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Posted by cole smith on August 28, 2006, 4:43 pm
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One would think by now the Russians have enough data on returned 200 day old
Soyuz capsules to know whether it is safe to extend their time on orbit. Is
it a cold soak issue with the heat shield, pyros, etc.? Getting them to
share that data may be part of the problem.
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> Mike Ross wrote:
>> What are the limiting factors there? Can that lifetime be extended on
>> a waiver, after a review of system status etc.?
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Posted by hop on August 28, 2006, 5:41 pm
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Mike Ross wrote:
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> What are the limiting factors there? Can that lifetime be extended on
> a waiver, after a review of system status etc.?
The main issue, AFAIK, is that the descent module uses H202 for
attitude control. This degrades slowly over time. On recent TMAs, the
Russians added some equipment to keep it cooler (thus degrading slower,
and extending the lifetime somewhat) but a real fix would be more
involved.
ISTR they have quoted a price for that, but don't want to spend the
money themselves.
Given that 6 months is the rotation of long term crews anyway, having
it match up with Soyuz replacement time isn't normally a big issue.
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Posted by Jorge R. Frank on August 28, 2006, 6:04 pm
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> On Sun, 27 Aug 2006 20:30:39 -0500, "Jorge R. Frank"
>
>>Soyuz is also used as the emergency crew return vehicle for the ISS
>>crew. Each Soyuz is only certified for a 200-day orbital lifetime, so
>>they must be changed out every six months or so.
>
> What are the limiting factors there?
The descent module RCS uses hydrogen peroxide as a monopropellant, and H2O2
decomposes over time.
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Posted by Mike Ross on August 28, 2006, 9:10 pm
Please log in for more thread options On Mon, 28 Aug 2006 17:04:52 -0500, "Jorge R. Frank"
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>> On Sun, 27 Aug 2006 20:30:39 -0500, "Jorge R. Frank"
>>
>>>Soyuz is also used as the emergency crew return vehicle for the ISS
>>>crew. Each Soyuz is only certified for a 200-day orbital lifetime, so
>>>they must be changed out every six months or so.
>>
>> What are the limiting factors there?
>The descent module RCS uses hydrogen peroxide as a monopropellant, and H2O2
>decomposes over time.
Makes sense - mate of mine had some fun with H2O2 a while back...
Mike
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I am the history within'
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>> What are the limiting factors there? Can that lifetime be extended on
>> a waiver, after a review of system status etc.?