A different direction after Challenger loss

In article om,
says...

On 13-02-18 11:54, Jeff Findley wrote:

Why would liquid boosters have made a difference? The ET would still
have had SOFI on the outside due to its cryogenic propellants.

It is my understanding that SRBs generate a hell of a lot of noise and
vibration compared to liquid fueled engines.

So I was wondering if a significant reduction of vibration would have
reduced foam shedding.

The aerodynamic forces on the stack is one of the reasons that foam
shedding seems to be worst when the stack is going through max-Q
(maximum dynamic pressure). I doubt that reducing vibrations caused by
the boosters would have reduced foam loss by much.

Another contributor to foam loss has been defects in the foam allowing
ice or liquid air to form in the foam. In flight, these pockets of ice
or liquid will heat up and expand causing foam loss. Quality control of
SOFI application is critical because of this. I believe that over the
years, some application of SOFI was changed from hand sprayed to robotic
spraying in order to reduce defects.

In fact, the problem could have been made *worse* as it's very likely
that liquid boosters would have been LOX/kerosene, which would have
introduced even more sources for ice and/or SOFI to be shed.

Would liquid boosters have changed the general shape of the stack ?
Longer ET to accomodate storage of more LOX, with kerosene stored in
the booster itself ? Or would each booster have been self contained and
thus likely taller ? ( a taller one exposes more of the orbiter to
potential for foam shedding).

Almost certainly the outer dimensions of the boosters would have
changed, at least somewhat.

Eliminating the solids would have reduced failure modes like the one
that destroyed Challenger or the case rupture failure mode which luckily
never happened during any shuttle flight (yet has happened with the
large Titan solids and other smaller solids).

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

"Jeff Findley" wrote in message
...


Another contributor to foam loss has been defects in the foam allowing
ice or liquid air to form in the foam. In flight, these pockets of ice
or liquid will heat up and expand causing foam loss. Quality control of
SOFI application is critical because of this. I believe that over the
years, some application of SOFI was changed from hand sprayed to robotic
spraying in order to reduce defects.


Ayup, and in fact this change was one of the things the CAIB looked at. The
bipod ramp though was still sprayed by hand because of its shape and
complexity.


In fact, the problem could have been made *worse* as it's very likely
that liquid boosters would have been LOX/kerosene, which would have
introduced even more sources for ice and/or SOFI to be shed.

Would liquid boosters have changed the general shape of the stack ?
Longer ET to accomodate storage of more LOX, with kerosene stored in
the booster itself ? Or would each booster have been self contained and
thus likely taller ? ( a taller one exposes more of the orbiter to
potential for foam shedding).

Almost certainly the outer dimensions of the boosters would have
changed, at least somewhat.

Eliminating the solids would have reduced failure modes like the one
that destroyed Challenger or the case rupture failure mode which luckily
never happened during any shuttle flight (yet has happened with the
large Titan solids and other smaller solids).

There's also the argument that while the engines may have been more
susceptible to damage from a salt-water landing, turn-around would have been
far easier since you wouldn't have to ship pieces to Utah and back and
restack them.

(now if you had gone all the way with a flyback booster, you'd eliminate the
salt-water issue).

But again.. "what ifs"



Jeff

--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
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