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Comment by dylan604 | Hacker News Reader

"The docking mechanism is simple—since the asteroid is likely to be iron-rich, Vestri will use magnets to attach itself."

While that sounds simple, it does make it sound like the mining part just became much more difficult.

Thinking about some of the sci-fi regarding asteroid mining, I've always liked the idea of bringing the asteroid to park into an orbit around earth to make it easier/cheaper for multiple deliveries, but I've always wonder what kind of ownership claims that would imply. If I took the time and effort to park an asteroid in orbit, would I have sole ownership of it or would you be able to mine from it as well?

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> I've always liked the idea of bringing the asteroid to park into an orbit around earth to make it easier/cheaper for multiple deliveries

I think you're dramatically underestimating the difficulty of doing this.

If you look at rockets, they're 90-95% propellant. Even relatively svelt upper stages like Centaur III (the upper stage from Atlas v) are more than 50% propellant. And that's for just taking payloads to LEO - for higher energy missions, the usable payload gets smaller, which means the percent of the upper stage that's propellant increases.

How difficult would it be to get an amount of propellant, say, 5 times the mass of the asteroid to the asteroid? You'd also have to get the engines and other structures to let you use the propellant in a productive way.

It's way easier to extract valuable parts from an astroid and move a lot less mass there and back.

Moving mass back with a free return trajectory is much easier than getting stuff out of Earths gravity well and up there. Escape velocity from an asteroid is low and if you yeet it with enough precision you can send it on a trajectory that will land it on Earth.

As for moving the asteroid you could use extremely high specific impulse ion thrusters, in situ propellant from the asteroid itself, or a solar sail. But you are right that simply firing the valuable stuff back to Earth is probably easier.

Not to mention the governance and liability implications of the plan. If a company mining something on Earth screws up really badly, they can ruin the environment for a hundred miles around. If a company mining an asteroid in LEO screws up really badly, the literal blast radius would wipe out a significant percentage of life on earth.

Why does it need to be parked in LEO? It could be kept in an orbit at the same distance as the Moon and it would still be relatively close compared to where it is now

Fair. I don't think we'd want that either, though, for the same reason. The moon is too close for comfort for smaller objects that we've proven we can move.

What about using the asteroid itself as fuel? Even if the asteroid is devoid of hydrocarbons that could be turned into fuel for conventional engines iron make a suitable (albeit inefficient) fuel for ion thrusters powered by solar panels.

Mass drivers and linear rails are also viable ways of bringing raw material into Earth's orbit from asteroids of a certain size.

This was my thought as well. Also for what it’s worth iron oxidation is slow but very exothermic.

So what you’d want is a LEO starting point/station. You launch a barge from there to snag an asteroid. You could use a mass driver using solar or nuclear and mass from a previously spent asteroid to get to the asteroid belt, then snag an asteroid and use its mass to get back. You strip the important parts of it, construct a capsule for what you mined, and nudge it so it falls someplace in say a shallow part of the ocean. Then recover from there.

Or hell why mine it up there? Simply nudge an asteroid on a collision course towards Earth to make sure it falls someplace “safe”. Sure most of it will burn up but not all. It’s free material after all.

Didn't the asteroid that destroyed the dinosaurs hit the ocean?

Sure. So size matters. If you drop a rock in the ocean it doesn’t darken the skies, does it?

Meteors fall onto Earth all the time. It is a matter of composition, trajectory, and mass, no?

> It is a matter of composition, trajectory, and mass, no?

We're talking very specifically about an asteroid made up of iron. Logic would follow that it would be on the more massive end of the scale. No? That's like the worst possible composition and the very type that worries the doomsday types.

Lead is much heavier than iron. A uranium asteroid is pretty bad too.

But that aside, we have plenty of iron right here on earth. There is zero reason to mine iron in space unless you need it in space. An asteroid of pure gold on the other hand…

But setting all that aside, you get to choose the size! And the trajectory! And the arrival point! Like if you toss a 100kg asteroid and get 1kg of gold out of it, no you won’t kill the planet. You get to choose all the variables.

Probably at very high speed (in excess of orbital velocity) and near head-on.

Ideally you’d put an asteroid in LEO, slow it below orbital velocity, and have it come down at a shallow angle so aero breaking removes most of the remaining velocity.

Ok, just park an ion drive on the asteroid and your descendant's descendants' descendants' get to mine it from LEO?

I don't think that moving the whole thing into our orbit would make much sense.

The biggest amount of delta-v is necessary to leave Earth's gravity well. Once you're there, going from and to asteroid is time-consuming but doesn't need that much delta-v, moving ore from the asteroid to Earth would cost some fuel, proportional to the mass.

So moving it into orbit would save time but require us to pay for the fuel all at once.

So why should someone do this, unless you need a permanent human presence on the asteroid?

> So why should someone do this, unless you need a permanent human presence on the asteroid?

Activity is only economically valuable if it is valued - i.e. by people.

Unless there's a population of people living in space, the ore or products derived from ore need to eventually make their way to Earth in order to be worth while.

I think we're all scared of the actual question posed or something as we've totally ignored it in everyone of these responses.

Nobody cares in sci-fi about whether something should/could be done. That's not the purview of the plot. It's also not the purview of the original comment.

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