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Uncertain Propulsion Breakthroughs?
- anotheryou 10y agoI hope we'll find out in practice: http://www.popularmechanics.com/science/energy/a22678/em-drive-cannae-cubesat-reactionless/ http://www.popularmechanics.com/science/energy/a22678/em-dri... (via lobster_johnson) "Proud to say that we have a partnership now - so the launch is already funded, and we hope to get a launch slot in 2017."
- cperciva 10y agoBeing in space doesn't solve the problem of errant forces completely. You can push against the earth's magnetic field, for example.
- JumpCrisscross 10y agoSatellite orbits degrade overtime due to drag, among other things [1]. Operators counter this decay with periodic boosts. (The International Space Station is boosted, on average, once a month [2].) Boosting, even electric propulsion boosting, consumes propellant. If this works by impelling against the Earth's magnetic field, provided it is more efficient than a simple magnet, it could still have a market with satellite manufacturers. [1] https://en.wikipedia.org/wiki/Orbital_decay https://en.wikipedia.org/wiki/Orbital_decay [2] http://space.stackexchange.com/questions/9087/how-often-does-iss-require-re-boosting-to-higher-orbit#9088 http://space.stackexchange.com/questions/9087/how-often-does...
- sandworm101 10y agoFor the power required to generate minimal thrust, this will not be useful in low orbit. The solar panels required to power the drive would result in more drag than the truster might overcome. So no market. And this test flight will not result in a clearcut "it stays up" rather "it fell slower than expected". There will be much calculation and debate re drag, magnetics and gravitational anomolies, so small are the expected forces. To get a clear result we need something out closer to geostationary, flying for months well away from the earth's irregularities.
- JumpCrisscross 10y ago> For the power required to generate minimal thrust, this will not be useful in low orbit A recent paper [1] quotes this system's predicted efficiency at 1.2 mN/kW. Hall thrusters, a propellant-throwing electric engine, perform at 60 mN/kW. Non-propellant systems like light sails, laser propulsion and photon rockets perform around 0.0033 to 0.0067 mN/kW. If this works, and that's a big if, a 50x performance improvement over the prototype is not unrealistic. [1] https://regmedia.co.uk/2016/11/09/q_thruster.pdf https://regmedia.co.uk/2016/11/09/q_thruster.pdf
- sandworm101 10y agoBut how big will the panels need be? And how much extra aerodynamic drag will they create in a low orbit?
- dom0 10y ago> If this works by impelling against the Earth's magnetic field That's a completely different premise than the em-drive has, though. It's supposed to not depend on an external field; developing a force between two magnets wouldn't exactly qualify as (non-)rocket science today.
- matheweis 10y agoBut it would represent an improvement on what we have today, which is a finite amount of fuel use to keep the satellite in orbit that eventually runs out.
- stale2002 10y agoThe way science works is by doing experiments. The people have been doing experiments on the EM drive and have been getting unexpected results. Nobody really knows why yet, but that's kinda the point. Is thermodynamics flawed? Is it pushing off of "dark matter"? Is it a completely new and novel scientific effect? Any of these circumstances would be interesting.
- DanielBMarkham 10y agoYes. Even if it's the most likely thing, experimenter error, for a half-dozen teams to all have errors and not spot them? That's quite interesting! It's the same situation we had with the FTL neutrinos a while back.
- euyyn 10y agoExcept the neutrino paper then was a big lot of physicists asking colleagues to help them review, so as to find where the problem was. What I see here is just hype. The former, as opposed to the latter, is what gives confidence that the people involved are doing their darnest not to fool themselves. That what they're doing is actually science.
- DanielBMarkham 10y ago
- roywiggins 10y agoElectrodynamic tethers push off the Earth's magnetic field directly and don't need fuel.
- evo_9 10y agoSo no proof will ever be enough for some? Are EM-Deniers going to be a 'thing' now?
- hwillis 10y agoIf it can accelerate forever, thats proof enough for everyone. However violating the conservation of momentum is a Big Deal. Mathematically that shouldn't be possible due to Noether's. The bar to proof is therefore very high.
- naasking 10y agoGeneral relativity doesn't conserve energy in some spacetimes, so it's not unheard of.
- andrewflnr 10y agoI'm fairly certain GR conserves momentum, even if it doesn't conserve energy.
- naasking 10y agoI thought so too until recently, but in GR energy and momentum are unified in an energy-momentum metric which is only locally conserved [1]. [1] https://en.wikipedia.org/wiki/Physical_theories_modified_by_general_relativity#Conservation_of_energy.E2.80.93momentum https://en.wikipedia.org/wiki/Physical_theories_modified_by_...
- gus_massa 10y agoI'm also a yeti-denier! With enough proof you can convince the physics community, even if the result is initially weird. My favorite examples are https://en.wikipedia.org/wiki/Wu_experiment https://en.wikipedia.org/wiki/Wu_experiment and https://en.wikipedia.org/wiki/High-temperature_superconductivity https://en.wikipedia.org/wiki/High-temperature_superconducti... . I think you can push a little against the magnetic field to rotate and change your orientation, but to gain height the magnetic field is not useful. [Edit: Mmmm I'd change "but to gain height the magnetic field is not useful." to "but to gain height pushing against the magnetic field is not efficient."]
- hwillis 10y agoIf it does, I think that would be detectable. As the device gets into higher orbits, the magnetic field will get weaker and the force will drop. I'm not sure how much the orbit would have to change to make that apparent though. It might take a very long time. Another way it might work is by freeing atoms from the backplate of the resonant cavity, like an ion thruster. I hope they include a method of measuring the degradation of the backplate. I suspect it just won't work, though.
- zamalek 10y agoAccording to the inventor, The Mach thruster (also discussed, and potential underlying physics for the EmDrive) supposedly "pushes against" the Earth's gravity.
- empath75 10y agotl;dr; > First, I cannot stress enough that there is no new EmDrive “effect” yet about which to theorize. The physical evidence on the EmDrive is neither defensible nor does it include enough operating parameters to characterize a new effect. The data is not even reliable enough to deduce the force-per-power relationship, let alone any other important correlations.
- Others 10y agoI don't think that's a fair summary... The author provides a more nuanced view than just "there is no effect." You're nitpicking from one section about theory, without considering the article as a whole. This is especially egregious considering that the article spends so much time talking about confirmation bias.
- jdoliner 10y agoIt even says explicitly: > Do you want to know our conclusions without any regard to how we reached those conclusions? ... If you answered “yes” to any of those questions, then you, like me, have natural human cognitive dysfunctions.
- StavrosK 10y agoI don't understand that. Since I can't educate myself on everything required to make an informed decision on whether the paper is true or not, I decide to just trust someone else's opinion. I pick people to trust based on various criteria (how well they've cited their sources, how much other trustworthy people trust them, etc) and then just blindly believe whatever they say. What else can I do?
- mquander 10y ago> how well they've cited their sources, how much other trustworthy people trust them, etc That sounds to me like a "regard to how they reached those conclusions" (maybe a regard to how they reached a subset of their conclusions, and extrapolating to the rest). It's not the most regard you could possibly have, but it's lots.
- thearn4 10y agoI know Marc Millis, let me know if anyone has any questions and I can try to get his feedback here.
- Analemma_ 10y agoHe did so partially in this article, but I would love to see a detailed explanation of a valid experimental setup to test the EmDrive effect. What would an experiment look like where, if thrust were observed, then we could really start to say there might be something here?
- extrapickles 10y agoThere is a list of improvements in the article under "Latest Paper". Its mainly the need to carefully characterize and document all the test equipment and EM Drive support equipment to make sure its not caused by the test setup. This would involve testing with a dummy load so things like interactions with chamber wall can be ruled out or if there are, the effect can be mitigated or accounted for. Basically they proved their test setup produces thrust, but haven't proven the thrust was a direct result of the EM Drive. They need to more rigor to prove its only the EM Drive and not a setup error (eg: something like the FTL neutrinos turning out to be a poorly tightened connector).
- greglindahl 10y agoHe gets bonus points for mentioning "extraordinary evidence for extraordinary claims" twice in the article!
- raverbashing 10y agoI remember him from the Nasa BPP page, that was a very nice work.
- ufmace 10y agoCool, I read all of the BPP pages a while back. I wonder what happened to them, they seem to have been down for a while. I had always wondered about something there, though it isn't related to the EM Drive. The original pages posted a few numbers claiming that even with a Fusion rocket-based propulsion system, interstellar travel was still wildly impractical, like thousands of supertankers of propellant to send a Space Shuttle-sized capsule past the nearest star system in 900 years without stopping. Yet many Sci-Fi and semi-scientific sources make it seem as if nuclear rockets are a viable interstellar propulsion. I always wonder who's right, and if I can find some more detailed numbers to back it up either way. Thought about it enough that I might actually try and calculate it myself one of these days.
- Animats 10y agoIt's so near the noise threshold. Most of the energy goes into heating the thing; only a tiny fraction comes out as possible thrust. The heating prevents using enough power to get more possible thrust; the thing would burn out. Very frustrating.
- halomru 10y agoIf we had any idea how they work (if they work) we could work on optimised designs that generate more thrust and are thus easier to study. But we're not yet anywhere near the stage and instead have to study a design that if it works, is so inefficient that we can hardly tell whether it does anything. Very frustrating indeed
- Animats 10y agoYet it's happened before in engineering history. Edison discovered the "Edison effect" - he put an extra plate in an incandescent lamp, and discovered that some current, not much, would flow to it through vacuum. This, in 1875, was the beginning of the vacuum tube. But lacking the theory to understand it, it couldn't be improved. Early on, it was thought that there had to be some air, or something, in the tube for it to work. But then it was discovered that hard vacuum worked better. This confused electrical inventors of the era - how could electricity conduct through a vacuum? It wasn't until 1904 that tubes started to be figured out. Tube filaments are quite different than lamp filaments - tubes need a material where electrons are easily emitted from the surface. Tungsten is good for lamps but terrible for tubes. A little thorium oxide or barium oxide helps a lot. But there was no theory to indicate in what direction to go, and it took 30 years before trial and error produced results.
- perlgeek 10y agoThat was quite a thoughtful, and IMHO balanced, discussion. I wish this was the usual level of discourse on scientific news.
- xupybd 10y agoWow, I've not read something like that in a long time. More news needs to be like this. Examining what we know presenting where we are. Not taking sides and polarizing the discussion. I do think people miss one small aspect of this story. How long has it been since we've had a device built that we've no understanding of the principles of it's operation? I think that's an amazing fluke and (if the effect is genuine) something worth celebrating (just because it's so rare).
- Animats 10y agoThere are others. There's cold fusion. There's a strange effect by which a rotating superconductor appears to induce gravity.[1] (Whatever happened to that? Articles from 2002-2006, then nothing.) They're all down near the noise threshold. [1] https://www.sciencedaily.com/releases/2006/03/060325232140.htm https://www.sciencedaily.com/releases/2006/03/060325232140.h...
- madengr 10y agoThere was another paper about 15 years ago where a electrically pulsed, superconducting thin film was able to displace a pith ball from tens of meters, through walls. I can't find the paper but it was on arxiv. Some sort of gravity pulse; weird shit.
- therein 10y agoMade me think of this. Maybe when they were doing the experiment, a gravitational wave happened and they somehow reflected it? > Thin superconducting films are predicted to be highly reflective mirrors for gravitational waves at microwave frequencies. The quantum mechanical non-localizability of the negatively charged Cooper pairs, which is protected from the localizing effect of decoherence by an energy gap, causes the pairs to undergo non-picturable, non-geodesic motion in the presence of a gravitational wave. https://arxiv.org/abs/0903.0661 https://arxiv.org/abs/0903.0661
- madengr 10y ago
- powera 10y agoIMO the "rational" approach is to treat the claims as a bunch of pointless lies until there's a repeatable demonstration. Remarkable claims demand at least some evidence before wild speculation commences. As it is, Harry Potter is just as credible a theory of reality. After all, they've made the same claim repeatedly for 15 years after their first experiments were demonstrably not what they claimed.
- stale2002 10y agoThis is what they are doing. They are sending something into space to demonstrate the effect. Let the experiments decide what is right or wrong.
- greglindahl 10y agoThere are a ton of simple experiments that can be done in the lab that aren't being done by the people claiming that this thing works. The article mentions a few. The people launching something are going to get another inconclusive result with a high price. At least it isn't tax dollars.
- samplonius 10y agoSo "space" is some magical place where measurement error does not exist? Low earth orbit isn't perfect either. You still have micro gravity. And the experiment requires a lot of power, and very sensitive instruments to measure the phenomenon. How do you get sensitive instruments which are expected to be operating near their error threshold into orbit without damaging them? Orbital experiments will have to be smaller, and use less power, so the effects will even be smaller. But the instruments will have to be tough enough to withstand 5G. And the apparatus could still be introducing other errors, like coolant momentum, which also isn't magically eliminated by being in space.
- stale2002 10y agoThe experiment is pretty simple. You put the engine in space, with solar panels, and you see if it stays there or falls back to earth. There is no experimental error, or even measurement devices. It is a space engine. Either it flys or it doesn't. Over the course of a year, it will be obvious if it works or not. Because if it doesn't work it will fall to earth.
- Trombone12 10y agoThe Summary: "this most recent report is a significant improvement, but has many shortcomings. Questionable subjective techniques are used to infer the “thrust” from the data. Other likely influences are not quantified. But also, despite those inadequacies, the possibility of a new force-producing effect cannot be irrefutably ruled out. This is intriguing, but still falling short of defensible evidence."
- disposablezero 10y agoBusted by Thunderf00t https://youtu.be/jCAqDA8IfR4 https://youtu.be/jCAqDA8IfR4 It's amazing people are still giving this bollocks the time of day.
- jayajay 10y ago"Inertial frames are the reference frames upon which the laws of motion and the conservation laws are defined, yet it is still unknown what causes inertial frames to exist or if they have any deeper properties that might prove useful." "...we must begin a more in-depth experimental program using qualified and impartial labs, plus qualified and impartial analysts." Maybe humans don't really belong in labs in the same way that they don't belong in factories.
- xt00 10y agoIf they have two versions of the resonant cavity, one that is tapered and one that is just a simple cylinder that to me would be a big step in the right direction to address many of the concerns. Basically the cylinder with no taper should show zero thrust. And the version with the taper should show a thrust. Then if they test that setup inside the huge Apollo program vacuum chamber far away from the side walls and change the orientation of the coolant and power wires into different orthogonal directions that sounds promising..
- mrfusion 10y agoWe don't know if the taper does anything though. If we don't have a working theory we can't really use variations of the working device to prove anything.
- mng2 10y agoFrom what I've read, the theory amounts to "there are more photons bouncing off the fat end versus the thin end hence thrust." Which personally I think is highly questionable given the low-energy regime involved.
- xt00 10y agoOh I had thought that the asymmetric shape with the tapered cone shape was an important feature from the original inventor. But yea, hard to guess without more systematic theory to leverage off of yea..
- pizza 10y agoAnybody know anything about the quantized Unruh radiation -> inertia theory?
- naasking 10y agoPerhaps this: https://arxiv.org/abs/1302.2775 https://arxiv.org/abs/1302.2775
- Nomentatus 10y agoRemember that "tacking"* in sailboats (going upwind, using only the force of that wind) was held to be impossible, a violation of the laws of nature until people actually witnessed it, too. Severe violations of our expectations don't always break the actual math of a physics model. *more properly said "beating to windward" https://en.wikipedia.org/wiki/Tacking_(sailing) https://en.wikipedia.org/wiki/Tacking_(sailing)
- trhway 10y agowe have several unexplained things which possibly look like some interaction between gravity and EM - em-drive, spinning magnet/superconductor gravimetric effects and unexpected velocity of stars in the galaxies (which are big rotating piles of plasma)