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Old September 23 2012, 04:46 AM   #173
Crazy Eddie
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Re: Envisioning the world of 2100

publiusr wrote: View Post
Flawed logic. The first thing they tell you in systems analysis is that bad money is bad money and throwing good money after it won't change that fact.

Bad money is throwing away LV after LV to fill a leaky Depot.
More flawed logic. It's only "bad money" if the depot itself is under-utilized and the amount lost to leakage hugely exceeds the amount lost to operations (in which case there's no point having a depot; you should launch the refueling tankers directly to the ships that need them). That would occur if you were using a depot to store cryogenic propellants for long periods of time, which is a silly idea and would be easily mitigated by switching to hypergolics.

Price per pound isn't the only think to look out. Shroud diameter is another plus SLS has over Falcon.
Thinking big is one thing, but don't forget to think LONG. At the time the Senate Launch System goes online, it will be the only launch vehicle in existence with an eight meter shroud. It will also be the most expensive launch vehicle in existence and will have the scarcest launch opportunities. At the same time, smaller rockets like Ariane V, Atlas V and Falcon 9(H) will have been flying for years or even decades with a 5.4 meter shroud, which means ten years worth of payloads will have adapted to that standard. Which means, in turn, that the most mature spacecraft designs will have always adapted to that standard. Actually, considering the number of spacecraft designs derived from the MPLM shell, that is already happening now. Even Orion is small enough to be launched on a medium lift vehicle, and I have a suspicion that it will be, more often than not.

That means that by the time the SLS goes online, there will be literally no one in the entire world who needs an 8 meter payload shroud. The only people who will EVER use the SLS is NASA, who -- if and when they ever develop a service module for Orion -- ALSO won't need an eight meter shroud diameter, because in the whole of NASA's history they have never designed a spacecraft that required one, and in the unlikely event they ever DO, your HLV will be retired by the time they get around to building it.

SLS uses D-IV as an insertion stage...
An insertion stage for WHAT? They still haven't figured out what they're going to USE this thing for.

Griffin wrote an AIAA textbook on spacecraft design.
Is he still beating his wife?
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