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Old June 7th 17, 05:39 PM posted to sci.space.policy
Niklas Holsti
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Posts: 168
Default Mining the moon for rocket fuel to get us to Mars

First, I want to highlight that I'm not advocating fuel production on
the Moon; I am not competent to evaluate the difficulty of that. I'm
only doubting the "first order approximation" that compares the amount
of fuel needed to send the equipment to the Moon (from the Earth's
surface, it is assumed) to the amount of fuel produced on the Moon.

On 17-06-05 13:43 , Jeff Findley wrote:
In article ,
lid says...
Yeah, I use a very simple first order approximation for this:
the mass of the fuel you'll get from the Moon has to be greater than
fuel used to get the mass to mine it to the Moon, otherwise it's a net
loss.

Simply put, if you're going to extract say 100 kilotons of fuel from the
Moon, you're going to have to use less than 100 kilotons of fuel getting
your mining and processing equipment there, otherwise it's a waste.


Perhaps you on purpose ignored this factor in your approximation, but
surely the *location* of the fuel must be considered?

If you use 100 kilotons of fuel to send equipment to the Moon, most of
that fuel is used up close to the Earth, and will not reach the Moon. If
that equipment then produces 100 kilotons of fuel on the Moon, that fuel
is on the Moon, which is "half-way to anywhere".

You would surely have to use *much* more than 100 kilotons of fuel to
deliver a payload of 100 kilotons of fuel from the Earth's surface to
the Moon's surface.


So let's revise the original statement a bit. If the goal is to refuel
a depot in lunar orbit, the fuel you mine, refine, and launch to that
depot must exceed the amount of fuel it took to originally land the
mining equipment, lander, and landing fuel when starting from roughly
the same lunar orbit as the depot.


I agree with that.

Ignore the delta-V to get to lunar
orbit, because it's the same for the 100 kilotons of fuel put in lunar
orbit or the 100 kilotons of lunar lander, fuel, and mining equipment
put in lunar orbit.


How did you get from Greg's assumed "100 kilotons of fuel getting your
mining and processing equipment there [to the Moon]" to "100 kilotons of
lunar lander" etc.?

The original statement assumed 100 kilotons of fuel would be used, in
total, for transporting the mining equipment from (presumably) the
Earth's surface to the Moon. The mass of that equipment, including
whatever is needed to bring it from lunar orbit to the lunar surface,
must then be assumed to be *much* less than 100 kilotons.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
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