The inability of spacecraft to achieve, in less than 4 Earth years, displacement to a place 4 light-years distant from Earth.. has nothing whatsoever to do with mass increase necessitating infinite fuel consumption. That notion is in widespread gossip, but there is no truth to it. High speeds are no impediment to thrust at all! That's because there's no such thing as "high speeds", only high relative speeds. How fast you
appear to be moving, by the reckoning of some arbitrary onlooker,
cannot change anything intrinsic to your craft; think about that! How many different arbitrary onlookers can you count, hmm? each one on a different relative trajectory? Which one of those onlookers' viewpoints will be arbitrarily chosen as the deciding factor in screwing up your life!?
