Brian Thorn wrote:
: On Sun, 1 Nov 2009 12:49:46 +0000 (UTC), Yama
: wrote:
: I just don't see where the savings are supposed to come.

: Canceling Altair. Scaling-down Ares V (sized for Moon/Altair) to
: existing ET diameter and 4- or 5-segment SRB (vs. 5 1/2 segment now
: planned.) Cancel Ares I and move everything to this Ares V-Lite.

: 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.

: Quite the contrary,
: all these proposed targets would need specialized craft and equipment to
: design and build. A Phobos mission would be nearly as expensive and difficult for
: Mars mission.

: The simplest asteroid-rendezvous concepts simply call for two Orions
: docked end-to-end. You don't really need a lander for a small
: asteroid, its really just proximity operations due to the low gravity
: (think NEAR's "landing".)

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.

: It seems to me that they were proposed because they SOUND easier.

: And they defer the high-cost mission modules (landers, labs,
: what-have-you) until later.

Given that the "high-cost mission modules" are the ones which make the whole
program meaningful in the first place, I again foresee no actual savings.
They will have to be developed at some point in any case.

: Not to mention that science return from asteroid mission is going to be
: fraction what can be gained from Moon or Mars mission.

: But potentially much more important if one is discovered on an impact
: trajectory.

So what's stopping sending a robotic mission to study one?

: Chicken meet Egg. There are no servicable observatories at the
: Lagrange points because there are no spacecraft that can go out to
: service them, and there are no spacecraft that can go out to service
: them because there are no observatories that can be serviced.
: Servicing something like WISE or SOHO doesn't make much sense, but
: when we start talking about something like James Webb at
: multiple-billion dollars, adding astronaut servicing starts to look at
: least worth considering.

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

: : Remote operation of rovers with only a second or two time delay.
:
: 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"? What is the precise value?

: : 90% or more of any deep space mission is propellant. Propellant is
: : cheap (compared to hardware). If we can use cheap, modestly reliable
: : rockets (90% reliablity instead of 99.5%... if we lose one now and
: : then, who cares? its mostly just LOX)
:
: 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.

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.