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Old May 27th 19, 04:49 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Default NASA?s full Artemis plan revealed: 37 launches and a lunar outpost

Jeff Findley wrote on Mon, 27 May 2019
06:51:00 -0400:

In article ,
says...
I think folks going to Gateway will do what Blue Origin has done and
opt for LH2/LOX engines, so it will be cryo either way. It will be
large volume 'mild cryo' in LEO (Starship) or deep cryo (LH2/LOX) at
Gateway.


True, but this depends on what lander parts NASA picks. HSF at NASA has
been risk averse since the Challenger disaster. That means they'll
likely pick lander parts that use hypergolic propellants.


Unlikely, since the stated goal is to shift to in situ fuel production
on the Moon and you aren't going to be making hypergolics down there.


So Blue
Origin would be out. Starship is never going to be picked as part of
the lunar architecture because it will be seen as "high risk".


I think it's quite likely that choosing LH2/LOX will be seen as a
feature for Blue Moon, not a bug. We've come a long way from the days
when we used to worry about being able to get a restart on a rocket
engine (which is one of the justifications for accepting the poorer
performance of hypergolics).


Plus NASA mandated a three stage lander. That screams hypergolics from
the start. Neither Blue Origin's Blue Moon lander nor Starship would
qualify in NASA HSF's mind.


Actually, no. The Transfer Element isn't part of the lander. The
Blue Moon lander is a Landing Element. Blue Origin doesn't seem to
think they'll have any problems adding a 7.6 tonne Ascent Element on
the cargo platform and the Blue Origin effort is pretty much EXACTLY
what NASA has asked for.

The big 'delay' in exploration beyond the Moon is that I
think the NASA plan assume in situ fuel manufacturing on the Moon
before they go for deep space. Deep Space exploration vehicles would
fly to Gateway, refuel with lunar LH2 and LOX, and depart. This makes
some sense in that getting fuel up from the Moon is much 'cheaper'
energetically than boosting it up from Earth, but it impacts your Mars
infrastructure as well, since now your in situ fuel factory there has
to find ice and make LH2/LOX out of water rather than making LOX and
liquid methane out of the atmosphere.


I've heard the water to LH2/LOX argument before. I find it lacking.


Well, if you're going to pick and choose which bits of reality you
accept you can arrive at any conclusion you like.


Again, we're talking NASA here. The agency who signed off on solid
aluminum wheels for all of its Mars rovers. The wear and tear on those
is mind boggling. They're literally falling apart after what I would
consider to be a pathetic number of miles/km traveled.


You say that as if it's somehow relevant. It's not. And what is the
design lifetime of these things supposed to be, again?


And we expect NASA to mine water, on the moon (with its abrasive dust
environment), and turn it into LH2/LOX? I'll believe that when pigs
fly.


No, I expect them to let some contract to have someone do it, just
like they're doing with landers and such. As I said, if you're going
to pick and choose which bits of reality you accept you can arrive at
any conclusion you like. Me, I'm going to go with what people have
said. You understand that one of the drivers behind the NRHO that
Gateway is in is ease of access to the Moon's south pole (where we
think the highest chance is of finding water), right?


All the engineering competitions (mostly college level) I see to mine
lunar regolith have everyone starting from scratch. Because we all know
that no one on earth moves around dirt/rock or mines anything, right?

There are industries on earth that know how to do this and they aren't
run by aerospace engineers. Adapting earth equipment to do this on the
moon would be the most straightforward way to go. The problem with that
is this equipment is *heavy*. But there are reasons it's heavy!

At any rate, once you reduce launch costs to put a reasonable amount of
equipment on the moon to start production of LH2/LOX in quantity, you
need to compare the new, lower, cost of launching LH2/LOX (or better
yet, methane/LOX) from earth to that mined on the moon. If you take
into account all the money it's going to take to maintain that
(expensive) infrastructure on the moon to produce that propellant, I'm
not convinced that it's going to break even in terms of the economics in
the next 25 years or so.


So Mars is right out, then, since in situ fuel production is so hard
and it's REQUIRED if you're going to do Mars?


I'm not arguing that we shouldn't invest in lunar water mining. I'm
just against putting it on the critical path to send people to Mars.
It's simply not needed if something like Starship/Super Booster works
out. It's quite simply a hell of a lot easier to refuel a
Starship/Super Booster on earth using methane/LOX (both super cheap on
earth) than it is to mine water on the moon.


I think I made that argument somewhere along the way. Mostly it's a
bad idea because it leaves you with Mars vehicles that are burning the
'wrong' fuel for in situ production on Mars. Yes, there's water
there, but going with LH2/LOX for Mars vehicles makes things harder.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw