[Spaceships] Reactionless Drives, Pseudovelocity, and NOT breaking a setting (much)

[Ulzgoroth]

Originally Posted by Emerald Cat

Energy and Angular Momentum are Conserved: you must pay an energy cost equal to the change in KE of your ship + PE due to changing your location. Also makes accelerating anything to c exorbitantly expensive.

This isn't possible.

If your drive conserves linear momentum (and doesn't use some kind of un-counted virtual velocity), it's not a reactionless drive, it's a reaction drive. If it conserves angular but not linear momentum it's...almost certainly mathematically impossible.

But you definitely cannot conserve energy, because the change in KE of your ship is a reference-frame dependent value. Picking up 1 m/s from rest is only 1/3 as much kinetic energy as increasing from 1 m/s to 2 m/s, but those are descriptions for the same thing from only very slightly different points of view.