Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!ucsd!sdcsvax!ucsdhub!hp-sdd!hplabs!hpda!hpcuhb!hp-ses!hpcc01!hpwrce!howeird
From: howeird@hpwrce.HP.COM (Howard Stateman)
Newsgroups: sci.space.shuttle
Subject: Re: 104% on shuttle launch
Message-ID: <9130002@hpwrce.HP.COM>
Date: 21 Apr 89 18:10:43 GMT
References: <883@sactoh0.UUCP>
Organization: Ye Olde Salt Mines
Lines: 32

>This is little bit old, but during the last shuttle launch I heard
>one of the radio messages say "...engines at 104%..."  This seems
>like a contradiction to me.  If someone has succeeded in making the
>perpetual motion machine let me know, an engine running at 104%
>sounds great though.  Please excuse my cynicism, but I truly don't
>understand.  Someone please explain?!
>
>Brian Cox
>pyramid!amdahl!pacbell!sactoh0!bncox
>----------

Well, the idea is that there is an optimum number of RPMs at which
the engine can run. If you rev it any faster, you're at over 100%
of the number of optimal RPMs. 

The FCC has a similar measurement for modulation of a radio signal.
When you are at 100% modulation, the signal is as strong as it can
get without being distorted. At 101%, your signal is stronger than at
100%, but it is distorted. At 99% it is still undistorted, but not
at full strength. 

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.  

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|Howard Stateman, Hewlett-Packard Response Center, Mountain View, CA |
|howeird@hpwrce.HP.COM      or     hplabs!hpwrce!howeird             |
|Disclaimer: I couldn't possibly speak for HP. I know too much.      |
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