Evacuate Earth

[Eluvatar]

I have to say, a Neutron star coming through exactly along the plane of the solar system is pretty absurdly over the top.

[Zakharra]

Wouldn't a star, neutron star or a normal one, do one hell of a number on the planets and their orbits?

[Eluvatar]

Wouldn't a star, neutron star or a normal one, do one hell of a number on the planets and their orbits?

Yes. Even without it going exactly along the plane, it would perturb the hell out of everything.

[joestej]

Wouldn't a star, neutron star or a normal one, do one hell of a number on the planets and their orbits?

Yes. Even without it going exactly along the plane, it would perturb the hell out of everything.

Hence our solar evacuation.

Hey, nobody said it was likely. I've probably got better odds of going out right now and buying a pair of million dollar lottery tickets in a row than we have of getting hit by a Neutron Star any time in the next hundred thousand years.

Still, rogue Neutron Star, 'mutating neutrinos', whatever the excuse, for the purposes of our discussion all we need to know is that Earth is going to be destroyed in about 70 years, so we need to leave in a hurry.

Now, whether we need to leave the entire system or just the planet would be two very different discussions. I've been assuming the former, but we could talk about the latter instead if the group wants. The biggest difference between the two is if we're going to be making colonies or colony ships.

[icekatze]

hi hi

Close passes by other stars are not completely improbable. HIP 85605 might even do that in the next 240,000 years. (Although the measurements from 2014 may well be inaccurate.) Or possible Gliese 710 in 1.4 million years.

If the entire solar system gets perturbed, it may be easier to build an arc-ship and wait for things to calm down before colonizing something in the existing system that it would be to colonize a different star system. Maybe if we already had good intel on an existing colonization target it could work, but 70 years is really not long enough to detect a suitable habitable world, even if we could build a ship to get there. (And if one is just looking for a rock to cling to, that's a different story.)

[Mjolnir]

An elevator would be one single big piece of infrastructure with hard and rather low limitations on payload volume and mass and number of active climbers. A Lofstrom loop would have similar limitations, while also being a control nightmare and constant power hog, not to mention the safety issues involved in a failure. You need a massive increase in throughput, not a highly specialized launch system that will end up being one big bottleneck. Start mass producing big dumb rockets and build launch sites scattered across the planet...you'll get moving far sooner and be able to launch people and materials as fast as you can build launch vehicles and places to put them.

[Absalom]

That's not even quite the limit on surviving population: the real limit is determined by the lesser of:
1) the population that the initial load(s) of mining, processing, & construction equipment and workers sent to the moon can build appropriate habitat capacity for, or
2) the population that the evacuation-stage orions can bus up to the habitats built from lunar materials.

Well, that's a bit of a question though. If the coming catastrophe is just going to wipe out Earth, then Lunar/Martian/space colonies are our obvious solution. But if the whole solar system is going to become uninhabitable, our problems are much more dire. I've been assuming that this more extreme threat is the one we'd be dealing with, because it's a more complex problem so there's more to talk about.

Sorry about the lack of clarity, I was assuming the more extreme threat as well, but with the quirk of building the escape ship from lunar materials instead of terrestrial materials, thanks to very early launches of mining equipment to the Moon via Orions. For bulk materials, it strikes me as a pretty good option (certainly better than asteroids, since you can partially use existing technology, and better than the Earth, since you can launch more easier). This wouldn't prevent Earth launches either.

[Sweforce]

The need to leave earth and the need to leave the solar system are not necessarily the same thing. The scenario used a neutron star but I doubt even that would destroy the whole solar system. As such, priority one is to get out of the way but once that is done, there is little need to hurry. One could lurk around in the solar system for long after a disaster mining stuff and building space habitats. Eventually you have a generation of people raised in those space habitats and they would see an interstellar trip as nothing unusual, apart of even slower connection to the neighbours at home. Indeed the solar system may never really be void of people. Humanity spreads to neighbouring systems with holdouts in the millions still living back home.

[Eluvatar]

For the sake of argument, suppose the Neutron Star is set to collide with the Sun.

[joestej]

For the sake of argument, suppose the Neutron Star is set to collide with the Sun.

This was the option I was assuming as well, though the reason we're leaving is ultimately unimportant. For the purposes of this discussion, all we need to know is that Earth/the whole Solar System will be rendered completely uninhabitable in 70 years so we need to leave.

Sorry about the lack of clarity, I was assuming the more extreme threat as well, but with the quirk of building the escape ship from lunar materials instead of terrestrial materials, thanks to very early launches of mining equipment to the Moon via Orions. For bulk materials, it strikes me as a pretty good option (certainly better than asteroids, since you can partially use existing technology, and better than the Earth, since you can launch more easier). This wouldn't prevent Earth launches either.

The data I've been able to find on Lunar minerals suggests that the most common resources would be anorthite (which can be refined into aluminum), iron, calcium (as a byproduct of anorthite refinement), and ilmenite (a resource that can be purified into titanium). Of those four, only the ilmenite and anorthite would be really useful as titanium and aluminum both have high strength for their mass and aluminum is used as fuel for some chemical rockets. Either way the mining will be much easier than the refining and forging. It'll take quite a bit of infrastructure before we can make moon-mines viable, but it still might be a good idea.

[Zakharra]

For the sake of argument, suppose the Neutron Star is set to collide with the Sun.

Then we are screwed. There is no way we could get -any- ship far enough out of the solar system to survive the energetic event that will happen to the sun after a neutron star smacks into it. Not without a warp, hyper or jump drive. Not to mention, don't neutron stars put out a LOT of radiation? Moreso than our sun? If so, the 70 year escape time frame is likely going to have some years snipped off the end.

[icekatze]

hi hi

For a stellar collision scenario, the best chances for survival would probably be building bunkers deep underground and waiting out the collision. Then, once the charred, airless world is in the middle of turning into a frozen hellscape, people in space suits can leave their underground bunkers and start building ships to go to another world.

I suppose if the colliding star is big enough, one might want to consider building giant bunkers deep underground on Mars, or one of the more distant solar bodies, but the important thing is probably avoiding the nova/gamma ray burst that is likely to result.

[Arioch]

For the sake of argument, suppose the Neutron Star is set to collide with the Sun.

That would be bad.

[joestej]

For the sake of argument, suppose the Neutron Star is set to collide with the Sun.

Then we are screwed. There is no way we could get -any- ship far enough out of the solar system to survive the energetic event that will happen to the sun after a neutron star smacks into it. Not without a warp, hyper or jump drive. Not to mention, don't neutron stars put out a LOT of radiation? Moreso than our sun? If so, the 70 year escape time frame is likely going to have some years snipped off the end.

For a stellar collision scenario, the best chances for survival would probably be building bunkers deep underground and waiting out the collision. Then, once the charred, airless world is in the middle of turning into a frozen hellscape, people in space suits can leave their underground bunkers and start building ships to go to another world.

I suppose if the colliding star is big enough, one might want to consider building giant bunkers deep underground on Mars, or one of the more distant solar bodies, but the important thing is probably avoiding the nova/gamma ray burst that is likely to result.

For the sake of argument, suppose the Neutron Star is set to collide with the Sun.

That would be bad.

After some quick research, it seems Zakharra and Arioch are quite correct. According to Wikipedia a stellar collision within a hundred light years of Sol would probably end all life on Earth. Sorry icekatze, I don't think anyone can make bunkers deep enough to survive if our own star exploded like that.

Still, Plan Vault-Tec wouldn't be a horrible idea to survive a nearby Neutron Star hit. I question why we'd ever want to come back up at all though if we were living fine down there before. We can mine and process stuff underground, and we'd be growing our own food down there anyway. It's not perfect, but still a lot safer than leaving for alien worlds on SLT Generation Ships.

[icekatze]

hi hi

First of all, the result of the collision is going to depend on the velocity and the angle of the collision. If the collision velocity exceeds the escape velocity, then you'll likely get a nova. If the collision velocity is lower than the escape velocity, it could potentially just form a Thorne-Zytkow object

Second of all, if you read the work by Dimitri Veras or John Debes, it may be very possible for planets to survive being ejected from the system during a post-main phase event.

The sun is certainly not 7 to 10 times the mass of the sun.

[Siber]

Hm, that's actually an interesting question. Being further out in the system would cut down on the intensity of any solar problems, but you're also better off the more mass you can put between you and the sun, and earth is the biggest rock around. Maybe the best bet would be to set up stations in jupiter orbit, timed so that they're behind jupiter when the first shockwave hits. Then you've got the whole jovian system to exploit afterwards, so that'd be nice. You'd want to be pretty spot on with that timing, though.

[Arioch]

I doubt very much that you would be able to accurately predict the exact path of a neutron star through our solar system 70 years in advance of the encounter. I don't think it's possible to know the mass of the object to a close enough precision to be able to say with certainty what would happen. The slightest perturbation would significantly alter the interaction of the system, and such perturbations could be introduced deliberately.

If it's possible to predict a disaster with absolute certainty 70 years in advance, there is probably going to be something that can be done in those 70 years to prevent or ameliorate the disaster that is much more practical than evacuating the entire planet. If what you're interested in is the evacuation scenario, then it's probably best not to worry at all about what the disaster is, because inventing such a disaster is probably more work than inventing the evacuation scenario.

[joestej]

If what you're interested in is the evacuation scenario, then it's probably best not to worry at all about what the disaster is, because inventing such a disaster is probably more work than inventing the evacuation scenario.

My thoughts exactly. Not that coming up with interesting ways to vaporize the planet wouldn't be fun, but this was originally supposed to be about how to evacuate Earth. We should probably stick with that.

Speaking of which, I think the biggest problem we're going to have now is that the nearest planet with any chance of being habitable is Tau Ceti e, 11.9 light years away. Even if we could build something like a Starwisp to check it out for us, it'll take 60 years to get there. Even if it can just go halfway and send us something back, we'll still be up the metaphorical creek if Tau Ceti e is useless (as it likely is).

I think our best shot is just building some space colonies with engines on them, pointing at the nearest star and going. So long as they can mine enough stuff to keep their reactors going and repair anything that breaks, they can just float around Alpha Centauri or any other star indefinitely. Not life as we knew it, but a lot better than taking a shot in the dark that there MIGHT be an Earth-like planet where ever we're going.

[Mjolnir]

I doubt very much that you would be able to accurately predict the exact path of a neutron star through our solar system 70 years in advance of the encounter. I don't think it's possible to know the mass of the object to a close enough precision to be able to say with certainty what would happen. The slightest perturbation would significantly alter the interaction of the system, and such perturbations could be introduced deliberately.

A neutron star may only be 20-some km across, but the minimum mass is about 1.4 solar masses, about 1500 times the mass of Jupiter. If you're dealing with an opponent that can meaningfully perturb an object that outmasses the entire solar system, your best bet is to very humbly ask them for forgiveness for whatever it is you did that displeased them so much, since running away or hiding probably isn't going to work.

Otherwise, I really don't see a problem in working out the orbit necessary to place yourself on the far side of Jupiter from the most energetic of the events. The gravitation of the sun is well known, the gravitation of the incoming star is in a fairly narrow range, and probes could easily make precision measurements if there are no conveniently nearby Oort cloud/Kuiper belt objects to observe as they interact with the invader. You also don't have to put the stations in their final orbit 70 years in advance.

[Mjolnir]

hi hi

First of all, the result of the collision is going to depend on the velocity and the angle of the collision. If the collision velocity exceeds the escape velocity, then you'll likely get a nova. If the collision velocity is lower than the escape velocity, it could potentially just form a Thorne-Zytkow object

It would have to be traveling at escape velocity, unless it had a close interaction with a third star that was also making a close pass of the solar system. I think it would initially go right through the sun...the sun doesn't have the mass to stop it, and that mass is too spread out. Whether they exchange enough momentum for the sun to be captured and eventually merge with the neutron star to form a Thorne-Zytkow object probably doesn't matter to us, since the sun and the rest of the solar system would most likely be parting ways. You probably wouldn't be able to recognize the sun anymore anyway.

I would expect the neutron star to emerge mid-nova as it fuses newly-gained hydrogen on its surface.