Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!amdahl!nsc!glennw
From: glennw@nsc.nsc.com (Glenn Weinberg)
Newsgroups: sci.space.shuttle
Subject: Shuttle computer reprogramming
Summary: Why is wind data hard-coded in the shuttle programming?
Keywords: shuttle, wind, programming
Message-ID: <6689@nsc.nsc.com>
Date: 29 Sep 88 21:20:11 GMT
Reply-To: glennw@nsc.UUCP (Glenn Weinberg)
Organization: National Semiconductor, Sunnyvale
Lines: 29

Everyone undoubtedly knows by now that the shuttle has made it into space
again.  You probably also know that the launch was delayed for over 90
minutes while NASA waited for favorable upper atmosphere wind conditions.

The networks explained the problem as being that a certain wind speed and
direction (determined by historical data) is programmed into the shuttle
computers and that reprogramming would be difficult and require retesting.

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?  A computation time issue?  Is the meteorological
data somehow massaged before it's loaded into the program?  Or is it simply
a testability issue, in the sense that the program couldn't be tested without
some data, and NASA wouldn't feel confident enough in the program running
with data not known in advance?

I'm interested in any information you folks out there might have, purely
from a professional curiosity point of view of course.

In any event, we software types should all be happy that the shuttle wasn't
grounded by software again, as it was the first time we tried to launch it!
-- 
Glenn Weinberg					Email: glennw@nsc.nsc.com
National Semiconductor Corporation		Phone: (408) 721-8102
(My opinions are strictly my own, but you can borrow them if you want.)