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  • 1
    facet.materialart.
    Unknown
    A flight experiment to determine GPS photochemical contamination accumulation rates (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: It was recently suggested that photochemically deposited contamination, originating from volatiles outgassed by a spacecraft, may be responsible for the anomalous degradation in power seen on the GPS Block 1 vehicles. In an attempt to confirm, or deny, the photochemical deposition rates predicted, a study was undertaken to design a flight experiment to be incorporated on the GPS vehicles currently in production. The objective was to develop an inexpensive, light weight instrument package that would give information on the contamination levels within a few months of launch. Three types of apparatus were studied, Quartz Crystal Microbalances, (QCM's), modified solar cells, and calorimeters. A calorimeter was selected due primarily to its impact on the production schedule of the GPS vehicles. An analysis of the sensitivity of the final design is compared to the predicted contamination accumulation rates in order to determine how long after launch it will take the experiment to show the effects of photochemical contamination.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA, Goddard Space Flight Center, 16th Space Simulation Conference Confirming Spaceworthiness Into the Next Millennium; p 435-446
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Contamination control engineering design guidelines for the aerospace community (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Thermal control surfaces, solar arrays, and optical devices may be adversely affected by a small quantity of molecular and/or particulate contamination. What is rarely discussed is how one: (1) quantifies the level of contamination that must be maintained in order for the system to function properly, and (2) enforces contamination control to ensure compliance with requirements. This document is designed to address these specific issues and is intended to serve as a handbook on contamination control for the reader, illustrating process and methodology while providing direction to more detailed references when needed. The effects of molecular contamination on reflecting and transmitting surfaces are examined and quantified in accordance with MIL STD 1246C. The generation, transportation, and deposition of molecular contamination is reviewed and specific examples are worked to illustrate the process a design engineer can use to estimate end of life cleanliness levels required by solar arrays, thermal control surfaces, and optical surfaces. A similar process is used to describe the effect of particulate contamination as related to percent area coverage (PAC) and bi-directional reflectance distribution function (BRDF). Relationships between PAC and surface cleanliness, which include the effects of submicron sized particles, are developed and BRDF is related to specific sensor design parameters such as Point Source Transmittance (PST). The pros and cons of various methods of preventing, monitoring, and cleaning surfaces are examined and discussed.
    Keywords: Engineering (General)
    Type: NASA-CR-4740 , NAS 1.26:4740 , M-810
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Low Earth orbit thermal control coatings exposure flight tests: A comparison of U.S. and Russian results (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Both the United States (US) and Russia have conducted a variety of space environment effects on materials (SEEM) flight experiments in recent years. A prime US example was the Long Duration Exposure Facility (LDEF), which spent 5 years and 9 months in low Earth orbit (LEO) from April 1984 to January 1990. A key Russian experiment was the Removable Cassette Container experiment, (RCC-1), flown on the Mir Orbital Station from 11 January 1990 to 26 April 1991. This paper evaluates the thermal control coating materials data generated by these two missions by comparing: environmental exposure conditions, functionality and chemistry of thermal control coating materials, and pre- and post-flight analysis of absorptance, emittance, and mass loss due to atomic oxygen erosion. It will be seen that there are noticeable differences in the US and Russian space environment measurements and models, which complicates comparisons of environments. The results of both flight experiments confirm that zinc oxide and zinc oxide orthotitanate white thermal control paints in metasilicate binders (Z93, YB71, TP-co-2, TP-co-11, and TP-co-12), are the most stable upon exposure to the space environment. It is also seen that Russian flight materials experience broadens to the use of silicone and acrylic resin binders while the US relies more heavily on polyurethane.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: NASA-CR-4647 , NAS 1.26:4647
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Plasma density, temperature and turbulence in the wake of the Shuttle Orbiter (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: In situ observations of the plasma density, temperature, and turbulence in the near wake, midwake, and far wake of the Shuttle Orbiter are presented. The results show that the plasma disturbances produced by the passage of the Orbiter extend downstream for a distance of several hundred meters behind the Orbiter. It is found that the electron density profile exhibits nonmonotonic behavior, and that most of the 6-40-Hz turbulence in the wake is confined to a region about 20 m downstream of the Orbiter. The saturation Delta N(e)/N(e) spectra rapidly decline in the 10,000-100,000-Hz decade, both in the ambient ionosphere and in the wake.
    Keywords: PLASMA PHYSICS
    Type: Planetary and Space Science (ISSN 0032-0633); 37; 1001-101
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Exposed high-voltage source effect on the potential of an ionospheric satellite (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A pulsed, high-voltage source, which is able to draw a current from the surrounding plasma, is seen to induce large changes in the potential of an ionospheric satellite (the Iowa Plasma Diagnostics Package flown on Space Shuttle flight STS-51F). This, in turn, may affect the operation of other instruments that use the chassis of the satellite as a ground for electrical circuits. The magnitude of the change in satellite potential is dependent upon both the orientation of the high-voltage source, relative to the plasma flow, and the characteristics of the high-voltage source. When the satellite is grounded to the Shuttle Orbiter, this effect is sufficient to change the potential of the Orbiter by a small, but noticeable, amount.
    Keywords: PLASMA PHYSICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 25; 64-69
    Format: text
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    NASA TECHNICAL REPORTS
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