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From: mike@ames.arpa (Mike Smithwick)
Newsgroups: sci.space.shuttle
Subject: Re: Throttling the Challenger
Message-ID: <3143@ames.arpa>
Date: Sat, 17-Oct-87 19:43:38 EDT
Article-I.D.: ames.3143
Posted: Sat Oct 17 19:43:38 1987
Date-Received: Sun, 18-Oct-87 12:11:27 EDT
References: <340@ablnc.ATT.COM>
Reply-To: mike@ames.UUCP (Mike Smithwick)
Organization: NASA Ames Research Center, Moffett Field, Calif.
Lines: 48
Keywords: Challenger Throttle

In article <340@ablnc.ATT.COM> rcpilz@ablnc.ATT.COM (Robert C. Pilz) writes:
>
>One thing about the crash has been haunting me. When I saw
>the replays of the explosion, I heard the commands to the
>crew to be at 105% throttle. They acknowledged that. Then they
>were told to go to 80% (or so). They acknowledged that. Then
>they were told (very quickly) to go back to 105%. At this point,
>the explosion happened.
>This was never discussed in the national news. At least I never
>picked up on it. What were they (the flight people) trying to
>do? I have a strong feeling that they knew something was wrong
>at that point and were trying to do something? Was the extra
>boost supposed to put out the flame? Use up the fuel? Could
>that have made things worse? 
>Nothing was said. I have not had a chance to read any of the
>detailed reports. 

What you noticed is merely standard procedures for a shuttle launch.
First, when you hear the engines running at "105%", that means that
they are running at 105% of their originally intended performance, and
not that the're pushing them beyond their limits ("Captain Kirk, the
warp drive is gonna blow if we keep this up . . ."). They crank them 
suckers up to 100% or more at the start of the launch,  then ease them 
back to 75 or 80% as they are going thru "Max-Q" or the region of
maximum dynamic pressure, so as to ease loads. They will then
go back to the 100%+ range at about T+ 65 seconds. With 51L, that
was only 5 seconds or so before the explosion.

Alot of the early speculation right after the accident by the newstypes,
centered around the "throttle up" call, and what effects it might've 
had.

This brings to mind, though, what Mission control might have done had
they noticed the burn thru. Would they have notified the crew and 
risked that chance of them doing something stupid, or would they just
keep quite and hope that they could ride it out.







-- 
				   *** mike (powered by M&Ms) smithwick ***
"ever felt like life was a game, and 
someone gave you the wrong instruction book?"
[discalimer : nope, I don't work for NASA, I take full blame for my ideas]