Newsgroups: sci.space.history
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Space Shuttle Propellants
Date: Tue, 11 Nov 1997 17:14:05 GMT

In article <3467931B.3D6E@ast.lmco.com>,
Jeff Lewis  <jeff.a.lewis@ast.lmco.com> wrote:
>> With regards to the space shuttle, what are the exhausts emitted...
>
>Main engines, SSMEs, produce water steam, reacting LOx and LH2.

There's also a lot of unburned H2 in the exhaust.  Plus traces of other
things; in particular, any rocket engine running within the atmosphere
will generate some oxides of nitrogen.

>The
>solids produce some burnt rubber kind of stuff plus chlorides, from
>burning basically tire rubber and ammonium perchlorate...

It's more complicated than that.  The solids' exhaust is a real witches'
brew.  The ammonium perchlorate oxidizer decomposes into, mostly,
nitrogen, water, oxygen, and hydrogen chloride (which becomes hydrochloric
acid if dissolved in water).  The rubber fuel, whose overall composition
is roughly CH2, burns with some of the oxygen to give CO2 and more water.
The powdered aluminum burns with more of the oxygen to give Al2O3, which
quickly condenses into solid particles, which is what makes the SRB
exhausts so smoky.  However, this process is complicated and disorderly,
and all kinds of things come out of it in smaller quantities.

>...The OMS react N2H4 and N2O4, so probably produce nitrogen,
>hydrogen, oxygen, ammonia, water...

Actually the fuel is not hydrazine but MMH, CH3NHNH2, so there's also CO2
and other odds and ends in there.  There won't be any significant amount
of oxygen in the exhaust, it all gets used up.  Assorted poorly-known
weird things form in small quantities, especially during startup and
shutdown when temperatures are lower.
--
If NT is the answer, you didn't                 |     Henry Spencer
understand the question.  -- Peter Blake        | henry@zoo.toronto.edu

Newsgroups: sci.space.history
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Space Shuttle Propellants
Date: Wed, 12 Nov 1997 13:54:35 GMT

In article <64bc5g$p9m@news3.his.com>,
Paul Michael Brown <paulo@mirror.his.com> wrote:
>...I had to sign a document that recited I was aware that
>if the wind blew in a certain direction, nasty chemicals might mess up my
>car's paint job. Anybody know what those chemicals were?

They were probably thinking mostly of the hydrogen chloride in the SRB
exhaust, which turns into hydrochloric acid in the presence of moisture
(and the Cape is generally rather moist).
--
If NT is the answer, you didn't                 |     Henry Spencer
understand the question.  -- Peter Blake        | henry@zoo.toronto.edu