Path: utzoo!attcan!uunet!cme-durer!paisley
From: paisley@cme-durer.ARPA (Scott Paisley)
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle computer reprogramming
Message-ID: <653@web.cme-durer.ARPA>
Date: 3 Oct 88 13:22:45 GMT
References: <6689@nsc.nsc.com> <6980@ihlpl.ATT.COM> <1938@kalliope.rice.edu>
Organization: National Bureau of Standards, Gaithersburg, MD
Lines: 35

In article <1938@kalliope.rice.edu>, 
   phil@titan.rice.edu (William LeFebvre) writes:

[deleted stuff]

> (and some of this is conjecture on my part)....They have calculated ahead
> of time a handful of different flight profiles.  The profiles are based,
> in part, on the wind velocities and directions at different altitudes.
> Apparently, this is a very complicated model and takes quite a bit of CPU
> time and power to calculate the expected route.  There is just no way that
> the on-board computers are going to be able to perform the calculations in
> real time.  I suspect that it's hard for any computer to do the
> calculations in real time (maybe a Cray).  So they perform all these tough
> calculations ahead of time and the on-board software becomes much simpler.

[more deleted stuff]

Why can't they download the programs onto the computers on the shuttle
just a few hours before launch?  Each program would be extensively
tested of course.  As for the wind velocity conditions, the programmers 
could have (say) 5 programs prepared and tested for different wind
conditions.  So, say six hours before launch they could get the
current atmosphere conditions, calculate all the magic numbers on the
cray, and then download the tested program (which they would apply
these magic numbers into) and then test the newly loaded program
onboard the shuttle. (however they would do that. :-) Now I admit that
this idea is very rough and I'm sure has some problems that I didn't
think of.  But I think that the flexibility of software is what makes
software so wonderful.  I would have hated to seen the launch aborted
because they didn't have flexibility of software.
-- 
Scott Paisley		ARPA : paisley@cme-durer.arpa (preferred)
			BITNET : paisley@cmeamrf

"Super Science mingles with the bright stuff of dreams."