In article .com,
wrote:
Heavy but skinny, so the second stage has to be skinny
too -- a problem for a stage that needs lots of bulky LH2, and also it
limits your engine options because there's no *room* for a multi-engine
cluster in such a narrow stage.

Ahem: aerospike or plug cluster. Would fit great.

As would other hypothetical large LOX/LH2 engines, but the point was to
try to do something with nearly-off-the-shelf designs. Of course, the
J-2X may have gotten pretty hypothetical by now...

they've got a choice between using an EELV variant for crew launches...

Which? The Putinsky or the Fireball?

Preferably both, at least long enough to insist that P&W really go through
with setting up US production capability for the RD-180. (The only way to
make that happen is to have a US alternative, and give LM/P&W a deadline
after which they get no orders if they haven't gotten their act together.)
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |