Arbolus

It has to be Pol. It's the furthest moon out, meaning that all the others will always be in the same celestial hemisphere as Jool, and it's also tidally locked. You could put a base on the near side and all four inner moons, plus Jool itself, would always be visible in roughly the same part of the sky.

We've got an unlimited supply of expendable Kerbals to experiment on already.

I was originally going to head for Duna. But after aerobraking, I found that my next apoapsis would put me in Ike's SOI, and I thought: why not? Luckily I'd built the ship to have more delta-v than I needed, and I still had enough afterwards to land on Duna as well and then return home.

It doesn't have any rocket engines or oxidiser. Even if you could get it into space, once there it would be impossible to make any manoeuvres without using some sort of tug.

Electric cars need batteries. Batteries have a low maximum energy density compared to petrol. If the electric car is to travel any further than a few miles between recharges, the batteries required to store the electricity are going to be much heavier than an internal combustion engine and the energy equivalent in liquid fuel would be. In KSP batteries are much lighter than they should be, while solar panels and RTGs are much more efficient. If it weren't for that, electric rovers would be of no use whatsoever for travelling any great distance across land.

Aargh, Tylo is horrible! I found Eve OK to return from - I simply equipped the ship with a few extra orange tanks and relied only on the atmosphere to slow me down enough to make a safe landing. Anywhere is easy to take off from if you have enough fuel - the trick is getting the fuel there in the first place. For Tylo however you can't aerobrake, and so landing the spare fuel itself requires even more fuel. I'm tempted to simply send over a kethane drilling platform and use kethane to refuel, but I'd rather finish the job with stock parts if I possibly can.

You would have to wait until you're near apoapsis for the SRB to be most effective, but yes it should work. You could get there, point retrograde, and then use a single actiongroup to decouple the rest of the ship, fire the SRB and activate the parachute all at once. Only problem I can see is that a close fly-by of the Mun will affect your trajectory. If you pass it on the correct side then you'll lose speed anyway. If you pass it on the other side you'll gain speed and there's no guarantee that the SRB will be enough to save you. So, if you're heading for the wrong side, it might be best to fire early before the Mun has a chance to ruin the escape.

It'll be orbiting the galactic centre. But one orbit will take so long (~100,000,000 years) that for all intents and purposes we can treat the planet as free-floating.

Something the size of Titan wouldn't break up in the short time that it's within Earth's Roche limit, though there would be plenty of huge earthquakes on both bodies and some loose rocks would be exchanged. And I don't think it would be slowed significantly, because only a small fraction of its surface would ever be in contact with Earth's atmosphere. However, one thing that is likely to happen is that the Earth would tear away quite a lot of Titan's atmosphere. How much of the gas is captured and how much escapes depends on many factors, but if enough is captured it would be comparable in mass to our own atmosphere and might end up asphyxiating us all.

It's much easier to get a heavy mass from Minmus to LKO than it is to get that same mass from Kerbin's surface to LKO. So, if I'm building an interplanetary ship or something else that needs a lot of delta-v, it's usually most efficient to only give it enough fuel to reach LKO and to then refuel it from kethane mines elsewhere in the Kerbin system.

Complacency. All of the other problems - famine, poverty, global warming, mineral shortages and so on - could probably be solved within a decade if people and governments were willing to take them seriously enough to actually take some meaningful action. As it is, the world's governments are agreeing loudly every time someone calls for a reduction in carbon emissions (for example), but otherwise they're doing almost nothing about it.

Perhaps by 15km the air density is so low that you're not generating enough lift to stay up. All I can suggest is to either make the wings much bigger and add more turbojets, or to switch to rocket engines sooner. Either way you'll need a lot more fuel. I think I could do this with a VTOL SSTO, but a spaceplane is a much harder challenge indeed. I'll have to have a think about it.

And of course there was the even larger Monster, although I suppose it wasn't intended to be a tank so much as a self-propelled siege fortress.

Try and make sure that your pre-braking trajectory passes Eve on the side facing away from Kerbol. The exact inclination is difficult to get right from a distance, but you can get reasonably close and then fine-tune it once you're in a circular orbit.

I always find it far simpler and more useful to do all the calculations in fractions and only convert it to decimals once I've found the answer. If I'm trying to solve something like mε = p²/2m + J²/2mr² - GMm/r I always prefer to see what cancels or simplifies and thereby saves me the effort of writing it out, and I never actually introduce any numbers until I've got a symbolic expression for the solution. Sometimes it can be slightly easier to use decimals. When coding I might type a*b*0.45*c*d rather than a*b*(1/5 + 1/4)*c*d just because it saves me a few characters, but I'd never do anything like that on paper.