Path: utzoo!attcan!uunet!husc6!rutgers!bellcore!faline!thumper!karn
From: karn@thumper.bellcore.com (Phil R. Karn)
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle computer reprogramming
Summary: space computers
Message-ID: <1344@thumper.bellcore.com>
Date: 6 Oct 88 19:01:34 GMT
References: <6689@nsc.nsc.com> <6980@ihlpl.ATT.COM> <1938@kalliope.rice.edu> <2994@jpl-devvax.JPL.NASA.GOV>
Organization: Bell Communications Research, Inc
Lines: 30

It is certainly clear that the shuttle computers are ancient technology,
and newer stuff would be much smaller and more capable. For example, the
AMSAT Microsat satellites, currently under development for a June 1989
launch, will carry a NEC V40 microprocessor and about 10 megabytes of
static RAM.  Running in this computer will be a real-time multitasking
operating system capable of executing .exe files generated by an MS-DOS
linker (with a special library) and uploaded from the ground. As far as
we know, this will be the first-ever spacecraft to support the TCP/IP
protocols.

In addition, there will be one UHF transmitter, four VHF receivers, I/O
interfaces, modems, power conditioner, Ni-Cd battery, solar arrays, etc.
Everything fits in a *7-inch* cube. Total power budget is something like
7 watts, with much of this going to the transmitter. Yet one of the five
modules making up the satellite is currently empty! (We call this the
"TSFR" module -- This Space For Rent).

Although I have every reason to believe that this design will work as
advertised, I'm not sure I'd be willing to bet my life on it -- yet.
Many of the component types will be flying in space for the first time,
and their reliability and radiation hardness aspects are not well known.
So I can understand NASA's reluctance to upgrade the STS computer
hardware unless or until the added functionality becomes necessary.

By the way, this is an excellent illustration of how excessive reliance
on large manned missions has hindered technological development. The
latter inherently requires risk-taking that is acceptable only when
human lives and/or extremely large sums of money are not at stake.

Phil