January 26, 2004

Damon Hill wrote in message :

This appears to be Boeing's thinking, since they are proposing stacking
two upper stages, most likely using single MB-60s. Two MB-60s on a
single stage would probably require increasing tank volume to get full
benefit. The Delta 4 payload guide mentions a Star 48B third stage for
planetary missions, but does not give performance figures.

http://boeingmedia.com/images/one.cf...8856&release=t

Getting significantly more out of the Delta 4 Heavy configuration with
existing launch facilities might mean something more radical as
converting the two strap-ons to LOX/kero and using RD-180 or a new
1 megapound kero engine being developed on the latter's technology,
and adapting the core stage to altitude ignition, as with Titan 3/4.

Actually, it would be very difficult to get much payload mass
improvement out of the existing Delta IV Heavy at all, without adding
additional CBCs, or drastically modifying the vehicle as you point
out. The CBCs have a fixed thrust to mass ratio. The multiple upper
stages will basically be the payload.

Thomas Lee Elifritz
http://elifritz.members.atlantic.net/rocket.htm