Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!pilchuck!seahcx!phred!petej
From: petej@phred.UUCP (Pete Jarvis)
Newsgroups: sci.space.shuttle
Subject: Re: 104% on shuttle launch
Message-ID: <2554@phred.UUCP>
Date: 24 Apr 89 14:23:28 GMT
References: <883@sactoh0.UUCP> <9130002@hpwrce.HP.COM> <2516@mentor.cc.purdue.edu>
Reply-To: petej@phred.UUCP (Pete Jarvis)
Organization: <2516@mentor.cc.purdue.edu>o
Lines: 15

In article <2516@mentor.cc.purdue.edu> ajk@mentor.cc.purdue.edu (Jeff Boerio) writes:
>
>My personal opinion, and something that I certainly don't know as fact, would
>be that the engines used were originally expected to operate at a level X,
>or 100%.  But, the production engines actually operate at X+4%, or 104%.
>

The SSME's have a nominal thrust for their use on the Shuttle at 100%.
The design limit is 109% of nominal thrust. The use limit is 104% of
nominal thrust leaving a 5% safety factor. In order for there to be
good guarantee of the engines working at the 100% point, they had to be
designed to guarantee reliable operation at a higher thrust, in this case
109%. However, they don't use them beyond 104%.

Peter Jarvis.............