Assuming we could build ships that can go that fast, we could cut aging in half. At 99.5% light speed, we would age at only ten percent relative to an observer at rest. The problem is physics. More acceleration means more energy. We could conceivably accelerate a ship in the vacuum of space given enough time, but slowing down the ship fast enough without killing us is another problem entirely. Ideally, we would accelerate the ship slowly, and then slow it down before stopping with enough lead time. The only problem is that it requires an energy source we can access on both sides. We may someday solve the challenges of near light-speed travel, but until then, any ship traveling less than 99.99999% the speed of light for distances greater than a dozen or so light-years will require some way to tackle aging. Science fiction movies have long touted suspended animation as one possibility. Bio-vitrification works by using a cryo-protectant liquid that dramatically lowers the temperature of human tissue to slow down decay to near zero. The liquid serves to prevent ice crystal formation, which can cause cells to rupture. While the process has been used on organ transplants, it hasn’t been used on living humans. It is, however, currently being used in higher concentrations on newly deceased patients at companies like the Alcor Life Extension Foundation whose goal is to one day revive those deceased patients. While no organization has brought a human back to life, they have brought back simple organisms. The technology is also continually being improved, so it’s conceivable this will someday occur. Some hospitals have already begun the process of cooling down patients in certain situations to extend the time needed to address emergencies. It’s not the same process as vitrification, but it’s a similar concept. Conceivably, we could one day use one or a combination of both processes on living, healthy subjects for suspended states for longer durations. Why would someone only want their brain and brain stem preserved? Presumably, if we have the technology to bring someone back by repairing the damage from whatever killed them, by that time we might also have the technology to clone a new body using the deceased person’s DNA.
Again, we’ve already made tremendous advances in cloning. While therapeutic cloning is still in its infancy, there is no theoretical reason why we couldn’t create a new body without a brain and simply implant the new brain into the cloned body. And with advances with CRISPR, it’s conceivable the body could come with some sophisticated upgrades. Those upgrades would come in handy if we plan on going to a new planet like the one in Avatar 2. Imagine having the ability to create a fully customizable body using your DNA to meet the requirements of any planet you visit. It’s the ultimate in life extension. While there are still technological hurdles to overcome like repairing the aging brain, imagine being able to grow your customizable avatar in transit while your current body is in suspended animation headed towards a different planet a hundred light years away. I must say, the future’s looking bright.