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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

A Balanced Model for Exploration of the Terrestrial Planets: Lessons from the Lunar Experience

The Moon is the only extraterrestrial rocky body for which we have a combination of surface-selected samples, high-resolution orbital photography (Lunar Orbiter), manned and robotic surface exploration (Surveyor, Apollo, Luna), and global compositional, mineralogical, and geophysical data (Galileo, Clementine, Lunar Prospector). Beginning in 1998, CAPTEM organized a series of workshops and conference sessions aimed at integrating these diverse data sets. The insights gained by bringing together scientists from the remote-sensing and sample-analysis communities have been singularly rewarding. Not least of these has been the recognition by both groups that having both kinds of data maximizes the scientific return and permits reconciling information from diverse scales and perspectives. The 20-20 hindsight of the Lunar experience thus provides important lessons; learning from mistakes as well as successes, we can derive a sensible scientific program for Mars exploration. In this abstract, we describe examples of key information from (a) in-situ geologic investigation, (b) laboratory analysis of returned samples whose geologic context and location are known, and (c) global remote sensing of mineralogy, composition, and geophysical parameters. We then show the value of integrating these diverse data sets.

Jolliff, B. L.↗
NASA NTRS2010

Use of Modal Acoustic Emission to Monitor Damage Progression in Carbon Fiber/Epoxy Tows and Implications for Composite Structures

ASTM-based ILH methods were found to give a reproducible, quantitative estimate of the stress threshold at which significant accumulated damage began to occur. a) FR events are low energy (<2 V(exp 20 microsec) b) FR events occur close to the observed failure locus. c) FR events consist of more than 30% fiber breakage (>300 kHz) d) FR events show a consistent hierarchy of cooperative damage for composite tow, and for the COPV tested, regardless of applied load. Application of ILH or related stress profiles could lead to robust pass/fail acceptance criteria based on the FR. Initial application of FR and FFT analysis of AE data acquired on COPVs is promising.

Waller, Jess M.↗
NASA NTRS1998

Microstructural, Chemical and Mechanical Characterization of Polymer-Derived Hi-Nicalon Fibers with Surface Coatings

Room temperature tensile strengths of as-received Hi-Nicalon fibers and those having BN/SiC, p-BN/SiC, and p-B(Si)N/SiC surface coatings, deposited by chemical vapor deposition, were measured using an average fiber diameter of 13.5 microns. The Weibull statistical parameters were determined for each fiber. The average tensile strength of uncoated Hi-Nicalon on was 3.19 +/- 0.73 GPa with a Weibull modulus of 5.41. Strength of fibers coated with BN/SiC did not change. However, coat with p-BN/SiC and p-B(Si)N/SiC surface layers showed strength loss of approx. 10 and 35 percent, respectively, compared with as-received fibers. The elemental compositions of the fibers and the coatings were analyzed using scanning Auger microprobe and energy dispersive x-ray spectroscopy. The BN coating was contaminated with a large concentration of carbon and some oxygen. In contrast, p-BN, p-B(Si)N, and SiC coatings did not show any contamination. Microstructural analyses of the fibers and the coatings were done by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction. Hi-Nicalon fiber consists of the P-SIC nanocrystals ranging in size from 1 to 30 nm embedded in an amorphous matrix. TEM analysis of the BN coating revealed four distinct layers with turbostatic structure. The p-BN layer was turbostratic and showed considerable preferred orientation. The p-B(Si)N was glassy and the silicon and boron were uniformly distributed. The silicon carbide coating was polycrystalline with a columnar structure along the growth direction. The p-B(Si)N/SiC coatings were more uniform, less defective and of better quality than the BN/SiC or the p-BN/SiC coatings.

Bansal, Narottam P.↗
NASA NTRS1973

Flight-service evaluation of composite structural components

A review of programs aimed at flight-service evaluation of composite materials in various applications is presented. These flight-service programs are expected to continue for up to 5 years and include selective reinforcement of an airplane center wing box a helicopter tail cone, and composite replacements for commercial aircraft spoilers and fairings. These longtime flight-service programs will help provide the necessary information required by commercial airlines to commit advanced composites to aircraft structures with confidence. Results of these programs will provide information concerning the stability of composite materials when subjected to various flight environments.

Dexter, H. B.↗
NASA NTRS1972

Structure of lunar glasses by Raman and soft X-ray spectroscopy.

X-ray spectra and Raman spectra have been measured from individual particles of lunar glasses. Each particle was analyzed separately by electron microprobe. Silicon emission shifts vary between parent rock types and can be interpreted as a range of Si-O distances from 1.612 to 1.637 A. Aluminum emission shifts relate to the amount of 4- and 6-coordinated Al in the glass. Raman spectra show broadened bands. Certain bands recur in many specimens and relate to the main normative minerals for the glass bulk composition, olivine, pyroxene, and anorthite.

Fabel, G. W.↗
NASA NTRS1976

Age-color relationships in the lunar highlands

The depth of the absorption feature near 1 micron in the reflectance spectra of immature lunar soils is determined primarily by the amount of pyroxene present in the soil. As a soil matures, the agglutinitic glass content increases and the Fe(2+) glass band dominates the absorption feature. An empirical relationship between the 1 micron band depth and the percentage of magnetic agglutinates, and hence maturity, is demonstrated for mature highland soils of a given composition. A similar variation of 1 micron band depth is observed in the telescopic spectra of lunar highland craters and is positively correlated with the surface maturity as determined by the small-impact erosion model of Soderblom (1970). Knowledge of both maturity and the 1 micron band depth of a lunar surface feature allows compositional information to be derived.

Charette, M. P.↗
NASA NTRS1977

Satellite spectrophotometry and surface compositions

A summary of available spectrophotometric data for planetary satellites is presented. Most data given is for the 0.3 to about 3 micron spectral region. The spectrophotometric results are compared with spectral reflectivity curves of cosmologically abundant substances to provide information on the possible composition of surfaces of planetary satellites, excluding earth's moon. Water ice and other frosts appear to be common in the outer solar system; however, most surface compositions cannot be unambiguously defined.

Johnson, T. V.↗