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What are the challenges involved in such a project? Could you use an asteroid re-direct style mission to do the job, or use some sort of fuel based thrust etc. Please limit answers to those concerning moving and terraforming just Titan, for the sake of my question.

What problems might we encounter?

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    $\begingroup$ You mean other than the obvious challenges, like it is far bigger than anything we could measurably move? Or that it is so far away that it takes years for a probe to get there? $\endgroup$ – mmesser314 May 29 '15 at 4:02
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    $\begingroup$ First lesson of practical science: not everything that can be done in theory will be funded by the taxpayer. Apart from that you wouldn't have much fun with Titan in Earth's orbit. It would lose its atmosphere very quickly and you would end up with a dead body similar to the Moon. Your better bet, by far, is the colonization of Venus. That, at least, is a lot of real estate. $\endgroup$ – CuriousOne May 29 '15 at 4:44
  • $\begingroup$ @CuriousOne and a lot of heat, sulphuric acid and pressure. You go first, soon as you fix a nice place up, I'll follow, honestly. That old SF story,Venus is Hell, was true. $\endgroup$ – Acid Jazz May 29 '15 at 5:16
  • $\begingroup$ @AcidJazz: Did you see that old blurb "Terraforming Venus quickly?" by Paul Birch? Disregard anything he writes about cost and you will find a few amazingly realistic ideas in there that could actually take care of the seemingly insurmountable problems with the Venusian atmosphere... I admit that I didn't check his numbers, but I think the man might be up to something that works, at least on the back of an envelope. $\endgroup$ – CuriousOne May 29 '15 at 6:13
  • $\begingroup$ Link for the OP www.orionsarm.com/fm_store/TerraformingVenusQuickly.pdf $\endgroup$ – Acid Jazz May 29 '15 at 6:32
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It might seem easy to move objects in space, but change in potential and/or kinetic energy to move a moon is enormous. It's easy to imagine that launching an entire moon into orbit would take an unfathomable amount of energy, but it takes a comparable amount of energy to move a moon out of orbit, either back to the planet or to push out out of orbit.

Quick and dirty mathematics, escape velocity = orbital velocity x the square root of 2, so if you take the orbital speed of an object (in the case of Titan around Saturn - about 20,000 Kilometers per hour), you would need to accelerate it to about 20,000 x root 2 or a bit over 28,000 KPH to get it to escape Saturn's orbit. Perhaps a hair less than that as Saturn's gravitational hold would lose out to the Suns past a certain point, but you'd still need nearly 8,000 KPH of additional velocity to get it out of it's Saturn Orbit. Then once it's escaped Saturn, you'd have an orbit around the sun - perhaps moving it towards an L1 orbit and from there, it would need to be decelerated towards Jupiter (acceleration is needed to expand orbits - away from Saturn, deceleration to contract them - towards the sun).

And, accelerating something that's 80% heavier than the moon to an additional 8,000 KPH requires a staggering amount of energy, unless you plan to spend tens of thousands of years doing it. There might be enough 3He on Titan and Saturn to provide fission fuel to undertake such a thing, but it's hard to imagine that there wouldn't be better uses for that much energy.

If you get it near Jupiter in just the right way a gravity assist is possible to send it more towards the inner solar system, but I imagine that would inevitably be an elongated orbit - not really an expert on gravity assists though, but Jupiter could help move it towards the inner solar system, then (maybe) a 2nd assist around Mars to level it out - maybe, into a possible orbit, but the timing would need to be just right. Such a project would not be easy.

You wouldn't need to get it as close to the sun as earth, cause all the CH4 would act as a powerful greenhouse gas. An orbit around Mars distance might work just fine, but it would be an enormous energy expenditure and I have a hard time seeing such a thing as practical or beneficial.

Also, as CuriousOne said - that close to the sun, with the low Gravity of Titan, it would probobly, over time, lose it's atmosphere as Mars did.

My 2 cents - leave Titan where it is and go there.

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    $\begingroup$ Small footnote, but sending Titan around Jupiter for a gravity assist might send a number of Jupiter's Moons hither and yon. Titan's too large to not have some kind of effect on Jupiter's moons during a near-by gravity assist. $\endgroup$ – userLTK May 31 '15 at 6:14
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Moving any planet or moon can be done, but as noted, requires an astronomical amount of energy. To move a planet, you need to scale up the gravitational "slingshot" manoeuvre that humans use today to change the paths of space probes.

When a spacecraft uses the gravitational energy of a planet to "slingshot" to its destination, it gains a bit of energy from the planet, which slows down by a corresponding amount. (Since a planet out masses the space probe by many orders of magnitude, this isn't going to be detectable to you or I).

It is theorized that the Gas Giant planets moved in their orbits in the formation of the solar system due to gravitational interactions with the billions of comets and asteroids that filled the early solar system. The same game of gravitational "crack the whip" was being played, but multiplied many millionfold. As hundreds or thousands of asteroids and comets were accelerated out of the Solar System, the Gas Giants moved inwards due to the amount of energy they had transferred to the smaller bodies. It is also possible to do this in reverse; accelerate a planet away from the sun by slowing down a stream of asteroids or comets so they drop inwards towards the Sun.

Future engineers wanting to move Titan would be making careful calculations and dropping asteroid sized bodies in from the Kuiper belt to intersect the orbit of Titan. Initially, they would trade energy with Titan to allow it to reach Saturn escape velocity. Once Titan was clear of Saturn, then the stream of bodies would be used to bleed energy from Titan until its orbit spiralled inwards to wherever you like (you could equally use this technique to send Titan outwards to Uranus or Neptune as well).

This would be extremely complex, however, since you would have to navigate through the Saturn system of moons without colliding with them. The passage of these bodies through Saturn's system of rings and moons wold probably be quite disruptive of the rest of the moons and rings as well. The Engineers, would also want to minimize the investment of time and resources, so once the bodies used to change the orbit of Titan had made a pass, they would be on a complex solar orbit that would eventually bring them back to Titan to be reused. You could imagine the engineers plotting orbits which took the bodies past Jupiter or deep into the Sun's gravity well to give them the proper amount of energy to change Titan's orbit by the required amount on the next pass.

A spacefaring civilization that can do this would also have to carefully monitor the rest of the Solar System to ensure these bodies were not going to interfere with spacecraft, orbiting space stations and satellites or impact on other moons or asteroids. This would be a project which would last for perhaps a thousand years, and involve more energy and computational power than exists on Earth today.

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