Mining the Asteroids

[uppi]

For it to be practical, the rock needs to be moved to someplace in Earth orbit.

Why would you want to move the whole asteroid near Earth's orbit? You would spend a huge amount of effort moving what is mostly useless rock. It would be much more efficient to extract the desired substances at whatever place the asteroid is and just haul that back to Earth.

Unless you want to crash land the asteroid on Earth, you need to put the extraction machinery into space anyway. And it should be much more efficient to move that, than to move a million tons of rock.

 

[El_Machinae]

I suspect it would either be cheaper to fling the 'good stuff' towards Earth, or the 'bad stuff' away from Earth to push the asteroid closer.

 

[Cutlass]

Why would you want to move the whole asteroid near Earth's orbit? You would spend a huge amount of effort moving what is mostly useless rock. It would be much more efficient to extract the desired substances at whatever place the asteroid is and just haul that back to Earth.

Unless you want to crash land the asteroid on Earth, you need to put the extraction machinery into space anyway. And it should be much more efficient to move that, than to move a million tons of rock.

The reason to move it is to make all the resources of it available. If you were to mine in in place, you would need to not only get the machinery into orbit, but also way out to the rock.

Here's my vision of it. You build a bunch of space robots that are cylinders with nuclear power plants. They go to the asteroid and place one end up against it. Then they use lasers to vaporize pieces of the asteroid, and ionize them and shoot them out of the other end to provide thrust. Slow, but you could eventually place the rock where you wanted it with a few dozen of these. Once you have it in place, all the remaining material of it could be used for whatever projects you have in mind. And most of the power once it is in Earth orbit can be solar.

But if you send the machines out to the rock, and then send the metals back, then you need to supply fuel coming and going. And you only get to use that small portion of metals that you can send back.

 

[Winner]

The reason to move it is to make all the resources of it available. If you were to mine in in place, you would need to not only get the machinery into orbit, but also way out to the rock.

That's hardly much of a problem. Don't forget, once you've achieved low Earth orbit, 90% of your worries are gone. Getting out of this deep gravity well is the single most difficult problem in spaceflight, the rest is relatively trivial in comparison.

Here's my vision of it. You build a bunch of space robots that are cylinders with nuclear power plants. They go to the asteroid and place one end up against it. Then they use lasers to vaporize pieces of the asteroid, and ionize them and shoot them out of the other end to provide thrust. Slow, but you could eventually place the rock where you wanted it with a few dozen of these. Once you have it in place, all the remaining material of it could be used for whatever projects you have in mind. And most of the power once it is in Earth orbit can be solar.

The energy to do that is simply too much. You don't want to move something that's 90% useless. It's easier to extract what you need on the spot, and then fling the useful stuff (water, platinum-group metals) to Earth.

What you described will probably be done much later, when we start moving icy asteroids from the outer Solar System to Mars (and explode them in its atmosphere to get heat, nitrogen, and water). Moving icy bodies makes sense because most of their mass is useful in one way or another.

But if you send the machines out to the rock, and then send the metals back, then you need to supply fuel coming and going. And you only get to use that small portion of metals that you can send back.

That's why you use in-situ resources to produce all the fuel you need to transport the extracted propellant/fuel to Earth.

 

[History_Buff]

That's why you use in-situ resources to produce all the fuel you need to transport the extracted propellant/fuel to Earth.

Yep. That's how we'll do Mars too, once we eventually decide to do it. The key to space exploration and exploitation is to stop hauling everything up from Earth, and learn to live off the land. Even if we draw resources from Mars (or Luna, but she doesn't have much of anything useful), it's still much more practical that drawing it from Earth.