Could you bubble-wrap a planet?

[mindstalk]

I suspect you'd need something like a Paul Birch mass stream flyby chain to spin it up. You know how we speed probes up via fly-bys? Well, those slow planets down infinitesimally. You can do it in reverse, too. Have a stream of masses cycling between Venus and the Sun, transferring angular momentum and kinetic energy between the Sun and Venus. Or Venus and Jupiter; I remember reading that other planets work better as angular momentum banks than the Sun, though that might have been more for outright moving planets.

But it'll take a while. Venus is 5e24 kg; a 2e11 kg mass flying by every second would mean about a million years for a virtual Venus mass to fly by. I don't know how much momentum exchange you can do in a fly-by, maybe you can do it in less.

Or a 60 km radius asteroid, one millionth the mass, of the planet, making annual flybys.

http://terraforming.wikia.com/wiki/Venus suggests using mirrors to simulate a 24 hour day instead.

Papers here http://www.orionsarm.com/fm_store/Pa...27s%20Page.htm

[jeff_wilson]

Can we instead add heat to drive the atmosphere off entirely?

Or what was it they used in WORLD OUT OF TIME to move planets? Some kind of giant ramjets that would slam into Uranus's atmosphere at Mach Zillion, blasting a column of gas out the back before being blown back themselves only to dive again.

Yes, just reviewed on Amazon; laser-pumped fusion rams.

[Anthony]

Originally Posted by jeff_wilson

Can we instead add heat to drive the atmosphere off entirely?

That's sort of in the category of 'yes, but...'. The energy requirements are, at best, 'melt the crust' level, and it's hard to apply them only to the atmosphere. Turning Venus into a molten blob that will cool in a million years isn't terribly helpful for terraforming.

[johndallman]

Originally Posted by jeff_wilson

Or what was it they used in WORLD OUT OF TIME to move planets? Some kind of giant ramjets that would slam into Uranus's atmosphere at Mach Zillion, blasting a column of gas out the back before being blown back themselves only to dive again.

There's a good explanation of this in a Schlock Mercenary strip. You could make use of this for terraforming Venus: use Uranus or Neptune to move Venus much further from the sun so it would cool off. Of course, you have to coordinate this with whatever you're using to process Venus' atmosphere. It's also rather beyond THS technology, and the politics in THS would be impossible.

[Ze'Manel Cunha]

Originally Posted by Fred Brackin

Yeah, Mars, maybe Titan and even the Moon before Venus.

Unless you have artificial gravity the Moon is totally a no-go, even Mars is likely a no-go though more research on the issue is still needed to fully nail that down.

Spin-habitats over no-go low gravity planetoids which you can't spin.


Problem with bubble-wrapping something like Ceres is that the gravity wouldn't be enough without spinning it, and if you spun it, you'd end ass up on the bubble, which just wouldn't work.

[Fred Brackin]

Originally Posted by jeff_wilson

Can we instead add heat to drive the atmosphere off entirely?

.

If you remember during the Venus wars some wanted to use asteroid impacts to drive off undesired atmosphere. My counter-proposal was that it you just wanted big explosions why didn't you use large fusion bombs?

Even though nuclear weapons are faster and more energy efficient that moving planetoids my suggestion was not well received. Rule of Cool I suppose.

[jeff_wilson]

Hmm, politics... Venus can be equipped with aerostatic habitats as on Saturn, and used as a dumping ground for dissidents, underperforming nepotists, and technology proscribed elsewhere cause it's such a crappy craphole. Maybe one of them will invent a way to make it suck less. Fusion air ram motorcycle? Sure! Dry nanotech goo? Knock yourself out!

[jeff_wilson]

Originally Posted by Fred Brackin

If you remember during the Venus wars some wanted to use asteroid impacts to drive off undesired atmosphere. My counter-proposal was that it you just wanted big explosions why didn't you use large fusion bombs?

I was thinking a mirror array/cloud would be cheaper on that scale and reusable.

[Anthony]

Originally Posted by Fred Brackin

If you remember during the Venus wars some wanted to use asteroid impacts to drive off undesired atmosphere. My counter-proposal was that it you just wanted big explosions why didn't you use large fusion bombs?

Even though nuclear weapons are faster and more energy efficient that moving planetoids my suggestion was not well received. Rule of Cool I suppose.

Actually, on the scale involved the asteroids might actually be cheaper. It takes about 1.2 km/sec to put a KBO at 30 AU onto a transfer orbit, and then around 30 years for it to arrive, at which point it will whack into Venus at around 18 km/sec. Depending on the details of your design and how much mass you're willing to waste, that 1.2 km/sec takes no less than 0.72 MJ/kg and probably takes less than 1.44 MJ/kg, and at the destination it will have a kinetic energy of about 80 MJ/kg, so you're looking at a gain of more than 50:1.

Now, the atmosphere of Venus has a mass of about 4.8e+20 kg, and the escape energy for Venus is about 53 MJ/kg, so with perfect efficiency, we can get rid of it using a mere 2.6e+28J (6.2e+12 megatons). Since the above asteroid has an energy of 8e+7J/kg, we only need a chunk that's about 3.3e+20 kg. That's only about 2.5% of the mass of Pluto, so we shouldn't have too much trouble finding a chunk of the appropriate size.

[Johnny1A.2]

Originally Posted by mindstalk

I suspect you'd need something like a Paul Birch mass stream flyby chain to spin it up. You know how we speed probes up via fly-bys? Well, those slow planets down infinitesimally. You can do it in reverse, too. Have a stream of masses cycling between Venus and the Sun, transferring angular momentum and kinetic energy between the Sun and Venus. Or Venus and Jupiter; I remember reading that other planets work better as angular momentum banks than the Sun, though that might have been more for outright moving planets.

But it'll take a while. Venus is 5e24 kg; a 2e11 kg mass flying by every second would mean about a million years for a virtual Venus mass to fly by. I don't know how much momentum exchange you can do in a fly-by, maybe you can do it in less.

Or a 60 km radius asteroid, one millionth the mass, of the planet, making annual flybys.

Note that even manipulating a 60 km/22 mile diameter rock precisely into the orbit you want and keeping it there over long periods is non-trivial, even for a THS level society.

Originally Posted by Ze'Manel Cunha

Unless you have artificial gravity the Moon is totally a no-go, even Mars is likely a no-go though more research on the issue is still needed to fully nail that down.

Spin-habitats over no-go low gravity planetoids which you can't spin.


Problem with bubble-wrapping something like Ceres is that the gravity wouldn't be enough without spinning it, and if you spun it, you'd end ass up on the bubble, which just wouldn't work.

We don't know if that's a major issue or not.

We know from experience that free fall and microgravity are ghastly in their effects over time, but we have almost no data at all about the effects of mid-range gravity, such as Luna or Mars or even the big asteroids, and I do mean almost no data.

We don't know how much gravity is 'enough' for long-term viability. It might be that anything much less than Earth is unworkable long-term, or it might be that even a small constant pull is sufficient, we just don't have any data.

(Now, there is the separate issue that a person who grew up on the Moon might (or might not) be unable to adapt to Earth's heavier weight. There, too, we have very little data, though slightly more than the other issue.)