Path: utzoo!utgpu!water!watmath!clyde!bellcore!faline!thumper!karn
From: karn@thumper.bellcore.com (Phil R. Karn)
Newsgroups: sci.space.shuttle
Subject: Re: gratuitous anthrophobia (was Re: Shuttle computer reprogramming)
Message-ID: <1356@thumper.bellcore.com>
Date: 21 Oct 88 22:30:14 GMT
References: <6689@nsc.nsc.com> <6980@ihlpl.ATT.COM> <1938@kalliope.rice.edu> <1988Oct20.175844.24740@utzoo.uucp>
Organization: Bell Communications Research, Inc
Lines: 24

> I'm not thinking of total satellite failures, but of subsystem failures.
> The specific one that comes to mind is those DRAMs aboard Oscar 10 (I
> think it was), which sounded good early on -- Phil posted a description
> and commentary which added up to "it's working great so far" -- but
> proceeded to fail, badly enough that I gather Amsat has given up on
> that approach.

Given up on what approach? We replaced the DRAMS with radiation-hardened
SRAMS in Oscar 13. We do not expect radiation damage to be the limiting
factor in this spacecraft's lifetime. As for Oscar-10 -- I and others
who researched the subject *did* expect memory problems. The decision to
fly them was made only when there appeared to be no alternative to get
the spacecraft to the launch pad in time.

Other than this change, many of the bus subsystems on Oscar-13 are
identical to those on Oscar-10; indeed, many of the modules were
originally constructed as flight-ready spares for the earlier
spacecraft. The differences are mainly in the communications
transponders (several more were added, but the same principles were
used) and in the kick motor control system (another mechanical gas
pressure regulator wasn't available for a reasonable price, so we
designed an active electronic replacement that actually worked better).

Phil