Path: utzoo!attcan!uunet!iconsys!mcd
From: mcd@iconsys.UUCP (Mark Dakins)
Newsgroups: sci.space.shuttle
Subject: Re: 104% Throttle ??
Keywords: Throttle up 104%
Message-ID: <280@iconsys.UUCP>
Date: 22 Oct 88 01:47:24 GMT
References: <8837@watdragon.waterloo.edu> <497@idsssd.UUCP>
Reply-To: mcd@iconsys.UUCP (Mark Dakins)
Distribution: sci
Organization: Icon Systems and Software Inc., Orem, Utah
Lines: 40

In article <497@idsssd.UUCP> bruce@idsssd.UUCP (Bruce T. Harvey) writes:
|In article <8837@watdragon.waterloo.edu>, hjespersen@trillium.waterloo.edu (Hans Jespersen) writes:
|| When the shuttle goes to 104% trottle what does the 104% represent.
|| 104% of what?? You would think 100% was full trottle and it would
|| not be possible to go any higher. What is full trottle??
|
|Previously, discussion seemed to accept that the 100% figure represents
|the ORIGINAL shuttle design specifications and that the design has been
|improved.
|
|			...but could it also (or instead) be that the
|specifications call for "reserve" power, and that the 100% refers to a
|kind of "cruise" rating and 104% refers to "all-out-hell-bent-for-leather?"
|

I tried posting this earlier but, it never got out so, I'll try again.
Mr. Harvey's speculation is close to being correct. When the RFP's
for the SSME's were issued they described an engine with certain
thrust, specific impulse, run time, and reliability parameters.

A particular thrust was defined as 100% and the run time and reliability
parameters were based on this thrust level. However, the spec also
called for the ability to run the engine at up to 110% of "rated"
thrust. Note: this was in the original spec, not a later, discovered
improvement. If run beyond 100% rated thrust the "run time before
overhaul" goes down, actually I think it goes way down. Yes I know
that they overhaul them after every flight but, this was a spec,
remember? It doesn't have to relate to reality.

I think that they try to keep the peak thrust down as far as possible
but I don't know if any launches have stayed at or below 100%. I
think they usually stay at or below 105% but, I seem to have a
vague memory of a launch that went to 109%.

The above info was gleaned from old AW&STs, various NASA and contractor
publications, and my memories of discussions and news briefings at STS-1.

-- 
					Mark Dakins, Icon International
uplherc!nrc-ut!iconsys!mcd@utah.cs.edu	774 South 400 East, Orem, UT.