Roy Smith wrote:
I read that the much denser LOX is on the top[*] of the ET, with the
LH below it. This seems counter-intuitive. I would think from a
structural point of view, you would want the heavier stuff on the
bottom, and it would also move the vehicle's CG aft, which I would
think would improve aerodynamic stability.


To make a missile (a rocket or an arrow, etc)
stable in the atmosphere, the center of gravity
should be forward of the center of pressure, so
mass forward actually increases stability.
Model rocketeers often find themselves adding
mass to the nose of their rockets (or adding fin
area) to improve stability.

- Ed Kyle