11 ms·
The quest for a reactionless space drive
- mrfusion 12y agoI wonder if you could rotate the capacitor about a central point instead of vibrating it?
- ajuc 12y agoWith magnetic bearings in vacuum and superconductor for the coil the only energy loses would be the ones that this theory predicts due to mass fluctuations I think? So either it does nothing and stays where it is, or it converts energy into movement at 100% efficiency?
- api 12y agoElectric motors can be ~90% efficient, or even higher for really well engineered ones, so very high efficiencies in converting electricity into movement are common. Electricity is basically movement already -- of electrons -- and is usually generated by spinning conductors and magnets around. It wouldn't be 100% since some energy would be lost due to internal friction and the need to actively cool the thing to maintain superconductivity (and pump away heat generated by friction). You'd also lose energy in the electronics in generating the oscillating signals, switching, power conversion, etc., and in EMF losses. If it really does work I could imagine it approaching the efficiency of a good motor, just one that creates directional force in a vacuum by pushing against... umm... something. That'd be a question for the theoreticians. :)
- ars 12y agoNo, you can not. Not without something to pivot against (and then it would not be reactionless). You can only shift your location, you can not develop any speed.
- deleted 12y ago[deleted]
- DennisP 12y agoWoodward's been doing physical experiments on this for quite a few years now. Eagleworks is testing a different idea.
- jcfrei 12y agoAh, seems like I've mixed up the reactionless drives - I thought it was also part of the tests at Eagleworks.
- ChuckMcM 12y agoActually it is a useful thought experiment because it cuts to the heart of the problem. You 'temporarily' reduce the effective mass of something. So understanding how that is, or is not, possible lets you follow the rest of his reasoning. (on the record, I'm not sure I buy the variable mass argument). That said, and I've suggested this before. The minimally sized mechanism is well within the mass capacity as a 'ride along' on a Space-X resupply flight to the ISS. Put it up in orbit and have it move itself to Geosyncrhronous orbit without fuel. Nobody would argue about the physics after that.
- tyw 12y agodon't really know what the power requirements are for his device as it currently stands. generating enough power in space would probably weigh enough to make the effects of the current device they've built all but unnoticeable over a reasonable amount of time. if they can advance their modeling of the effect and figure out what effects efficiency they'd likely be able to design and launch a device that could deliver much more convincing results.
- api 12y agoIf that orbital transfer took a long time, someone would argue it's interacting with the Earth's magnetic field. The only real absolutely unambiguous test I can think of -- other than finding a way to massively boost the effect to the point of undeniability -- would be to launch something at Earth-Moon escape velocity and then see if it can continue to accelerate as long as it's got solar power to do so. For a small test rig this could be done with a small SRB booster from the ISS. ... though on second thought ... I wonder what would happen if you put one of these on a centrifuge? It should spin faster, and faster, and faster... or not. :) If the effect is too small to overcome friction you could do an experimental / control setup with two centrifuges, one with this device + a normal motor and one with only a normal motor and a ballast of equal mass to the device. Then swap which centrifuge has the device. Repeat many times. The one with the device should consistently accelerate more. The heat problem sounds like they need to be using superconductors or some means of high-efficiency cooling. I'd look into Peltier effect cooling built into the device or something if superconductivity isn't an option.
- vadman 12y ago"The problem is, crowd funding requires a significant investment of time, which might be applied more productively to research." So they can't arrange for a capable student to take care of that as part of a work-study program? WTH. Perhaps I'm underestimating the amount of work involved, but it's not like they need to have contributor tiers with silly T-shirts.
- api 12y agoTry to crowd fund this and you'll bring out hordes and hordes of Skeptic Movement Skeptics who will scream "con man!" and "pseudoscience!" and do everything they can to sabotage the campaign. Kickstarter would probably start getting e-mail campaign letters to de-list his account for fraud, etc. You see, he needs more money to try to boost the signal and further test the effect. But since the effect is novel and controversial, attempting to raise such money means he's a con man and invites comparisons to that e-Cat dude from Bologna. If I were him I would avoid publicity outside the scientific community simply to avoid the character assassination. I'd work with interested other scientists and publish in obscure journals until I could either find the flaw my measurements or generate data so unambiguous that it overcomes the howling.
- blacksmith_tb 12y agoHave other crowdfunded scientific projects had this problem? It's easier to see why people might unleash a lot of criticism at projects that might receive federal funding, but wouldn't the critics just... not back a crowdfunded test of Woodward's work?
- aperrien 12y agoBecause, unfortunately, some people are just jerks, and will troll for the luz.
- adrianN 12y agoI think that would depend on how it is marketed. If they clearly state that it's a novel effect and that it's really likely that it will turn out to be a measurement error, then nobody can accuse them of being dishonest.
- msandford 12y agoThis seems much more plausible to me than the microwave thruster previously reported all over the internet. I think it's a clever application of relativity and motion. It feels crazy to say this, but it seems to be on a solid theoretical footing.
- dnautics 12y agoMy thoughts exactly. Why don't they crowdfund this? For about $200k they could probably stick a prototype on a nanosat and just hit go. With the right tracking equipment the results should be pretty conclusive.
- trishume 12y agoFrom my limited understanding, it seems that the current prototype requires a ton of power (far more than you could fit in a nanosat) and produces a miniscule amount of thrust (even in space with a nanosat it might not move much).
- tjradcliffe 12y agoSeveral points: 1) "Foundations of Physics" is closer to a philosophy journal than a physics journal. It's full of fascinating stuff, but it's far more speculative than any other legitimate journal. When libraries were cutting budgets in the '80's and '90's it was generally the first to go. 2) When highly theoretical phenomena are talked about in engineering terms, the odds of confirmation bias are huge. Who wouldn't want a reactionless-ish thruster? 3) Measuring transient forces of the kind being applied here is extremely hard, and the number of confounding factors is extremely large. The article mentions a mu-metal shield, which will screen some of the Earth's magnetic field from the apparatus but which is useless for screening transient magnetic fields, which get generated by transient electric fields thanks to the magic of Maxwell. Ampere's law tells us CurlB = mu_0epsilon_0dE/dt. So the possibility of residual electro-magnetic forces is non-trivial to say the least, particularly in a room full of conductors and time-varying EM-fields (from the wiring, the pump, etc). Putting the whole apparatus in a Faraday cage would help, but the history of measuring small (and transient) forces in physics in the past couple of decades (the fifth force mess, Joe Weber's coherent neutrino scattering work) argues that we take these experimental measurements with a large grain of salt, unless they can be shown to be in precise numerical agreement with the theory's predictions over an order of magnitude variation in power input and rate of variation. The theory may not be wrong, but it needs a lot more experimental investigation and likely theoretical examination as well. Theorists tend not to spend a lot of time critiquing things that look really likely to be wrong, because proving something that everyone thinks is probably wrong, wrong can be incredibly time-consuming and utterly unrewarding. So the lack of theoretical disproof is not very compelling. So far as I know Joe Weber's coherent scattering theory was never dis-proven in publication, either: it was mostly dismissed by informal but compelling arguments at conferences (the best one was simply that there was nothing special about neutrinos in Weber's theory, so if what he said was correct single crystals would coherently scatter x-rays in exactly the same way, which would have shown up as an anomalous low-energy contribution to EM cross-sections that would have been an obvious problem for decades if anyone had observed it.)
- api 12y ago"When highly theoretical phenomena are talked about in engineering terms" That may be true, but you also mention that measuring tiny transient forces is incredibly hard. Thus, the only way to actually get an accurate measurement for this thing is to attempt to scale it up until the force is either unambiguous or the confounding culprit can be found. You've got to try to amplify the signal. I also don't get the impression that these folks are dummies. I'd be surprised if they haven't done experiments to attempt to rule out electromagnetic effects. Simple ones would involve moving stuff around, doing this in the presence of various magnetic fields imposed by outside sources to see if the underlying effect is still there, etc. Edit: some more info here: https://en.wikipedia.org/wiki/Woodward_effect#Test_devices https://en.wikipedia.org/wiki/Woodward_effect#Test_devices In particular: "In 2004, Paul March of Lockheed Martin Space Operations, who started working in this research field as of 1998, presented successful replication of Woodward's previous experiments at STAIF." There are a few other less conclusive attempts at replication, but only one claimed negative result. But as you say, measuring forces this tiny is hard.
- jules 12y agoSo many pseudoscience articles today! We got one about solving NP complete problems in polynomial time with a new kind of "brain-like" computer, and now there's one about violating conservation of momentum. Next up: Peano arithmetic is inconsistent & telepathy proven to work based on quantum mechanics.
- api 12y agoWhat exactly makes this pseudoscience? Is it pseudoscientific to investigate unlikely or speculative possibilities? They have presented evidence and a proposed mechanism, have fully published the details of their work, and have invited others to attempt to replicate it or to show where they're wrong. Where's the "pseudo"? It's also important to note that in experimental physics it's more than enough to show an effect that can be replicated. Their currently proposed theoretical explanation could be wrong, but that wouldn't matter.
- jules 12y agoThey have an experimental setup that spits out some data. That data goes against the theory of general relativity. Extraordinary claims require extraordinary evidence. The article also sets off various other pseudoscience alarm bells, such as the fact that their paper is published in a philosophy journal, and the guy having a history degree instead of a physics degree. But that goes against the naive rebellious spirit of HN that dictates that anybody can overthrow fundamental physics with an experimental setup in his basement, so downvote away!
- mikeash 12y agoGoing against established theory has nothing to do with "pseudoscience". Pseudoscience is how you treat it. If you say, this is the next best thing, all my doubters are idiots, and invest now! Then that is pseudoscience. But if you just go, "hmm, that's funny" and keep investigating what's going on, that's just plain science. The article is very much written in the second form, at least as far as I can tell.
- dang 12y agoCan someone please suggest an accurate, neutral title?
- rudolf0 12y ago"The quest for a reactionless space drive"? That's the article's URL slug, though not its title.
- dang 12y agoThanks! Title changed from "Strange thrust: the unproven science that could propel our children into space".
- TeMPOraL 12y agoDang, I see you consistently active in many a thread, always telling what was the original title when changing it, and asking for suggestions when you're not sure. Thank you very much for that. It feels much better when the reason for title change is explained and open for discussion. I like how HN is improving itself recently.
- dang 12y agoThanks for saying so! It's good to hear.
- phaemon 12y agoOh...so it's not a way to get rid of the kids?
- rasz_pl 12y ago"Warp drive just ten years away says the scientist".
- joshuaheard 12y agoSo, a change in the movement (flux) inside a capacitor is the key? A "flux capacitor" you say?
- dnautics 12y agoA really amazing, honest, and straightforward account from the grad student in the lab. http://www.otherhand.org/home-page/physics/graduate-studies-in-physics-at-cal-state-university-fullerton/ http://www.otherhand.org/home-page/physics/graduate-studies-...
- ajuc 12y ago"Your access to this site has been limited" Http 503.
- cygx 12y agoSome quotes from the end of the article: As time progressed and the experimental apparatus more refined, the “effect” seemed to get smaller, and that’s a REAL bad sign. It was already well below what the theory predicted. That sets off alarm bells. After all this time, if something isn’t in hand to float around a table top, its should still at least be producing unequivocal results. I am aware of only one positive replication attempt, and even that experimenter (Paul March) had concerns over its validity. All other replication attempts have either been negative or ambiguous. My own experiments were ambiguous. It seems to make the effect happen, a lot of parameters for the test devices, some not clearly understood, need to be “just so”. The question remains, are the devices being dialed in to create a real effect, or do things need to be just so to cause merely a false positive?
- dnautics 12y agoit's (sadly) very refreshing honesty from a scientist. In grad school, I counseled a junior grad student on this sort of phenomenon, she didn't take my advice and learned a very hard lesson - spending 4 years of grad school chasing down ghosts. On the other hand, it wasn't a waste, she got a very good job in the pharma industry on the back of her commitment to sussing out errors, her honesty and introspection.
- deleted 12y ago[deleted]
- waterlesscloud 12y agoI want to go to physics grad school just so I can have a lab full of equipment like that, with a lot of it stuff I machined myself.
- pm90 12y agoJust join your local hackerspace instead, and you will still do all those cool things, and more! If you're in Austin: http://atxhs.org/wiki/Main_Page http://atxhs.org/wiki/Main_Page
- TeMPOraL 12y agoIt's late for me as I just finished my CS studies, but I realized recently that the university is nothing but a more formalized Hackerspace with much, much more expensive equipment. I'm thinking about re-enrolling, for biotech this time, to get access to the lab.
- jmount 12y agoJeeze, really HackerNews/BoingBoong news are not good science sources. This "reaction-less" drive is simple variation of the "Dean drive" (another "space thruster" that only works if it is on a kitchen floor so that it can do standard work and exploit the different scales of static and slipping friction). I thought this was at least going to be the "microwave thruster" that works in cheap partial vacuum (but not in actual deep vacuum). Not even new bad ideas.
- dang 12y agoIt sounds like you know something about this topic. I don't, and I'm sure that many other HN users don't either. Your comment would be better, I think, if you assumed that people here are curious to learn and shared your knowledge in a way that was easier to absorb. If bad ideas are circulating, offer better ideas and explain why they are better. That strategy may not work everywhere, but at least some of the time it does work here.
- deleted 12y ago[deleted]
- jmount 12y agoI guess I would say if you are truly curious about physics read about conservation of momentum, Noether's theorem, and things like that. You get really neat things like: if you assume general relativity is position invariant then you can prove it has conservation of momentum (i.e. you don't have to directly assume conservation of momentum!).
- scott_s 12y agoI think what Dan was trying to nudge you towards was sharing some of your knowledge with us, and starting some good discussion on those topics.
- deleted 12y ago[deleted]
- gus_massa 12y ago> The result is a drive that exerts an intermittent net force in one direction. [...] Nor does it violate the principle of conservation of energy, because the system requires power for its operation. Well, you actually can't do that. In special relativity when you change of reference frame, the momentum and energy mixes. If you break the momentum conservation in one reference frame, then you break the momentum conservation and the energy conservation in almost all the other reference frames. If you do the experiment on Earth and in that reference frame the energy is conserved, then the astronauts from the ISS will see that the energy is not conserved, if Elon go to to Mars he will see that the energy is not conserved, even the people on the other side of the Earth will see that the energy is not conserved. If you put two of these devices in opposite orientations in the opposite sides of a spinning carrousel (and assume that the angular velocity of the carrousel is small enough to ignore it in the calculations) you will see that each of the devices gain some energy and you can harvest it.
- arh68 12y agoI found the mention of Mach's Principle beyond intriguing. How have I not heard of this?! I'm quite glad to ponder it [1] You are standing in a field looking at the stars. Your arms are resting freely at your side, and you see that the distant stars are not moving. Now start spinning. The stars are whirling around you and your arms are pulled away from your body. Why should your arms be pulled away when the stars are whirling? Why should they be dangling freely when the stars don't move? ...There have been other attempts to formulate a theory which is more fully Machian, such as Brans–Dicke theory, but most physicists argue that none have been fully successful. At an exit poll of experts, held in Tubingen in 1993, when asked the question, 'Is general relativity perfectly Machian?', 3 respondents replied 'yes' and 22 replied 'no'. To the question, 'Is general relativity with appropriate boundary conditions of closure of some kind very Machian?' the result was 14 'yes' and 7 'no'. [1] https://en.wikipedia.org/wiki/Mach%27s_principle https://en.wikipedia.org/wiki/Mach%27s_principle
- sopooneo 12y agoSomeone who understands the notion here, please tell me: would this violate conservation of momentum or not?
- ars 12y agoIt does not change momentum or speed. But rather allows you to shift your location. You do not wind up with any net velocity, or momentum.
- sopooneo 12y agoIsn't it meant to help a spacecraft accelerate? And if that happens, doesn't that mean that its mass has accelerate? And thus its momentum has increased?
- ars 12y agoNo. It just makes it move, but in between machine cycles (or if you turn it off) the speed of the spacecraft is zero. It requires no energy or momentum to just change position. Except it's impossible to do in space, but this machine makes it possible (supposedly).
- sopooneo 12y agoVery helpful. Thank you. But then why were they trying to demonstrate efficacy by measuring torque, which I assume is just a proxy for force?
- ars 12y agoI don't know. It should only develop cyclical force (back and forth - but pushing against nothing). I'm not 100% sure this thing actually is real, I'm just going by the description in the wired magazine, plus reconciling it with the statement that it doesn't violate Newton's laws.
- deleted 12y ago[deleted]
- matt_kantor 12y agoThis article acts surprised about the possibility of changing an object's mass by varying its energy, but I thought that was common knowledge among relativists, as per [the classic "a compressed spring weighs more than a relaxed spring" meme][1]. [1]: https://news.ycombinator.com/item?id=4196182 https://news.ycombinator.com/item?id=4196182
- zvrba 12y agoUm. From what I remember of having learned about capacitors in a basic physics course a long time ago, the net charge of the capacitor is always the same. When voltage is applied to a capacitor, it generates an electric field between the plates, which causes charge separation. The charge is already there, its source is the dielectric between the capacitor plates. So charging the capacitor may make one plate slightly lighter, the other slightly heavier, but its overall mass is the same. Is it this mass change he's trying to use?
- mnw21cam 12y agoIt isn't the charge on the plates that alters the mass - it is the stored energy.
- brador 12y agoSecond picture, anyone know what brand those keyboards are?
- MaysonL 12y agoI found it really noteworthy that a science fiction enthusiast, writing about a "reactionless drive", would fail to mention the Dean Drive. http://en.wikipedia.org/wiki/Dean_drive http://en.wikipedia.org/wiki/Dean_drive