Henry Vanderbilt wrote:

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.

No, but if you do other than nose-first docking you're now loking at a
bigger heatsheild and thus a bigger vehicle because the heat shield has
to protect the docking mechanism, which if it's going to fit people
through comfortably, and probably at a minimum in a spacesuit, requires
at least a meter wide hatch.

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.

Can you design such a thing as a small, multi-port docking adapter? Now
you're talking about lofting a Unity node along with the CEV. That's
exactly the parasitic type of mass you want to avoid.

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.
Why will NASA need to do it sooner or later? That sounds suspiciously
like the reasoning used to fund ISS, "to develop technologies
required..." yuck.

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.

Henry Vanderbilt

True.