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From: palmer@nntp-server.caltech.edu (David Palmer)
Newsgroups: sci.space,sci.astro,sci.space.shuttle
Subject: Re: Shuttle scrubbed again
Message-ID: <1990Sep28.171605.10912@nntp-server.caltech.edu>
Date: 28 Sep 90 17:16:05 GMT
References: <1990Sep17.224055.1343@murdoch.acc.Virginia.EDU> <993@dg.dg.com> <1990Sep25.152824.15327@murdoch.acc.Virginia.EDU> <1001@dg.dg.com>
Organization: California Institute of Technology, Pasadena
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ahughes@dg-rtp.dg.com (Arch Hughes) writes:

>Why is there such a great gap between the launch limit and the 4% 
>concentration?  If the limit was 2% (20K ppm) wouldn't there be ample
>time to scrub as the limit was exceeded, and vent the gas?

If the amount of Hydrogen exceeds the launch limit, that means that
there is something wrong, and something wrong may become very wrong.

If you analyzed some food, and found that its cyanide content was only
1% of the LD50 (the dose required to kill half the people eating it),
you probably would want to avoid that food, even though it would
probably have no ill effects on your health.

The area into which the Hydrogen leaks is flushed with Nitrogen, so
it wouldn't explode even at 4%, but the principle still holds.

-- 
		David Palmer
		palmer@gap.cco.caltech.edu
		...rutgers!cit-vax!gap.cco.caltech.edu!palmer
	I have the power to cloud men's minds -- or at least my own.