^Yeah... all the stuff about relativistic mass increase is true, but the thing I was trying to get at is that there are a lot of other problems you'd have to overcome before you could get anywhere near fast enough for that to become an issue at all. A lot of people seem to think that relativistic effects like time dilation and mass increase happen linearly with increasing speed, but really they're exponential -- you don't get your mass doubled until you get to 90 percent of lightspeed, and by 99 percent it's only increased seven times, and it's only in that last percentage point that the effects really skyrocket, approaching infinity as speed approaches c
But if you look at the theoretical work that's being done on advanced starship design these days, people are talking about velocities of ten percent
of lightspeed as a high-end goal. The speed of light is so incredibly huge that even ten percent is well beyond our current capabilities and would take vast amounts of energy to reach. The fastest speed a human-built spacecraft has ever achieved is about 70 kilometers per second, which is a measly fortieth of a percent of lightspeed. And that was a probe launched inward toward the Sun, so it got added acceleration from the Sun's gravity.
So it's really kind of misleading to focus on the relativistic aspects here. There are plenty of simpler reasons why it's prohibitively hard to get to the point where relativity would even begin to have a noticeable effect.