Re: Griffin Wants Inline SDLV and 5 Segment SRB/CEV


"Rand Simberg" <simberg.interglobal@xxxxxxxxx> wrote in message
news:42e5c915.159716009@xxxxxxxxxxxxxxxxxxxxxxxxxxx
> On Sun, 10 Jul 2005 17:52:32 -0400, in a place far, far away, "Murray
> Anderson" <murraya@xxxxxxxxxxxx> made the phosphor on my monitor glow
> in such a way as to indicate that:
>
>
> >> >> >In a practical sense though, it makes no difference why they did
> >things
> >> >the
> >> >> >way they did 30 years, except if the the facts tell why they failed
to
> >> >> >achieve their objective.
> >> >>
> >> >> They do.
> >> >
> >> >I think I'd wonder if they really were trying to minimize development
> >costs.
> >>
> >> Why? They requested ten billion. They were given five. Bye bye,
> >> liquid flyback booster (among other things).
> >>
> >
> >It wasn't necessary to have a fly-back booster - just recover the liquid
> >boosters the way the SRB's are recovered.
>
> That would still have cost more than they had budget for (solids are
> cheaper to develop than liquids, honest), and it's not at all clear
> how refurbishable a liquid in that class would be after being dropped
> in the ocean, Truax's limited experiments aside.

They didn't know how refurbishable the solid would be either.

> >
> >> >Perhaps rather because the solid rocket engineers had been excluded
from
> >> >Apollo and had to be part of the next National Project - or they'd
cry.
> >>
> >> No.
> >>
> >> >Do you think the shuttle SRB is being proposed as the first stage of
the
> >new
> >> >launch vehicle because it minimizes development cost?
> >>
> >> Yes.
> >>
> >
> >So it's cheaper to develop, with large upper stage, than Delta IV Heavy,
> >which already exists?
>
> Delta IV heavy doesn't have the payload they want, and getting it
> (with man rating) probably will cost more than the development of the
> Satay.
>

The payload was supposed to be 25 tons, and could be met or increased by
using two RL10's on the upper stage. They'd have to use a shorter nozzle to
fit them both on, but that's nowhere near as hard as developing the upper
stage for the stick.

> >> >Makes the system safer?
> >>
> >> Well, they seem to think so. Others' mileage (like mine) may vary.
> >>
> >
> >But the belief is so unreasonable that it's hard to take seriously. It's
> >rather like the pre-Challenger failure probabilities for the shuttle.
>
> Well, they argue that the SRB actually has an excellent reliability
> record, and that the failure that caused Challenger wouldn't be a
> problem for the stick.
>

The record is good for solids, and is consistent with the view reported by
Feynman that you can about halve the failure rate with careful selection of
parts. It still has the characteristic of being hard to turn off, and the
steering in the proposed booster is more difficult than in the shuttle. So
they're ignoring the downside and emphasizing the upside.
As for liquids, they have similar reliability to solids, and higher
performance, so the upper stage can be smaller.


> >> >As for why the shuttle failed so completely to achieve its goals, I
> >wouldn't
> >> >be so sure I knew the answer.
> >>
> >> Again, that's pretty well understood, to people who've studied the
> >> issue.
> >
> >I confess to not understanding. I can understand the high fixed cost, but
> >not really why the number of flights is so small, and can't be increased.
I
> >accept that they can't do any better but don't quite see the connection
> >between original design decisions and the flight rate. I'm not talking
about
> >the fantasies of 50 flights a year, but 10-12 a year would have been very
> >helpful after the space station was started.
>
> Because they didn't design it for rapid turnaround, again due to
> limited development budgets.

That's a restatement of the problem in other words, together with a
rationalization. What was it they wanted to do and didn't have the money
for? A better thermal protection system would help, but that wasn't on
offer, was it? Similarly, the external tank shouldn't shed foam to damage
the tiles, but what tank design was turned down because it cost too much?
They didn't realize this was a problem till after the flights started, then
didn't deal with it.

They were planning to do 16 flights in 1986 when Challenger blew up, so
obviously they thought it was designed for a more rapid turnaround than it
ever achieved.

If it was not designed for rapid turnaround because of money problems,
someone must have known from the start. Otherwise any extra money would have
been spent on something else. Failures of foresight have to be distinguished
from problems due to lack of money.


Murray Anderson


.

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