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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 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

ERTS-1 imagery as an aid to the definition of the geotectonic domains of the southern African crystalline shield

Portions of two geotectonic environments in South Africa have been studied on ERTS-1 imagery. It was found that the broad synoptic view provided by this imagery is ideally suited to a study of the diagnostic macro-structures, and that the different geotectonic styles are clearly recorded. ERTS-1 imagery thus allows a more accurate definition than exists at present of the contact zones and internal structures of the two domains. The importance of this investigation as an aid to gaining on insight into the relevance of plate tectonics in Precambrian times is briefly discussed.

Viljoen, M. J.↗
NASA NTRS1973

Modified fused silicide coatings for tantalum (Ta-10W) reentry heat shields

Results are presented of a program of research to develop a reliable, high performance, fused slurry silicide coating for the Ta-10W alloy. The effort was directed toward developing new and improved formulations for use at 2600 to 2800 F (1700 to 1811 K) in an atmospheric reentry thermal protection system with a 100-mission capability. Based on a thorough characterization of isothermal and cyclic oxidation behavior, bend transition temperatures, room- and elevated-temperature tensile properties, and creep behavior, a 2.5 Mn-33Ti-64.5Si coating (designated MTS) provides excellent protection for the Ta-10W alloy in simulated reentry environments. An extensive analysis of the oxidation behavior and characteristics of the MTS coating in terms of fundamental mechanisms also is presented.

Packer, C. M.↗
NASA NTRS1973

Low-cost fabrication and installation of ablative heat shields for the space shuttle orbiter.

Description of the formulation and evaluation of low-density elastomeric ablative compounds and low-cost techniques for fabricating and installing ablative panels being considered for the Space Shuttle orbiter's thermal protection system. Sixteen large panels, both flat and contoured, were successfully fabricated and time-studied to develop and refine tooling and manufacturing methods and to establish a realistic baseline for estimating costs. Six of the panels were bonded to a DC-3 airframe. The work included a detailed estimate of fabrication and installation costs.

Norwood, L. B.↗
NASA NTRS1973

Thermal shielding by subliming volume reflectors in convective and intense radiative environments.

The behavior of dielectric materials having densely packed internal scattering centers subject to extreme convective and radiative environments is analyzed. Experiments have shown that these materials act as volume reflectors of incident radiation even when the exposed surface is being eroded by thermochemical ablation. The analysis was applied to interpret experiments of subliming Teflon models exposed to combined radiative and convective fluxes up to 1.7 kW/sq cm for several seconds. Results show that, although the exposed surface receded at an apparently steady rate, the internal temperature climbed continually, due to internal absorption of radiation and would have caused failure internally if the test duration were extended a few seconds. Thus, performance is time-limited by the internal absorption coefficient. Results were obtained for larger configurations and other materials. Typically, Teflon shells may withstand radiant fluxes up to 20 kW/sq cm for about 5 sec and fritted quartz up to 50 kW/sq cm for about 8 sec (corresponding to the Jupiter entry).

Howe, J. T.↗
NASA NTRS1974

Volume-reflecting dielectric heat shield

White, volume-reflecting dielectric material absorbs essentially none of the incident radiant energy, and continues to reflect even though in severe environment its surface is melted and is being vaporized. Process of overall reflectance in dielectric material, involving internal refractions and reflections, is similar to process of reflection in paints.

Nachtsheim, P. R.↗
NASA NTRS1973

Space vehicle engine and heat shield environment review. Volume 1: Engineering analysis

Methods for predicting the base heating characteristics of a multiple rocket engine installation are discussed. The environmental data is applied to the design of adequate protection system for the engine components. The methods for predicting the base region thermal environment are categorized as: (1) scale model testing, (2) extrapolation of previous and related flight test results, and (3) semiempirical analytical techniques.

Mcanelly, W. B.↗
NASA NTRS1974

Energy transfer in volume-reflecting heat shields

An approximate analytic solution is provided for the unsteady radiative heating of a highly scattering medium under constant heat flux boundary conditions. The accuracy of the method in representing the reflectance, radiative flux, and radiative flux divergence of the materials was also explored, as was the influence of anistropic scattering on these parameters.

Weston, K. C.↗
NASA NTRS1974

Energy transfer in volume-reflecting heat shields

An approximate analysis of radiative transfer in highly scattering materials was developed based on the Kubelka-Munk differential equations--a set of two differential equations representing the spatial rate of change of radiative half-fluxes within the scattering media. These approximate solutions of the Kubelka-Munk equations together with analytic solutions for the steady state temperature distribution for two types of boundary conditions are given. These solutions show the influence of back surface reflectance, scattering power, incident radiative flux parameter and boundary conductive flux parameter on overall reflectance and temperature distributions. This radiation field analysis, adapted to spherical geometry, was applied to the evaluation of the thermal performance of teflon and fritted quartz as heat protection materials for entry into the atmosphere of Jupiter.

Weston, K. C.↗
NASA NTRS1975

Reflecting heat shields made of microstructured fused silica

Heat sheidls constructed from selected monodisperse distributions of high-purity fused-silica particles are efficient reflectors of visible and near-UV radiation generated in shock-layer of space probe during atmospheric entry.

Congdon, W. M.↗
NASA NTRS1975

Prediction and verification of creep behavior in metallic materials and components for the space shuttle thermal protection system. Volume 3, phase 3: Full size heat shield data correlation and design criteria

Analysis methods for predicting cyclic creep deflection in stiffened metal panel structures, were applied to full size panels. Results were compared with measured deflections from cyclic tests of thin gage L605, Rene' 41, and TDNiCr full size corrugation stiffened panels. A design criteria was then formulated for metallic thermal protection panels subjected to creep. A computer program was developed to calculate creep deflections.

Cramer, B. A.↗
NASA NTRS1974

Castable thermal insulation for use as heat shields

Structural members supporting the afterburners of high thrust rocket engines are subjected to extreme heating, along with severe vibration and high acceleration levels during early lift-off. Chemically-bonded, castable, zircon composite foams were developed and successfully tested to meet specific, laboratory simulated lift-off conditions.

Mountvala, A. J.↗
NASA NTRS1975

Test evaluation of potential heat shield contamination of an Outer Planet Probe's atmospheric sampling system

An Outer Planets Probe which retains the charred heatshield during atmospheric descent must deploy a sampling tube through the heatshield to extract atmospheric samples for analysis. Once the sampling tube is deployed, the atmospheric samples ingested must be free of contaminant gases generated by the heatshield. Outgassing products such as methane and water vapor are present in planetary atmospheres and hence, ingestion of such species would result in gas analyzer measurement uncertainties. This paper evaluates the potential for, and design impact of, the extracted atmospheric samples being contaminated by heatshield outgassing products. Flight trajectory data for Jupiter, Saturn and Uranus entries are analyzed to define the conditions resulting in the greatest potential for outgassing products being ingested into the probe's sampling system. An experimental program is defined and described which simulates the key flow field features for a planetary flight in a ground-based test facility. The primary parameters varied in the test include: sampling tube length, injectant mass flow rate and angle of attack. Measured contaminant levels predict the critical sampling tube length for contamination avoidance. Thus, the study demonstrates the compatibility of a retained heatshield concept and high quality atmospheric trace species measurements.

Kessler, W. C.↗
NASA NTRS1975

Stratospheric ozone - Fragile shield

Atmospheric models that have been used in major studies on the possible impact of SST exhausts and Freons on stratospheric ozone are discussed and compared. An overview is given of ozone-reduction estimates that they produce, together with an assessment of possible effects of atmospheric testing of thermonuclear bombs in an attempt to find direct observational evidence for ozone depletion resulting from human activities. It is concluded that clear validation of atmospheric-model predictions is lacking.

Hoffert, M. I.↗