So .. if time exists .. and space exists .. and spacetime exists .. and spacetime can be bent, curved, etc as Einstein said, it can also be compressed .. a way to shorten space travel is to compress space time. Now .. in submarine ballistics the Russians abandoned the streamlined head of a torpedo for a concave head .. then fired the torpedo at high speed .. the concave head of the torpedo converts the water impacted to gas so that the torpedo travels through gas instead of water .. result .. 500 mph underwater torpedo. So .. we somehow compress spacetime to reduce both distance and time traveled through .. but compressing spacetime increases its resistance, so we scoop in the spacetime and use its energy in the spaceship engines .. like the old V1 German rockets .. pulse jet engine or whatever they were called .. buzz bomb, ramjet, whatever. As we are no longer travelling through spacetime, but converting it to energy, the theoretical law that nothing travels faster than light is escaped from as the speed of light is speed through spacetime.