Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: shuttle computers; big solids
Message-ID: <1988Oct5.170746.7942@utzoo.uucp>
Organization: U of Toronto Zoology
References: <6689@nsc.nsc.com> <1543@hp-sdd.HP.COM> <1988Oct1.230542.11512@utzoo.uucp> <252@studsys.mu.edu>
Date: Wed, 5 Oct 88 17:07:46 GMT

In article <252@studsys.mu.edu> jetzer@studsys.mu.edu (jetzer) writes:
>> Space also imposes some special constraints like radiation resistance, which
>> affects the issue; the dynamic RAMs used in PCs and the like are not usually
>> considered fit for use in space.
>
>What does 'fit for use in space' mean?

It depends on what you're doing.  For running some small experiment where
you don't care much if there's a 1-in-100 chance of the computer failing,
you can use most anything.  Model 100s have flown in space.  For long stays
in space, e.g. controlling satellites, it is necessary to have something
that can take a substantial accumulated dose of radiation without trouble.
Dynamic RAMs do not qualify, unless perhaps only a short lifetime is
needed.  (Amsat had some dynamic RAMs on board one of their birds, although
in a non-critical role, and has since regretted it.)  Remember that the
shuttle computers spend quite a bit of time in space over their lifetime,
and continued correct functioning of those machines is *very* important.
-- 
The meek can have the Earth;    |    Henry Spencer at U of Toronto Zoology
the rest of us have other plans.|uunet!attcan!utzoo!henry henry@zoo.toronto.edu