Originally Posted by gyldenlove
This may sound defeatist, but we as a species have nothing to fear from the sun. By the time the sun kills off all life on earth we will either have moved elsewhere or destroyed every opportunity of ever going anywhere ourselves. We have all the resources we need.
Fusion would definitely be a good power source. Magnetic fields are not the only option for radiation protection, electronically charged shielding may be a lot better. Fake gravity can be done by making a rotating vessel, protection against debris, you are probably going to have to go low-tech with a Titanic like solution, compartmentalize and accept that if there is an impact you may take casualties, so make sure you have very high redundancy. Water generation is trickier, you would need to bring a lot of water from the outset and you would need to recycle like crazy, so you would need to purify urine and bathing would be a thing of the past. Food is a bit easier, it is much more compactable than water and diets that are very high nutrients can be devised.
I think the best option of going far (out of solar system) would be to create either flotillas of smaller ships or a few bigger ships so groups of 50.000 to 100.000 can go together, that would leave room for redundancy and provide enough genetic variance to avoid inbreeding problems among descendants.
The water thing can be helped, by dragging meteors along with us in our convoy of ships. Also, they've shown that water is more abundant in the universe then previously thought. We could stop off nearby planets that had ice and extract the water. We would just have to have some monster sized floating tankers in our convoy
I honestly think before we would be taking long space travel, millions of years from now most likely, I think humans will tweak their DNA and you would probably see hybrid humans in the future better suited for long space travel.