Andrew Gray wrote:

Isn't OV-200 generally interpreted as 'shape, size, plugs, stay - but
make the rest better'? - which'd imply that the designs, at least as
regards LES and other such macro-changes, are pretty firm.

That's what I was thinking of when I posted, a new-build airframe of the
same design as the existing orbiters, but with upgraded systems (eg
electric APUs, perhaps non-toxic OMS/RCS, etc).

On the other hand... if you had sufficient silly money, it's not
implausible to retrofit an LES of the form of "two damn great solid
rockets by the wing roots"... which, if memory serves, was where it got
to in the design stage before falling off the board.

Doing that would add weight to the orbiter's structure, but that could be
comphensated for if the abort SRMs were fired and jettisoned shortly after
SRB separation (at which point they would be unnecessary, and could
probably be retrieved for refurbishment).

--Chris