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From: lmc@cisden.UUCP (Lyle McElhaney)
Newsgroups: net.columbia,net.space
Subject: Re: Why we care
Message-ID: <488@cisden.UUCP>
Date: Fri, 7-Feb-86 17:10:32 EST
Article-I.D.: cisden.488
Posted: Fri Feb  7 17:10:32 1986
Date-Received: Tue, 11-Feb-86 06:15:59 EST
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Xref: watmath net.columbia:2238 net.space:5742

>                There's  no question it was the main tank that blew.  In one
> frame you can distinctly see the  start  of  the  major  explosion  at  the
> forward  tip  of  the tank.  This was preceded by flames at the rear of the
> tank and one or two minor explosions near the center between the  tank  and
> the Shuttle.
> 
With reference to the posting I made about 20 minutes ago about blaming
various subsystems on the shuttle, well....there it is. Obviously, if
something goes badly wrong on the stack, eventually the lox and lh are
going to go up; its hard to image an accident that wouldn't involve the
tank. Was it then the tank's fault (or that of its designers/builders)?

> The Shuttle was doing Mach 3 at the time and the main tank is very fragile.
> Even  a  minor  compromise  of  its  integrity  at  that  speed would allow
> aerodynamic forces to tear it to shreds. [Personal speculation:  The  minor
> explosion  blew  a  hole in the side of the tank which allowed external air
> pressure to collapse the nose.]

I beg to differ. The tank is holding the stack together; It is
transmitting the 3,000,000 lb thrust of the SRBs to carry both itself and
the orbiter through its structure. The maximum aerodynamic force on the
tank is at Mach 1; at that point the main engines on the orbiter were at
65% thrust, and even more than at any other time, the tank was "carrying"
the orbiter. Not only max-Q was involved at that point, but also max
structural loading on the tank. And it made it. And continued to make it
until something else happened. It is *not* a fragile structure. True, it
is engineered close to its margins; it is huge, and any increase in skin
thickness, for example, would have a decided disadvantage in its weight.
The paint job that was left off the ET alone resulted in 400 lbs of
savings. But to point the finger there on the basis of the released
footage is irresponsible.

Lyle McElhney
...hao!cisden!lmc