Outgassing in a vacuum
Outgassing is a challenge to creating and maintaining clean high-vacuum environments.
NASA maintains a list of low-outgassing materials to be used for spacecraft, as outgassing products can condense onto optical elements, thermal radiators, or solar cells and obscure them.
Materials not normally considered absorbent can release enough light-weight molecules to interfere with industrial or scientific vacuum processes.
Even metals and glasses can release gases from cracks or impurities, but moisture, sealants, lubricants, and adhesives are the most common sources.
The rate of outgassing increases at higher temperatures because the vapour pressure and rate of chemical reaction increases.
For most solid materials, the method of manufacture and preparation can reduce the level of outgassing significantly.
Cleaning surfaces or baking individual components or the entire assembly before use can drive off volatiles.
NASA's Stardust spaceprobe suffered reduced image quality due to an unknown contaminant that had condensed on the CCD sensor of the navigation camera.
A similar problem affected the Cassini-Huygens spaceprobe's Narrow Angle Camera, but was corrected by repeatedly heating the system to 4 degrees Celsius.
Outgassing is a challenge to creating and maintaining clean high-vacuum environments.
NASA maintains a list of low-outgassing materials to be used for spacecraft, as outgassing products can condense onto optical elements, thermal radiators, or solar cells and obscure them.
Materials not normally considered absorbent can release enough light-weight molecules to interfere with industrial or scientific vacuum processes.
Even metals and glasses can release gases from cracks or impurities, but moisture, sealants, lubricants, and adhesives are the most common sources.
The rate of outgassing increases at higher temperatures because the vapour pressure and rate of chemical reaction increases.
For most solid materials, the method of manufacture and preparation can reduce the level of outgassing significantly.
Cleaning surfaces or baking individual components or the entire assembly before use can drive off volatiles.
NASA's Stardust spaceprobe suffered reduced image quality due to an unknown contaminant that had condensed on the CCD sensor of the navigation camera.
A similar problem affected the Cassini-Huygens spaceprobe's Narrow Angle Camera, but was corrected by repeatedly heating the system to 4 degrees Celsius.
全站熱搜
留言列表
走過 (7)
