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irizarry
January 21st, 2003, 08:00 AM
Has anyone ever seen film of the Space Shuttle opening its payload pay doors?

There is this initial storm of debris, dust and particles. Some of this has been attributed to “Outgassing” or “Offgassing”. Which is the correct term?
SEDShead
January 21st, 2003, 09:31 AM
Neither - that I'm aware of. Its just debris and particles.

'Outgassing' is the process of things losing their entrained volatiles due to the low pressure, and the material's vapor pressure. Things destined for use in vacuum (space) are often "baked out" at high temperature and vacuum for a period of time to allow this to happen in a controlled process on Earth.
Kirsten
January 21st, 2003, 11:30 AM
This is a somewhat unrelated tangent, but the topic made me think of it. Chris (or anyone else), have you ever heard of any problems with plastic encapsulated devices popcorning during rapid ascents to high altitudes? I assume that since many component manufacturers are getting out of mil-spec parts completely, there must be a fair number of PEDs used on spacecraft. Is there a rule of thumb for what moisture sensitivity level is acceptable for space applications?

Kirsten
SEDShead
January 22nd, 2003, 12:40 AM
Originally posted by Kirsten
This is a somewhat unrelated tangent, but the topic made me think of it. Chris (or anyone else), have you ever heard of any problems with plastic encapsulated devices popcorning during rapid ascents to high altitudes? I assume that since many component manufacturers are getting out of mil-spec parts completely, there must be a fair number of PEDs used on spacecraft. Is there a rule of thumb for what moisture sensitivity level is acceptable for space applications?
Kirsten

Probably somewhere, but as I don't yet design any of these boards, I don't know for sure, only what I see come down the pipe. Most things we use are still Milspec, unless its a GSE-only circuit. Also, lots of things are taken care of by a healthy dose of conformal coat. AMSAT has probably done the most pioneering work with regards flying off-the-shelf (literally from the radio shack down the street) equipment.