Xref: utzoo sci.space:12269 sci.space.shuttle:3354
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!grebyn!rich
From: rich@grebyn.com (Rich Kolker)
Newsgroups: sci.space,sci.space.shuttle
Subject: Re: space news from May 15 AW&ST (replacing computers)
Message-ID: <12207@grebyn.com>
Date: 10 Jul 89 23:36:10 GMT
References: <1989Jul2.054432.5054@utzoo.uucp> <3827@phri.UUCP>
Reply-To: rich@grebyn.UUCP (Rich Kolker)
Followup-To: sci.space
Organization: Grebyn Corp., Vienna, VA, USA
Lines: 31

In article <3827@phri.UUCP> roy@phri.UUCP (Roy Smith) writes:
>In <1989Jul2.054432.5054@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes:
>> the Atlantis crew replaced one of the orbiter's five general-purpose
>> computers after it failed [...] it took about four hours because the
>> computers are behind some of the middeck lockers and are not easy to get at.
>
>	I don't understand.  I thought that the various computers were all
>constantly checking each other and if one failed, it would be taken off line
>automatically and the others would continue to operate without it.  Why the
It's been a while since I've been on the net, but let me take a crack at
this one.  The GPC's are not taken off line automatically,  In the case
of
a problems, there is a 5x5 grid above the commander's chair that shows
GPC
status.  One axis is which computer is voting and the other is which
computer the voting computer says is going bad (has gone bad).  The
GPC control switches are directly above the CDR's seat and are taken
on/off line manually.  Generally, only three are kept powered up during
orbital flight although flight rules say all five are to be up, running
and available for launch and entry.  This from my feeble memory,
although
if something is really wrong, catch me and I'll go back to the manuals
for the final say (I've got the 2102s for the GPC's around here
somewhere).

++rich
+-----------------------------------------------------------------------+
| Rich Kolker
|
| uunet!telenet!richk  (not the reply to above)
+-----------------------------------------------------------------------+