The Astronomy Thread

Keep in mind that the larger the asteroid, the harder it will be to move. I don't see us moving planet killers into orbits without some future tech. With current technology it would take many years just to alter the orbit enough to miss the Earth if it were on a collision course.

Also, the reason why some asteroids are rich in valuable metals is because of differentiation. When large bodies form, the denser metals sink to the center. Earth's core has a great deal more gold and platinum than the crust does. Some of the early bodies in our solar system were large enough to differentiate, and then they smashed into other bodies and broke apart, leaving pieces of differentiated cores full of nearly pure iron and all sorts of good stuff. We know enough about asteroids to know which bodies the pieces came from.

SpaceX is designing reusable launch vehicles as well. The major factor in the cost of rockets is that they are one time use only; if they can land safely back on earth, the reusability will reduce costs by a factor of 20, so even existing chemical rocket propulsion may allow us to do some interesting things. That and the brits are making a hybrid engine that breathes atmospheric air on the way up, allowing for entirely reusable single stage orbiters. (it was linked here recently)

http://www.sciencenews.org/view/gene...llision_debris

Looks like all of the elements heavier than iron are not created by large supernovas but from colliding neutron stars. I heard that said before but this seems like better evidence for it.

Szlia_sl said:

2) Supply an demand. The reason why the mineral content in asteroid is worth a lot of money is because we can't get it as of yet: it is not part of the supply As soon as we can access it: the price plummets.

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But that's actually a good thing. It's an incentive to be the first as well as an incentive to be the most efficient even if you're not the first.

As long as the materials are useful they will always be worth something. And as long as they are worth something they will be worth exactly that amount of effort to extract them. It's not like we go grab 500 million tons of iron and all of a sudden we don't have any reason to build anything out of iron anymore. And if we have so much that it's worth less to get more than it costs to actually go get it -- well shit, that's a good thing too. And self correcting over time.

I imagine companies will just meter out the supply. When we get to that point I seriously doubt there will be much competition, especially at first and the requirements to get permitted to do this are likely to be ridiculous.

heh, one of the things I wonder about extensive space based resource extraction is at what scale do we have to seriously start worrying about orbital mechanics and the like? Our fossil fuel usage initially wasn't enough to cause any big problems with the Earth's atmosphere until shit went ballistic in the past 100 years. I wonder what sort of scale asteroid mining would have to reach before we start to realize that we're slowing/speeding the Earth's rotation, or causing our orbit to get larger/smaller, or fucking around with some obscure orbital/rotational oscillation.

At least the orbital change deniers will be easier to laugh at: it'll be fairly easily demonstrated physics.

Eomer_sl said:

At least the orbital change deniers will be easier to laugh at: it'll be fairly easily demonstrated physics.

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Because science has did such a great job of preventing stupid people from believing stupid shit in the past, stupid people will continue to be stupid regardless of the evidence you put in front of them.

Newton's fascination with pescher codes and elemental transmutation were extremely useful.

Shit, if Newton couldn't figure it out I reckon it's beyond the rest of us too.

Anything large enough to mess with the Earth's orbit is way out our current league, and all current mining schemes will instead focus on much smaller objects.

For example, NASA's JPL study proposes to capture, at most, 2,193.24 tons of material for study which will be left in orbit. The commercial ventures aim to capture a lot more, but at most they plan to place ~100,000 tons in orbit at any given time. That's about the size of an aircraft carrier, so it shouldn't mess with the orbit appreciably. Keep in mind that the commercial ventures want to mine in place and transport raw material back to Earth. One company plans to send down whiffle balls of metal that weigh a ton or so at most and simply collect them as they come down with relatively "soft" landings. The other technique being developed is to electroplate the mined metal onto a giant airfoil. Once it's achieved a sufficient mass of about 100,000 tons it'll be sent to Earth over several years, and it will intercept and land "softly" in the desert as its flight path intersects with the Earth's instead of simply crashing. Both companies are already deep into the approval/negotiating process with several countries for landing rights, and one has all but guaranteed rights in at least two countries with large uninhabited deserts.

Eomer_sl said:

... I wonder what sort of scale asteroid mining would have to reach before we start to realize that we're slowing/speeding the Earth's rotation, or causing our orbit to get larger/smaller, or fucking around with some obscure orbital/rotational oscillation...

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We already have the moon slowing the Earth's rotation down for us. Considering the sheer size of the moon and how slowly it is occurring, I doubt we will take on anything that would have any appreciable effect on the Earth. (With exception of it crashing down out of orbit)

Because the Moon's mass is a considerable fraction of that of the Earth (about 1:81), the two bodies can be regarded as a double planet system, rather than as a planet with a satellite. The plane of the Moon's orbit around the Earth lies close to the plane of the Earth's orbit around the Sun (the ecliptic), rather than in the plane perpendicular to the axis of rotation of the Earth (the equator) as is usually the case with planetary satellites. The mass of the Moon is sufficiently large, and it is sufficiently close, to raise tides in the matter of the Earth. In particular, the water of the oceans bulges out towards the Moon. There is a roughly opposing bulge on the other side of the Earth that is caused by the centrifugal force of the Earth rotating about the Earth?Moon barycenter. The average tidal bulge is sychronized with the Moon's orbit, and the Earth rotates under this tidal bulge in just over a day. However, the rotation drags the position of the tidal bulge ahead of the position directly under the Moon. As a consequence, there exists a substantial amount of mass in the bulge that is offset from the line through the centers of the Earth and Moon. Because of this offset, a portion of the gravitational pull between Earth's tidal bulges and the Moon is perpendicular to the Earth?Moon line, i.e. there exists a torque between the Earth and the Moon. This boosts the Moon in its orbit, and slows the rotation of the Earth.

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https://en.wikipedia.org/wiki/Tidal_acceleration

Ironically, these same tidal forces are not only slowing down the Earth's rotation but also slingshotting the moon out of our orbit over time.

Yeah, I'm aware of all that. I'm just saying that in a couple hundred years, we could well be bringing enough mass in to orbit around the Earth (or rather in to the Earth/Moon system) that it could cause issues. It's not going to be something that's an issue any time soon, but it's conceivable that down the road it would be something we have to monitor as a civilization. The Earth's orbit and rotation along with the Moon's orbit are a lot more complicated than most people realize, and they're responsible for shit like ice ages and so on. What if we accidentally fuck up Milankovitch cycles, for example:http://en.wikipedia.org/wiki/Milankovitch_cycles

Again, I have no idea what kind of scale we'd need to hit for that to become a worry, and I know it's far enough away that we won't have to worry about it for hundreds of years. But it's an interesting thought experiment. And it goes both ways: if we build a couple dozen space elevators and start sending huge amounts of mass in to orbit or deep space, that could screw with things too.

^^^ This.

The sheer amount of concentrated mass you need is just staggering.

Jysin_sl said:

^^^ This.

The sheer amount of concentrated mass you need is just staggering.

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Absolutely true. But do you think that James Watt could conceive of humanity producing and consuming 80+ million barrels of oil a day, to say nothing of coal or gas? Who knows where things will be in 250 years.

Tuco_sl said:

I'm no physicist but I find the idea of us pulling in an asteroid into orbit and having us ruin our own orbit/lands pretty ridiculous.

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I'm not talking about one asteroid, I'm talking about the cumulative effects of thousands or millions of them, over centuries. And I'm not talking about us spiraling in to the Sun or out of the solar system, but causing minute changes that could significantly effect our climate, tides, seasons, whatever.

Fuck, where is Tea when you need him! Back me up bro!

Eomer_sl said:

I'm not talking about one asteroid, I'm talking about the cumulative effects of thousands or millions of them, over centuries. And I'm not talking about us spiraling in to the Sun or out of the solar system, but causing minute changes that could significantly effect our climate, tides, seasons, whatever.

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It's certainly possible in theory to do something like this over time, but I think it's not a huge concern. Consider that only necessary material will normally be brought back. Resources are currently extremely scarce in space, and everything will get used. It's not like the asteroids would be pulled and parked in orbit. They'd be processed and retrieved for specific purposes. Even the basic carbon is processable for use in making fiber and assorted constructs, and there'll be a big demand for it as 3D printing and zero G manufacturing are perfected. If we possessed the technology to pull such a staggering amount of mass into orbit, it'd simply be far more efficient to travel out to the asteroids themselves and mine them on the spot. Why waste the fuel bringing thousands of them back, when you can just take your fleet out to them? Even right now, NASA wants to capture an asteroid and bring it back just so they can crawl all over it and get sciency with it up close. There's no real benefit to haul back a second moon and just leave it there.

The only situation where I see this as a plausible and active concern is if we face technological stagnation after developing a cheap and effective drone delivery system that's capable of retrieving them, but not actually mining them which would necessitate parking them in orbit. If that were the case you might see us bite off more than we could chew, but it's still something that's very foreseeable.

I'm honestly more worried aboutKessler Syndrome.

I got your back Canadabro.

Shit could fuck us all up. Like biblical fucked.

Phazael_sl said:

but a fast moving hunk of iron where the retros fail to fire on approach is another story entirely.

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This is one of the big fears nations have, and the resource extractors have two main solutions. The first is to break things up and drop down whiffle balls of ore the size of a VW bug so the damage will be limited. The second is to send the ore back all at once in the shape of an airfoil that will intersect with the Earth's orbit which will create a much softer landing at around ~500 mph, and it'll be aimed at the Arabian desert or the Outback. Both areas are large enough that the margin for error is quite large. A variation of the 2nd theme is to capture the minerals in the moon's orbit then decelerate them as necessary. Once a proper speed has been achieved, a tether system with a counter weight will be used to break the lunar orbit and put the ore on a proper flight path to its intended desert landing zone. The benefit of a tether system is that if something goes wrong you just release the payload back into the lunar orbit for later retrieval.