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Old May 27th 19, 01:24 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Default Two Starships in "bolas" rotation

Jeff Findley wrote on Sun, 26 May 2019
08:16:34 -0400:

In article , says...

And that actually makes sense since all this
hardware can be tested out far more easily on lunar missions.


Disagree. The hardware will be very different between the two.


I agree with Jeff on this one. While some hardware designed for Mars
can be tested on the Moon (or on Earth, for that matter) and might be
useful for lunar landing and settlement, there are lots of
differences.


For
starters, the landing mode is different. Mars has a thin atmosphere
which you want to use to shed as much delta-V as possible. The moon
lacks any atmosphere. This also means that in situ propellant
production will be completely different. On Mars it will rely on CO2
from the atmosphere. On the moon, it would rely on any water which can
be produced from local resources. This means different fuels will be
produced (methane on Mars, LH2 on the moon). So even the engines will
need to be different. In fact, the difference in atmospheres drives a
lot of the engineering, so the hardware just won't be the same at all.


Yep. This is why Blue Origin's Blue Moon lander is an LH2/LOX
vehicle. It's specifically intended for lunar work. Meanwhile,
Starship can also do lunar work but does so by refueling in LEO just
like it would for a Mars mission and then NOT requiring a refueling at
the Moon to take off and get back to Earth.


Second, power generation challenges are different. The long lunar night
makes for a large electricity storage requirement. Mars night is much
shorter. Mars dust storms provide a challenge for solar arrays. The
moon has no dust storms, but does have dust which can be kicked up by
human and robotic activity and then stick to surfaces via static
electric forces.


I don't think anyone is seriously planning on solar for either Moon or
Mars. Blue Origin is planning to use hydrogen fuel cells run by boil
off from the Lander Element LH2 tank so as to get through that two
weeks of frigid night on the Moon. I think Mars settlements are
expected to use small nuclear reactors like KRUSTY. Once on the
surface of either the Moon or Mars I would expect that Starship would
deploy one or more of these for 'shore power'.

snip


If you want to go to Mars, go to Mars. Going to the moon first is
largely a distraction because most of that "experience" gained will be
thrown out and nearly everything will need to be re-engineered
specifically for the Martian surface environment.


I want to go to both and I think Starship is the only feasible system
being talked about that can do that. After all, ships that return
from Mars need SOMETHING to do until the next conjunction.

There is a
push within NASA to refocus on the Moon and a lunar base, by any means
possible. If that means contracting with private enterprise to do it, so
be it. We will have to wait and see how Starship does in this regard.


Clearly, especially since the current NASA plan of record doesn't
include Starship in any meaningful way. It still relies heavily on
SLS/Orion, so we will be limited to one crewed mission per year. That's
pretty weak sauce considering how "close" the moon is.


Starship doesn't fit their desired architecture. Once they admit that
Starship is real, all their plans and hardware go into a cocked hat.
If you think the graphic Musk showed of Starship docked to ISS looked
a little silly, imagine the same thing with the much smaller Gateway.


We are along a familiar trajectory here. Same one as was taken for
recoverable Falcon 9 stages. I think Starship will focus on P2P
suborbital trajectories first to establish launch and return procedures
that must work anyway.


Only if they can find a paying customer. Such flights without Super
Booster would be severely limited in P2P range. All P2P promotional
videos made to date show Starship being lofted by Super Booster. I
personally think we'll see Starship only flights for testing, but
nothing else.


I'm inclined to agree. The big stumbling block for P2P, though, is
having all the facilities on the ground built to support it and
getting through the regulatory hurdles.

Then a push to orbit, then a push beyond.


I personally think the "push beyond" will take a very long time. Once
Starship/Super Booster is flying to earth orbit, its primary mission
will be Starlink satellite deployment. Yes you can keep flying up to 60
Starlink satellites at a time on Falcon 9 (more polar orbits will either
have less satellites or require Falcon Heavy launches), but when the
goal is on the order of 12,000 satellites (by the mid 2020s), that's at
least 200 Falcon/Falcon Heavy launches in a few short years! If we
guess those launches cost on average $50 million each, that's $10
billion in launch costs just to get the initial constellation up and
running!


It takes a Falcon 9 launch every week just to maintain things once
they're up. However, I disagree with you. I think you'll see "push
beyond" in parallel with satellite deployment. Remember, these are
fast turnaround reusable vehicles.


And keep in mind the lifetime of these satellites is relatively short
(from memory something like 3-5 years), so this isn't a "one time"
thing. If Starlink is successful, SpaceX will be continuously launching
its own Starlink satellites for some time to come.


Yep. They're going to have to replace something like 2500 satellites
a year once the full system is up.


SpaceX needs Starlink for the potential revenue to attract investors to
develop Starship/Super Heavy. But SpaceX also needs Starship/Super
Heavy to launch and maintain the Starlink constellation.


You're starting to make this sound like trying to fly by tugging on
your own bootstraps. SpaceX has gotten over a billion in investment
and it is ALL going to StarLink (and none to Starship/Falcon Super
Heavy).


Mars is still Musk's ultimate goal, but Starlink will need to come first
in order to provide the massive cash flow needed to turn Starship from a
cargo launcher into a true crewed spaceship capable of performing an
actual Mars mission. IMHO, of course.


While I think Musk is overly optimistic (as usual), I think you are
overly pessimistic. I'd bet on a manned Mars mission before 2030 with
the potential for lunar missions before that.


--
"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