On Wed, 4 Nov 2009 11:39:07 +0000 (UTC), Yama
wrote:

: Big savings and a more robust launch system.

Except you'd have to man-rate Ares V Lite, and still design all the
equipment you need for interplanetary travel. Only except that because
of launcher limitations, it is harder.

Man-rating is whatever NASA declares it to be, and they've already
recently lowered the requirements for EELV. Stick to as much
Shuttle-heritage hardware as possible (SSME, 4-segment SRB, ET
tankage) and you've gone a long, long way toward man-rating. And NASA
already wants Ares V to be "man-ratable", so we're probably going to
pay for it anyway, Ares I or not. So dump Ares I.

Two Ares V-Lites offer *more* payload than an Ares V and an Ares I,
and because both launchers are identical both pads can be the same,
simplifying ground handling and launch preparations. Dumping Ares I
for Ares V-Lite improves the situation, rather than limiting it.

Even if this were practical (which I doubt), you'd still have to come up
with the larger craft for Mars mission, even if it's just Phobos or Mars Flyby.

The craft, but not the lander/launcher. Getting down to the Mars
surface and launching again are going to be the monster costs of a
Mars mission. Flexible path does things incrementally, instead of
paying for everything in one fell swoop, which is the case if
President Obama announces "we're going to Mars by 2025!"

Given the high costs involved, seems dubious. They could have built another
space telescope at the cost of HST service missions.

Perhaps they could have, but probably wouldn't have. There was no
Einstein 2, no IRAS 2, no OAO-2. No NEAR-Shoemaker 2, no Magellan 2,
no Mars Global Surveyor 2. Instead, we got completely new successors
to them all. Internal and external politics generally forces NASA to
order a new 'bigger and better" satellite, which is much easier to
explain to Congress why you need it (versus "Another Hubble? Didn't we
just pay for that?") And that bigger and better means an all-new
design, which is invariably expensive. The only "bigger and better
than Hubble" we have seen so far is James Webb Space Telescope, now
approaching $4.5 billion. Shuttle missions range from $400 million
each for the early Hubble servicing missions to $900 million for the
last two or so. We updated Hubble with state-of-the-art instruments
about four times for less than the cost of JWST.

: I see absolutely no point whatsoever sending people to two-year mission merely
: to act as remote rover operators.

: Others do.

Who are these "others"?

The Augustine Commission, for one.

What is the precise value?

Operation of rovers in areas that have limited contact with Earth,
such as Valles Marineris.

: But doesn't ISS etc use hypergolic fuels, not LOX?

: Same concept.

No, not really. It is much more complicated with cryogenics, which is why it hasn't
been done yet.

Its more complicated, but potentially hugely rewarding. And it has
been tested to a degree, with NASA's SHOOT (Superfluid Helium On-Orbit
Transfer) aboard Shuttle mission STS-57. Small scale, but no
showstoppers.

ULA, which has tons of experience with cryogenic stages, doesn't seem
to think it will be that big a problem. They've already outlined one
concept, which uses a big folding sunshade to keep the cryo stage cool
during loitering/prop transfer.

And really. We're going to have to learn how to do that eventually.
We'll never explore the solar system if we have to take all the fuel
for the mission with us at one time from the launch pad.

And really, again, the supposed "savings" seem to evaporate: now you have to
develope technology to store and transfer cryogenic fuels in the orbit,
and to test it with specialized missions.

A couple of development missions (which could be used to launch
satellites or cargo to the Space Station as their primary objective)
eats up all the savings of full-scale development and, say ten years
of Ares V launches? I don't think so. And we just happen to have a
Space Station up there just waiting to take on an experiment like
that.

Brian