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From: raveling@venera.isi.edu (Paul Raveling)
Newsgroups: sci.space.shuttle
Subject: Re: 104% on shuttle launch
Message-ID: <8056@venera.isi.edu>
Date: 24 Apr 89 16:22:26 GMT
References: <883@sactoh0.UUCP> <9130002@hpwrce.HP.COM>
Reply-To: raveling@venera.isi.edu.UUCP (Paul Raveling)
Organization: Information Sciences Institute, Univ. of So. California
Lines: 24

In article <9130002@hpwrce.HP.COM> howeird@hpwrce.HP.COM (Howard Stateman) writes:
>>This is little bit old, but during the last shuttle launch I heard
>>one of the radio messages say "...engines at 104%..."  

	If my memory's not too foggy, the main engines were originally
	certified for a given power level.  After enough testing they
	cleared them first to 104% of that level, then to 109% for
	limited burn periods.
>
>So to carry this over to your engine running at 104%, it is running 
>harder than at 100%, but it is past its point of peak efficientcy, and
>may do something non-user-friendly, like blow everyone all to Hell.  

	Last night I found a note in Feynman's Appendix F to
	the Challenger Commision's report, where he spoke briefly
	about blade cracking in the high pressure fuel turbopump.
	Info at that time suggested that running at 109% rather
	than 104% would reduce the blades' safe lifetime by a
	factor of 2.


----------------
Paul Raveling
Raveling@isi.edu