(John Carmack) wrote in message . com...
I certainly agree with you regarding the value of a lifting-body, but
I would contend that there are circumstances where a single vehicle
design may still win out for moon missions. A VTVL SSTO can do the
LEO to lunar surface and back trip after refueling in orbit. While it
certainly wouldn't be optimal for it,

A VTVL SSTO has the raw delta-V capability to perform a lunar mission.

Can its main propulsion system start in zero and 1/6 g?
Can it handle the thermal environment of trans-lunar cruise?
Can it handle the thermal environment on the lunar surface?
Do its engines throttle deeply enough to allow sane lunar landing
trajectories?
Is it capable of weeks of on-orbit propellant storage?
Or weeks of on-orbit power generation?
Or a week of life support for the crew?
How will you get down to the lunar surface from the cargo/crew
compartment?

And that's only the things that I could think of faster than I could
type.

Now you could probably address most of these issues, but any SSTO is
going to be operating on a very steep part of the mass ratio curve, so
you'd probably have to address them by modifying one (or a couple)
vehicles specifically for the lunar trip. At which point it might
very well end up that the modifications would cost more than designing
an in-space transport from scratch, possibly reusing some components
(flight computers, RCS, etc) from your hypothetical SSTO.

Something that seems like a better and easier-to-make-work idea is
launching large components of a Mars mission (trans-mars cruise stage,
surface habitat, etc) on an ELV but not separating the second stage,
refueling it, and using it for trans-mars injection. The requirements
are much more alike in that case...

-jake