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From: johng@ecrcvax.UUCP
Newsgroups: sci.space.shuttle
Subject: Re: Throttling the Challenger
Message-ID: <447@ecrcvax.UUCP>
Date: Thu, 29-Oct-87 11:29:45 EST
Article-I.D.: ecrcvax.447
Posted: Thu Oct 29 11:29:45 1987
Date-Received: Sun, 1-Nov-87 20:36:05 EST
References: <187@scdpyr.UUCP> <5270001@hpisof0.HP.COM> <9298@tekecs.TEK.COM>
Reply-To: johng@ecrcvax.UUCP (John Gregor)
Organization: ECRC, Munich 81, West Germany
Lines: 29

In article <9298@tekecs.TEK.COM> philb@maya.UUCP (Phil Biehl) writes:
>In article <5270001@hpisof0.HP.COM> campbelr@hpisof0.HP.COM (Bob Campbell) writes:
>>SSME Specifications     (Full power level)
>.
>.
>>Flowrates:
>>   Total                 1,130 lb/s     22,557 gpm
>>   Hydrogen                160 lb/s     16,436 gpm
>>   Oxygen                  970 lb/s      6,121 gpm
>
>Does the above flowrates indicate tha actual combustion mixture present at the
>combustion chamber? If so then why is there a greater ratio than 2 parts H to
>one part O? I would think that the extra hydrogen would be unconsumed making
>the engine less efficient than it could be... What am I missing?
>
>Phil Biehl

True, some of the hydrogen goes unconsumed.  There are two problems with
the perfect 8:1 mass ratio:

    1) The metals of the engine cannot handle the temperature of the
       reaction.  So the hydrogen acts as a coolant.

    2) *I'm not positive of this one*  The temperature of the 8:1
       reaction is enough to disassociate some of the water back into 
       hydrogen and oxygen therefore *lowering* the efficiency.
       *Anybody know for sure?*

			    John Gregor