[extropy-chat] Relativity drive: the end of wings and wheels?

[Hal Finney]

Keith's example may not have worked, but Dirk Bruere explained a few
months ago that a reactionless drive is inconsistent with conservation
of energy.  This is true even if the drive uses power to produce thrust.

Suppose constant power leads to constant thrust, as the principle of
relativity would require.  Constant power implies that total energy used
will be proportional to time; but constant acceleration makes velocity
proportional to time, and kinetic energy is proportional to v^2, which
means it is proportional to time squared.  Any time you have input energy
proportional to time while output energy is proportional to time squared,
you will go over unity after enough time.

Hal