On 9/29/21 11:19 AM, Poul-Henning Kamp wrote:
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Bob kb8tq writes:
Road building and graders sort of implies moving large amounts of “stuff”
onto the lunar surface. While a “road to nowhere” on earth might happen,
I’d bet you only build one on the moon to connect inhabited installations
to other full blown (inhabited or not) sites of some sort.
It's funny how peoples thinking about this is still firmly cast in
a 1950'ies NASA/science-fiction mindset.
People really do not grasp how much work robots can do.
One place I really see this is when people look at my lawnmower robot
and go "There's no /way/ that can handle 5000 m² of lawn..."
But the thing is: If a human did it on a garden-tractor once a week,
we'd want it done quickly, so lots of power, wide cutting board and
so on.
But the robot has 168 times as much time[1] for the same job, so
it does not even need one percent of the power of the garden-tractor,
in particular because it does not have to lug 100 kg of human &
associated creature-comforts around.
If we need a road on the moon, we will launch robots and let them
get on with the job, and they'll be done way ahead of when we arrive,
probably not even leaving us a few really largish boulders to blow up.
In other words: The grader on the moon will at most be a meter wide.
We are getting astray from time- nuts here...
BUT
You probably want to be bigger than a meter - thermal management is
easier with larger (surface area to volume ratio), and if you're solar
powered, you need more solar panel area. However, the "grading width"
might be a meter, just the vehicle around it might be significantly
bigger. It's not like a Bobcat skid steer where you're trying to fit it
down the side of your house through a 1 meter gap.
Bigger also probably has advantages mechanically - mechanical tolerance
requirements tend to go as a fraction of the size, so bigger boxes have
looser tolerances in absolute terms. When you're moving around in an
environment of electrostatically charged, incredibly abrasive dust, this
helps.
If you're flying a reactor for power (which would be nice to get through
the cold night), then there's also an advantage to going bigger. The
"overhead" for a reactor (shielding, etc.) is highly nonlinear with
respect to output power. A 100 kW reactor isn't a lot bigger than a 100
W reactor.
There is, also, serious research into doing stuff like sintering or
melting the regolith, which, as one can imagine, is a power intensive
activity. Civil Engineering on the Moon is an interesting topic, but
way off topic for this list.
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