“poor BLEO performance, no support for cryogenic upper stages.”

Ugh, Falcon Heavy could never launch a single payload BLEO and still be the superior option for exploration because there are Earth Orbit Rendezvous scenarios that can utilize its strengths.

A difference being that billions are being pumped into fielding and operating the SLS while Falcon Heavy receives no such advantage nor requires such a parasitic cost. Falcon Heavy also has a possible reusability scenario that could impact costs favourably while SLS locks us into a billion dollar throwaway rocket model.

It’s also a mistake to compare the single vehicle’s characteristics since the MLV argument is that the cumulative launch performance of many launches is a strength in both upmass and volume.

Point of order. SpaceX is an experienced and successful rocket development firm and they could certainly take on such a project were they tasked with it. That includes being contenders for a competed heavy lift vehicle development contract from NASA. SLS was uncompetitively awarded due to unjust legislation, it was a corrupt continuing handout to Boeing and ATK, and cancelling that graft for a fair competition is certainly within the actionable options available to NASA if it pursues heavy lift.

NASA is no saint. Various constituencies within NASA are institutionally biased to favour a continuation of the space shuttle program through other means as that program and its beneficiaries was thoroughly enmeshed in the fabric of NASA, not to mention that the agency lives under the shadow of the glory of Apollo and is not immune from the influence to mimic their Apollo idols. HLV mania and SDHLV mania runs deep, and leads to a lack of fair consideration of options pursueable.

This is the same NASA that endorsed the Ares 1 and was headstrong for Constellation.

Extended trips in cis-lunar space are excellent for proving out longer duration trips to Mars. As to visiting an asteroid, you’re correct. There is nothing about an asteroid visit that retires risk for Mars missions *except* that it takes some time to get there. The asteroid itself is, you see, just a lame excuse for taking that time.

As to proving out roving vehicles on the Moon, for use on Mars, that’s the hard way to do it. It is well understood that for proof of vehicular mobility as well as coordination of EVA astronauts, we’re far better off doing it at Earth analog sites, which have landforms, dust, and regolith types that are similar to that on Mars. That is VASTLY easier than trying to do it on the Moon because, for one thing, one can do a lot of experimentation.

As I said, there is no lunar-phobia here. The phobia is about spending large amounts of money to do things on the lunar surface that could be done more reliably, meaningfully, and less expensively elsewhere. In fact, as you say, lunar orbit is a nice place to exercise these capabilities simply because it does create understanding that could be used for future lunar development. Now, Low Lunar Orbit is a dynamically crappy place to do this, because most such orbits are unstable. That’s not where you’d ever put a long-term depot or habitat. Lagrange points make a lot more sense, and there are other excellent orbits as well.

MSFC has lowballed the SLS cost at $500M, but few people really believe that, given the likely flight rate. In fact, we’ll be surprised if it even comes in at $1B a pop

As to propellant crossfeed, SpaceX is saying that they can do 45 mT to LEO without it.