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Comment by cubano | Hacker News Reader

So wouldn't the obvious thing be that this asteroids composition would be almost identical to the earth's since, of course, our planet was formed by billions of these things crashing into it?

Now maybe that makes them incredibly valuable, and of course I am sure there must be some statistical distribution of asteroids with valuable minerals and those without hardly any, but I feel there is currently this idea that all asteroids are a hugely valuable to be mined no matter.

Is this true?

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I don't think anyone (credible) is claiming that all asteroids are valuable. There are however many asteroids that would be valuable (or so we suspect). When earth formed heavy stuff sunk to the bottom and light stone rose to the top, and as a consequence e.g. most metal is in Earth's core, out of reach. On some asteroids valuable material is much more plentiful than in the parts of earth we can reach

A heavy phase went to the Earth's core, but there's plenty of metal up here, and some metals (like, uranium) are strongly concentrated in the crust, because chemically they segregated into light silicate phases.

Well, just to address the value of asteroids question--the Earth itself has many incredibly valuable minerals and metals; however, most of that material is extremely far below the surface, rendering it virtually inaccessible. In contrast, this material is readily accessible on smaller asteroids. While I personally doubt that the cost of transporting the material anywhere near Earth will make asteroid mining worth it in comparison to better exploiting the material already on Earth, that's the basic logic here.

It will make sense to mine them for construction projects in space before dropping them to earth. But given the size and composition of some of these objects, mining asteroids could eventually answer a lot of resource scarcity.

Exactly, there are always comments about how it's not worth it right now, but that is now, who knows what the future will bring. We maybe be mining, refining, and doing all our manufacturing in space.

All our industrial waste could just be jettisoned into the endless vacuum of space and the earth might just be for residential and commercial use.

Maybe I'm being fanciful, naive, or just dreaming too much, but it's nice to imagine that kind of future where the earth is just a sanctuary to live and space is where the factories and the rubbish goes.

I’m always curious how heat dissipation is supposed to work in these space projects. The vacuum of space is a hell of a good insulator as far as I know, no?

You don't get heat conduction and convection in space, but thermal radiation works.

At the rate of about 100--350 W/m². More energy -> more radiators. At about 12 kg/m^2 launch budget * $10k/kg LEO.

https://en.wikipedia.org/wiki/Spacecraft_thermal_control#Rad...

The ISS has 156 m² of radiators, compared with 3,246 m² of solar PV arrays.

>More energy -> more radiators.

Which you can make out of the asteroids you're mining for the cost of shipping up the production facilities. It's a bootstrap cost problem rather than a fundamental efficiencies problem.

>$10k/kg LEO.

$2.5k last I heard with the Falcon 9 and SpaceX is aiming to go much lower.

edit: And by much lower Musk means $10/kg to lunar orbit (that's dollars not thousands of dollars). Even if he's off by an order or two of magnitude it's still a lot cheaper.

Launch costs are falling, though (and despite being proved wrong several times by Musk) $10/kg Lunar sounds delusional. Consider that typical bulk freight costs on Earth are in the range of $0.40/tonne-day (180,000 DWT Capesize vessel at $48,000/day https://www.easyship.com/blog/bulk-shipping-for-delivery), or roughly $5/tonne for a 14 day transoceanic voyage (8,000 mi, 12,000 km, very roughly).

Only twice that to Lunar surface is ... dubious.

In situ construction is an option, and while asteroids can be metal-rich, useful in fabricating condenser and evaporator coils, they tend to be refrigerant poor. Substances which have properties of good refrigerants (boiling and volatility at low pressures and temperatures) are poorly retained by microgravity bodies in vacuum.

You dump heat into chunks of asteroid and throw them away, once you have disposable mass available dissipating heat is fairly simple.

The Earth is highly differentiated. What's at the surface is not representative of its average composition, or of the average composition of the material it was formed from.

In particular, the Earth's surface is highly depleted in platinum group elements compared to carbonaceous chondrites. That's because those elements strongly segregated into the molten metal that flowed into the Earth's core when the planet was very hot. Ditto for gold. The Earth's surface is also depleted in tellurium; this is thought to be due to the volatility of TeH2. On the other hand, the earth's continental crust has three orders of magnitude higher concentration of uranium than the chondritic average; the Earth is likely the best place in the solar system to mine that element.

Probably, but since Earth was molten lava for a long time, all the heavy materials are at the center, while the surface we stumble around on is the lightest materials.

What little surface metal we have come from volcanoes and late era asteroids, as I understand it.

This is why a single metal asteroid could revolutionize Earth's economy, even though we have billions times more of the same material under our feet.

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