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Old June 5th 17, 07:56 AM posted to sci.space.policy
Niklas Holsti
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Default Mining the moon for rocket fuel to get us to Mars

On 17-06-05 04:06 , Greg (Strider) Moore wrote:
"Jeff Findley" wrote in message
...

First, this isn't my "subject", it's the title of this article:

Mining the moon for rocket fuel to get us to Mars
May 14, 2017 8.04pm EDT ?Updated May 18, 2017 9.01am EDT
http://theconversation.com/mining-th...-to-get-us-to-
mars-76123

I saw this article (or a variation of it from another online
publication) on Twitter. I replied something to the effect that this
article glosses over all of the hard stuff, like the fact that the lunar
soil and rock is horribly abrasive and that mining equipment isn't
anything like the lightweight rovers that NASA/JPL has flown in the
past.


[snip]

Don't get me wrong, I think *eventually* we'll be mining the moon for
water to turn into LOX and LH2 (or possibly methane) to supply a fuel
depot in lunar orbit. But, needless to say, I think the supporters of
this notion are daft if they think it's going to happen in the next 20
years or so by building a freaking factory on the moon that's capable of
building mining equipment that's not JPL class "toys" that wear out
faster than you can build them.

Jeff


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.

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Niklas Holsti
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