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From: cew@venera.isi.edu (Craig E. Ward)
Newsgroups: sci.space.shuttle
Subject: Re: holds in countdown
Summary: Do it out of habit
Keywords: historical reasons
Message-ID: <7832@venera.isi.edu>
Date: 23 Mar 89 19:08:37 GMT
References: <8.UUL1.3#5131@mvac.UUCP>
Reply-To: cew@venera.isi.edu.UUCP (Craig E. Ward)
Followup-To: sci.space.shuttle
Organization: OASIS, A Chapter of the National Space Society
Lines: 28

In article <8.UUL1.3#5131@mvac.UUCP> mvac!space@udel.edu writes:
>This may be a nieve question, but I'll post it anyway:  Countdowns for launches
>begin much earlier than the time alloted in the countdown timer (ie a launch is
>set for 72 hours away, but clock says T-50 hours, or whatever).  I know that
>'built in holds' are the reason why the two clocks do not agree, but my ques-
>tion is why are they there?  If you *know* that you are going to stop the clock
>for 1 hour and 20 minutes when the countdown clock says T-xxx, than why not 
>just add one hour and 20 minutes to the countdown clock and just say that from
>T-4:20 to T-3:00, there is no planned activity.  

The story I got (sorry, I don't remember the source) was that in the early
days, it seems that something would always go wrong so one team leader just
said "We're going to plan to have something go wrong at this point."  

As to why not just add the time, they probably still kept the old schedule
format out of habit (the old historical reasons).  Also, if something does go
wrong, it might not be fixable within the hold time.

		Craig
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