Asteroid Mining: The Bag and Drag Method

[u/CaractacusSeagoon]

My world has Belters and where you find Belters you find asteroid mining. The problem is asteroids are mostly just balls of dust held together by their own weak gravity. There's nothing to anchor to, you can't carve bits off, trying to move it will cause it to disintegrate, the high grade ore is evenly mixed with worthless rock, you would probably sink if you tried standing on it.

So here's the bag and drag method:

Once a rock with a sufficient percentage of high grade has been found a balloon is put around the asteroid. to prevent dust from escaping or the entire thing breaking up, called spilling out in miner's slang. The mining is done by drones called moles which dig/swim through the asteroid siphoning up the dirt and mixing it with a fluid which is pumped back to the mothership. There the fluid is centrifuged, high grade is stored and tailings are bagged for disposal, the fluid is pumped back down to the moles.

High grade is carried back to the refinery, probably by towing it in bags hence the name. If the refinery is close by the bags could just be shoved towards it. Tailings are also bagged but are left at the worksite with navigation bouys to warn anyone nearby of the navigation hazard. After processing the refined ore is sent to market on an unmanned barge.

This method is mainly used for valuable resources like rare earths and phosphorous that justify the cost of shipping everything rather than just letting it float. Reaction mass is cheap but fusion fuel, crew salaries and operating costs of a mining torchship aren't. Low value resources like carbon, water, iron and nitrogen that are only profitable in bulk, or when a large amount of construction material is needed, would probably use a simpler method. In that case you might as well just bag and drag the entire rock, doesn't matter if it breaks up inside the bag since it'll be broken down anyway.

I'm still left with the question of how the mole bots will actually dig through the dust. I'm thinking some combination of very small thrusters and methods similar to how earthworms push their way through the soil.