Chuck Stewart wrote:

Hmm?... but what about heat conduction via carbon strands in
contact with both RCC and wing structure? It might not be much, but
it'd be there.

It needn't be zero, it need only be less than the heat transmitted
by radiation.

There are already inconel radiation baffles behind the RCC to reduce
the radiative heat transfer.

I'll note that carbon aerogel would have the problem of eroding
rapidly if exposed to high temperature air. A combination carbon/SiC
aerogel might get around that problem.

Paul