glass ceramic exposed on the Long Duration Exposure Facility (LDEF) have revealed no damage exceeding experimental limits of error after exposure. The measurement technique subjected less than 5 percent of the sample surface area to stresses above 90 percent of the failure strength. Seven micrometeorite or space debris impacts occurred at locations which were not in that portion of the sample subjected to greater than 90 percent of the applied stress. In consequence of this, the impact events on the sample were not detected in mechanical strength measurements. The physical form and structure of the impact sites was carefully examined to determine the influence of those events upon stress concentration associated with the impact and the resulting mechanical strength influence. The size of the impact site insofar as it determines flaw size for fracture purposes was examined. Surface topography of the impacts reveals that six of the seven sites display impact melting. The classical melt crater structure is surrounded by a zone of fractured glass. Residual stresses arising from shock compression and from cooling of the impact fused zone cannot be included in fracture mechanics analyses based on simple flaw size analyses. Strategies for refining estimates of mechanical strength degradation by impact events are presented.

Kinser, Donald L.↗
NASA NTRS1993

Cratering in glasses impacted by debris or micrometeorites

Mechanical strength measurements on five glasses and one glass-ceramic exposed on LDEF revealed no damage exceeding experimental limits of error. The measurement technique subjected less than 5 percent of the sample surface area to stresses above 90 percent of the failure strength. Seven micrometeorite or space debris impacts occurred at locations which were not in that portion of the sample subjected to greater than 90 percent of the applied stress. As a result of this, the impact events on the sample were not detected in the mechanical strength measurements. The physical form and structure of the impact sites was carefully examined to determine the influence of those events upon stress concentration associated with the impact and the resulting mechanical strength. The size of the impact site, insofar as it determines flaw size for fracture purposes, was examined. Surface topography of the impacts reveals that six of the seven sites display impact melting. The classical melt crater structure is surrounded by a zone of fractured glass. Residual stresses arising from shock compression and from cooling of the fused zone cannot be included in the fracture mechanics analyses based on simple flaw size measurements. Strategies for refining estimates of mechanical strength degradation by impact events are presented.

Wiedlocher, David E.↗
NASA NTRS1992

OSEE responses on D6AC steel due to sample preparation

A cleaning procedure and a contamination method developed at NASA Langley to contaminate sample surfaces with a certain thickness of HD-2 grease are demonstrated. Varying levels of contamination are obtained. Optically stimulated electron emission (OSEE) measurements were performed using the parallel electric field cell and the Pat scan device for clean and contaminated samples with a known amount of common contaminant. The OSEE response is found to be more sensitive for the clean sample than for the contaminated one. It is concluded that the OSEE measurements obtained using these techniques are sensitive to surface conditions and the contaminant thickness variations. It is also shown that the wavelength of illuminating light can have a profound effect on OSEE current levels.

Abedin, M. N.↗
NASA NTRS2011

Post-Flight Microbial Analysis of Samples from the International Space Station Water Recovery System and Oxygen Generation System

The Regenerative, Environmental Control and Life Support System (ECLSS) on the International Space Station (ISS) includes the the Water Recovery System (WRS) and the Oxygen Generation System (OGS). The WRS consists of a Urine Processor Assembly (UPA) and Water Processor Assembly (WPA). This report describes microbial characterization of wastewater and surface samples collected from the WRS and OGS subsystems, returned to KSC, JSC, and MSFC on consecutive shuttle flights (STS-129 and STS-130) in 2009-10. STS-129 returned two filters that contained fluid samples from the WPA Waste Tank Orbital Recovery Unit (ORU), one from the waste tank and the other from the ISS humidity condensate. Direct count by microscopic enumeration revealed 8.38 x 104 cells per mL in the humidity condensate sample, but none of those cells were recoverable on solid agar media. In contrast, 3.32 x lOs cells per mL were measured from a surface swab of the WRS waste tank, including viable bacteria and fungi recovered after S12 days of incubation on solid agar media. Based on rDNA sequencing and phenotypic characterization, a fungus recovered from the filter was determined to be Lecythophora mutabilis. The bacterial isolate was identified by rDNA sequence data to be Methylobacterium radiotolerans. Additional UPA subsystem samples were returned on STS-130 for analysis. Both liquid and solid samples were collected from the Russian urine container (EDV), Distillation Assembly (DA) and Recycle Filter Tank Assembly (RFTA) for post-flight analysis. The bacterium Pseudomonas aeruginosa and fungus Chaetomium brasiliense were isolated from the EDV samples. No viable bacteria or fungi were recovered from RFTA brine samples (N= 6), but multiple samples (N = 11) from the DA and RFTA were found to contain fungal and bacterial cells. Many recovered cells have been identified to genus by rDNA sequencing and carbon source utilization profiling (BiOLOG Gen III). The presence of viable bacteria and fungi from WRS and OGS subsystems demonstrates the need for continued monitoring of ECLSS during future ISS operations and investigation of advanced antimicrobial controls.

Birmele, Michele N.↗
NASA NTRS1979

Determination of secondary electron emission characteristics of lunar soil samples

A procedure is described for the determination of the 'apparent crossover voltage', i.e. the value of the primary (bombarding) electron energy at which an insulating sample surface changes the average sign of its charge. This apparent crossover point is characteristic of the secondary emission properties of insulating powders such as the lunar soil samples. Lunar core samples from well-defined, distinct soil layers are found to differ significantly in their secondary emission properties. This observation supports the suggestion that soil layers were deposited by an electrostatic transport process.

Gold, T.↗
NASA NTRS1980

Reactivity of stratospheric aerosols to small amounts of ammonia in the laboratory environment

Trace ammonia in laboratory air reacts easily with sulfuric acid aerosol samples to form crystalline ammonium sulfate. Argon atmospheres, however, protect sampling surfaces from ammonia contamination. It is found that atmospheric aerosols treated in this way contain only sulfuric acid. After an hour exposed to laboratory air, these same samples convert to ammonium sulfate. Aerosol particles have been collected, using argon control, to determine if the absence of crystalline sulfate is common. But so far there is no evidence that aerosols are neutralized by ammonia in the stratosphere.

Hayes, D.↗
NASA NTRS1983

Current collection from the space plasma through defects in high voltage solar array insulation

For spacecraft operation in the near Earth environment, solar cell arrays constitute the major source of reliable long term power. Optimization of mass and power efficiency results in a general requirement for high voltage solar arrays. The space plasma environment, though, can result in large currents being collected by exposed solar cells. The solution of a protective covering of transparent insulation is not a complete solution, inasmuch as defects in the insulation result in anomalously large currents being collected through the defects. Tests simulating the electron collection from small defects in an insulation have shown that there are two major collection modes. The first mode involves current enhancement by means of a surface phenomenon involving the surrounding insulator. In the second mode the current collection is enhanced by vaporization and ionization of the insulators materials, in addition to the surface enhancement of the first mode. A model for the electron collection is the surface enhanced collection mode was developed. The model relates the secondary electron emission yield to the electron collection. It correctly predicts the qualitative effects of hole size, sample temperature and roughening of sample surface. The theory was also shown to predict electron collection within a factor of two for the polymers teflon and polyimide.

Stillwell, R. P.↗