A reactionless thruster that (apparently) really works - no, seriously!

On 09/09/06, ANTIcarrot wrote:
> > From: Ian Woollard
> > Additionally, I read the article and then was able to show that if the
> > thruster were to be able to be placed in space and gain speed when
> > they put energy into it; it violates conservation of energy as well as
> > linear momentum. So it would be possible to build a perpetual motion
> > machine.
>
> Unfortunately, whether it works or not, I do not believe you're correct
> about conservation of energy. There's a comparison with ESA's Smart-1
> engine. Using those numbers (700W, 88mN, 9kg system weight) you get 4.3*10-4
> joules of kenetic energy out for every 700J of electrical energy you put
> into the system. To my understanding, that does not violate the conservation
> of energy principle, since you are not outputting more energy than you are
> inputting. If on the other hand you're wondering where the energy is comming
> from in the first place, solar panels (for example) would stop it from being
> a closed system, and hence CoE would not even be applicable.

That's different. I've seen the energy equation for an ion drive; it's
a bit counterintuitive. What happens is that the propellant gains
kinetic energy as the vehicle accelerates and the vehicle gains back
some of that kinetic energy when the propellant is emitted; and that's
why an ion drive vehicle can accelerate with constant acceleration
with a constant energy source. And the external source of energy makes
no difference to the result.

With a reactionless thruster that doesn't happen, because there's no
propellant. So you would have to put more energy in as you accelerate
to keep 0.5 m v^2 true.

But for the reactionless thruster to work in the same way, I believe
it would need a prefered reference frame since it has nowhere to store
the energy (no propellant) that it has gained from accelerating. That
violates the relativity principle, and hence also violates Maxwell's
equations.

> John

--
-Ian Woollard

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