Honestly it doesn't matter. When you do the math the way GoatGuy proposes, any thruster will eventually go overunity. The higher the thrust, the more quickly it will go overunity. This isn't changed by putting limits on the fuel. Doing the math the way GoatGuy proposes, we could take literally any rocket thruster, put it on such a swing arm, and attach it to a generator. It would eventually produce more energy than it can account for because acceleration is linear with force but energy is quadratic with velocity. In fact, I think if you look at the problem carefully you find that you have the same issue with a DC motor.CaptainBeowulf wrote:The idea of feeding a rocket thruster "fuel" can still raise an objection: you are supplying power to the thruster from an external source, so it never really goes over-unity, while the M-E thruster is getting over-unity by operating without an external "fuel" source.

This objection arises because people usually think of chemical rockets when they think of rockets. In the case of a chemical rocket like a hydrolox rocket, the "fuel" is both the power source AND the propellant.

Again, it doesn't matter where the thrust comes from, what the thrust efficiency is, etc. If the thruster puts out a constant thrust of any level--and they all do, chemical, electric, nuclear--then doing the math the way GoatGuy proposes will inevitably arrive in a failure to conserve energy. That's because the math is wrong. In all these instances, acceleration is linear with force, but energy is quadratic with velocity, so there will always be a velocity and hence some time t, that you have an overunity condition arise. The answer is not to say you can't have thrusters that generate constant force. It is to say you're doing the math wrong.

It would be interesting to see this method of GoatGuy and Andrew applied to Deep Space 1. It seems to me possible it has already gone overunity by these accountings. One could at the very least say when it is due to go overunity, given it produces a constant force.

I should note to you too, that because velocity and hence energy are relative, there are always circumstances where all thrusters will appear to violate conservation using this method. If GoatGuy had realized this he would have abandoned the method.