In article ,
Terry Goodrich wrote:
Let's see, a Soyuz booster around $30 million or so...

The old Luna sample-return missions maxed out the Proton -- in fact, they
needed Proton performance enhancements and reduction of safety margins --
to return a few hundred grams of sample. Yeah, the hardware was pretty
crude stuff and we could do better, but it's a demanding mission, and
trying to squeeze maximum payload out of a mass-limited system will get
expensive fast.

This leaves the descent and ascent module along with recovery systems and
guidance system, which I have no clue on cost.

They are, alas, the key systems. It's a propulsion-intensive mission, and
needs precision guidance en route and for landing, and at least a minimum
of guidance for the return trip.

Hmm, 20kg payload. Perhaps: 5kg of packaging, 10kg heatshield, 5kg
parachutes, 5kg main structure, 5kg misc. subsystems. That's 50kg at
reentry. 5kg of electronics, 5kg midcourse maneuvering, 5kg power and
misc. gives 65kg payload for the ascent stage.

5kg engines, 5kg controls, 5kg tanks and general structure, with the
payload handling guidance, gives 80kg dry mass for a pretty light ascent
stage. Assuming unimpressive pressure-fed propulsion, mass ratio is going
to be 3 or so, giving lunar liftoff mass of 250kg.

25kg of cameras and sample handling etc., 25kg engines, 10kg controls,
50kg tanks and general structure (including structural bracing for the
ascent stage so it can be lightweight), 15kg of landing guidance sensors,
25kg RCS and maneuvering, 25kg power and misc. subsystems, 25kg legs and
shock absorbers, gives a landed mass without main propellants of 450kg.

Surveyor landed about 30% of its launch mass. With similar descent
propulsion performance, we need 1500kg at post-TLI separation.

Add 100kg for general margin, and we are right at the limit of what a
Molniya (Soyuz with an injection stage) can inject to a lunar trajectory.

Almost all of those numbers are wild guesses. Some of them I think I
could beat. But there are probably things I've forgotten, and I might
also have been optimistic here and there. At this by-guess-and-by-golly
level, 100kg margin out of 1600kg is uncomfortably small. I'd say we're
marginal here for a Molniya launch; it could easily need something bigger.

How much all this will cost is unclear. Not very much of the hardware is
available off the shelf. Much will depend on how confident you want to be
that the first one will work. Surveyor (less ambitious mission, but also
using a lower technological base) cost maybe $3G in today's dollars, and
that is the sort of number you'd be looking at for business-as-usual
development with a reasonable chance of first-attempt success.

What could be done with a leaner development philosophy... is unclear.
The cheap-satellite community hasn't done landers or major propulsion
much, so we lack calibration data. Moreover, for something this novel,
there's going to be a considerable debugging period. That is to say, with
a low-cost approach, the first few attempts probably won't work.

Wild guess, assuming sweet-talking the Russians into a steep discount for
a bulk buy of Molniya launches, *and* assuming it doesn't threaten too
badly to outgrow Molniya, *AND* assuming upper management that will bite
its lip and keep quiet when attempt after attempt fails, $250-300M gets
you ten attempts of which two or three should be full successes.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |