Re: [Spaceships] Real Life Non-Super Science Reactionless Engines
 

That's right. It only applies full thrust if it isn't accelerating. And the only condition under which it won't be accelerating is? If it is opposed by an opposite force. So this gadget won't accelerate the vehicle itself, but will prevent another force from doing so.

Re: [Spaceships] Real Life Non-Super Science Reactionless Engines
 

Which in addition to the conservation of momentum violations, gets you into issues of preferred frames of reference.

Re: [Spaceships] Real Life Non-Super Science Reactionless Engines
 

This is relevant: http://space.io9.com/a-new-thruster-...1615361369/all

Re: [Spaceships] Real Life Non-Super Science Reactionless Engines
 

Hey, if I understand the science correctly (And I'm thinking I DON'T) I'm pretty sure the no preferred frames of reference stuff causes causality violations.

Re: [Spaceships] Real Life Non-Super Science Reactionless Engines
 

Only if you also have faster-than-light transport or communications.

The "no preferred frames I'd reference" stuff, otherwise known as "the Principle of Relativity" goes back to Galileo, and without it the theory of electromagnetism gets very hairy. It has been very firmly established since the Michelson-Morley experiment, and if you dump it you need a new explanation for all the relativistic phenomena that have been observed.

The maxim is "relativity, causality, FTL: choose only two", and nearly everyone agrees that it's FTL that didn't make the cut in this universe.

Re: [Spaceships] Real Life Non-Super Science Reactionless Engines
 

Not really. It just needs to not be privileged for purposes of any phenomena we've observed. Of course, the odds of the EmDrive producing such a phenomenon is basically zero.

Re: [Spaceships] Real Life Non-Super Science Reactionless Engines
 

I'm going to have to think about that.

Re: [Spaceships] Real Life Non-Super Science Reactionless Engines
 

'Our FTL drive seems to always move forward on the time axis in this particular reference frame, which I have called the Subspace Reference Frame'.

Re: [Spaceships] Real Life Non-Super Science Reactionless Engines
 

I'll give you an example based upon my understanding of the problem. You're on a satellite that due to the speed of it's orbit experiences some time-dilation. Now the satellite your on only communicates once per day with Earth, at precisely midnight, Greenwich Mean Time, with asynchronous computer transfers. One day you notice that the daily upload from the ground has started early, you realize that it's because of relativity, but no special frames of reference says that the clocks on Earth are running slow, not yours, and that causality has been broken.

Re: [Spaceships] Real Life Non-Super Science Reactionless Engines
 

Doesn't help. Relativity is about the relationship between reference frames, there is no special "frame you are traveling in", you are traveling in all of them.

Simplifying some (because I don't want to hunt it out and the math got pretty ugly with sub and superscripts I probably can't do in ASCII anyway when we actually worked through this) it's roughly if there exists some frame in which you have your ship at point A at time T0, and at point B at time T1, such that T1>T0 then *either* (B-A)/(T1-T0) <= c *or* there exists some equally valid frame in which T1' < T0', and in which (B'-A')/(T0'-T1') is less than c, allowing you at B'T1' to fire your laser back at yourself at A' and blow yourself up before T0' happens and you start the trip.

It does not actually matter how you moved between A and B, all the coordinate transformations say is that if you did in some frame, then there's another frame you travelled backward in time. No you didn't in the first frame, but so what? The contradiction *is* the causality problem. Stuff happened when you look at the universe one way that didn't if you look at it another, is what doesn't make sense about violating causality.