> The shuttle engines are ammonium perchlorate, aluminum, and a binder,
which
> is what the Aerotech reloads are made from.  Not black powder. The failure
> was due to a rubber O-Ring that lost it's flexibility in the low
temperatures.
>

The solid rocket boosters are ammonium perchlorate, aluminum and binder. The
failure was due to a combination of poor judgement on managment's parts, and
bad luck.
The O-Ring was not rated for use at that low of a temperature. There was ice
on the shuttle that day. Several people advised against a launch attempt.
Management decided to go anyway. This happens all the time, for a variety of
reasons. It is still going on today. There were at least 4 counts that I
know of in the last 12 months that were recommended against. (Usually for
low probability of acceptable weather.) One was a successful launch. That's
what they pay the guys for, to make the go/no-go call on the launch
attempts. They almost always try, and they frequently get away with it. One
time they didn't. Actually they fail to get away with it all the time, its
just that it usually doesn't result in quite so press coverage.

James Womack Sr's first launch as director of expendable vehicles was a real
disaster. He is the father of a hunting buddy of mine, and he had been
working on the manned side for many years. On the expendable side the rules
a lot different because the payload is owned by a company interested in
getting it in orbit and on line to get the revenue stream going. They have a
whole lot more say in when an attempt is made and when you scrub. This
results in different language being used when you get weather advisories.
The time of launch approached, James asked for a call on the weather, which
was dicy at best, and the weather advisor told him that it was go if James
desired, meaning if the customer wanted to risk it, it was his payload.
James was used to manned weather reports. They launched, the bird blew up
and a grand time was had by all.

Back to the bad luck bit. Few people know it, but the SRB nozzles were
slewwed over, trying to compensate for the side thrust from the leak at the
field joint. (The SRB's are actually sections because you can't cast that
much propellant in one go. The sections are then pinned together and a metal
band hold the pins in place. The result is called a field joint.) They kept
the shuttle on track, leak and all. If that leak had developed on a slightly
different section of the O-Ring, the flame would have jetted out into space,
never would have burned through the external tank, and only a few of us
space workers would have ever known about it. 30 degrees of danger and we
ended up unlucky.

Wynn Rostek

Former Shuttle Worker
CBEP (SRB Power Distribution and Control)

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