Okay so I have a question about time dilation, kinetic energy and classical mechanics. My question is, if an object were travelling at very high relativistic speeds and experienced time dilation, would the time it experience and measure during the travels be equivalent to the travel time if it were travelling in a classically mechanical universe where FTL is possible? Assuming the same amount of energy is used the accelerate the object in both cases? For instance, say I have a small space pod that weighs 1000 kg. And classically (no relativity) If I were to accelerate the ship to, say, 5c, the KE of the ship should be 1.125e+21 joules. And if I'm five light-years from some location that I'm approaching, then my travel time will be 1 year until I arrive at that location. So now relativistically, I have the same ship (1000 kg) and I spend 1.125e+21 joules to accelerate it. I know it won't be FTL, but my question is, if I travel 5 light years in roughly 5 years, will I only experience 1 year due to time dilation? Basically, my question is, can I use classical mechanics to calculate classical FTL travel times to see what my time dilation would be relativistically with the same amount of KE?