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

[vicky_molokh]

Originally Posted by RogerBW

My mental model of pseudo-velocity drive is something like 2300AD's stutterwarp, or the drive used in Poul Anderson's Polesotechnic League stories.

In that case, the energy cost of moving from point A to point B needs to vary with gravitational potential difference. If you move your 100-ton ship "up" by 100 metres from Earth's surface, that costs you the same 100MJ or so that you would have needed to feed into an electric motor (though the inefficiency level will be different).

So the standard perpetual motion setup, where you jump something upwards and let it fall down, is circumvented.

In game terms what this will mean is that outward acceleration drops off sharply when you're in any sort of gravity well. It may even be that ships can't use this drive near planets at all, and need rockets or something else for surface-to-orbit.

Is this a useful starting point?

Well, that is in fact one of the starting points in the OP, that is, "at a minimum, that changes in potential energy due to lifting off from a planet must come from actual, real energy of capacitors aboard the ship". It's a thought in the right direction, but I'm not yet sure what are the less-obvious implication for the world based on such a postulate, aside from avoiding gravitic perpetual motion.

Originally Posted by johndallman

Pesudovelocity drives usually seem to work by means of rapid short-distance teleports. You need to consider what the movement speed is during the teleport, the maximum rate of the teleports and their maximum distance. These considered together will give you a limiting speed for the drive.

Well, a multi-teleport still means a mass moves with an observed velocity without absorbing a corresponding amount of kinetic energy. I'd like to see what sort of collateral damage results from that, and how it can be minimised. Notably, what consequences do we get from bending or breaking momentum-conservation, perhaps.