"Murray Anderson" wrote in message ...
"Michael Walsh" wrote in message
...
Dholmes wrote:

If you take the first stage of SeaLaunch and then use the first stage
of a
Delta 4 as a second stage you have a rocket that can launch (based on my
quick calculations) over 60,000 lbs to LEO.

It would make more sense to put the Delta IV upper stage on the Sea Launch
first stage, in place of the two kerosene-burning upper stages used
currently.


Agreed, and they almost seem a perfect match too.

Zenit 3SL with 5250 kg GTO Payload
Mi(kg) Mf(kg) ISP Total ^V (m/s)
S1 467450 146550 337 3833
S2 112950 32050 342 8057
S3 22450 7800 361 11799

Delta 4M with 3900 kg GTO Payload
Mi(kg) Mf(kg) ISP Total ^V (m/s)
S1 257000 57000 365 5390
S2 27000 6600 462 11771

Notional Zenit First Stage/Delta 4 Second Stage
with 5250 kg GTO Payload
Mi(kg) Mf(kg) ISP Total ^V (m/s)
S1 382850 61950 337 6018
S2 28350 7950 462 11778

The above neglects gravity losses, etc., and I've
made no attempt to consider problems that could
arise from higher g-loads during the Zenit first
stage burn, etc. Structural issues might also
limit the LEO capability of such a vehicle, but
the massive liftoff thrust of the RD-173 (1.63
million pounds of thrust) sure provides a lot of
leeway - and 12,000 kg to LEO doesn't seem out of
the question. Such a rocket, with a 1.9 thrust to
mass ratio (GTO), would pop off of its launch pad
with no need for costly strap-on boosters. The
liquid hydrogen fuel used by the upper stage would
likely require the booster to be land-based.

Of course, Lockheed Martin would argue that it has
already built a rocket almost exactly like this....

- Ed Kyle