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At least 973 records · Page 54

Investigation of environmental effects on coatings for thermal control of large space vehicles

The objective of significantly advancing the state-of-the-art of white, spacecraft-radiator coatings has been realized in a comprehensive goal-oriented, pigmented-coatings research program. Considered were inorganic pigments and coatings, silicone polymers and coatings, the design and construction of a combined ultraviolet-plus-proton irradiation facility, the development of zinc orthotitanate pigment and coatings, and the effects on several low alpha sub s/epsilon paints of combined ultraviolet and proton irradiation.

Zerlaunt, G. A.↗

Shuttle ascent and shock impingement aerodynamic heating studies

The collection and analysis of aerodynamic heating data obtained from shock impingement experimental investigation were completed. The data were categorized into four interference areas; fin leading edge, wing/fuselage fin/plate corners, and space shuttle configurations. The effects of shock impingement were found to increase the heating rates 10 to 40 times the undisturbed values. A test program was completed at NASA/Langley Research Center to investigate the magnitudes and surface patterns of the mated shock interference flowfield. A 0.0065 scale thin-skin model of the MDAC 256-20 space shuttle booster mated with a Stycast model of the MDAC Internal tank orbiter was tested in the 20-inch M=6 tunnel, the 31-inch M=10 tunnel, and the 48-inch Unitary Plan Tunnel. The gap region of the ascent configuration was the principal area of interest where both thermocouple and phase-change paint data were obtained. Pressure and heat transfer distributions data on the leeward surface of a 75-degree sweep slab delta wing are presented. The effects of surface roughness on boundary layer transition and aerodynamic heating were investigated.

Lanning, W. D.↗

Heat transfer to four fineness-ratio-1.6 hexagonal prisms with various corner radii at Mach 6

An investigation was conducted in the Langley 20-inch Mach 6 tunnel to define the aerodynamic heat transfer to the radioisotope fuel cask (heat source) of the SNAP-19/Pioneer power system. The shape of the SNAP-19/Pioneer heat source is that of a hexagonal prism with flat ends; the fineness ratio, based on maximum (edge to edge) diameter, is 1.61. Phase-change-paint heat-transfer data and schlieren photographs were obtained on four possible 1/2-scale entry configurations of the SNAP-19/Pioneer heat source. Tests were conducted over a wide range of attitudes and at nominal Reynolds numbers, based on the length of the unablated configuration, of 33,000; 84,000; and 2,200,000.

Hunt, J. L.↗

Facilities and support systems for a 90-day test of a regenerative life support system

A 90-day test is reported of a regenerative life support system which was completed in a space station simulator. The long duration of the test and the fact that it was manned, imposed rigid reliability and safety requirements on the facility. Where adequate reliability could not be built into essential facility systems, either backup systems or components were provided. Awareness was intensified by: (1) placing signs on every piece of equipment that could affect the test, (2) painting switches on all breaker panels a bright contrasting color, (3) restricting access to the test control area, and (4) informing personnel in the facility (other than test personnel) of test activities. It is concluded that the basic facility is satisfactory for conducting long-duration manned tests, and it is recommended that all monitor and alarm functions be integrated into a single operation.

Malin, R. L.↗

Heat transfer investigation of two Langley Research Center delta wing configurations at a Mach number of 10.5, volume 1

Heat transfer tests for two delta wing configurations were conducted in the hypervelocity wind tunnel. The 24-inch long models were tested at a Mach number of approximately 10.5 and at angles of attack of 20, 40, and 60 degrees over a length Reynolds number range from 5 million to 23 million on 4 May to 4 June 1971. Heat transfer results were obtained from model surface heat gage measurements and thermographic phosphor paint.

Eaves, R. H.↗

Space shuttle: Heat transfer investigation of the McDonnell-Douglas delta wing orbiter at a nominal Mach number of 10.5

Heat transfer tests for the delta wing orbiter were conducted in a hypervelocity wind tunnel. A 1.1 percent scale model was tested at a Mach number of approximately 10.5 over an angle of attack range from 10 to 60 degrees over a length Reynolds number range from 5 times 10 to the 6th power to 24 times 10 to the 6th power. Heat transfer results were obtained from model surface heat gage measurements and thermographic phosphor paint. Limited pressure measurements were obtained.

Eaves, R. H.↗

Particle impact and optical property analysis of the surfaces of Surveyor 3 materials

As part of the investigation of Surveyor 3 materials, a study was conducted to determine the effect of the lunar environment on some of the painted and unpainted exterior surfaces. Examination of the camera parts and tube sections was conducted using three techniques: (1) optical and scanning electron microscopy, (2) energy dispersive X-ray probe analysis, and (3) spectral reflectance measurements.

Anderson, D. L.↗

Movement of the Surveyor 3 spacecraft

It was concluded that the Surveyor 3 spacecraft moved, probably as a result of a sudden failure of the leg 3 shock absorber, between May 1967 and November 1969. The time at which the movement occurred can be estimated only from comparison of the shielded and unshielded portions of footpad 3 and a knowledge of the mechanism and rate of the process that tans the painted surface.

Scott, R. F.↗

Preliminary results on tritium in Surveyor 3 material

Painted aluminum samples taken from Surveyor 3 were examined for possible tritium implanted by the solar wind. There was found to be a correlation of tritium content with exposure to sunlight. The amount of tritium in sample 1011,2 nearly perpendicular to the lunar surface exceeded the amount expected from the tritium content of lunar rock 12002 by at least a factor of 3. It is concluded that if there is tritium implanted by solar wind on lunar rocks, it is not retained by them.

Fireman, E. L.↗

High voltage transmission microscopy of Surveyor 3 camera shrouds

The internal structure of painted and unpainted aluminum alloy sheet samples from the TV camera shrouds were examined by high-voltage transmission electron microscopy. No clear-cut evidence of radiation damage effects was observed. Noticeable differences in microstructures between the upper visor and the sides and bottom of the lower shroud suggest different thermal histories, and the maximum temperatures due to solar heating are estimated to be between 164 and 319 C. Some correlation between microstructures and maximum estimated temperature is noted. It is felt that the apparent temperature rise due to solar heating will not affect the structural integrity of spacecraft components except possibly for very long periods of exposure. However, substantial thermal diffusion could affect interpretation of solar wind rare gas studies.

Fisher, R. M.↗

Calibration of a laboratory spectrophotometer for specular light by means of stacked glass plates.

Stacked glass plates have been used to calibrate a laboratory spectrophotometer, over the spectral range 0.5-2.5 microns, for specular light. The uncalibrated instrument was characterized by systematic errors when used to measure the reflectance and transmittance of stacked glass plates. Calibration included first, a determination of the reflectance of a standard composed of barium sulfate paint deposited on an aluminum plate; second, the approximation of the reflectance and transmittance residuals between observed and computed values by means of cubic equations; and, finally, the removal of the systematic errors by a computer. The instrument, after calibration, was accurate to 1% when used to measure the reflectance and transmittance of stacked glass plates.

Allen, W. A.↗

Analytical and experimental studies of an all specular thermal control louver system in a solar vacuum environment.

Thermal control louvers are used on the ATS-F&G spacecraft to regulate temperature by varying the effective radiating area. Since solar energy on louvers has a detrimental effect on their ability to radiate energy, an analytical and experimental program was developed to evaluate the performance of an all specular louver system as a function of sun angle and blade angle. Solar simulation tests and analyses show a maximum effective absorptance of .25 for the full open condition. The application of white paint to the blades resulted in lowering the blade temperatures by 130 C without significantly affecting the system performance.

Michalek, T. J.↗

Damage of thermal control coating properties by energetic mercury ion bombardment.

The thermophysical properties (absorptance and emittance) of five commonly used spacecraft thermal control coatings have been measured in situ after exposure to 1.5 and 3 KeV mercury ions. Sample temperature was varied from 20 to 150 C. The results showed negligible change in emittance but significant degradation of the solar absorptance at fluences of 10 to the 17th power ions/sq cm. Plots of absorptance as a function of ion fluence are presented, along with pre- and post-exposure ex situ spectral absorptance measurements. The widely used Z93 white paint exhibited quantitative degradation from mercury ions similar to that reported by other experimenters for hydrogen and helium ions.

Kelley, L. R.↗

Recent advances in spacecraft thermal-control materials research.

The state-of-the-art of spacecraft thermal-control materials technology has been significantly advanced during the past 4 years. Selective black coatings are discussed together with black paints, dielectric films on metal surfaces, and white radiator coatings. Criteria for the selection of thermal-control surfaces are considered, giving attention to prelaunch protection, the capability of being measured, reproducibility, simulator response, and aspects of a nonindigenous space environment. Progress in space simulation is related to vacuum technology, ultraviolet sources, solar wind simulation, and the production of protons. Advances have been made in the protection against space environmental effects, and in the development of thermal-control surfaces and pigments.

Zerlaut, G. A.↗

Solar radiation calibration facility.

A recently completed calibration facility for the NASA Mississippi Test Site is described. It combines the spectrum of water cooled long arc xenon radiation sources with the integration sphere concept covered by a special barium sulfate diffusely reflecting paint. The sphere is six feet in diameter and completely encompasses the four xenon sources (2.5 kW each) and the five pyranometers under calibration. The sources are contained within the base of the central pedestal and allow the radiation to be emitted into the lower hemisphere. Only through diffuse reflection and multiple scattering is the radiation finally incident upon the test zone, which is in the equatorial plane of the sphere on the top of the pedestal. The sphere is temperature controlled.

Hershey, T. L.↗

Hypersonic shock wave interaction and impingement

An experimental investigation was conducted on space shuttle type, body-wing configurations. The purpose of the investigation was to determine the effects of body and wing geometry on the hypersonic shock structure about these vehicles and on the resulting surface impingement of interior flow field shock and expansion waves. Schlieren photographs and thermographic phosphor paint data were obtained on three body cross sections with three wing planforms at 40, 50 and 60 degree angles of attack. Specific configuration data were obtained at 0 and 30 degree angles of attack to develop trends. These data were obtained at a nominal Mach number of 13.5 and a freestream unit Reynolds number of 0.7 million per foot. For comparison with these straight wing configurations, data were also obtained on a model of a point design, high cross-range, delta wing orbiter at 40, 50 and 60 degree angles of attack. As expected, the data on this delta wing orbiter indicated that the shock intersection/impingement phenomena associated with straight wing vehicles are considerably more complex than, and result in both windward and leeward surface heating regions not present on, the delta configuration.

Kessler, W. C.↗