Is it possible?? I am not familiar with the idea due to not having studied anything about it yet, but I am curious I mean it is theorized that you need unfathomably large amounts of energy (some sources say infinite amounts of energy) and gravity is, in a sense, an unlimited amount of energy so why couldn't it be used to obtain relativistic (near light speed) and maybe even light speed travel. This would have to mean that there is no limit to how fast an object can be accelerated by a bigger body with higher gravity, I am not quite sure how that would work because there needs to be a limit to how fast something can go right? So does the increase in speed result in an increase in mass until it gets to the point where the accelerating object then has the SAME amount of mass and gravity as the object which accelerated it??