this post was submitted on 31 Jul 2023
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So I have two questions from that.
How much mass can we remove from the moon until we affect it's rotation around earth?
What will the ecological impact on earth be if a dozen companies start launching rockets at the moon on a regular basis?
Mining enough to alter the orbit of the moon would require a pretty ridiculous amount of time and effort. Much more than our global mining efforts combined and multiplied and on a timescale of thousands of years.
And we only have to launch a few rockets, enough to set up a self-sufficient base which can then produce more rockets and fuel from resources on site. Not to mention it's much easier, and even feasible with existing materials, to build a space elevator on the moon.
But then we need to get the resources back to earth... probably multiple launches per week.
Well, first off, if the rocket launches from the moon, is that such a bad thing? Any exhaust would remain on the moon. Not to mention that lunar rockets are much much smaller than earth rocket. Secondly, we probably wouldn't use rockets for it, we would probaby use a lunar space elevator to skip the lift stage entirely and just have enough thrust to move the payload into an orbit that eventually gets to the Earth. Or we could use a mass driver, a massive coilgun that magnetically propels payloads to speeds that let it fall down to Earth in one go. For none of these do we need an Earth launch, the payload just needs to be picked up after falling to the Earth. With maths and timing you could probably designate a single landing area on Earth that all lunar payloads fall into.
Any launch from the moon would require launch back from earth to retrieve the rocket so it can be put to use again.
Space elevator and orbit launch is an interesting thought. I think it's a tough sell. In that case we would be launching uncontrolled asteroid-like dumps towards the earth. Sounds like a nightmare waiting to happen. Every city would need a missile defense system 🤣. The resource dumps would have to be big enough to warrant the investment in the space elevator and not burn up in Earth's atmosphere, or, we would need a space elevator on earth too (which would be the biggest engineering and political feat humans have ever done).
Mass driver. That's another cool idea. From some research it looks like most metals have a temperature which they stop being magnetic and getting into Earth's atmosphere would put most metals past that. Having a mass driver on top of a space elevator, or just a giant mass driver, also sounds like a head scratcher if most resources we would want can't be 'slowed down'
The problem with all these cool engineering ideas is that they seem to require a united human race. The universal earthling concept is probably lifetimes away or until we face some (un)natural disaster that causes countries to unify. With the way the world is right now, I am having a hard time imagining uniting for 'progress'.
If you launch a rocket from the moon it doesn't have to be a reusable one. It can be a cheap, one-use rocket that burns up in atmosphere and crashes into the ocean. Like most rockets in history.
A space elevator is actually the best bet for launches. The resources we would send from the moon wouldn't be unrefined clumps of regolith, we would have foundries on the moon to process the lunar resources into a refined state. That would make payloads a lot smaller and neater than moving ore to be smelted and processed earth-side. And it's very possible to aim a payload at a specific landing site. They did that in the 60's for the moon landings, for the exact reasons you mentioned. Not to mention a lunar space elevator can be constructed of cheap materials like kevlar, and would pay itself off after a few payloads. Not to mention it can be used for other purposes, like servicing spaceships headed out of the earth-moon system, or as a transit hub. And while atmospheric re-entry gets hot, it's not hot enough that it destroys everything. Remember, people go up and down to space all the time, like with the moon programs, the space shuttle program, every space station, and a few satellite maintenance missions like Hubble.
A mass driver is essentially a big cannon, but instead of a chemical propellant it uses electromagnets to launch a payload. But like a normal cannon, it stops acting upon the payload after it's launched. It doesn't project a constant stream of magnetic energy onto the payload to propel it. All the necessary kinetic energy for the payload to reach earth is imparted onto it by the mass driver during launch.
Firing a cannon at the earth might sound dangerous, but it's only as dangerous as launching a small rocket from the moon, like we did during the moon landings. The "bullet," or payload, would consist of the main cargo, in this case processed resources, and a guiding system like any rocket has, if simpler. It only needs to do some course corrections to make sure the payload lands where it's supposed to, and doesn't crash onto a city. And putting a mass driver on a space elevator wouldn't be much better than having one built on the lunar surface.
And none of these ideas are such massive undertakings that they need global unity. They would be very simple when you get down to it, because every nation knows how to build an elevator, or a cannon.
Would it not be super cool to have all those minerals until we have extracted that much from the moon that it's orbit becomes unstable and then spirals into earth?
First, figure out how much the Moon weighs. The find out how much we mine form the Earth each year.
Second, the impact of dozens of flights a day will be much less than the impact of mining the Earth