Some of the commenters in my Dragon post brought up the possibility of using a Dragon for lunar flyby tourism flights. I think this is an intriguing idea. The Dragon is about the same diameter as the old Apollo CM (about 30cm narrower), but much more roomy. They are meant for short jaunts to the station, but if you traded out say half the seating, and used some of that weight for extra food and sleeping equipment (and a thicker heat shield), it might just work.
Here, let’s play with some numbers:
The Falcon IX has a payload capacity to a LEO of about 9300kg. However, this is probably to a 200km circular orbit launched out of Canaveral (a usual way of rating launch vehicles). That means that to a 400km ISS orbit, it may be as little as 7000kg or so, so I’ll guess that the Dragon is about that size. If you assume that the upper stage of the Falcon V/IX vehicles is about a 94% drymass ratio (similar to that of their Falcon I first stage), with a 2700m/s delta-V for GTO, and then see how much payload the various systems could loft into a TLI trajectory, you get about 5600-5700kg for Falcon 9-S5, or somewhere around 8400kg for the Falcon 9-S9 variant. If you drop the number of crew/passengers from 7 to 3 (which would be a lot less cramped for that long of a trip), could you shave off enough to launch it on an S5 instead of an S9? Maybe. If you could squeeze it into an F9-S5, and assume 1 crew and two passengers, they could probably offer a ticket for only $50M each, and that’s for a much simpler system than the one Space Adventures or CSI were proposing. If you had to go with the S9 option, you might need more like $60-75M per ticket to make enough money off of the deal.
Since SpaceX has already said that it only intends to field the S5 and S9 variants once they have at least one prepaid customer, it might be possible to launch instead on a Falcon 9 with no payload and just a CBM connector on it, and then launch a second Falcon 9 with a Dragon, and with something like the Canadarm Mini idea I just posted about, and berth the two together. Doing it that way would likely still get you a ticket under $60-75M each, and more importantly would be using what would by then be an off-the-shelf booster.
Any way you look at it, this is an intriguing alternative to the other translunar options that have been previously discussed. The biggest win is the fact that it would be done out of a US launch site with a US company, with no need to go to Russia for 6 months of training. There are a lot of details I glossed over, but I don’t think there’d be any showstoppers for doing a Dragon flight around the moon.