> Perhaps I can point people at a letter in the Sept 12 "Space News" by
> Stephen A Evans.
>
> Titled "Throwing out the Wheat and keeping the Chaff" it appears he was
> involved in some of the design studies, and has some interesting comments.

While I'm certain I can't claim expert status as I'm sure Mr. Evans can, I
do see some flaws in his points.

> Quote 1
> "Engine design decisions started with aerospike vs staged combustion engine
> and progressed to details like extendible vs fixed nozzles. When the
> re-usable booster was abandoned, we knew that most of the promise of the STS
> was lost."

We aren't talking about another STS, just reusing some of the proven parts.

> Quote 2
> "Two items assumed to be low technology, an O-ring and foam insulation,
> caused the loss of the Challenger and Columbia orbiters, while many
> high-technology items operated as planned."

The O-ring problem is fixed- there hasn't been another SRB failure
since then.  I think the SRBs can be considered a proven and solid
piece of equipment.  As for the foam, the piece that has been a problem,
repeatedly, is the piece of foam covering the joint between the orbiter and
the tank.  No orbiter, no joint.  Plus, nothing for any foam falling off to
damage.

Worth noting is that a very similar problem occured in prior generations
of spacecraft- bits falling off as the ship ascends.  In that case, it was
usually ice from condensation freezing on the side of the rocket due to
the super cold LOX.  It just never caused a problem before because
there was never anything for the debris to hit on its way by.

> Quote 3
> "The orbiter itself has never experienced a failure. The parts of the STS
> that have caused mission loss are the solid rocket boosters and the external
> tank. Neither performed as originally designed. By treating the solid rocket
> booster and the external tank out of specification performance as
> maintenance issues, NASA doomed two orbiters and their crews. Maintenance
> only applies to re-useable parts. The solid rocket booster and external tank
> are non-conforming parts whose problems are caused by a faulty design or
> manufacturing process.
> NASA is thinking of retaining the external tank and the solid rocket
> booster. The logic seems to be that by eliminating the orbiter, the part
> that works, the other parts can be used because there will be no orbiter for
> them to damage."
>
> He has a number of other things to say along the same line.

What NASA is really doing here is spinning chaff into gold.  Despite Mr.
Evans assertion that an orbiter never failed, the "truth" is that the central
failure in both cases was the orbiter- it failed to pull the crew to safety
when the SRB blew up, and it failed to bring the crew back to earth
safely after being struck by a relatively small piece of debris.

Of course, it's all opinion.  Obviously, NASA's opinion is that the bits
worth saving are the SRBs and SSMEs.  To save the SSMEs, you
need to save some variation on the ET.  Remember, the STS was
built as a cargo plane that flies a little higher than most.  Even the
Delta IV Heavy can't deliver the load a space shuttle can to orbit.

During an early Mercury test lauch (MA-3?), the Atlas booster exploded,
violently, shortly after liftoff.  Gus Grissom and Gordon Cooper were
both almost killed, flying chase planes following it up, but the ship on
top was pulled to safety by the escape tower and its crew would have
survived.  The shuttle doesn't have such an abort mode- it's tethered
to the ET, at least, until quite late in the game.  The CEV is intended
to shear away these shortcomings and leave just the best elements
of the STS.

Mike H.

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