re: Elon: “When the mass driver on the Moon gets going, I’m not sure money will be relevant”

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Rockets get you to the Moon. The Moon gets you everywhere else.

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I think it’s easy to overstate the benefit here. It takes something like 15 km/sec of delta-V to go from the surface of Earth to the surface of the Moon. It takes something like 18 km/sec of delta-V to go from the surface of Earth to the Surface of Mars.. only about 20% more than going to the Moon.

Delta-V isn’t really the biggest hurdle for manned interplanetary missions. The big hurdles are 1) the duration of the trip / life support requirements and 2) the return. The duration of the trip means you need a larger payload for the same crew size, compared to a lunar mission. The return trip means you need a much larger payload (including chemical rocket stages) because you have to take off from another body with atmosphere. You also need chemical rocket stages for maneuvering and capture burns. The tyranny of the rocket equation makes it difficult to launch such a large payload without some form of orbital assembly/refueling.

So the utility of a lunar mass driver as a staging point for other missions largely depends on the payload fraction that can be fully manufactured in situ on the Moon. Considering a large portion of that payload for manned missions is likely to be fuel for the return trip, I think the benefit becomes marginal. Now.. if you can find a way to manufacture rocket fuels from lunar regolith, that changes things considerably.

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I'd really like to EAT cows in low/no gravity.

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FIFY