Leonard Erickson wrote:
 > I think you blew your calculations *badly* somewhere.

Yes. I was wrong. I posted the wrong equation initially and then
corrected. The energy-momentum relation is:

(energy)^2 = (momentum x c)^2 + (rest mass x c^2)^2

So the quantity
(energy)^2 - (momentum x c)^2 = (rest mass x c^2)^2
must be the same in all inertial frames if the rest mass doesn't change.

Your examples can be generalised to *any* space vehicle or cosmic body.
This doesn't make their motion impossible ;-)

Traveller reactionless drives don't make sense because they violate
conservation of momentum and energy as written.

To enable momentum conservation, momentum needs to be generated locally
(by 'pushing' against space-time itself?) or harvested from the general
vicinity.

My initial post proposed a range of fuel values and drive efficiencies
that would allow conservation of energy. The momentum generated by
making photons or neutrinos from the fuel is far less than the
performance level required by canon.

Rob O'Connor