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Chinese Say They're Building 'Impossible' Space Drive, the EmDrive ('Relativity Drive')
- nazgulnarsil 18y agointeresting. in essence what we have here is a variation on the photon drive where instead of being bounced off an open reflector to generate momentum you have a closed cone. at first glance this would seem absurd since the forces acting on the two ends of the cone should cancel each other out. where it gets interesting is that this guy claims that the math shows that the photons are operating in a special frame of reference: essentially even though the photons are enclosed they behave as if they were not. thus momentum is imparted in one direction and all you have to do is keep pumping microwaves into the cone. being able to use electricity instead of some sort of stored propellant would be a huge step towards sustainable space flight. here's hoping it works. and even if it doesn't, science needs weirdos who are willing to work on edge cases. tesla's professor told him that the AC motor was a perpetual motion device and thus impossible.
- mechanical_fish 18y agoscience needs weirdos who are willing to work on edge cases Yes, but there's more than one kind of edge. The edge of scientific knowledge is worth paying people to explore. The edge of your own knowledge is worth exploring on your own. The edge of your funding agent's credulity is very profitable to explore, but such work doesn't help science at all.
- DougBTX 18y agoHe ignores the forces on the sides of the tapered wave-guide, calculating forces only for the end caps[1]. If he was to include the forces on the sides, I'm quite sure he would find that F_g1 = F_g2 + F_sides exactly. [1] page 2, http://emdrive.com/theorypaper9-4.pdf http://emdrive.com/theorypaper9-4.pdf
- nazgulnarsil 18y agoHe mentions that axial forces (the momentum imparted by deflection off the tapered sides of the cone) are taken into account, it might still be wrong but he didn't just ignore it. keep in mind that the force being produced here is tiny: 85 milli newtons, and it obviously needs a power source to run. assuming that the math doesn't add up to a 100% or greater efficiency in the conversion from electrical energy to momentum i see no reason why this is impossible. If the drive works as claimed i wonder what the efficiency is in the transformation from electrical energy to momentum.
- DougBTX 18y ago> He mentions that axial forces are taken into account If he does, he's not included it in his theory paper. Take a look, there is no mention of "axial forces" or "deflection" in the paper. In equation 7, he calculates the thrust T using only the difference in propagation velocity at each plate, but makes no mention of how the propagation velocity changes. If he did, it would be obvious that you have to account for radiation pressure on all sides on the tube, not just sides which happen to be perpendicular to the tube's axis. > efficiency in the conversion from electrical energy to momentum The efficiency will be about 0%, so no need to worry.
- nazgulnarsil 18y agoyou're right. in the paper he is simply doing F2-F1 to give the thrust without any mention of the surface area of the cone walls. he mentions constructing the cone to give a "reflection free transmission" which is impossible. i guess junk science is right. oh well. from page 6: Note that the reflection-free interface, with matched wave impedances , will ensure no forces are produced at the interface. <-- that doesn't sound possible.
- tlrobinson 18y ago"According to Roger Shawyer, the British scientist who developed the concept, the drive converts electrical energy into thrust via microwaves, without violating any laws of physics." Wouldn't it be much more interesting if they actually did violate the laws of physics?
- rms 18y agoSounds like a hoax.
- Eliezer 18y agoChina doesn't seem to have very good science filters. They're also funding one of the most hopeless AI projects I know of.
- hugh 18y agoI'll be more interested once they start building a possible one.
- DanielBMarkham 18y agoHow about just a plain improbability drive?
- MaysonL 18y agoObviously, this is a crazy idea. But, with Feynman, I have to ask: "Is it crazy enough to be worth taking seriously?". I wish I had enough physics to answer that question.
- DanielBMarkham 18y agoI have no doubt that one day one of these crazy web stories will be true -- somebody will invent a field propulsion system. Odds are this ain't it, though.
- ghiotion 18y agoThe Chinese also said their female Olympic gymnasts were 16 years old. I think it's a good policy to take what the Chinese say with a grain of salt.