NASA cannot do anything that doesn’t take 10 years and $10 billion minimum to accomplish.
DARPA should run screaming from any NASA involvement with this program.
Just look at what NASA did to the DARPA DC-X.
The DC-X was the stupidest idea ever to come out of the aerospace community.
Well, maybe second to the POGO concept.
Why was the DC-X the second stupidest idea in aerospace? Because just look at the Space Shuttle. Look at all the crap, the external tank, the two SRBs, just to get the thing up into orbit. Then with the SSTO concept you expect the thing to carry enough fuel to land again? Not with any known propulsion technology, you won't.