Inflatable habitats and reentry shields have reached some level of
acceptance. With this in mind there no longer seems any good reason why
the two should not be combined to construct significantly lower drymass
capsules and even space transports.

Inflatable propellant tanks would seem less challenging development-wise
than either inflatable habitat modules or heat shields. And so fully
inflatable space transports seem potentially quite possible.

In adopting such an approach drymass can be greatly reduced, perhaps by
as much as a half depending on details, tank mass can become near
negligible, as can structural mass. Hence payload might also be greatly
increased.

At such low drymass fractions the design margins are greatly eased such
that SSTO becomes favoured with regard to development costs. For
example, the Falcon 5 lower stage so modified could become a reusable
SSTO of modest payload. Suborbital applications promise similar
advantages.

If the time is not yet right to bite the bullet of inflatable space
transports, then it is not far off. It definitely has the potential to
quickly make a lot of more traditional approaches obsolete and I am
somewhat surprised someone is not already covering the possibility.

Pete.