If such a rogue planet were the result of ejection from its previous planetary system, I wouldn't expect that its speed would much exceed its previous orbital v

If such a rogue planet were the result of ejection from its previous planetary system, I wouldn't expect that its speed would much exceed its previous orbital velocity in terms of order of magnitude. For reference, the orbital velocity of Mercury is about 60km/s [0], which is about 130,000 mph, or 2e-4*c. We'd certainly notice something as big as a planet coming at us when it's at around the same distance as the Oort cloud, which NASA says lies at a distance of at least 2000 AU [1], or 3e12 km. Since it would take almost 1600 years to travel 3e12 km at 60km/s, I would say we'd have a fair amount of preparation time, even if my estimate for the body's speed were off by a factor of 15. ;-) As for choosing your course, I would say if a rogue planet is about to enter the Solar System, beggars can't be choosers. What I find more interesting is that in order for people to live on or near such a planet, it would almost have to have enough of its own internal heat to create temperatures suitable for life. So, you're almost certainly not looking at a rocky planet with a surface. Therefore, you'd want to design your habitat to orbit or exist within the atmosphere of a gas giant. To my knowledge, there hasn't been any serious proposal for such a habitat, and I'm unaware of the sci-fi perspective on this issue. Of course, the other issue is that at 2e-4*c, you're not going anywhere very fast. :P --- [0]: https://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.html https://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.... [1]: https://solarsystem.nasa.gov/solar-system/oort-cloud/overview/ https://solarsystem.nasa.gov/solar-system/oort-cloud/overvie...