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new propellantless drive company

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m98:
The physics sound whacky, and I can say that nobody in the EP community is taking any of this seriously. That said, I'm looking forward to Martin Tajmar getting bored again and trying this out.

ejeffrey:

--- Quote from: Nominal Animal on April 24, 2024, 08:00:18 pm ---Propellantless drives violate conservation of linear momentum, but not necessarily conservation of energy. 

--- End quote ---

A violation of conservation of momentum in one reference frame would violate conservation of energy in another reference frame.  Although if you are throwing out conservation  laws I guess you might as well throe out special relativity too.

Nominal Animal:

--- Quote from: ejeffrey on April 25, 2024, 03:06:30 am ---
--- Quote from: Nominal Animal on April 24, 2024, 08:00:18 pm ---Propellantless drives violate conservation of linear momentum, but not necessarily conservation of energy. 

--- End quote ---

A violation of conservation of momentum in one reference frame would violate conservation of energy in another reference frame.  Although if you are throwing out conservation  laws I guess you might as well throe out special relativity too.

--- End quote ---
:P

I'm not "throwing out conservation laws"; the one possibility I pulled from my backside could conserve both linear momentum and energy.

Let's consider two inertial reference frames, one before and one after some acceleration with a propellantless drive.  In the first, the violation of conservation of momentum appears to increase the total energy, and decrease in the second.  This is special relativity.  For special relativity to hold, in actuality, the total energy must be conserved instead.

One solution to that problem is to couple the drive, somehow, to a larger system, so that for the entire system both energy and linear momentum is conserved.

If we consider warp drives like Alcubierre drive, they only seem to violate conservation of linear momentum.  They do not, because the (let's say) "anomalous velocity" of the warp drive does not increase the linear momentum; it only exists as long as the drive is "active", and is actually due to the space contracting and expanding with the drive.  (If we observed such a drive, we'd probably see an optical distortion caused by such a drive, but had no other "hints" that it wasn't violating conservation of momentum or energy.)

Now, I have not examined all propellantless drives to find out if they only seem to violate conservation of linear momentum but actually do not (either because of spacetime distortion or by coupling forming a larger system where both linear momentum and energy is conserved), or if there are other solutions to the conservation of energy in different inertial reference frames while violating conservation of linear momentum, for example via quantum-scale effects.  Because of this, I prefer to err on the optimistic side, and assumed other ways might be possible.  If I had preferred to err on the side assuming all of important physics is already known, I would have written something like "Propellantless drives only seem to violate conservation of linear momentum.  They do have to conserve both linear momentum and energy, just like for example the Alcubierre drive does, to not violate physical laws."

I did expressly write I think the one discussed in this thread is extremely unlikely to be a real effect, but it has more to do with the physics models ("laws") that have survived the tests of new measurements –– including special and general relativity –– refining or extending previous models rather than replace them.

Infraviolet:
I haven't followed the recent news on the EM "drive", but when it first made headlines in 2015 or so, I swear I remember that the thrust it supposedly gave per watt of supplied power was actually worse than the thrust one gets from a "photon drive" (that is to say shining a bright light out of the back and using the conservation of momentum to get a forward thrust, a photon drive gets you 1 N per 300 Megawatts). It seems like the EM "drive" is an experimental error with performance worse than that which would be achieved if one end were removed to make it an ordinary microwave emitter.

coppercone2:
That is no reason to investigate an effect. Then its just boring physics instead of popsci physics.

I recall reading that it was significantly above photon drive levels though (according to their experiments), IIRC the whole point was that there is a force that is bigger then the force expected from photons.

The usual problem, that is high power electronics lol. the ones that a experienced engineer sees it as a running lawn mower engine hanging on some springs, being measured with a caliper

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