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The Fact and Fiction of the NASA EmDrive Paper Leak
- ComputerGuru 10y agoI know absolutely zero about rocket physics or quantum mechanics but isn't this a fairly easy and "cheap" thruster to prototype and test in actual space? Nothing beats real world results, and this doesn't seem that hard to test. It might even be faster and cheaper than what's already been done, no?
- huragok 10y agoNo one will pony-up the millions of dollars it will need to design, build, test and launch a satellite based on (possibly) unconfirmed science.
- ComputerGuru 10y agoYet they will gladly throw away ten times that amount investing in a silly app idea on the off-chance it will be the next facebook or snap chat...
- roywiggins 10y agoIn fairness, we know Facebook is physically possible. Not so reactionless drives. If a Facebook is unlikely, a reactionless drive is spectacularly so. If they are possible, the question of where all the aliens are becomes much more acute. If it's actually cheap to accelerate mass around the universe we ought to be crawling with visitors.
- dragonwriter 10y agoIf it's cheap to accelerate mass around the universe, spreading beyond one planet is easy, but provides less insulation against non-natural disasters, like species-ending war.
- arcticfox 10y agoCouldn't you theoretically take one of these way out from Earth, turn it 180, and wait for a massively powerful kinetic energy weapon to return? "Cheap to accelerate mass" just sounds like a crazy weapon
- headcanon 10y agoPerhaps we are 0.o
- imglorp 10y agoI don't think the claim is free energy. The claim is no propellant. So you might still need tons of energy to get a decent acceleration. If it's working, it's just not clear by what mechanism the energy is being converted to momentum.
- DuskStar 10y agoOr it might just be that reactionless drives can make nukes look like firecrackers, while presumably also being a lot harder to restrict access to. And thus would make a very good 'great filter' candidate.
- throbaway339 10y agoYou have left out the part about the vast distances we still need to cover. Accelerating mass could very well be cheap enough, but HOW fast we can accelerate to still matters. Perhaps they're on the other side of the galaxy, or in a different galaxy altogether and the EmDrive will only ever reach top speeds near that of a Ford Pinto.
- bertiewhykovich 10y agoI believe that if the EmDrive produces real force its top speeds are, in a vacuum, only limited by relativity and the amount of energy it can carry.
- grzm 10y agoThat's true of any propulsion system, isn't it?
- bertiewhykovich 10y agoyeah
- evgen 10y agoNo, most other systems run out of reaction mass first. With this and a good fission reactor you are halfway to everywhere.
- grzm 10y agoSo I don't get any points for E = mc² ? :) In all seriousness though, I was noting the parallel "limited by … the amount of energy it can carry" and "limited by the amount of mass it can carry" in the sense that, yeah, you're going to be limited by what you can take with you.
- hossbeast 10y agoNo, real propulsion systems also require propellent
- bertiewhykovich 10y agoThere are still incomprehensible numbers of stars, and awe-inspiring distances between them. Even if acceleration is cheap, there are only a few thousand stars that would have been reached by any human-produced signal yet -- and the chances of one of those containing intelligent life, the chances of those containing intelligent life that happens to detect our signal, the chances of those containing intelligent life that detects our signal and also has a space program, the chances of those containing intelligent life that detects our signal, has a space program, and decides to mount a voyage to Earth, the chances of those containing intelligent life that detects our signal, has a space program, decides to mount a voyage to Earth, and would have been able to get anywhere close by now...
- imglorp 10y agoedit - bad math deleted. thank Tossrock for the correction.
- Tossrock 10y agoNo it wouldn't. At a constant 1g acceleration, you're in the .9c range in less than a year. So to get to Alpha Centauri would take < 6 years, accounting for acceleration and deceleration. And because you're constantly accelerating, and accelerating to relativistic velocities, you would experience dramatic time dilation as well, meaning the amount of time passed for the ship would be even less.
- IanCal 10y agoPeople are at least claiming to be sending them up: http://www.popularmechanics.com/science/energy/a22678/em-drive-cannae-cubesat-reactionless/ http://www.popularmechanics.com/science/energy/a22678/em-dri...
- nsxwolf 10y agoIf I won the Powerball Lottery today I would do it.
- semi-extrinsic 10y agoAt the extremely low level of thrust we're talking about here, I suspect it would be a lot harder to be certain about removing all sources of error if they did this in space. See also Pioneer Anomaly.
- deleted 10y ago[deleted]
- amiga-workbench 10y agoThe article mentions that the test was ran at only 80W of power, surely that could be scaled up to a few thousand watts and a more appreciable result could be seen even with another ground based test?
- TTPrograms 10y agoI think at those power levels you start vaporizing significant amounts of metal - the walls were heating up a fair bit at current power levels. You might be able to plate to increase reflectivity at GHz (gold, maybe something else is better up there, could do multi-layer metamaterial). But if you're vaporizing metal on the walls that's going to act like a propellant, so it will be very hard to distinguish what's causing the thrust (since thrust via propellant can be much stronger per Watt than the proposed propellant-less technique).
- joezydeco 10y agoWord on the street is that one is already in space on the USAF X-37B. And China is flying one too. http://www.ibtimes.co.uk/space-race-revealed-us-china-test-futuristic-emdrive-tiangong-2-mysterious-x-37b-plane-1590289 http://www.ibtimes.co.uk/space-race-revealed-us-china-test-f...
- andygates 10y agoThat's a low-quality source in a hype-loop with a True Believer from Reddit, so take that 'word' with a bushel of salt.
- andygates 10y agoIt can be easily measured in the lab. When the effect keeps diminishing with better measurement, it's strongly suggestive of no effect. This paper seems to have some areas where the next round of tests could be obviously improved. Time for me to break out the Tech Readiness Levels: this proposal is TRL 0 (1 if you're a True Believer). Observe the TRL required by NASA for a flying prototype. https://en.wikipedia.org/wiki/Technology_readiness_level https://en.wikipedia.org/wiki/Technology_readiness_level
- Nokinside 10y agoNASA seems to be minimally involved. The group has been working five years in their own time in this small laboratory with shoestring budget. White has a day job in NASA and he and others are working with this project in their free time. To best of my knowledge - and correct me if I'm wrong - NASA only gave them $50,000 and a room in Johnson Space Center 2011. They don't seem to be involved in any other way but "NASA Eagleworks Laboratories" makes it sound like official NASA organization. Their results are consistently close to the detection threshold of their sensors. They are always flirting with the measurement error.
- 0xffff2 10y agoI think your view reflects a misunderstanding of how NASA works. The vast majority of the research done at NASA is done by small teams working on shoestring budgets. Where do you get the idea that they did all of this research on their own time?
- Nokinside 10y agoThe team he claims to lead seems to be nonexistent in NASA organization. Biography: "Advanced Propulsion Team Lead for the NASA Engineering Directorate at JSC"
- lobster_johnson 10y agoConsidering that wording is from an official NASA biography, it's probably not non-existent: He currently serves as the Advanced Propulsion Theme Lead for the NASA Engineering Directorate and is the JSC representative to the Nuclear Systems Working Group. In his role, White is serving to help the Agency incorporate high TRL advanced power and propulsion technologies into near and mid-term human exploration architectures. He also is pursuing theoretical and laboratory research on developing lower TRL advanced propulsion and power technologies in the advanced propulsion physics laboratory known as Eagleworks that is located at the Johnson Space Center. https://www.nasa.gov/ames/ocs/2014-summer-series/harold-white https://www.nasa.gov/ames/ocs/2014-summer-series/harold-whit...
- deleted 10y ago[deleted]
- jchung 10y agoSo far I've failed to grok the many arguments for and against this drive's "impossibility". I'd love to find an ELI5 for it. I think at this point, I'm resigned to waiting for an emdrive cubesat to just prove it once and for all: http://www.popularmechanics.com/science/energy/a22678/em-drive-cannae-cubesat-reactionless/ http://www.popularmechanics.com/science/energy/a22678/em-dri...
- cjensen 10y agoAgainst is pretty simple Argument #1: it violates Newton's Third Law of Motion. Argument #2: every time they improve the test apparatus, the measured force declines and is "coincidentally" close to the measurement limits of the apparatus. Argument #3: It was originally designed based on a misunderstanding certain principles of Physics. Now they are trying to find a new explanation for why it works. What are the odds that you misunderstand physics, design something based on that misunderstanding, and that it then works in a barely-detectable way due to "unknown mechanism"?
- danielmorozoff 10y agoAren't new physics drawn from violations of old laws?
- mikeash 10y agoYes, which is why violating a known law isn't automatically disqualifying. But it is highly suggestive, and requires extremely good evidence to surmount. So far, such evidence has not been forthcoming, so this remains a good reason to doubt. Every so often, something comes along that overturns an established law, like the photoelectric effect or the Michelson–Morley experiment. But the vast majority of the time, the laws remain intact and it's the claim which is somehow flawed. (See the Pioneer anomaly for a recent example where new physics was long considered as a potential explanation, but it ended up being a completely mundane effect.)
- danielmorozoff 10y ago
- maverick_iceman 10y agoSad to see this nonsense pseudoscience constantly making HN's front page. Whenever it appears I debunk it using the same post[1] (in short, conservation of momentum cannot be violated) but it keeps coming back. Looks like even highly intelligent people like HNers are easily fooled by pseudoscience. [1] http://www.preposterousuniverse.com/blog/2015/05/26/warp-drives-and-scientific-reasoning/ http://www.preposterousuniverse.com/blog/2015/05/26/warp-dri...
- outworlder 10y ago> in short, conservation of momentum cannot be violated Why?
- piannucci 10y agoSpeaking somewhat loosely, the relationship between the local state of spacetime and its energy, the Lagrangian density, does not seem to depend on where you are or when you are. Emmy Noether gave us a straightforward proof that each such "differentiable symmetry" (in this case, translation invariance) implies that the state of spacetime maintains a corresponding "conserved current" (in this case, momentum and energy density).
- dbingham 10y agoThe moment we get overconfident in our understanding of the universe is the moment that understanding stops advancing.
- FeepingCreature 10y agoNo law restrains nature but nature's own. Do not tell nature what it can and cannot do. (Evidence, of course, weighs very heavily against the EmDrive. But this sort of "it can't be doing that because that's against natural law" is just as unscientific.)
- pklausler 10y agoThanks. I wish more people would help filter out the bad science (anything >= 1 nanoChopra).
- danielmorozoff 10y agoActual paper from NASA recently on EmDrive (from Eagle Works) https://news.ycombinator.com/item?id=12906254 https://news.ycombinator.com/item?id=12906254 Actual paper: https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU/view https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU...
- david-given 10y agoJames Woodward's one of the old names in propellentless thrust --- he's been working on Mach Effect based systems for a long time now. His approach is my favourite of all the anomolous science thruster systems, because (a) he actually has a testable theoretical model to back up his experiments, and (b) he doesn't talk about it much; in the fairly rare interviews, he tends to be focused more on coming up with ways to disprove his experiments, rather than self-aggrandisement; which to my mind is the main mark of a serious scientist. By which I mean to say, in the nicest possible way, that he's not an impartial observer when talking about this thing, so it's worth being careful about what he says.
- deleted 10y ago[deleted]
- jwtadvice 10y agoThere's been breakthroughs in a fully quantified theory of how electromagnetics can be used to create propulsion reliably and at (still incredibly small but) orders of magnitude larger than prior designs provided by the aeronautics research team from the Northwestern Polytechnical University in Xi'an. The research team published their breakthroughs in 2008, and excitingly, they've been highly reproducible. Unfortunately, the paper appears to be behind a paywall: http://en.cnki.com.cn/Article_en/CJFDTOTAL-YHXB200805027.htm http://en.cnki.com.cn/Article_en/CJFDTOTAL-YHXB200805027.htm Does anyone on HN have the background necessary to explain the mechanics of EM propulsion to laymen?
- binarycoffee 10y agoAs an electric propulsion engineer used to measure thrust in the uN range, what disturbs me much more than thrust levels close to the sensitivity threshold is the fact that thrust is only detected some 10-20s after the RF is turned on (figs 9,8,13). I am rather confident that there is no physical time scale in the RF generation process that would account for a 10-20s ramp, and this would contradict their own report of the fast RF power stabilization. It definitely looks like thermal drift; in fact, thermal drift is _always_ the first thing to suspect when you get strange measurements with a low thrust balance. It appears as well that the authors have conveniently prepared an answer for this objection with fig.5 which attempts to mislead the reader by suggesting that the very slow evolution of the balance displacement is to be expected as an artifact of the combined effect of thermal drift and RF pulse onset. But conveniently, the time units are arbitrary so that hopefully nobody will notice that RF onset was assumed in that figure to have exactly the same characteristic time as the thermal drift... When all measurements actually show that RF power stabilizes much faster.
- dpark 10y ago> which attempts to mislead the reader Even if you're right, assuming malice seems premature and pessimistic.
- jwatte 10y agoIf they feed electricity into the microwave horn, how strong is the induced magnetic field around the wires? Would that push against anything? How is that compensated for in measurements?