Reactionless Drives

[WarDaft]

So, a reactionless drive (that is, a motor that produces a net change in global momentum other than 0) violates conservation of energy in some reference frame. This is a known result. (Project Rho has a section covering this)

But what exactly do we have to do to (or can we even) make it violate conservation of energy in its own reference frame? That is, given a complex device D initially at rest, with no initially moving parts, in a total void, how simple can we make D such that in D's reference frame there is a violation of the conservation of energy?


The basic idea, is that if you're going to go ahead and allow the existence of a reactionless drive in your universe, you might as well actually take advantage of it as an unlimited power source as well, if possible locally. Such as a power station on a planet, or a reactor core in a space craft.

[Charlie!]

You can't directly get out energy from changing velocity, you'd need contact with some outside object to be able to run your generator. "Some outside object" could still be inside the ship, though, as long as the motor has to exert a force to get this object to move.

[frogman]

Depending on how weird you want to get, you could introduce some fictional "negative energy" and have the drive release that.

[Joeldi]

In a sci-fi context, negative energy really doesn't seem all that far-fetched.