OVERVIEW

The Material and Processes Working Group studies all types of materials used in spacecraft: metals, ceramics, polymers, composites, lubricants, adhesives, solar cells, and others. The group seeks to quantify environmental effects, accurately simulate them in laboratories and computer models, and promote research and development of more durable materials.

General

Candidate materials for external use on   spacecraft must be able to maintain desired mechanical, optical, and electrical properties in the harsh environment of space. This environment includes hard vacuum, thermal cycling, atomic oxygen (low Earth orbit only), ultraviolet radiation, particulate radiation, and plasma. In addition, impacts by manmade space debris and micrometeoroids damage materials and may alter optical properties as in this silvered FEP Teflon thermal blanket from the leading edge of LDEF.

The dark spots are space debris and micrometeoroid impacts. Though some impacts are as small as 0.1 mm diameter, the darkened area around the impact can be several millimeters in diameter.

Another manmade component of the spacecraft external environment is contamination. Contamination can be either molecular (from outgassing) or particulate (unburned fuel, dust). Molecular contamination can adversely affect thermal control coatings by increasing solar absorption. Both molecular and particulate contamination are special concerns for sensitive optics.

Synergism between all elements of the space environment, though difficult to simulate in the laboratory, must be considered. This half-exposed Z-853 paint sample from Long Duration Exposure Facility (LDEF) demonstrates atomic oxygen erosion, ultraviolet radiation darkening, and a meteoroid/space debris impact. The experiment was positioned 38° from the RAM direction, so the holding fixture provided some shadowing. If this sample had not been exposed to atomic oxygen but only to the UV radiation, the paint would have uniformly darkened. Atomic oxygen bleaching has been noted on a number of different materials, but atomic oxygen erosion is more prevalent in paints with organic binders. Atomic oxygen erosion on this sample resulted in a mass loss of 0.94 mg/cm**2 and a drop in solar absorption from 0.491 to 0.428.

Materials and Process SEE Related Experiments

One durable material developed under a SEE contract is AORimide polymer. This material exhibits lower atomic oxygen erosion than currently used materials. It is being tested in film and thread forms for use in multi-layer insulation blankets.

Because materials returned to Earth from space experience some bleaching in air, the best measurement of space environment effects would be in-situ. The Space Portable Spectroreflectometer is being developed for use on the Russian Mir Space Station and the International Space Station. An astronaut or cosmonaut will measure solar absorptance of external spacecraft surfaces, without disassembly, during EVA.

back to Materials and Processes TWG