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Path: utzoo!watmath!clyde!burl!ulysses!allegra!alice!alb
From: alb@alice.UUCP (Adam L. Buchsbaum)
Newsgroups: net.columbia
Subject: Re: Shuttle Engine Starting
Message-ID: <4104@alice.UUCP>
Date: Sat, 3-Aug-85 12:28:56 EDT
Article-I.D.: alice.4104
Posted: Sat Aug  3 12:28:56 1985
Date-Received: Sun, 4-Aug-85 08:36:09 EDT
References: <1397@peora.UUCP>
Organization: Bell Labs, Murray Hill
Lines: 8

The sparks you see are to ignite any hydrogen that may have leaked
before ignition.  The engines each have their own ignition system;
they ignite separately, 120 milliseconds apart, in the computer
controlled sequence.  They do not ignite again after launch because
(1) there is no more fuel left once in orbit and (2) the main
engines are not designed to be reignited.  The solids, too, have
their own ignition devices.  The solid fuel is basically an aluminum
powder.