Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!mailrus!cornell!uw-beaver!fluke!ssc-vax!adolph
From: adolph@ssc-vax.UUCP (Mark C. Adolph)
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle computer reprogramming
Keywords: shuttle, wind, programming
Message-ID: <2270@ssc-vax.UUCP>
Date: 3 Oct 88 19:14:02 GMT
References: <6689@nsc.nsc.com> <1543@hp-sdd.HP.COM>
Organization: Boeing Aerospace Corp., Seattle WA
Lines: 29

In article <6689@nsc.nsc.com> glennw@nsc.UUCP (Glenn Weinberg) writes:
>The question I, as a software engineer, have is: why should this require
>reprogramming at all?  Why couldn't the program have been written to
>accept input as to meteorological conditions at launch time?  Seems to me
>that hard-wiring this data into the program isn't particularly good
>programming practice.
>
>I don't want to believe that the shuttle programmers simply missed this.
>Is it a memory space issue?  ... [deleted possibilities]

I heard on a newscast an explanation of the problem.  The shuttle
computers included in them data to handle the expected range of
atomspheric conditions for September over the Cape.  The upper
atmospheric winds happened to be outside the range covered by the data
in Discovery's memory.

As a real-time programmer, this seems like a reasonable explanation to
me.  If you have limited memory and limited time to search tables, you
want to include the minimum data that it will take to accomplish the
mission.  I'm sure that the software accepts inputs and makes
corrections in real-time.  This would be much tougher to do if one had
to consider all possible atmoshperic conditions for all times of the
year during each launch.  Often, things that look like bad programming
practices become indispensible in a real-time, embedded application.

-- 

					-- Mark A.
					...uw-beaver!ssc-vax!adolph