On Aug 7, 4:25*am, Robert Clark wrote:
*This Astronautix page gives the old Saturn F-1 engine a vacuum thrust
of 1,740,134 lbf at a weight of only 18,498 lb for a thrust to weight
ratio of nearly 100 to 1:

F-1.http://www.astronautix.com/engines/f1.htm

*The Astronautix page on the Ares I solids give it vacuum thrust of
3,480,122 lbf but an empty weight of 221,230 lb (!) for a thrust to
weight ratio of only 16 to 1 (!):

Ares.http://www.astronautix.com/lvs/ares.htm

The tank mass for a kerosene-LOX engine is only about 1/100th that of
the propellant mass. So even if you used the same propellant mass as
the Ares I solids of about 1,400,000 lb that would only add 14,000 lb
to the lower stage empty mass. But actually the propellant mass would
probably be less since the F-1 had a better Isp at 304 s compared to
265 s for the Ares I solids.
Given this, how much larger payload could we launch to LEO using the 2
F-1 engines in place of the Ares I solids as the 1st stage?
*How much could we launch to LEO using just 1 F-1 engine as the 1st
stage?



The Russian RD-171 and RD-180 are high thrust, liquid-fueled engines
still in active operation. Here's the Astronautix pages on the RD-171
and RD-180:

RD-171
http://www.astronautix.com/engines/rd171.htm

RD-180
http://www.astronautix.com/engines/rd180.htm

You would need 2 to 3 of these to match the thrust of the Ares I
first stage solids. But the thrust to weight is so much better you
might be able to match the payload to orbit just using one of these
engines. (You would have 200,000 lbs less dry mass at launch.)


Bob Clark