Results of apparent atomic oxygen reactions with spacecraft materials during Shuttle flight STS-41G
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Zimcik, D. G.↗
Engineering topics
Maag, C. R.
Publications and source records attributed to Maag, C. R..
The effect of Low Earth Orbit space environment on polymeric spacecraft materials
The Advanced Composite Materials Exposure to Space Experiment flown on shuttle mission STS-41G was designed to investigate the effect of low Earth orbit space environment on polymeric spacecraft materials. The effect of the phenomenon attributed to atomic oxygen on Kapton and advanced composite materials of carbon-epoxy and kevlar epoxy is described. The results of true space exposure are compared to duplicate specimens subjected to a simulated environment in an Earth-based nozzle beam test facility utilizing microwave discharge to form atomic oxygen. Although the energy level for atomic oxygen in the beam facility did not achieve the orbital energy level of 5 eV, similar effects of surface erosion and degradation are observed after equivalent exposure times.
Zimcik, D. G.↗
Results of apparent atomic oxygen reactions with spacecraft materials during shuttle flight STS-41G
The effect of atomic oxygen interaction experienced by polymeric-based spacecraft materials is described. An experimental package (ACOMEX) flown on shuttle mission STS-41G carried out the investigation of advanced composite specimens such as carbon-epoxy and Kevlar-epoxy both with and without protective coatings added to thermal protective paints and films. Information on the exposure environment of the specimens was provided by a carbon coated atomic oxygen fluence monitor together with a photographic record. Mass loss measurements and photomicrographs made possible the analysis of the effect of interaction. After a total of about 38 hours of equivalent normal exposure at 225 km altitude the results showed that unprotected exposed surfaces exhibited severe erosion and mass loss with the possibility of seriously degrading structural and thermal performance. However, the specimens with a thin fluorocarbon overcoat showed promise of providing a protective barrier to the attack without altering the base properties of the material.
Zimcik, D. G.↗
Spacecraft contamination environment; Proceedings of the Meeting, Arlington, VA, May 4-6, 1982
Aspects of IECM debriefing are considered, taking into account preliminary results of the induced environment contamination monitor measurements of STS-2, the humidity monitor and dew point hygrometer, the induced environment contamination monitor cascade impactor, the optical effects module and passive sample array, temperature-controlled quartz crystal microbalance measurements on STS-2, camera/photometer results, the mass spectrometer, and a summary regarding the induced environment contamination monitor/space transport system. Other subjects explored are related to contamination management and control, contamination/optical degradation, and contamination assessments and measurements. Attention is given to approaches for controlling contamination before launch, the coronagraph as the ultimate device to monitor orbiting particulates in the Space Transport System environment, and the contamination sensitivity of typical mirror coatings.
Maag, C. R.↗
Starprobe thermal shield system design concepts
The mission goals, flight trajectory, and material durability requirements for the NASA Starprobe spacecraft are reviewed. The spacecraft will use a Jovian gravity assist to pass within four solar radii of the sun to study fields and particles near the sun, perform experiments dealing with relativity and gravity, and observe the structure of the solar atmosphere from the photosphere to the corona. Constraints on the system size and mass design are given, and the system is noted to be required to withstand 2500 K at perihelion, thermally insulate the instrument payload, have a tube for optical measurements, and provide protection from meteorite damage. A secondary shield is also required to dispense thermal radiation that passes the primary shield and could endanger the payload. Design options are discussed, along with temperature control requirements and a conical carbon-carbon primary shield with mass-loss rate characteristics sufficient to meet a 2.5 mg/sec criterion.
Maag, C. R.↗
Assessment of contamination in the Shuttle bay
The results of an analytical study to determine the contamination potential of the Galileo probe instruments while in the STS bay are presented. The study covered conditions wherein the instruments weren't covered, covers were used with vent paths of varying sizes, and if the instruments were sealed and a nitrogen purge was employed. The contamination limits for each of the Galileo instruments are considered. Analytic approximations are devised for the diffusion of particles from surfaces and materials in the Shuttle bay during the ascent phase, using Fick's second law of diffusion. It is recommended that an instrument purge be implemented during the first 15 min of Shuttle flight in order to carry the contaminants from both the bay fixtures and from the instruments into space. Covers are suggested as necessary for the most sensitive instruments.
Jeffery, J. A.↗
Spacecraft contamination prediction and testing techniques
Techniques used in the prediction of spacecraft contamination for the Galileo Jupiter Orbiter and in the determination of the effects of such contamination are presented. Following a quick-look assessment of the contributions of ground-based initial contaminant loading, launch vehicle interface effects, vacuum-exposed outgassing deposition and attitude control thruster impingement and venting to the spacecraft contamination burden, the evaluations centered on the effects of the attitude control thruster on the scan platform optics, including calculations of thruster flowfields and a high-fidelity computer simulation of contaminant distribution. The evaluations revealed a considerable problem with thruster contamination, which could be solved by the use of a thrust shield and the avoidance of thruster operation at certain scan platform orientations. The effects of the various possible contaminants on spacecraft thermal and optical system performances were also investigated in studies of the optical transmittance of deposited monomethyl hydrazine nitrate, vacuum optical degradation due to contaminant outgassing and re-emission outgassing, and an operational satellite contaminant monitor on the NOAA-C satellite. It is concluded that with a good evaluation and testing program, contamination control may become a necessary portion of system design procedures, and recommendations for the implementation of various practices and tests to minimize contamination effects are presented.
Jeffery, J. A.↗
Photovoltaic module soiling studies, May 1978 - October 1980
Comparative electrical and optical performance data from photovoltaic modules and materials subjected to outdoor exposure at field test sites throughout the United States were collected and examined. The results show significant time and site dependence. During periods when natural removal processes do not dominate, the rate of particulate contamination accumulation appears to be largely material-independent. The effectiveness of natural removal processes, especially rain, is strongly material-dependent. Glass and acrylic top cover materials retain fewer particles than silicone rubber does. Side by side outdoor exposure testing for long duration is presently the most effective means of evaluating soiling differences between materials. Changes in spectral transmission as a function of time and location and limited scattering data are presented.
Hoffman, A. R.↗
Contamination control of the Infrared Astronomical Satellite
The Infrared Astronomical Satellite, to be launched in August 1981, will perform an all-sky survey in the 8-120 micron wavelength region. High sensitivity to thermal radiation and the low operating temperature of optics and thermal control surfaces make the IRAS telescope extremely vulnerable to contamination. Four special topics of importance are discussed in this paper: (1) deposition of atmospheric gases; (2) sighting of particles released from the satellite; (3) functions of a deployable aperture cover; and (4) degradation of a radiatively cooled sunshade from spacecraft outgassing. These topics demonstrate how mission strategy, ground cleaning and handling, and hardware design are used to avoid contamination which would degrade telescope performance.
Andreozzi, L. C.↗
Effect of bipropellant plume exhaust effluents on spaceborne optical instruments
Analytical tools together with a good data base are necessary to predict the transport of plume contaminants and their effects on spacecraft surfaces. The present paper describes an assessment of bipropellant thrusters, the production and transport of plume contaminants from these thrusters, and the use of the JPL contamination analysis program to assess the effects of plume contamination on the Galileo spacecraft. It is shown that, in the case of the Galileo mission, contamination from the liquid engines has been effectively reduced to nothing by the use of predictive tools. Plume shields together with precise scan platform stowage have been designed to protect the optical instruments.
Maag, C. R.↗
National Oceanic and Atmospheric Administration /NOAA/ contamination monitoring instrumentation
The JPL has designed and built a plume contamination monitoring package to be installed on a NOAA environmental services satellite. The package is designed to monitor any condensible contamination that occurs during the ignition and burn of a TE-M-364-15 apogee kick motor. The instrumentation and system interface are described, and attention is given to preflight analysis and test.
Maag, C. R.↗
Airborne particulate soiling of terrestrial photovoltaic modules and cover materials
Results are presented for the first phase of a photovoltaic-module soiling study that was carried out with NASA participation to investigate the problem of the electrical performance degradation of flat-plate photovoltaic modules exposed at outdoor sites that is due to the accumulation of airborne particulates on sensitive optical surfaces. The results were obtained in both field and laboratory soiling experiments, as well as in materials field experiments using candidate encapsulants and top covers. It is concluded that: (1) the electrical performance degradation shows a significant time and site dependence, ranging from 2% to 60% power loss; (2) the rate of particulate accumulation appears to be largely material independent when natural removal processes do not dominate; (3) the effectiveness of natural removal processes, especially rain, is strongly material dependent; (4) top-cover materials of glass and plexiglass retain fewer particles than silicone rubber; and (5) high module voltages relative to ground do not appear to affect the rate of dirt accumulation on modules.
Hoffman, A. R.↗
Contamination enhanced electrostatic discharge mechanisms
The two problems of enhanced electrostatic discharge (ESD) and contamination are discussed. It is shown that there is a synergistic relationship between them such that one enhances the probability of occurance of the other. The action of both provides substantially more deleterious affects than the effects of both separately. Mechanisms for such a relationship are discussed as well as application to large advanced technology systems.
Jeffrey, J. A.↗
Space station thermal control surfaces
Mission planning documents were used to analyze the radiator design and thermal control surface requirements for both space station and 25-kW power module, to analyze the missions, and to determine the thermal control technology needed to satisfy both sets of requirements. Parameters such as thermal control coating degradation, vehicle attitude, self eclipsing, variation in solar constant, albedo, and Earth emission are considered. Four computer programs were developed which provide a preliminary design and evaluation tool for active radiator systems in LEO and GEO. Two programs were developed as general programs for space station analysis. Both types of programs find the radiator-flow solution and evaluate external heat loads in the same way. Fortran listings are included.
Maag, C. R.↗
Space station thermal control surfaces. Volume 1: Interim report
The U.S. space program goals for long-duration manned missions place particular demands on thermal-control systems. The objective of this program is to develop plans which are based on the present thermal-control technology, and which will keep pace with the other space program elements. The program tasks are as follows: (1) requirements analysis, with the objectives to define the thermal-control-surface requirements for both space station and 25 kW power module, to analyze the missions, and to determine the thermal-control-surface technology needed to satisfy both sets of requirements; (2) technology assessment, with the objectives to perform a literature/industry survey on thermal-control surfaces, to compare current technology with the requirements developed in the first task, and to determine what technology advancements are required for both the space station and the 25 kW power module; and (3) program planning that defines new initiative and/or program augmentation for development and testing areas required to provide the proper environment control for the space station and the 25 kW power module.
Maag, C. R.↗
Space station thermal control surfaces. Volume 2: Literature search
For abstract, see N78-22136.
Maag, C. R.↗