A NASA engineer, David Burns is currently working on an engine that could theoretically bring the top speed of its propulsive capabilities to 99% of the speed of light. This could bring us to farther reaches in space and make the possibilities of even greater capabilities seem even more reachable.
The "Helical Engine" by design, would use mass and its change at relativistic speeds. The Helical chamber of the engine, in order to work (theoretically), would require to be 656 feet long and 40 feet in diameter. It would need 165 megawatts to produce 1 newton of thrust, which is the equivalent of a power station to produce the amount of force needed to move a kilogram of mass per second squared.
With all this being said and or written, David Burns also added that no expert has checked out his math to see if it all adds up, but it is quite interesting all the same that we may be getting closer to faster space travel. At 99% the speed of light, it would take 1.3 seconds to travel to the moon, 4 hours to travel to Neptune, and 12.5 seconds to travel to Mars. Just think of what we could do with that?