Comment by cletus | Hacker News Reader

Comment by cletus | Hacker News Reader

I'm not sure what substance you could mine on an asteroid that could possibly be economical.

The first obvious assumption is would have to be launched from space and return to space because the cost of getting a payload from Earth to LEO is a huge extra expense.

Then you have to consider the delta-V of getting to the asteroid, doing a rendezvous and getting back. If that's so significant that the Earth launch cost is trivial then the delta-V budget is so huge, it must make the endeavour even more uneconomical.

I believe humanity's future is in a Dyson Swarm. There are simply too many advantages. This is a deep topic. The question is how do you bootstrap that? Where do you get raw materials?

I don't think it's from asteroids. I very much suspect it's from a larger body and my money is on Mercury. Why? On pretty much any body in the Solar System you're living underground so Mercury is at no disadvantage here. It has no atmosphere. That's an advantage. Mars's super thin atmosphere is the worst of both worlds. Additionally, Mercury is metal rich and due to its proximity to the Sun, energy is abundant (ie solar power). Interestingly, it has a higher orbital speed than Earth (47km/s vs 30km/s). That's really interesting because it's free velocity to leave the Solar System.

Resources on EArth are so ridiculously cheap. You can mine iron ore for a few dollars a ton at scale. You can convert it into steel really cheaply too (again, at scale). Doing anything in space requires having truly stupendous amounts of cheap energy available.

Mercury sounds interesting. Requires a certain scale though (gravity is a bitch).

Considering just the initial mining and construction, bodies with low gravity and proximity to the earth feel like an efficient starting point, right? I always thought the moon would be a good place to bootstrap the first few thousand space habitats.

Your point about energy will probably be the biggest deal. Wondering how complicated it would be to ship a bunch of nuclear reactors to the moon. There seems to be quite a few companies working on small, "mass produced" reactors currently.

In terms of delta-v, the asteroids are much closer to us than mercury. A small one in the belt is like delta 1.5km/s from earth escape, versus 11km/s to mercury. Heck, the Mars moons are technically closer to us than 'our' moon. (Overview i.e deltavmap.github.io/)

And the sun is a gravity well. Mercuries higher orbital speed will not help you leave the solar system. In fact, it is the other way around.

Oh, and solar cells are already crazy good. With all the space you have out there, higher energy density on mercury will be very marginally important.

Send a piece of lead in orbit around the sun so it heats up but not melts, when it comes around heat some water to steam. Free power!

Once all of your water is steam, how do you get it back into a liquid phase so that you can do it over again?

Or so that you can do other things, like drink it...

The internet is a messed-up place, because as much as I'm convinced this is a joke, I'm also certain somebody could write the same comment in all seriousness and think they are making a great discovery.

We can't even just laugh.

the idea is actually workable, it just isn't competitive with other ways of exploiting solar energy

It has some really serious drawbacks, like needing to repeatedly synchronize and desynchronize orbits. That makes it crazy complex even on the context of crazy futuristic space machinery.

That "isn't competitive" is quite an understatement. But yeah, technically it doesn't break any law of Physics.

There are neutron stars that create chunks of gold and platinum larger than the size of earth itself.

Highly doubt such chunks are floating around our solar system but it's an amusing thought that one day hundreds of years from now we could nudge a (much) smaller chunk into orbit or park it in a Lagrange point and shave off pieces to return to earth.

> There are neutron stars that create chunks of gold and platinum larger than the size of earth itself.

Aren't neutron stars 12 miles in diameter on avg?

Neutron stars are the literal limit to how much matter can be collapsed before it turns into a black hole and yet still remain a star.

A neutron star 12-16 miles in diameter contains the mass over HALF-MILLION earths, it is very hard to fathom but yet they exist!

So popping out an earth-sized chunk of gold after collision with say another neutron star (kilonova) and ejecting matter to "normal" density is plausible.

re: delta V, the chaotic nature of orbits involving many bodies means that a very well-timed nudge ought to be sufficient to move certain asteroids quite a long distance for "free". So the problem becomes finding the right asteroid, and the right time, and the right nudge vector. More about computation than rocket fuel: the deeper into that chaotic system we can penetrate, the less we have to spend on influencing it.

You've also got to slow it down when it gets to where your smelters are. For that I'd propose we just let it smash into the moon and then mine it on the surface. We can alternate which sides we smash into in order to prevent the moon's orbit from changing significantly.

Of course you still need to provide the initial nudge, which ain't nothing, but it's a far cry from towing an asteroid or towing a smelter.

A medium-sized asteroid identified had something like $3T of titanium on it. Of course, that's gross value and you can’t clear your supply at that price. But even if it costs hundreds of billions to extract you should be able to net a profit.

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