It’s not news to anyone who has been reading him (and me, among others) for years, but Henry Spencer explains once again why NASA’s architecture choice is the wrong one (and no, I’m not talking about Ares):

There is also a longer-term advantage: if you decide to launch everything on one big rocket, what happens when you outgrow that rocket? Even if your early expeditions stay within the rocket’s capacity, presumably you’ll want to do bigger and more complex ones later. What then? Develop a still-larger rocket?

Even people who don’t want to depend on orbital assembly for the first expeditions to the Moon (or Mars, or wherever) often will concede that it will be necessary eventually. But then, where’s the gain in delaying it?

If you’re going to want to do orbital assembly anyway, you’re better off starting it right away, so even early expeditions can benefit from it. The only reason to delay it is if you think there won’t be any later expeditions – if you’re planning a dead-end programme.

I’ve never seen anyone even attempt to refute this logic.

[Update on Tuesday afternoon]

Well, here’s an attempt, but it uses ludicrous analogies:

One can only imagine someone talking to Prince Henry the Navigator circi 1410 and trying to convince him that adapting steam power (then known since Heron of Alexandria) to ships would be desirable to why not start now and stop messing with those quaint, wind powered caravels. Or someone else trying to sell jet engines to Lindbergh before crossing the Atlantic. Forever delaying doing things until the technology is “just right” doesn’t work very well.

No one is proposing the equivalent of steam power in the fifteenth century or jets in the nineteen twenties (though in the latter case, they weren’t far off). That would be akin to demanding a space elevator, or anti-matter rockets.

Nor is anyone, including me or Henry, proposing “forever delaying doing things until the technology is ‘just right.'” The technology for propellant depots could have been well in hand years ago had NASA stayed in the technology business, instead of cutting off all funding to it to redo what was done forty years ago. An assembly-based architecture could still easily be in place just as fast as NASA’s Constellation plans, and much cheaper, particularly given appropriate incentives to private industry. We are proposing that NASA plan for the future, with an affordable and sustainable plan, instead of looking to the past.

[Bumped]

[Mid-afternoon update]

It strikes me that this paragraph from my extended version of The Path Not Taken is relevant:

While the report of the Aldridge Commission on the new vision, released in June, had some good recommendations in it, it also had a few potentially disastrous ones. Perhaps the most damaging statement in it was to declare heavy-lift launch systems to be an “enabling technology” for carrying out the vision. This is a phrase of art in the engineering world meaning that, absent such a technology, the goal is unachievable. The commission is claiming that we cannot send humans beyond low earth orbit without a much larger launch vehicle than anything existing. If they had used the phrase “enhancing technology,” meaning that it’s not an absolute necessity, but that it makes things easier to do, I’d have less complaint, but as they’ve stated it, it commits us to an expensive development of a new launch system, that shows no promise of actually reducing costs. Moreover, it commits us to an approach to exploration that, like Apollo, is not affordable or sustainable.

I hope that this is a recommendation that can be revisited.