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From: kent@vf.jsc.nasa.gov
Newsgroups: sci.space.shuttle
Subject: Re: Fire near tail of shuttle after landings.
Message-ID: <1991Apr12.102633.1@vf.jsc.nasa.gov>
Date: 12 Apr 91 16:26:33 GMT
References: <1991Apr11.223534.12896@pandora.matrox.com>
Sender: news@aio.jsc.nasa.gov (USENET News System)
Organization: NASA Johnson Space Flight Center
Lines: 36

In article <1991Apr11.223534.12896@pandora.matrox.com>, hobrien@pluton.matrox.com (Hugh O'Brien) writes:

>     Sometime in 1985 I remember seeing a shuttle landing on TV where
> there was a clean flame emanating from near the base of the tail 
> after the orbiter had come to a stop.  If my memory serves me correctly,
> it was 4 to 6 feet long.  It looked exactly like the flame from a 
> butane lighter. 
> 
>     I was completely freaked out, I was half-expecting the shuttle to
> blow-up any second.  I cringed when the ignorant (stupid?) announcer
> on TV commented on it by saying, "Well look at that, the shuttle got
> so hot on reentry that it's on fire."  He said this in a jovial way,
> not taking it seriously.
> 
>    Recently I saw another landing where there was a nasty trail of
> smoke coming from the same section of the tail.  The smoke persisted
> for the full five minutes that I watched.
> 
>    What gives?  Did some sort of gas/hydraulic line rupture?  How come
> nothing like this was ever mentioned in the layman press?
> 
>                           I have been pondering this for years.  
> 

What you are seeing is the exhaust gases from the Auxiliary Power Units (APU).
The three APU's use Hydrozine for fuel.  The APU's drive the Hydraulic pumps
on the Orbiter. The Shuttle uses hydraulic power to move the control surfaces 
during landing and move the main engines during ascent.  The APU are kept on
for about 5 minutes after landing so the main engines can be repositioned 
to the "rain drain" position after landing.  During reentry, the engines are
in the highest position.  After landing they moved down.

-- 

Mike Kent -  	Lockheed Engineering and Sciences Company at NASA JSC
		2400 NASA RD One, Houston, TX 77058 (713) 483-3791