wrote:
Ed Kyle wrote:

Or NASA could do something remarkable and design
CEV to fly atop existing EELV assets.
...
It won't happen.

The astronaut corp apparently desperately hopes not. The hydrogen
fire
on Delta IV scared the bejeesus out of everyone who saw it; DIV
cannot
fulfill the CEV mission without solid-rocket strapons (up to 7, if
memory serves), thus negating the already dubious safety superiority
to
solids; and the DIV has to fly an odd trajectory (due to structural
concerns) that means that there are points in the ascent when abort
is
*not* survivable. Atlas V heavy is a bit of an unknown, but apprently
has a number of the same performance issues.

The Delta IV Heavy hydrogen flare was wild, but the
rocket is designed to catch on fire (!) - and such
events can reportedly be damped out if a water
suppression system is added to the pad. Still, the
sight could not have been good "PR" for Boeing's
rocket. (An aside - I once watched a hydrogen fire
burning on Pad 39A after an abort. The flames
licked right up the side of the orbiter (Discovery
I think it was - with crew on board and ET fueled)
discoloring the exterior. It burned for awhile and
was more than a little uncomfortable to watch).

The Heavy trajectory kept the rocket over land
for a longer time than a thrust-augmented Medium,
but I suspect it took Saturn V as much time to
clear the beach.

Both Delta IV and Atlas V have the same problems
when it comes to CEV adaptation. Neither can handle
a projected 20 ton CEV without core booster
augmentation, (solid or liquid strap-on boosters).
But NASA is either going to have to live with
this or go shuttle-derived. I don't see the U.S.
government (at least not the current one) coming up
with the billions it will take to develop a new,
more powerful core rocket just to launch CEV a few
times a year.

- Ed Kyle