Re: Griffin Calls STS, ISS "Mistakes"



Magnus Redin wrote:

Btw they had a very good idea back then. Design the first stage to
drop off at the speed that gives a reentry that needs no other thermal
protection system then slightly increasing the thickness of the metal
in some places to act as a heatsink.



You've got to get up to Mach 25 to get into orbit, and for the sake of overall vehicle size and cargo capacity, you want as much as that velocity as possible to be provided by the booster component of the two-part vehicle.
You get it much beyond Mach 6 and you are going to start getting heating problems on reentry that titanium, Inconel X or stainless steel are going to have a tough time handling. Besides which, the ballistic path of the reentry is going to generate a lot of structural stress on the booster as it falls into an atmosphere that is getting rapidly denser and decelerating it very quickly.
If you keep the the booster stage's contribution fairly modest to over-all vehicle velocity for the sake of low entry heating and simplicity, then you end up with a orbital component that has a lot of its weight and volume devoted to propellant storage. That makes it larger to haul a given payload to orbit, and that in turn means that the booster component grows in size to carry it. You end up with a overall vehicle of the Shuttle's cargo capacity but at least twice its size.
Wanna see how big?: http://www.abo.fi/~mlindroo/SpaceLVs/Slides/sld029.htm
http://www.astronautix.com/lvs/shuenara.htm
You're going to have to build something that goes faster than a X-15 and is around twice the size of a 747, with another 747 riding on its back. That'll be easy, won't it?
(I love Faget's estimate that around 200 people will be required to keep six of these beasts operational and flying a total of around 50 missions per year. For starters, you have a total of 13 SSMEs to check after every flight; then there are those God-knows-how many Lockheed LI-1500 tiles to check on both the booster and the orbiter.)
The funding simply wasn't there to build something of that size and complexity.
Heck, they even scrapped liquid-fueled boosters, the escape rockets for the Orbiter, and burn-through sensors on the SRBs in their quest to bring it in as cheaply as possible.
The Shuttle was probably a case of "If you can't do it right, then don't do it at all.", but the aerospace industry was smarting from the end of Apollo, and so they tossed it this bone.
Nixon almost nixed the Shuttle in favor of a very modest and unmanned space program, but thought it would look like he was revenging himself on Kennedy's space program out of spite.

Pat

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