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Due to global warming, Earth has become uninhabitable. The rich left off to colonize 'New Earth' while everyone else is left behind.

For whatever reason, the people left behind have survived, but out of sheer hatred have decided to go out to 'New Earth' and plunge it into an even worse but similar demise as the original Earth.

Their plan? To create a massive ship, fill it up with the solid form of a green-house gas and crash the ship into New Earth.

'New Earth' is a little smaller than earth and the surface is 90% water.

To define a 'successful' attack would to heat up the oceans enough to produce a large amount of steam. With steam also being a green-house gas, the planet would assumably begin to heat itself up and literally cook everyone on it.

What is the absolute best compound to use as the green-house compound to fill the crash ship and,

assuming distance isnt a problem, how large would this ship have to be?

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    $\begingroup$ This makes no sense. First you say, "fill it up with the solid form of a green-house gas and crash the ship into New Earth*", and then you say that "a 'successful' attack would to heat up the oceans enough to produce a large amount of steam" (which can only mean... boil the oceans). So, which do you want: adding more CO2 and methane, or boiling the oceans (which is an utterly separate problem)? $\endgroup$ – RonJohn Mar 3 '18 at 23:47
  • $\begingroup$ I nominate antimatter. One kilogram of that will boil about 1.4*10^14 cubic meters of seawater. $\endgroup$ – Beta Mar 3 '18 at 23:55
  • $\begingroup$ @Beta Trivially antimatter isn't a greenhouse gas. Your idea would certainly achieve the OP's result with added radioactivity. So in that sense, it is an improvement. Must admit the solid greenhouse gas idea doesn't feel exactly right. $\endgroup$ – a4android Mar 4 '18 at 1:41
  • $\begingroup$ I have no time to post an answer now. I might do it later, but the short version is that your ship would have to be comparable to Pluto in size, maybe larger. $\endgroup$ – Renan Mar 4 '18 at 2:14
  • $\begingroup$ We need a lot more information to even begin an actual answer. We need to know the solar irradiance of New Earth or it’s star class and it’s distance from said star. Additionally, over what time scale are you expecting this to happen? It’ll take a lot more greenhouse gas if you want it to happen over 100 years than 10,000. Finally, I suspect the problem may be more complex than sending a bunch of greenhouse gas. Even if we were able to cause the oceans to turn into steam, that steam would raise the planetary albedo with an increase in cloud cover, which undermines our warming ability. $\endgroup$ – Dubukay Mar 4 '18 at 3:14
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If you get down to it, boiling or vapourizing the oceans needs a metric crap ton of energy. The Atomic Rockets "Boom Table" tells us we need the following amounts of energy:

Boil the oceans: 6.6 × 10^26J 158 Pt

Vapourize the oceans 4.5 × 10^27J 1 Et

To put that in perspective, the Sun's output per second is:

                    3.9 × 10^26J    92 Pt

The best way to apply lots of energy at once would be to accelerate you spacecraft to relativistic velocities. One Kilogram can release:

1 kilogram at 75% c 4.6 × 10^16J 11 Mt

1 kilogram at 90% c 1.2 × 10^17J 29 Mt

At that point the aggressor can be using wadded up recycled paper and still getting impact energies straddling the "Castle Bravo" nuclear device.

enter image description here

The worst part is the huge yield was actually an accident

Once you have an idea of the parameters of the planet (i.e. how much water is in the oceans) then you can scale the device and the speed to match your capabilities. Of course anyone on the receiving end of that may have a few more pressing issues than the oceans boiling.

For a slightly different take read this answer: What would a relativistic kill vehicle hitting the moon look like from earth?

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  • $\begingroup$ I would replace accelerate you spacecraft to relativistic velocities with accelerate you green house to relativistic velocities( literal house that was painted green) ... ha ha. $\endgroup$ – ArtisticPhoenix Mar 4 '18 at 11:27
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I think you are going about this the wrong way.

Send a stealth mission. Build an under-the-ocean plant to produce some long lived, powerful greenhouse gasses like Sulphur Hexafluoride. Release them as quickly as you can make them, leading to a greenhouse effect building up in just a few years - before the inhabitants even realize what is going on.

To expand:

From wikipedia, SF6 has a global warming potential 16,300 times that of CO2. Now, the mass of CO2 in the atmosphere is given as 3x10^12 tonnes here, but that's a recent value for Earth, so you could reasonably, assume 1.5x10^12tonnes for your fictional planet (starting, pre-industrial).

Dividing the CO2 mass by GWP gives roughly 1x10^8 (100 million) tonnes of SF6 for the equivalent of CO2 doubling. Assuming we want a rapid catastrophic greenhouse, you might want ten times this - 1 billion tonnes of SF6. That would represent the smallest load you could deliver directly - a lot, but not totally implausible. Obviously just steering a billion-tonne impactor into your target planet would be pretty devastating..

World sulphur production is c. 80 million tonnes, and Flouring is c. 2.6 million tonnes a year, so the limit here is the amount of Florine you can obtain. If you wanted to make it in situ, then you'd want your base to be close to a deposit of Fluorite, extract the Sulphur from seawater, and release the SF6 by diffusion. They'd never know what hit them..

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  • $\begingroup$ Sulphur Hexafluoride has the unfortunate attribute of being much heavier than air. You're likely to suffocate people before you get a decent greenhouse going. You're much better off using something like methane: roughly the same per-year global warming effect, and it's far more subtle. $\endgroup$ – Mark Mar 5 '18 at 9:32
  • $\begingroup$ Problem is, you'd have to make a LOT more methane, and it goes away fairly quickly.. SF6 can be mixed into air. It is all a bit far fetched, yes. $\endgroup$ – Andrew Dodds Mar 5 '18 at 10:30

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