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Comment by mabbo | Hacker News Reader

At some point in the next few decades, I expect to see humanity use this technology to divert an asteroid away from the Earth. And that's pretty neat.

Chelyabinsk was only a 20m asteroid, yet thousands were injured and a lot of damage was done. It's not inconceivable that in the next couple decades, we could predict that sort of event years out, and send a (likely much smaller) redirector mission to give it a tiny push, preventing the asteroid from entering Earth's atmosphere.

What scares and fascinates me though is what happens when we start asking 'okay, but where is it going to hit, and how many of my voters live there?'

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Maybe, but you should watch Scott Manley's videos about keyholes. Asteroids can have orbits that are highly sensitive to initial conditions so you can't predict that much in advance even for some asteroids with known orbits.

I actually expect them to route them towards Earth, to some stable orbit, to be mined. But yes first the collision protection, that's much simpler to achieve and important

An asteroid already on a collision course with Earth only needs a tiny push to miss if we hit it early enough -- think about slightly bumping a sniper before he takes the shot. An asteroid a month out, heading straight for Earth's center, could be redirected to just skim the outer atmosphere with only about 4 m/s of delta-V.

On the other hand, getting a near-miss asteroid to orbit Earth instead means taking it from above escape velocity (11.2 km/s) to an orbital velocity, which means at least a thousand times more delta-V (more like 4 km/s). And that's the easy case -- getting an asteroid from the belt to fall toward Earth is another several km/s on top of that. Besides, ejecting 1M kilograms into a busy Earth orbit in order to slow the asteroid down sounds like a pretty scary idea. Especially since we'd have to do it hundreds of times for one asteroid.

So no, it wouldn't be the same technology at all.

The problem is that we have no ability to conclusively determine whether or not an asteroid is on a near-collision course, or on an actually-collision course.

And if it's the former, giving it a small bump is just as likely to put it on an actually-collision course as not doing anything at all.

You can always ask CIA. They know _everything_.

Wait, before deflecting them? Why?

There’s at least a plausible need there, what with the whole “don’t want to slam an asteroid into the planet” problem.

Mining is still an utter fantasy. It’s completely economically unviable to mine anything from an asteroid and bring it down the gravity well, and we have close to zero ability to actually mine and manufacture anything in space. We are a long long long time away from that.

It's an interesting question. The assumption is that it will never (or at least not for a very very long time) make sense to mine or manufacture in space for use on Earth. Mining/Manufacturing in space for use in space will presumably happen in only a very long time.

That said; what the bigger issue - for in situ operations, the distance to get the raw materials or just doing anything with the raw materials at all? Is it going to be - we could do anything at all but going all the way past the orbit of Mars is too much trouble - or - Getting to a rock past Mars is easy but it's hard to do anything practical with it (compared to just getting it off Earth presumably)

I got no clue as to which way it could go but it doesn't seem a question that answers itself to me.

If you want a fun read, "Delta V" by Daniel Suarez is a fantastic near-future hard scifi novel on the topic.

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