The Environmental Effects Branch contributes to NASA’s missions in space transportation, space science, advanced space propulsion, flight projects such as the International Space Station, and the Vision for Space Exploration by providing valuable information on materials and processes related to contamination control and the space environment. The Environmental Effects Branch consists of the Contamination Control Team and the Space Environmental Effects Team.
Contamination Control Team
The Contamination Control Team is responsible for establishing and implementing contamination control requirements during all phases of hardware development, including design, manufacturing, assembly, test, transportation, launch site processing, on-orbit exposure, return, and refurbishment. The team’s mission is to reduce the risk of component/hardware failure due to molecular contamination, particulate contamination, and damage from foreign object debris. Contamination is a concern in propulsion systems with sensitive bondlines and reactive fluid (liquid oxygen) compatibility as well as for spacecraft with sensitive optical elements such as space telescopes and thermal control systems.
The Contamination Control Team has a variety of facilities and instrumentation capable of contaminant detection, identification, and monitoring. State-of-the-art portable inspection techniques currently available include optically stimulated electron emission (OSEE); near infrared (NIR) spectroscopy utilizing fiber optics; Fourier transform infrared (FTIR) spectroscopy; ultraviolet (UV) fluorescence; and x-ray fluorescence. Inspection instrumentation is evaluated for capability to detect contaminants (silicone, hydrocarbons and fluorocarbons) on a variety of material substrates (metallics, composites, optics, etc.). The team of engineers and technicians also audit facilities/processes, develop contamination calibration standards, evaluate new surface cleanliness inspection technologies, and analyze enhanced deposition of contaminants in the presence of UV radiation. Databases are maintained by the team for process materials as well as outgassing and optical compatibility test results for specific environments.
Space Environmental Effects Team
The Space Environmental Effects (SEE) Team studies materials' behavior in the space environment. Laboratory capabilities include simulation of orbital atomic oxygen, ultraviolet (UV) radiation, electron and proton radiation, plasma, thermal vacuum, and meteoroid and space debris impacts. The team’s world-class Combined Environment Effects Facility (CEEF) test system has the capability of exposing materials to protons, low- and high-energy electrons, near-ultraviolet (NUV) radiation, and vacuum ultraviolet (VUV) radiation, either simultaneously or sequentially, then measuring reflectance in vacuo. Ambient space plasma environments and directed plasma beams are analyzed and their effects on materials/components evaluated in team facilities. Flight experiment studies such as the Long Duration Exposure Facility (LDEF), the Passive Optical Sample Assembly (POSA) - I experiment, and the Materials on International Space Station Experiment (MISSE) are used to improve our understanding of space, especially the synergistic effects from all elements of the environment. Data from ground simulations of the space environment combined with results from various flight experiments help determine the optimum materials for use on spacecraft.
The SEE team studies all types of materials used in spacecraft: metals, ceramics, polymers, composites, optics, lubricants, adhesives, thermal control coatings, visual aid coatings, solar cells, insulation, solar sail thin films, etc. These materials must maintain desired mechanical, electrical, and optical properties in the harsh environment of space to insure reliable system performance.
Unique Capabilities
Test facilities to simulate spacecraft charging of materials and components at cryogenic temperatures are available to verify spacecraft system designs. Electrical arcs occurring during these tests can be measured and material/system degradation predicted. The team also maintains a solar wind test facility that includes low energy protons (1 to 30 KeV), low energy electrons (1 to 100 KeV), vacuum UV, and near UV exposure capability. The facility is capable of providing a one square foot beam spot for sample exposure.
The Environmental Effects Branch maintains an Impact Test Facility for evaluation of micrometeoroid and orbital debris (MMOD) impacts on material and subsystem performance. These facilities were used in International Space Station debris shield design evaluations. The Branch also maintains environmental impact testing facilities considered national assets by the Department of Defense. Branch capabilities include powder, compressed gas and exploding wire guns that provide rain, single and multi-particle impacts allowing material and subsystem impact performance testing over the m/sec to km/sec velocity range. Smooth Particle Hydrodynamic Code (SPHC) analysis is also available for simulation of a wide variety of test scenarios.
The Environmental Effects Branch conducts materials research/characterization utilizing electrostatic levitation and high temperature emissivity systems. Electrostatic Levitation (ESL) provides an ideal method for study of ultra-high-temperature and reactive materials including metals, alloys, oxides, semiconductors and glasses. Data can be obtained for determination of: total hemispherical emissivity, creep resistance, density/coefficient of thermal expansion, surface tension, viscosity and phase behavior. Other investigations in the facility have studied nucleation, undercooling, metastable state formation and metallic glass formation. Branch facilities provide a means to study materials (solids and melts) at temperatures of interest to advanced technical applications (ESL can provide data from 200o C to 3400o C) that conventional methods cannot. Additional information about the facility can be found at: http://esl.msfc.nasa.gov/
reactive fluid (liquid oxygen) compatibility as well as for spacecraft with sensitive optical elements such as space telescopes and thermal control systems.
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