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Comment by redthrowaway | Hacker News Reader

I realize that my post is unclear, so I'll edit it. Yes, Earth -> LEO is by far the most challenging, but LEO -> Earth is far from free of pitfalls. Absent a space elevator, there seems to be no reasonable way to get the necessary components for a smelter to space, so any ore coming back would be coming back raw. Throwing bits of asteroid at the planet seems inefficient, to say the least.

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IIRC a space-based smelter is a mirror to concentrate sunlight, a system to collect the melty bits.

Some of this we might be able to make in space - boot strap a mirror factory and you've made the tools to make the tools.

Throwing bits of asteroid at the planet seems inefficient, to say the least.

How so? You can land the goods anywhere you want on earth. Sending stuff down a space elevator and you still need to ship it from the equator to wherever you need it.

After you apply the brakes, you don't need any more energy - the stuff is going downhill.

Granted, we can't simply drop iron on Cleavland where they can process it. Even if we assume pin-point delivery people are going to be reluctant to be at a potential ground-zero.

However lots of potential users are near water. The Great Lakes would make a great catcher's mitt for a few tons of air-dropped iron.

The Great Lakes would make a great catcher's mitt for a few tons of air-dropped iron.

Not without an environmental impact study first.

Maybe China will volunteer some remote quarter of their vast stretches of land as a crash landing pad. It might be worth completely sacrificing the environmental quality of a few dozen square miles of land (there's already tons of land that's naturally uninhabitable) to gain the resources available from space.

I think you're missing the point.

Wrap the goods in a capsule. Attach a parachute.

Now you can land it anywhere you want, lawyers permitting.

(snicker)

> Throwing bits of asteroid at the planet seems inefficient, to say the least.

It might be inefficient in the sense that you lose much or even most of your materials during re-entry/collection, but (for all we know) it could still much more economical than mining here on earth. If you can bring gold back to earth at a price of $1k/kg, it's not going to matter that half (or even 90%) was destroyed in the process.

I assume here that you'd look around for asteroids that were of a Goldilocks size: not too small so that a large fraction of the material survives re-entry, but not too large so that it creates a serious risk of destruction.

I was assuming you'd have parachutes to avoid vaporizing the rocks when they hit the ground.

And if we have parachutes then we can wrap an ablative capsule around the rocks.

Add a guidance system to make the lawyers and citizens happy.

I think parachutes would be a waste, but a cheap, spray-on ablative layer could make sense.

Think of it this way - with parachutes and a guidance system you can land the stuff wherever you want.

This might not be so important for tons of raw metal. Could be a good tech to have around when you want your orbital factories to compete with terrestrial concerns.

And where would you get the parachutes, ablative capsule and guidance system?

Make them in orbit.

Send them up as freight.

Gold is rare everywhere; is there any evidence that there's a large amount of it floating around the asteroid belt?

Yes. 433 Eros is estimated to contain something on the order of $100 trillion worth, with similar amounts of other valuable elements.

There is some evidence that most of the precious metal deposits on earth came from collisions with such asteroids.

I've done quite a bit of looking around re: 433 Eros's composition. I have found very little to suggest to me that there's large amounts of valuable minerals there. Can you cite someone that's done a composition extimate? This: http://www.psrd.hawaii.edu/Feb02/eros.html suggests such estimates are spotty at best, since the formation of the object hasn't even fully been agreed upon.

I'd welcome the evidence about precious metals coming from collisions, that meshes with some of my understanding of the early solar system, but would be glad to know more.

Does that estimate take into account the way such vast amounts affect the price curve? I would think that the gold price will fall if it is available in abundance.

Yes, because Gold is not rare everywhere, just in the Earth's crust because of gravity differentiation (Gold sinks--there's probably quite a bit of it in the mantle/core).

There are individual asteroids out there with more platinum-group elements than has been extracted from the Earth in all of human history.

The end game might be to send parts and robots to make the mining equipment itself on site. Rebellious human operators / colonists not required.

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