Thanks for your civil reply, Kim - now if only the Mars Nuts would follow your example

I found Publius Rex's comments on shuttle upgrade over at www.spacer.com to be of great interest - you may want ot take a look at it. He calls for taking the SSMEs (engines) off the orbiter and mounting them on a parachute recoverable pod which goes under the external tank. Center of gravity, structural, and other issues are not examined... but he ends up with a heavy lift launcher.

The key problem here is the complete lack of demand for a heavy lift launcher, as there is very very little public demand for sending men to Mars. That leaves the Moon, but that can be handled quite well with existing medium lift launchers.

The trading space depends on the costs of the EELVs.

As for Dark Horse, if NASA goes with a capsule, then keeping the hypersonic research going strikes me as having a high priority, and Dark Horse could lower costs to orbit significantly for a low total cost of development -

all best -
ep