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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Non-catalytic surfaces for metallic heat shields

The magnitude of the atom recombination coefficients needed for metal heat shield surfaces on Shuttle-type vehicles is analyzed and discussed. Prior work which identifies surfaces having low catalytic activity is reviewed. Arc tunnel tests to evaluate catalytic activity are described and the difficulties of such tests are discussed. Results are presented which show major differences between atom recombination and atom exchange from molecules. Results of surface analysis show that bulk and surface composition of a coating are different.

Swann, R. T.↗
NASA NTRS2008

Correlations for Boundary-Layer Transition on Mars Science Laboratory Entry Vehicle Due to Heat-Shield Cavities

The influence of cavities (for attachment bolts) on the heat-shield of the proposed Mars Science Laboratory entry vehicle has been investigated experimentally and computationally in order to develop a criterion for assessing whether the boundary layer becomes turbulent downstream of the cavity. Wind tunnel tests were conducted on the 70-deg sphere-cone vehicle geometry with various cavity sizes and locations in order to assess their influence on convective heating and boundary layer transition. Heat-transfer coefficients and boundary-layer states (laminar, transitional, or turbulent) were determined using global phosphor thermography.

Hollis, Brian R.↗
NASA NTRS1974

High purity silica reflective heat shield development

Progress is reported on the development of a high purity reflective heat shield material. Silicon dioxide was selected as the material because it is highly reflective in the correct wavelength band, has good ablation characteristics, is thermal shock resistant, and is readily fabricated to full size at reasonable cost. Conclusions indicate that: reflectance is affected by purity and morphology; the pure material is readily available; required purity and morphology can be maintained with reasonable care; high reflectances are determined (0.99 from 0.4 to 1.2 microns); major processing steps are defined; and the material appears to be cost effective. It is indicated that the materials are developed to the point of readiness for full scale fabrication and characterization.

Blome, J.↗
NASA NTRS1982

Trajectories of solid particles spalled from a carbonaceous heat shield

Trajectories are calculated of solid carbon particles that spall from a carbonaceous heat shield and travel through a given flow field. The mathematical model takes into account mass, momentum, and energy conservation during evaporation of the particles in an effort to understand spallation phenomena and their consequences in a physical way. The solution technique is applied to available Galileo Probe flow field solutions. Plots of trajectories and other particle parameters are presented for a range of initial particle sizes and velocities. It is shown that a significant amount of gaseous carbon is deposited in the inviscid region and ahead of the bow shock as well as in the ablation layer.

Davies, C. B.↗
NASA NTRS1986

Oxidation and emittance of superalloys in heat shield applications

Recently developed superalloys that form alumina coatings have a high potential for heat shield applications for advanced aerospace vehicles at temperatures above 1095C. Both INCOLOY alloy MA 956 (of the Inco Alloys International, Inc.), an iron-base oxide-dispersion-strengthened alloy, and CABOT alloy No. 214 (of the Cabot Corporation), an alumina-forming nickel-chromium alloy, have good oxidation resistance and good elevated temperature strength. The oxidation resistance of both alloys has been attributed to the formation of a thin alumina layer (alpha-Al2O3) at the surface. Emittance and oxidation data were obtained for simulated Space Shuttle reentry conditions using a hypersonic arc-heated wind tunnel. The surface oxides and substrate alloys were characterized using X-ray diffraction and scanning and transmission electron microscopy with an energy-dispersive X-ray analysis unit. The mass loss and emittance characteristics of the two alloys are discussed.

Wiedemann, K. E.↗
NASA NTRS2011

Isotherm Sensor Calibration Program for Mars Science Laboratory Heat Shield Flight Data Analysis

Seven instrumented sensor plugs were installed on the Mars Science Laboratory heat shield in December 2008 as part of the Mars Science Laboratory Entry, Descent, and Landing Instrumentation (MEDLI) project. These sensor plugs contain four in-depth thermocouples and one Hollow aErothermal Ablation and Temperature (HEAT) sensor. The HEAT sensor follows the time progression of a 700 C isotherm through the thickness of a thermal protection system (TPS) material. The data can be used to infer char depth and, when analyzed in conjunction with the thermocouple data, the thermal gradient through the TPS material can also be determined. However, the uncertainty on the isotherm value is not well defined. To address this uncertainty, a team at NASA Ames Research Center is carrying out a HEAT sensor calibration test program. The scope of this test program is described, and initial results from experiments conducted in the laboratory to study the isotherm temperature of the HEAT sensor are presented. Data from the laboratory tests indicate an isotherm temperature of 720 C 60 C. An overview of near term arc jet testing is also given, including preliminary data from 30.48cm 30.48cm PICA panels instrumented with two MEDLI sensor plugs and tested in the NASA Ames Panel Test Facility. Forward work includes analysis of the arc jet test data, including an evaluation of the isotherm value based on the instant in time when it reaches a thermocouple depth.

Santos, Jose A.↗