How do I actually mine an asteroid?

Question

Obviously, you can't just send a bunch of out-of-work Kentucky coal miners up there to give it a go. You need some sort of specialized equipment. What I want to know is: what equipment will it be?

What machine(s) buildable with current day technology would allow you to economically mine a near-Earth asteroid?

Condiderations

• Current day technology only

• Must be launched into orbit by a rocket no more powerful than Saturn V (49 tons to a Lunar orbit). Multiple launches are fine.

• For the elemental composition of the meteorite in question, use Table 2 here.

• Must be able to remove useful ore and pack it in some way for transit. Returning the mined stuff to Earth is out of the scope of this question.

• The key factor that must be considered is how much refining is to be done in space to make this economical. The edge case solution is just to return the whole asteroid to Earth and mine it on the surface after it cools down, but that seems a little too bombardment-y to be politically feasible.

Answer 1

The simplest and cheapest means to do so would require large amounts of metal foil as the basis of the mine.

Step one: find your asteroid or NEO and wrap it on a large metal foil "bag". Strips of metal foil can be arranged and the edges "welded" together to encompass almost any size of asteroid. there need to be two openings, which are explained below.

Step 2: using more metal foil, create a mirror capable of focusing the sunlight onto the bag you created in step one. The solar energy goes through the first opening (which can be a transparent window) and heats the materials within. The size of the mirror depends on the distance from the sun (the farther away you are, the larger the mirror needed) and if you are setting an arbitrary limit based on what you want to mine. Ideally, you want to heat the material to a plasma and collect everything, but some materials are more valuable than others, so you might simply settle on heating the asteroid to the boiling point of whatever element you are interested in.

Mirror arrays can be scaled to provide the amount of solar energy needed

Step 3: The only heavy and massive part of the mine is a mass spectrometer used to separate the stream of ions being released by the heat energy being deposited on the asteroid, and a series of cold traps to cool and solidify the materials after separation. This is placed in the opening opposite to the mirror to protect the machinery from the mirror's energy.

Basic idea of a mass spectrometer. Scaled up, it can separate a plasma stream into valuable materials leading to cold traps

Answer 2

Vacuum distillation of metals

Take advantage of the vacuum and the ability to heat objects without convective or conductive losses, or risk of pollution. This scheme will allow you to refine your metals by distilling them out of the asteroid into the vacuum of space. Once cooled, condensed crystals of pure metal will be swept out of the vacuum and collected. This is analogous to what is done with crude oil.

What you need: solar lens, space sweeper. Some explosives might be nice as it will be easier to heat boulder sized chunks than an asteroid of many cubic km.

1: Identify region of asteroid containing metals of interest. A small asteroid might be heated in its entirety or you might break chunks off with explosives to facilitate even heating

2: Apply solar lens to heat region of interest. This will be more efficient than on Earth without pesky convection.

3: Raise the heat slowly.

4: Molten metal will stay together via surface tension. I am not sure if the heat will cause convective mixing and homogenization or if the various liquids will stratify. It does not matter for the end result but the appearance of the process can be something to describe as it happens if this is for a work of fiction.

5: As temperature reaches evaporation point of various components, hold temperature steady as undesirable components volatize off. A gentle puff of gas will allow these waste materials to move off into space.

6: Just as with cracking crude oil, your various metal fractions will come off one by one and bubble off of the liquid surface. Puff away the undesirable fractions as they come off, but gather desirable fractions. You might allow the metal gas to condense back into solids first - probably crystals.

Answer 3

Judging that asteroids have a ton of dust on them, you could probably use a harpoon to anchor yourself on it, like Britain did with the first rover on a asteroid, and then use a vacuum or large filter/net to catch the dust or minerals.

The drone would be launched like every other craft, but would use ion cannons to get from place to place, with oxygen based pressure rockets to use for maneuvering.

The minerals could be stored inside of a container inside of the drone, where it would then return to an orbital station, like the ISS, but this one has refineries.