[Spaceships] Your preferences regarding plausible/playable Reactionless Drives

[teviet]

Originally Posted by teviet

Okay, so let's take another look at Molokh's "quantum roundoff" drive. Why not? Lots of people interested in quantum gravity have imagined it as some sort of Planck-scale gridwork (pre-geometry) or cellular automata.

<SNIP>

Okay, before Luke beats me to it, I'll add that a pseudovelocity drive still violates energy/momentum conservation. Why? Well, consider a closed surface around the spaceship. It contains the spaceship's rest energy. Now the spaceship moves outside: the surface now contains no energy. But because the velocity of the spaceship at any moment is zero, the energy flux across the surface at any moment is also zero. Hence: no local energy conservation.

So probably we do need something like an Alcubierre negative-energy field to nullify a ship's mass first. Before I'd said that Alcubierre drives could violate causality, that's without quantum gravity! According to some studies, the Alcubierre warp bubble may quantum-mechanically unstable (it could be disrupted by amplified vacuum fluctuations in the same manner as a wormhole-based timewarp). So, (hands start waving) maybe only particular configurations can be made stable, and (hands waving faster) these might correspond to discrete pseudovelocities that are less than c.

TeV