Henry Spencer wrote:
Not necessarily. The lower Isp is more than made up for by the higher
propellant density and the better engine T/W ratio. Sure, you need a
higher mass ratio, but it's actually easier to do. Dense-propellant
stages with SSTO-class performance were built years before LOX/LH2 ones
started to show up, and with considerably less difficulty.

Also note that the mass-ratio disparity is not as large as you'd think,
because a dense-propellant SSTO needs less delta-V to reach orbit. Lower
Isp, and thus higher propellant mass-flow rate, means it loses mass
faster, thus reaches higher accelerations sooner, thus suffers smaller
gravity losses. It's not a big advantage -- circa 300m/s -- but it's on
the steep part of the curve, so it drops the required mass ratio quite
substantially. (This effect was known in the early 60s, but got forgotten
in the rush of enthusiasm for hydrogen the wonder fuel.)


Okay.
(crawls back under rock)
We've read up on your "Brown Bess" booster concept; if you were going to
make an unmanned expendable SSTO, how would you go about it, and what
propellant combo would you use?

Pat