Implications of a terraformed Venus/Triton

[acrosome]

Yes, but only a trivial fraction of that power is used planetside. Most is used in space, where waste heat gets radiated into the cosmos, and it's very distributed- it's not all in one place.

[Flyndaran]

Radiated in all directions, not just "out there". We're not talking about energy outputs where that is near trivial.

[Fred Brackin]

Originally Posted by acrosome

Yes, but only a trivial fraction of that power is used planetside. Most is used in space, where waste heat gets radiated into the cosmos, and it's very distributed- it's not all in one place.

Right now most of that energy isn't "used" at all. It's omnidirectionally radiated away from the Sun. A Dyson structure is apparently all about re-directing that energy and the waste heat from that will normally be radiated away from the site of use.

You'd have to do something complicated such as only use that absorbed and re-directed solar energy on the side of the system away from the Earth. I'd only build a Dyson structure (after I'd come up with a reason to build one) in a system without a naturally habitable world. There should be many such systems.

[acrosome]

Originally Posted by Flyndaran

Radiated in all directions, not just "out there". We're not talking about energy outputs where that is near trivial.

Right now all of the Sun's 10e26W output is, in fact, radiated in just such a manner. Yet, surprisingly, Mercury is not a blob of molten lava. Let alone Earth.

Not to mention, I described the society as "aspiring" to Kardishev II status.

So, how ridiculous an amount of energy to move Triton? Or, are there better candidates that are closer? Ceres seems small. I mean, it would give you a visible moon, but not really any tides. And by the time someone terraformed Venus it would probably have inhabitants who might object. Other ideas?

Mercury? That'd be a hell of a lot of energy, again.

[johndallman]

Originally Posted by acrosome

So, how ridiculous an amount of energy to move Triton?

Triton gives you a different problem. You have to haul it out of Neptune's gravity well, but then you have an energy dissipation problem as you move it closer in. It has a lot of gravitational potential energy, which will naturally convert itself into kinetic energy as it falls towards the sun.

You need to get rid of that energy to get it into orbit around Venus. This is one of the cases where efficiency matters a lot. If you can apply, say, 1% of solar output, 10e24 Watts, to Triton, you need nigh-perfect efficiency to avoid boiling away its atmosphere.

A way of doing this which was good enough for Larry Niven's style of SF appears in his novel A World Out of Time, and in Schlock Mercenary, which has an explanation online. Having built a fusion rocket powered by a gas giant you then use the gas giant's gravity to move things around. The orbital navigation calculations are somewhat complex, but being TL12 should handle that.

[acrosome]

Originally Posted by johndallman

Triton gives you a different problem. You have to haul it out of Neptune's gravity well, but then you have an energy dissipation problem as you move it closer in. It has a lot of gravitational potential energy, which will naturally convert itself into kinetic energy as it falls towards the sun.

But presumably I could use that energy to help in other terraformation goals, like spinning or moving Venus, couldn't I?

Originally Posted by johndallman

You need to get rid of that energy to get it into orbit around Venus. This is one of the cases where efficiency matters a lot. If you can apply, say, 1% of solar output, 10e24 Watts, to Triton, you need nigh-perfect efficiency to avoid boiling away its atmosphere.

In my scenario Triton probably won't have much atmosphere by the time it's moved. The atmosphere gets moved to Venus via wormhole, first. This also means that Triton masses less when it's moved, by the way.

But.., maybe if I just steal Triton's nitrogen and water then some closer body would be a better candidate for a moon. Mercury would be a suitably massive one, but I suspect energy budgets get extreme, again. Same for any significant moon of Jupiter. But a smaller Jovian moon might suffice...

Thinking.

Originally Posted by johndallman

A way of doing this which was good enough for Larry Niven's style of SF appears in his novel A World Out of Time, and in Schlock Mercenary, which has an explanation online. Having built a fusion rocket powered by a gas giant you then use the gas giant's gravity to move things around. The orbital navigation calculations are somewhat complex, but being TL12 should handle that.

Hmm. I'll read up.

EDIT-- Yes, but it'd be damned slow. I kind of like the wormhole-sun-rocket idea... :) I mean, the math ain't hard- It's just a Hohmann transfer. Stop Venus's rotation such that it's totally locked, then wormhole-sun-rocket using a gigantic magnetic nozzle. But the issue is the ridiculous amount of energy needs to get the dV, and just what effect this might have on the Sun, and that I don't know the maths for.

[Fred Brackin]

Originally Posted by acrosome

But presumably I could use that energy to help in other terraformation goals, like spinning or moving Venus, couldn't I?

An arbitrarily convenient and efficient means of tapping into that energy would be required. None occurs to me at the moment.

You're well past any point where I'd work with "hard-ish" and "detailed". This is the area where I have the Sufficiently Advanced Aliens use a SM+46 ship to do their terraforming.

Bring the SM+43 planet into the hangar bay with a tractor beam, such off the undesired atmosphere, spin it up with a combination of tractors and pressors, cook it in a hypertime chamber until; the ecosphere is done and then put it where you want it. Fly off in your giganto-ship to do it again in the next system.

[johndallman]

Originally Posted by acrosome

But presumably I could use that energy to help in other terraformation goals, like spinning or moving Venus, couldn't I?

If you have some way to apply or convert it. The simple way to spin up Venus is to smack it with some large body, as an oblique impact, but you have to wait for the surface to solidify again afterwards. A more practical way with the technology you've given yourself is to mount a couple of large wormhole thrusters at the equator and spin it up by thrust. This will not melt the entire surface, but it will get rid of most of the atmosphere, and what remains will probably only take a couple of decades to cool down.

If you want to spin it up without having such drastic effects, you need a way of remotely exerting large forces on a ball of rock that has no significant magnetic or electric field, and that tends to involve TL12^, not just TL12. Gravity isn't very good for this unless you have a very small and massive body, and using black holes for terraforming is liable to fail safety assessments.

[AlexanderHowl]

Ignoring unproven phenomena (wormholes are completely hypothetical and stable wormholes are impossible by our understanding of science), the 'best' way to spin Venus would be to use the carbon dioxide and sulfur diixide in the atmosphere as reaction mass for a monoxide ion engine. While the engineering is challenging, it is physically possible, especially if you use a network of solar power satellites in LVO to power a system of monoxide ion engines that extend from the surface to above the upper atmosphere. You can actually create a 'weightless' ion engine if you enclose it is a structure with Earth normal atmospheric pressure carbon dioxide. Of course, you are talking about adding 1.8e26 J of rotational energy to Venus, so it would take 90% of the atmosphere and probably 1,000 years.

[Anthony]

Originally Posted by AlexanderHowl

Ignoring unproven phenomena (wormholes are completely hypothetical and stable wormholes are impossible by our understanding of science), the 'best' way to spin Venus would be to use the carbon dioxide and sulfur diixide in the atmosphere as reaction mass for a monoxide ion engine.

Eh, it doesn't take that much energy to spin up, though getting rid of the CO2 might be a goal anyway. You can also arrange for your water delivery to be off-center.