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Evacuate Earth 
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Post Re: Evacuate Earth
How is the radiation and heat supposed to go around the shielding pusher plate in space?


Mon Dec 07, 2015 7:56 am
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Post Re: Evacuate Earth
Eluvatar wrote:
How is the radiation and heat supposed to go around the shielding pusher plate in space?


By being emitted from matter that has gone around the pusher plate. If the event is large enough to produce a usable impulse on a pusher plate, it will engulf the vehicle. It'd be like relying on waterproof boots to keep you dry as you cannonball into a swimming pool.

It's not quite a totally unsurvivable environment, it's a lot easier to wreck a planet than it is to wreck a buried bunker, but you'd want a lot of distance and a lot of shielding. Kuiper belt objects might suffice, Neptune and Uranus might be of use. If it's just a nova, Earth might be survivable, especially if it's shielded from the worst by the sun. There's a wide range of outcomes depending on what exactly happens..


Mon Dec 07, 2015 3:49 pm
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Post Re: Evacuate Earth
Mjolnir wrote:
Eluvatar wrote:
How is the radiation and heat supposed to go around the shielding pusher plate in space?


By being emitted from matter that has gone around the pusher plate. If the event is large enough to produce a usable impulse on a pusher plate, it will engulf the vehicle. It'd be like relying on waterproof boots to keep you dry as you cannonball into a swimming pool.


That was my thought. The nova/supernova is simply too big for a ship to survive it while in the start system.

Mjolnir wrote:
It's not quite a totally unsurvivable environment, it's a lot easier to wreck a planet than it is to wreck a buried bunker, but you'd want a lot of distance and a lot of shielding. Kuiper belt objects might suffice, Neptune and Uranus might be of use. If it's just a nova, Earth might be survivable, especially if it's shielded from the worst by the sun. There's a wide range of outcomes depending on what exactly happens..



How would Earth be shielded? It would be screwed even if it was just a nova. The atmosphere would be gone, the planetary crust shattered and magma coming out in countless places. The radiation burst would have fried, killed any lifeforms and the heat boiled away any water with the atmosphere. I cannot see how the outer planets could survive that well, the radiation and heat burst (which could last for days(?)) would put paid to anything possibly alive there. It would destroy any ship even in the outer system. The Kuiper belt would likely survive, but I am not sure how well any habitats would survive the radiation burst.


Fri Dec 11, 2015 4:42 pm
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Post Re: Evacuate Earth
Zakharra wrote:
Mjolnir wrote:
Eluvatar wrote:
How is the radiation and heat supposed to go around the shielding pusher plate in space?


By being emitted from matter that has gone around the pusher plate. If the event is large enough to produce a usable impulse on a pusher plate, it will engulf the vehicle. It'd be like relying on waterproof boots to keep you dry as you cannonball into a swimming pool.


That was my thought. The nova/supernova is simply too big for a ship to survive it while in the start system.

Mjolnir wrote:
It's not quite a totally unsurvivable environment, it's a lot easier to wreck a planet than it is to wreck a buried bunker, but you'd want a lot of distance and a lot of shielding. Kuiper belt objects might suffice, Neptune and Uranus might be of use. If it's just a nova, Earth might be survivable, especially if it's shielded from the worst by the sun. There's a wide range of outcomes depending on what exactly happens..



How would Earth be shielded? It would be screwed even if it was just a nova. The atmosphere would be gone, the planetary crust shattered and magma coming out in countless places. The radiation burst would have fried, killed any lifeforms and the heat boiled away any water with the atmosphere. I cannot see how the outer planets could survive that well, the radiation and heat burst (which could last for days(?)) would put paid to anything possibly alive there. It would destroy any ship even in the outer system. The Kuiper belt would likely survive, but I am not sure how well any habitats would survive the radiation burst.
Not sure about the Earth comment (I originally understood it as referring to the same sort of thing as the Neptune and Uranus bit), but I know what he was referring to with the outer planets: you can use them as shielding from the initial event by placing yourself in their shadow. Depending on the magnitude of the event, anything that happens afterwards might be survivable, as long as you don't have to deal with the full magnitude of the initial disaster.


Fri Dec 11, 2015 5:37 pm
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Post Re: Evacuate Earth
hi hi

Well, novae are likely not to be symmetrical, especially one that is externally triggered, so it could be better or worse depending on where the Earth is located with respect to the blast. If a type I supernova were to go off, symmetrically distributed, in an instant, then by my rough calculations, that would be enough energy to reduce the Earth to gravel. (approximately 8.9x10^32 Joules over the Earth's sun facing surface) I'll have to check the numbers for more distant bodies another time though, but I have a feeling that Neptune might be a nice place to hang out.

Now, if the event is longer than an instant, it might not involve vaporizing the entire planet. Supernovae are known to take more than a week to reach peak intensity, but I don't know enough about that process to do even a back of a napkin estimate.


Fri Dec 11, 2015 6:06 pm
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Post Re: Evacuate Earth
Hiding behind Neptune sounds generally safe-ish. Assuming the Neutron star hasn't already eaten Neptune of course.


Fri Dec 11, 2015 6:09 pm
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Post Re: Evacuate Earth
Absalom wrote:
Zakharra wrote:
How would Earth be shielded? It would be screwed even if it was just a nova. The atmosphere would be gone, the planetary crust shattered and magma coming out in countless places. The radiation burst would have fried, killed any lifeforms and the heat boiled away any water with the atmosphere. I cannot see how the outer planets could survive that well, the radiation and heat burst (which could last for days(?)) would put paid to anything possibly alive there. It would destroy any ship even in the outer system. The Kuiper belt would likely survive, but I am not sure how well any habitats would survive the radiation burst.
Not sure about the Earth comment (I originally understood it as referring to the same sort of thing as the Neptune and Uranus bit), but I know what he was referring to with the outer planets: you can use them as shielding from the initial event by placing yourself in their shadow. Depending on the magnitude of the event, anything that happens afterwards might be survivable, as long as you don't have to deal with the full magnitude of the initial disaster.


I was referring to the possibility of Earth being in the sun's shadow. The nova's going to be from hydrogen piling up on the neutron star from its collision with the sun. The sun would be massively disrupted, but better off being exposed to that than being in direct line of sight of what's going on with the neutron star immediately after the collision. (More of an x-ray burst than a nova, probably.)


Fri Dec 11, 2015 8:39 pm
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Post Re: Evacuate Earth
hi hi

So I had a moment to do the math, and if all (1.0x10^42) Joules of a type Ia nova were evenly distributed across the surface area of a sphere with Neptune's average distance from the Sun (2.548x10^20) kilometers, in an instant. That should only be (3.92x10^21) Joules per square kilometer. So not quite enough to instantly blow up the Earth at that distance, so probably not enough to blow up Neptune either. (although I don't have an estimate on how many Joules it would take to do that.)


Sat Dec 12, 2015 12:02 am
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Post Re: Evacuate Earth
icekatze wrote:
So not quite enough to instantly blow up the Earth at that distance, so probably not enough to blow up Neptune either. (although I don't have an estimate on how many Joules it would take to do that.)
Check stardestroyer.net, I believe they ran those numbers for the Death Star.


Sat Dec 12, 2015 8:58 am
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Post Re: Evacuate Earth
hi hi

What I could find was for a solid Earth and Jupiter.
Quote:
The energy required to destroy the planet in question is 2.25 ⨉ 10^32 J. However, the destruction of large planets such as Jupiter can require much larger energy demands... we can estimate this energy to be 2 ⨉ 10^36 J.


Of course the Death Star delivers its energy at a single point that drills in and explodes outward, rather than on an entire surface that pushes in one direction. Not sure what kind of a difference that would make, but I think given the non-instantaneous nature of novae, their output is already low enough not to destroy a gas giant, so maybe it is a moot point.


Sat Dec 12, 2015 10:00 am
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Post Re: Evacuate Earth
icekatze wrote:
hi hi

What I could find was for a solid Earth and Jupiter.
Quote:
The energy required to destroy the planet in question is 2.25 ⨉ 10^32 J. However, the destruction of large planets such as Jupiter can require much larger energy demands... we can estimate this energy to be 2 ⨉ 10^36 J.


Of course the Death Star delivers its energy at a single point that drills in and explodes outward, rather than on an entire surface that pushes in one direction. Not sure what kind of a difference that would make, but I think given the non-instantaneous nature of novae, their output is already low enough not to destroy a gas giant, so maybe it is a moot point.
Adjust the energy to compensate for the reduced mass, compare with averaged-out nova output, and you've got a decent first-guess. If you want to get fancy then consider the possibility of shearing off the surface, and figure out what would be required for the mass in question to be permanently lost instead of just turned into a very odd ring.


Sat Dec 12, 2015 5:58 pm
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Post Re: Evacuate Earth
Mjolnir wrote:
Absalom wrote:
Zakharra wrote:
How would Earth be shielded? It would be screwed even if it was just a nova. The atmosphere would be gone, the planetary crust shattered and magma coming out in countless places. The radiation burst would have fried, killed any lifeforms and the heat boiled away any water with the atmosphere. I cannot see how the outer planets could survive that well, the radiation and heat burst (which could last for days(?)) would put paid to anything possibly alive there. It would destroy any ship even in the outer system. The Kuiper belt would likely survive, but I am not sure how well any habitats would survive the radiation burst.
Not sure about the Earth comment (I originally understood it as referring to the same sort of thing as the Neptune and Uranus bit), but I know what he was referring to with the outer planets: you can use them as shielding from the initial event by placing yourself in their shadow. Depending on the magnitude of the event, anything that happens afterwards might be survivable, as long as you don't have to deal with the full magnitude of the initial disaster.


I was referring to the possibility of Earth being in the sun's shadow. The nova's going to be from hydrogen piling up on the neutron star from its collision with the sun. The sun would be massively disrupted, but better off being exposed to that than being in direct line of sight of what's going on with the neutron star immediately after the collision. (More of an x-ray burst than a nova, probably.)



If the sun goes boom, even from a neutron start smacking into the other side of it, Earth is still dead cause that event will affect the entire sun and system.I do not see anyway the Earth can survive this intact enough to shield even deeply buried bunkers. There will be a hell of a lot of seismic activity at the least, and being buried underground when massive earthquakes hit isn't a good thing.


Sun Dec 13, 2015 1:12 pm
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Post Re: Evacuate Earth
hi hi

Zakharra, we've just gone over the amounts of energy involved in a hypothetical event. The Earth will almost certainly lose its atmosphere even in a best case scenario, but not all scenarios end with the Earth's crust being destroyed. Novae aren't instantaneous, and they aren't symmetrical. So there's a chance that a bunker might survive, if the Earth was not in a direct hit, but the more probable candidate remains one of Neptune's moons.

(I've been using the Boom Table as a helpful reference guide myself.)


Sun Dec 13, 2015 2:36 pm
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Post Re: Evacuate Earth
Zakharra wrote:
Mjolnir wrote:
I was referring to the possibility of Earth being in the sun's shadow. The nova's going to be from hydrogen piling up on the neutron star from its collision with the sun. The sun would be massively disrupted, but better off being exposed to that than being in direct line of sight of what's going on with the neutron star immediately after the collision. (More of an x-ray burst than a nova, probably.)



If the sun goes boom,


Then you're talking about a different scenario from the one I am, and an event that is probably not possible given the low mass of the sun.


Sun Dec 13, 2015 2:52 pm
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Post Re: Evacuate Earth
Mjolnir wrote:
Zakharra wrote:
Mjolnir wrote:
I was referring to the possibility of Earth being in the sun's shadow. The nova's going to be from hydrogen piling up on the neutron star from its collision with the sun. The sun would be massively disrupted, but better off being exposed to that than being in direct line of sight of what's going on with the neutron star immediately after the collision. (More of an x-ray burst than a nova, probably.)



If the sun goes boom,


Then you're talking about a different scenario from the one I am, and an event that is probably not possible given the low mass of the sun.



Hhmm.. probably. But a neutron star hitting, or even passing close by the sun isn't going to do good things to the Earth. I cannot imagine there not being some sort of seismic events on the planet. Big ones. And this is assuming the orbits of the inner planets aren't shuffled/disarrayed.


Sun Dec 13, 2015 4:38 pm
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Post Re: Evacuate Earth
Zakharra wrote:
Hhmm.. probably. But a neutron star hitting, or even passing close by the sun isn't going to do good things to the Earth. I cannot imagine there not being some sort of seismic events on the planet. Big ones. And this is assuming the orbits of the inner planets aren't shuffled/disarrayed.


A neutron star hitting or making a close pass by the sun is most likely going to separate it from all the planets. The neutron star will have a mass at least around 1.4 times that of the sun. It's going to be the dominant gravitational body during the encounter. Assuming a pretty typical initial velocity for nearby stars, the sun will be on a hyperbolic trajectory resulting in almost a 90 degree change in direction with respect to the neutron star. The planets, passing at similar velocities but widely varying distances, will each be affected very differently.

If there's no near collisions with the planets or cataclysmic explosions from a collision with the sun, there's not likely to be much seismic activity. If the neutron star doesn't make a close pass with Earth, the overall tidal forces will only be about 2.4 times as strong as the two are passing each other. In that situation, you just have a bunch of x-rays from the neutron star and temperature extremes from disruption to the sun, and a very cold and dark future ahead of you.


Sun Dec 13, 2015 6:25 pm
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