"ed kyle" wrote in message
om...
"The Ruzicka Family" wrote in message
...
I chose the Delta IV family because
it seemed to cover the largest range in payload weights in a single
family of rockets.


While I'm not totally sure about Delta IV Heavy vs. Atlas V Heavy, I do
know
that the other Atlas V configurations (401 through 551) cover a better
range
than the Delta IV family.

Delta IV is optimized for GTO missions. Atlas V, with
its higher thrust hydrocarbon first stage, has better
LEO-hauling ability than Delta IV - an important detail
when it comes to potential NASA use. Atlas V is also
proving to be commercially competitive while Delta IV
isn't even being offered for commercial launches. This
probably means that Atlas V is going to cost less than
Delta IV - another important detail for NASA to consider.

- Ed Kyle


What do you mean by "optimized for GTO missions"? I'm truly not trying to
be argumentative here; I'm honestly curious. If you're saying that Delta IV
is somehow "better" for GTO missions than Atlas V, I'd really like to know
how. Obviously, there are a whole range of missions that can be classified
as "GTO", from the basic 100nm x 19,323nm orbit, to super-syncs, minimum
delta-v to GSO, descending-node vs. ascending node injections, etc. When
you compound things with a large range of spacecraft weights for GTO
missions, that's where I get confused as to what "optimized for GTO
missions" might mean.
I know that an Atlas V 401 has better performance to GTO than a Delta IV
with 2 strapons, so I guess you could say that the basic Delta IV, with no
strapons, is better suited to "smaller" GTO payloads than an Atlas IV 401.
Whether or not Atlas V will end up costing less than Delta IV, I have no
idea. A lot might be riding on the next EELV government buy.

P. Ruzicka