[nerflad]

Isn't a second now officially defined as a single period of atomic decay of a certain atom (I think Cessium?)? So this theoretical near-lightspeed craft could adjust it's accelerators based on an onboard atomic clock that would not be based on seconds as we tend to perceive them, but on SI seconds. I assume these would be getting longer as velocity approached 1c. Unless radioactive decay is also affected by relativity (obviously I am not a scientist), in which case of course that wouldn't work.

[saagarjha]

One of the consequences of the theory of relativity is that there is no "absolute time". The atomic clock will perceive time just as you will–that is, slower than an inertial reference frame.