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

On Sun, 10 Jul 2005 19:07:35 -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:

>> >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.

They did, since they don't refurbish it--they rebuild it from the
recovered segments, with new grain.

>> >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

Emphasis on "was."

>which 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.

They apparently disagree.

>> >> >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.

Go argue with "them."

>> >> >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?

With more money, yes. They could have, for example, used a titanium
structure underneath, instead of aluminum.

>Similarly, the external tank shouldn't shed foam to damage
>the tiles, but what tank design was turned down because it cost too much?

The one that was incorporated into the Orbiter.
.

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