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German Test Reveals That Magnetic Fields Are Pushing the EM Drive (arstechnica.com)
"Researchers in Germany have performed an independent, controlled test of the infamous EM Drive with an unprecedented level of precision," writes PvtVoid. "The result? The thrust is coming from interactions with the Earth's magnetic field." From the report: Instead of getting ahold of someone else's EM drive, or Mach-effect device, the researchers created their own, along with the driving electronics. The researchers used precision machining and polishing to obtain a microwave cavity that was much better than those previously published. If anything was going to work, this would be the one. The researchers built up a very nice driving circuit that was capable of supplying 50W of power to the cavity. However, the amplifier mountings still needed to be worked on. So, to keep thermal management problems under control, they limited themselves to a couple of Watts in the current tests. The researchers also inserted an enormous attenuator. This meant that they could, without physically changing the setup, switch on all the electronics and have the amplifiers working at full noise, and all the power would either go to the EM drive or be absorbed in the attenuator. That gives them much more freedom to determine if the thrust was coming from the drive or not.
Even with a power of just a couple of Watts, the EM-drive generates thrust in the expected direction (e.g., the torsion bar twists in the right direction). If you reverse the direction of the thruster, the balance swings back the other way: the thrust is reversed. Unfortunately, the EM drive also generates the thrust when the thruster is directed so that it cannot produce a torque on the balance (e.g., the null test also produces thrust). And likewise, that "thrust" reverses when you reverse the direction of the thruster. The best part is that the results are the same when the attenuator is put into the circuit. In this case, there is basically no radiation in the microwave cavity, yet the WTF-thruster thrusts on. So, where does the force come from? The Earth's magnetic field, most likely. The cables that carry the current to the microwave amplifier run along the arm of the torsion bar. Although the cable is shielded, it is not perfect (because the researchers did not have enough mu metal). The current in the cable experiences a force due to the Earth's magnetic field that is precisely perpendicular to the torsion bar. And, depending on the orientation of the thruster, the direction of the current will reverse and the force will reverse. The researchers' conclude by saying: "At least, SpaceDrive [the name of the test setup] is an excellent educational project by developing highly demanding test setups, evaluating theoretical models and possible experimental errors. It's a great learning experience with the possibility to find something that can drive space exploration into its next generation."
Even with a power of just a couple of Watts, the EM-drive generates thrust in the expected direction (e.g., the torsion bar twists in the right direction). If you reverse the direction of the thruster, the balance swings back the other way: the thrust is reversed. Unfortunately, the EM drive also generates the thrust when the thruster is directed so that it cannot produce a torque on the balance (e.g., the null test also produces thrust). And likewise, that "thrust" reverses when you reverse the direction of the thruster. The best part is that the results are the same when the attenuator is put into the circuit. In this case, there is basically no radiation in the microwave cavity, yet the WTF-thruster thrusts on. So, where does the force come from? The Earth's magnetic field, most likely. The cables that carry the current to the microwave amplifier run along the arm of the torsion bar. Although the cable is shielded, it is not perfect (because the researchers did not have enough mu metal). The current in the cable experiences a force due to the Earth's magnetic field that is precisely perpendicular to the torsion bar. And, depending on the orientation of the thruster, the direction of the current will reverse and the force will reverse. The researchers' conclude by saying: "At least, SpaceDrive [the name of the test setup] is an excellent educational project by developing highly demanding test setups, evaluating theoretical models and possible experimental errors. It's a great learning experience with the possibility to find something that can drive space exploration into its next generation."
... it's the field being created by the planetary body we call Earth. Surprise! No one has ever tested an EM Drive beyond the influence of Earth. If they had, its efficacy would have quickly been dis-proven.
Could it at least be used to reposition satellites? It appears to be an energy hog but if one first accumulates sufficient solar power then it might work.
Once you've taken an EM drive and removed the useless cavity and microwave emitter, what you are left with is an electrodynamic tether which may indeed be useful, but doesn't owe anything to the EM drive.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
Yep. In 5 billions years, give or take, our sun will become a liability.
In less than 1 billion years earth will go into "moist earth" runaway with surface temperatures hot enough to melt iron.
We will *have* to move our planet if we want to keep it.
This is possible with current level of technology. You need only nudge a few asteroids close to earth to selectively transfer kinetic energy a few times per century to keep up with increasing output from the sun while still on the main sequence.
..If the folks over at nasaspaceflight are to be believed
Looks like the setup was very sloppy indeed.. with the wattage too low making any signal disappear into noise..
Quoting:
Looking at the pictures of Tajmar's experiment, no wonder they are seeing nothing but Lorentz. First of all their twisted pairs do not appear to be twisted enough. There should be at least two twists per inch. In the image below it appears that there is maybe one twist per two inches or so. And then look at the location of the main amplifier and the length of the main leads! :o
At only 2W of RF power, no wonder they are only seeing Lorentz. It's almost like they designed their experiment to be susceptible to this form of error.
It's the field being created by the planetary body we call Earth. Surprise! No one has ever tested an EM Drive beyond the influence of Earth. If they had, its efficacy would have quickly been dis-proven.
Good grief.
If it's the Earth's field, put the device inside a pair of helmholtz coils (or the slightly more complex coil systems that can smooth out the residual ripples further). Give them enough current to cancel the Earth's field and, if the gadget is getting its thrust from this interaction, the thrust will stop. Give them twice that, reversing the field, and the thrust will be in the opposite direction.
I thought this test had already been done, by pretty much everybody including NASA.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
So, where does the force come from? The Earthâ(TM)s magnetic field, most likely. The cables that carry the current to the microwave amplifier run along the arm of the torsion bar. Although the cable is shielded, it is not perfect (because the researchers did not have enough mu metal).
Also: What's wrong with using twisted pair? The individual half-twists may interact with a DC magnetic field, but on the average across a twist they cancel out.
This has been used since at least the early days of telephony (where they used twisted pair - with the wires occasionally swapped as they go from pole to pole - not just to cancel out coupling to electrical noise from lots of sources (including power lines) but also - with different rates of twist on different pair and phantom-group - to cancel it out between different lines running along the same poles.
Just like the four pair in your cat-N Ethernet cable each have a different rate of twist, so their signals stay separate.
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(I DO like the idea of swapping in the dummy load and seeing whether the thrust disappears. B-) )
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
The researchers used precision machining and polishing to obtain a microwave cavity that was much better than those previously published. If anything was going to work, this would be the one.
Now that reminds me of a story, back in my programming-for-the-auto-industry days.
Seems that Rolls Royce, after sticking with manual transmissions for a long time, decided to consider manufacturing a car with an automatic transmission. So they got hold of the best on the hoi polloi market - the GM 350 turbo-hydramatic - to use as a reference.
First they tested the heck out of it - and found it did exactly what an auto-tranny should. So how could they make something better? So they tore it down to see if there was anything they could improve. But everything was beautifully designed and machined. Except for one surface on one part, which was a little rough.
So they machined it smooth and reassembled the transmission. And it didn't work at all. That surface was SUPPOSED to be a little rough. B-)
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Now personally, as much as I'd like to see a working reactionless electronic thruster, I'm not holding my breath waiting for a violation of the law of conservation of momentum. But it would be nice if something DID show up that worked.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
For interplanetary space travel, yes. But that's not very exciting. Chemical rockets work fine for interplanetary travel on the order of years and decades at most with ion drives showing promise as a next step.
The reason the EM drive was so exciting was because of the potential for interstellar travel in reasonable timeframes (sub-100 year) without having to lug around huge quantities of propellant (mass to throw out the back to accelerate you). If it actually worked, you could power it with a nuclear reactor and accelerate away without needing any propellant (violation of conservation of momentum).
Traveling to Alpha Centauri (4.367 light years) in 100 years (assuming constant acceleration to the halfway point, decelerating the second half of the trip, and ignoring relativistic effects) would require reaching a peak speed of
d = 0.5*vavg*t
vavg = 2*d/t = 2*(4.367 c years)/(100 years) = 0.08734 c
vmax = 2*vavg = 0.17468 c = 52,368 km/s
To accelerate, you need to dump the energy you're producing into the propellant that you're ejecting in the direction opposite you're accelerating. The energy needed reach Earth's escape velocity (11.2 km/s) and to escape the solar system from Earth's orbit (16.6 km/s) are roundoff error compared to the energy needed to reach Alpha Centauri in 100 years.
Energy for Earth escape velocity = 0.5*m*(11.2 km/s)^2
Energy for solar system escape velocity = 0.5*m*(16.6 km/s)^2 = 2.2 times the energy to escape Earth
Energy to reach Alpha Centauri in 100 years = 0.5*m*(52367 km/s)^2 = 21,861,469 times the energy to escape Earth
So a trip to Alpha Centauri in 100 years would require nearly 22 million times more energy (and propellant to absorb that energy) than needed to escape Earth's gravity.
Moreover, if you violate the conservation of momentum then Noether's theorem tells you that you've violated the principle of invariance under translation. If that were true, no two observers in different locations could ever agree on the laws of physics because the outcome of identical systems would be different if they were in different places.
The correspondence between conservation laws and physical symmetries is immensely useful when reasoning about systems like these. Noether's theorem doesn't require conservation of momentum to be true, but it explains the consequences if it is/isn't.
The EM drive, if it works, violates conservation of momentum, which can easily be used to also violate conservation of energy.
1) Momentum is not conserved in our universe.
2) Conservation of momentum is not required for conservation of energy
3) Energy is not conserved in our universe
Your argument is so over-simplifying physics that it's nonsense. Conservation of energy and of momentum are mathematical consequences of Euclidean space and time, by Noether's theorem. We don't, of course, live in Euclidean space or time. Note that the two conservation principles are unrelated - conservation of momentum comes from spatial symmetry, while conservation of energy comes from time symmetry. Either can be true without the other being true. That's just math.
Under special relativity, momentum is not conserved because of course we don't inhabit Euclidean space. Even so, energy is conserved in special relativity. The thing is, while momentum is not conserved, a different quantity is - we call it "relativistic momentum", but it doesn't look much like momentum except at low energy levels.
Do you see the point? If this EM drive thingy were to turn out to violate conservation of Newtonian momentum, that would be very interesting, but it would "only" imply new physics, and a new conserved quantity, not the ability to build perpetual motion machines.
Of course, under general relativity energy isn't conserved anyhow, because time flows at different rates at different places and times. And yet you still can't build a perpetual motion machine. Once again, there's new physics and a different conserved quantity, that happens to look like energy in the familiar special case of low gravity.
Socialism: a lie told by totalitarians and believed by fools.
A "bug" is defined culturally, not scientifically ...
100% False. Bugs are a specific order of insects whose defining characteristic is a particular arrangement of sucking mouthparts. Examples include tree-hoppers, box elder bugs, and stink bugs.