Henry Spencer wrote:
[...]
...the SSME can be cut off and returned.

I don't believe that CEV, by current notions, is big enough to return it.
This is a theoretical future possibility, not something that can
reasonably be cited as a virtue of the current system.

It's only a lack of
even moderate imagination that makes the 2nd stage expendable.

No, it's the lack of a reentry system that could return it for reuse. I
agree that the hardware itself isn't inherently limited to a single use --
as best one can tell, given how little detail exists -- but as currently
conceived, that stage is 100% expendable.

Demonstartor 2R tells us that cheap recovery systems for the SSME (and
CMGs when shuttle stands down) are still "just around the corner".

/dps

P.S. D-2R is "fluffy" without the tubesocks cooling system, Pete.