Tom Cuddihy wrote:

Henry Vanderbilt wrote:


Another possibility: For longer missions, launch two four-man CEV's
with three aboard each, dock them to each other in orbit, then operate
them as a dual-redundant unit with a bit of extra elbow room.

Which eliminates the need to fly a six-man CEV with attendant new
larger-than-EELV-heavy booster every time you rotate Station crew.
(Might as well still be flying Shuttle; it'll end up costing about
as much per flight.)

Henry

Sounds easy, simple and efficient, but ignores some practicalities of
CEV design. IF you go with a standard capsule shape, that means the
docking mechanism is going to end up at the bow of the capsule, as
every 'docking' capsule so far launched has done. Have you heard of a
design that does not do a bow-forward docking? with the exception of a
winged shape like lockheed's that would clearly not be intebded for
lunar or other than LEO travel, I just don't see it.

Hmm. Didn't they look at a Gemini design with a hatch through
the heatshield? Regardless, nose-first docking is hardly a
law of nature - look at how Shuttle docks, for instance.

Now you have two small capsules docked end-to-end, with heatshields on
either end. There's no reasonable way to dock to anything else that
allows personnel access, like a space station, a lunar orbiter, an L-1
station, or, most importantly for the near term, a lunar lander. You've
created a dead-end system, useful for transport of 4 or 8 personnel.
And not much else, unless you're willing to go to ISS-type gigantic
modular vehicle assembly.

You can prove anything impossible if allowed to burden it with
arbitrary assumptions. You can design to dock nose-to-nose, side-to
side, back-to-back should you so choose - you're starting with a
clean sheet of paper. You can also carry a small multi-port docking
adapter for longer/more complex missions and put together arbitrarily
complex clusters - look at Mir in its later days.

There seems to be an institutional terror of orbital assembly
at NASA, but as the other Henry points out, they'll need to
do it sooner or later, so it might as well be sooner and save
considerable money on big new booster developments.

Perhaps that's possible if you're willing to ignore the architecture of
the 'Constellation' program that's been put forward to this point, or
if you're willing to limit yourself to 4 people. I just don't see that
happening, and obviously now neither does Mike Griffen.

Ah, now we're wandering from "what's possible and makes sense" to
"what might Mike Griffin do given his constraints". I'm not trying
to guess what he might do yet - he's shown himself willing to deep-six
some of his constraints already. I'm just pointing out some of
the benefits of not assuming "the approach so far" is the only
possible way.

We'll see soon enough what NASA actually goes for.

Meanwhile, this is more nested-quotes than I usually do. Ta!

Henry Vanderbilt