Cuddihy's Cut

Cuddihy's Cut on the events of the day....


Sunday, April 02, 2006

There's no such thing as an incrementally tested space launcher

I didn't realize how hard it is to stay off the internet. I've already messed up a few times during the last work week--now here it is on the weekend, when I should be catching up, and it's not until Sunday night when I can find some time to blog around a little bit.

I admit, first of all, that I fell off the Lent non-blogging wagon on wednesday to comment on Rand's blog, on the SpaceX failure.

Blogging is all about responsiveness, so when I can't legitimately post on a subject till the weekend, I'm not sure there's much point in sounding off about it. But it's definitely a challenge not to respond to things I think are off the deep end.

Like the meme about SpaceX's chosen method that has been forwarded by quite a few members of the space blogosphere: namely, that ELVs are more prone to failure than a launcher that you can 'test incrementally.' as opposed to one you 'have to test all-up.'

I'd like to point to statistics proving this to be a fallacy, but I can't. Those statistics don't exist.

Because, of course, there never has been a working RLV space launcher built, and there won't be for a long time. I would estimate at this point that breakeven on controlled nuclear fusion is closer to implementation (hey--we're just 20 years away!) than a fully reusable launch vehicle.

So, space vehicles you can test incrementally, rather than all-up are less prone to failure? Woop dee doo. I'm sure the East Indian Tea Company had people telling them it'd be quicker to sail to India through the Northwest passage than around Cape Horn. Until somebody did it though, the smart money kept sending ships around Africa. In fact, the ships still go around Africa.

The point is that, reusable, incrementally tested vehicles run into many of the same problems that incrementally tested ones do. Sometimes worse ones. Incremental testing probably wouldn't have prevented a fuel leak. A fire that depressurized the helium system 200 feet up would still have crashed the rocket. The difference is if it had been resuable, the rocket would have been much more expensive.

The truth is that a resuable vehicle would have taken longer to test, would have cost more money to design and build, and would have been more disasterous when it crashed.

Musk probably would have gotten out of the launch business by last Thursday if that had been a $700 million dollar fully reusable Falcon 1.

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