Jon Goff has some more good posts up on exploration (and particularly lunar) architectures. Here’s a key point that undercuts NASA’s rationale for HLVs:

Why doesn’t NASA land enough stuff to support 4 people for 6 months on a single lander? Or 6 people for a year? Because it would require much too big of a lander, which would cost too much to develop, and way too much to operate. By making the lander smaller, and less capable, but using LSR, ESAS provides a much cheaper approach than trying to do a Battlestar Galactica scale lunar lander. However, you could see where that logic goes…

And Doug Stanley more or less admitted it. He said that had the 4 people for 7 days edict not been “blessed” by Mike Griffin as one of the ground rules, that EELV based architectures would have traded a lot better compared to the chosen ESAS architecture. And he’s right. All the numbers I’ve run show that you could probably do a reasonable 2-man lunar architecture using st0ck, or nearly st0ck EELVs (or EELV equivalents like Falcon IX if it becomes available).

They admit the need for assembly on the moon, because they know that (as Jon notes) it’s completely unrealistic to get a full-up base to the surface with a single launch of any vehicle short of Sea Dragon (come to think of it, that’s one HLV that I could get behind, because it’s innovative and wouldn’t necessarily cost that much). Now admittedly, it is easier to do assembly in a gravity field (though in some ways, it’s harder as well, since with weight, you need cranes, etc.). But it’s not so much easier that they should have ruled out doing orbital assembly, something that we need to learn to do anyway, and that they will have to do for Mars, even with Ares V.

Again, as Jon points out, the entire architecture, and justification for an expensive (in both development and operations) heavy lifter is based on an arbitrary requirement–four crew for seven days. Remove that constraint, and the trade space blossoms tremendously. But it apparently doesn’t satisfy political imperatives, whatever their source.