  I found it very interesting that Atlas depended on pressure to
maintain tank geometry....leads me to the question: ? have any 
of the SSTO concepts explored pressurized tankage such that the
launch configuration would be significantly different from the
reentry one?  I have long been facinated by pnumatic structures
as conceived and built by Frei Otto and others, a "ballon" tank
SSTO sounds very clever. 

