Space, time, and microwave ovens
April 30, 2015 1:49 PM   Subscribe

Previously on MetaFilter, we discussed a strange new form of propulsion that NASA was investigating. There are variants to the EM Drive, but the basic principle is the same: put lots of microwaves into the right shaped chamber, and thrust appears. Electricity to motion in free space? Much skepticism. But nearly a year and much more testing later - the story is getting weirder.
posted by Devonian (162 comments total) 38 users marked this as a favorite
 
That puts us ahead of schedule. Let's just watch out for unintended consequences.
posted by Halloween Jack at 1:59 PM on April 30, 2015 [6 favorites]


Brb running this pic of the engine through reverse image lookup to make sure it wasn't taken in the 1890s Old West.
posted by Potomac Avenue at 2:01 PM on April 30, 2015 [3 favorites]


The only practical use for this will turn out to be getting a piping-hot Pizza Pocket five minutes before you got one out the freezer.
posted by scruss at 2:04 PM on April 30, 2015 [10 favorites]


Potomac Avenue: That's obviously the Orb from Brisco County JR.
posted by I-baLL at 2:09 PM on April 30, 2015 [15 favorites]


I'm going to call this right now as misconfigured monitoring instruments.
posted by kokaku at 2:09 PM on April 30, 2015 [14 favorites]


Brb running this pic of the engine through reverse image lookup to make sure it wasn't taken in the 1890s Old West.

NASA goes steampunk! This will get the hipsters and millenials "down with it!" Space: it's on fleek!
posted by prize bull octorok at 2:10 PM on April 30, 2015 [8 favorites]


Misconfigured instruments, boo. This is a warp drive and you know it.
posted by humanfont at 2:15 PM on April 30, 2015 [4 favorites]


Not going to get my hopes up YET.
But really want this to be real. Please don't let this be a bad joke.
posted by daq at 2:20 PM on April 30, 2015 [2 favorites]


Greg, stop telling me to punch it.
posted by the uncomplicated soups of my childhood at 2:22 PM on April 30, 2015


Dean Drive 2.0.
posted by The Tensor at 2:23 PM on April 30, 2015 [3 favorites]


"I'm going to call this right now as misconfigured monitoring instruments."

So when it wasn't done in a vacuum and showed results the criticism was "that thrust measurements were due to thermal convection." So now it's been done in a vacuum the criticism is "misconfigured monitoring instruments."?
posted by I-baLL at 2:24 PM on April 30, 2015 [2 favorites]


There's a reasonable-ish summary of the various 'news' items on this on /r/Futurology though it's a bit too credulous for my liking. Also note that "nasaspaceflight.com" is a respected space news outlet but is not affiliated with NASA the government agency.

I believe that Eagleworks is an official NASA project, based on this NASA doc but I don't know enough about the inner workings to be sure of that. The one original source I read seemed to omit a lot of details that I thought would have been useful to mention but I'm a layman so maybe there's things that can be taken as read by those in the industry.

This does seem to be moving past "bullshit" into "huh, that's weird" territory, which, as we know, is the most exciting phrase a scientist can utter.
posted by Skorgu at 2:26 PM on April 30, 2015 [27 favorites]


So when it wasn't done in a vacuum and showed results the criticism was "that thrust measurements were due to thermal convection." So now it's been done in a vacuum the criticism is "misconfigured monitoring instruments."?

Next it'll be "radiation from experiments alerts the Vulcans who decide we're not ready for this technology yet." We're never getting to Alpha Centauri.
posted by griphus at 2:26 PM on April 30, 2015 [3 favorites]


For the last three years, Dr. White’s team has been conducting experiments to find out whether it is possible to measure, with an interferometer, a distortion of spacetime produced by time-varying electromagnetic fields.

The ultimate goal is to find out whether it is possible for a spacecraft traveling at conventional speeds to achieve effective superluminal speed by contracting space in front of it and expanding space behind it.


I love how we're trying to go faster than the speed of light with a technology we don't understand. Probably we're going to end up in an alternate dimension or send the southern hemisphere back to the Devonian.
posted by congen at 2:28 PM on April 30, 2015 [10 favorites]


I can vouch for this, actually. I once left a spoon in the microwave, and the energy produced with the vacuum and by me cleaning up after the propulsion of my dinner onto the kitchen ceiling was far in excess of what initiated the experiment.
posted by It's Raining Florence Henderson at 2:29 PM on April 30, 2015 [14 favorites]


I love how we're trying to go faster than the speed of light with a technology we don't understand.

Where we're going, we don't need eyes to see.
posted by Drastic at 2:31 PM on April 30, 2015 [25 favorites]


I want to believe. ™
posted by Splunge at 2:31 PM on April 30, 2015 [8 favorites]


That puts us ahead of schedule. Let's just watch out for unintended consequences.

Funny that we should link to Memory Alpha with the first comment, as the first picture in the article is an early USS Enterprise.
posted by ricochet biscuit at 2:31 PM on April 30, 2015


In my previous comment I described how a direct electricity->thrust engine could be trivially adapted to produce infinite energy. If this device actually works, then boosting the ISS, and indeed space flight in general, is not the most interesting application.

So what I'm saying is that this is still bullshit.
posted by ryanrs at 2:32 PM on April 30, 2015 [9 favorites]


Where we're going, we don't need eyes to see.

How Can Mirrors Be Real If Our Eyes Aren't Real?
posted by Talez at 2:33 PM on April 30, 2015 [3 favorites]


...is not the most interesting application.

Well, it will be until the Kzin wars.
posted by griphus at 2:33 PM on April 30, 2015 [8 favorites]


Next it'll be "radiation from experiments alerts the Vulcans who decide we're not ready for this technology yet." We're never getting to Alpha Centauri.

It would be pretty hilarious if Star Trek were actually quite accurate about alien species, and if the Vulcans and Klingons all had their own versions of it where humans were portrayed very differently.
posted by clockzero at 2:35 PM on April 30, 2015 [1 favorite]


Brb running this pic of the engine through reverse image lookup to make sure it wasn't taken in the 1890s Old West.

I say we embrace this aesthetic and just go full steampunk for our next shuttle. Giant wooden steering wheel, mechanical gauges, gears and pistons galore. Also, the captain is required to wear a bespoke vest and carry a pocket watch.
posted by dephlogisticated at 2:39 PM on April 30, 2015 [4 favorites]


So what I'm saying is that this is still bullshit.

I agree that it's almost certainly some kind of measurement problem. That said, what level of result would it take for you to change your mind? Actually producing thrust we can see with the naked eye in a macro-scale object?
posted by Justinian at 2:41 PM on April 30, 2015 [1 favorite]


"So what I'm saying is that this is still bullshit."

Wait, if I'm reading your other comment correctly, your assumption is that this device produces unlimited acceleration?
posted by I-baLL at 2:43 PM on April 30, 2015


what level of result would it take for you to change your mind?

Building the perpetual motion machine and demonstrate sustained kilowatt-level surplus power for a few days. That would go a long way towards allaying my suspicions.

Because that is what this device is proposed to be: a perpetual motion machine.
posted by ryanrs at 2:45 PM on April 30, 2015 [1 favorite]


Stop treading on our dreams.
posted by Justinian at 2:46 PM on April 30, 2015


Once again (and as ryanrs has pointed out): a "reaction-less drive" would be functionally equivalent to a perpetual motion machine. Keeping the ISS in orbit would be trivial: we could use it to build a massive dyson's sphere around our entire Galaxy and accelerate it to .999... the speed of light for some x-treme space travel.

The problem with these "discoveries" -- always, always -- is not that people poo-poo them, but that their supporters fail to recognize the actual implications of truly breaking the laws of physics. It's not that their imaginations are too big .... they're actually too small.

Either "NASA Eagleworks" has misinterpreted their results, or we are on the cusp of the singularitarian revolution and the post-human era. Those are basically your options.
posted by Avenger at 2:47 PM on April 30, 2015 [20 favorites]


your assumption is that this device produces unlimited acceleration

Well, yeah? Electricity to thrust without reaction mass = constant acceleration with constant input power.

Has there been some strong limitations discovered that preclude unlimited acceleration? (And I'm talking unlimited in people-scale terms, not relativistic speeds, etc).
posted by ryanrs at 2:47 PM on April 30, 2015


So what I'm saying is that this is still bullshit.

Well, maybe there's a preferred frame of reference and it can only accelerate so fast relative to that.
posted by GuyZero at 2:48 PM on April 30, 2015 [1 favorite]


I'm ready for the rapture of the nerds if you guys are.
posted by Justinian at 2:48 PM on April 30, 2015 [4 favorites]


Really, anything whose isolated, free-standing effect is measured in N/W is suspect.
posted by ryanrs at 2:51 PM on April 30, 2015


Uh, can't we already turn electricity into motion without reaction mass? A simple DC motor hooked up to a flywheel and an alternator does pretty much what your scenario proposes, and yet somehow we haven't been violating the first law of thermodynamics all this time.
posted by figurant at 2:53 PM on April 30, 2015


If the singularity ends up being powered by a fancy space drive rather than AI or 3D-printers, then I say suck on that, technolibertarian sci-fi, bring back '50s rocket opera!
posted by Apocryphon at 2:53 PM on April 30, 2015 [7 favorites]


hold my beer and DUPLICATE MY RESULTS WOOOOO HOOOOOO *meager acceleration ensues*
posted by gorestainedrunes at 2:55 PM on April 30, 2015 [10 favorites]


Figurant, that's not isolated. The motor armature exerts force against the stator, and increasing power is needed to maintain constant acceleration as speed increases (because of back emf).
posted by ryanrs at 2:56 PM on April 30, 2015 [5 favorites]


Eh, just use Hyperedit for an endless supply of fuel.
posted by Brandon Blatcher at 2:57 PM on April 30, 2015 [2 favorites]


No solid theory behind this as of yet, and so far none of the testing equipment has been ruled out. If it works as they think it might, then what theories we have about the quantum field will need to be re-worked. This is not being tested with real funding behind it, which is part of the problem - start throwing huge sums at it and you'll find out if it works or not.

A good summery and etc.

Once they test everything in a very hard vacuum multiple times and THEN put one in orbit to test, we might have something - until then, we'll see.

Oh, and energy density is a problem: you'll need a nuclear pile and all of that assorted shielding and piping to supply the energy for it, and that's only if it scales up (the current belief is that is might not).
posted by Old'n'Busted at 2:58 PM on April 30, 2015 [2 favorites]


it's in no way a "perpetual motion machine." It's still requires input energy. It doesn't produce more energy than it takes in.

And I'll bet, if this turns out to be true, there's some kind of hidden "reaction mass" involved here. I mean, beyond the photons themselves which can "push" matter on a small enough scale.
posted by ghostiger at 3:00 PM on April 30, 2015 [3 favorites]


Why would you need a nuclear pile? Just use a second drive as a generator.
posted by Pyry at 3:00 PM on April 30, 2015 [4 favorites]


Well, as far as I'm aware it's not thought to be reactionless nor to break conservation of momentum. There's also the factor that as it gets faster, Doppler shift reduces its efficiency (dramatically, since it's a high-Q system), and I haven't seen any discussion of how far you can fix that by shifting the input frequency. Neither Shawmer (who came up with the idea in the 60s while working on satellite systems) nor White think this breaks any of the laws of physics, although they have different ideas why it might work. There is a theoretical framework, and a computer model, and they match up with observations. And there have been lots of measurements in lots of configurations, and everyone - everyone - has been looking for instrumentation errors.

As Shawmer says, when you turn this thing on you can feel it press against your hand. This isn't a edge-of-detection blip.

For lots of reasons, I'm beginning to thaw on this one. There just seems to have been so much work on it by so many people over so long, that systematic or mensuration errors start to become less plausible than 'yeah, this may be happening'.

But we shall see. This is not a complex thing to make. People won't stop playing with it unless the flaw is found.
posted by Devonian at 3:00 PM on April 30, 2015 [11 favorites]


Uh, can't we already turn electricity into motion without reaction mass? A simple DC motor hooked up to a flywheel and an alternator does pretty much what your scenario proposes, and yet somehow we haven't been violating the first law of thermodynamics all this time.

Yes, but without something to push against, it can't travel. This can.
posted by kafziel at 3:01 PM on April 30, 2015 [1 favorite]


Brb running this pic of the engine through reverse image lookup to make sure it wasn't taken in the 1890s Old West.
It looks like you use it to make moonshine (no space pun intended).
posted by pibeandres at 3:02 PM on April 30, 2015


> … or send the southern hemisphere back to the Devonian.

I'm not sure what the OP would do with a whole hemisphere.
posted by scruss at 3:04 PM on April 30, 2015 [3 favorites]


How much does this prototype mass? Put it together with a .5kW RTG -- wikipedia says there's one massing 13.6kg in the Pioneer 10/11 spacecraft. If the total assembly masses twice that, 25kg, and the output is a power-proportional one of 150 millinewtons, it'll be trundling along at about 190km/s after its first year. That would convince me. Even if the whole thing is 250kg, it'll be going 19km/s after the first year, and I'll still be convinced. I didn't do the arithmetic, but it looks like it would take just a few years for this (hypothetical 250kg) thing to overtake all other probes (pioneer/voyager) in distance from the sun, since it would be going 2x as fast as them after 2 years and 4x as fast after 4 years. That would convince me.
posted by jepler at 3:04 PM on April 30, 2015 [3 favorites]


it's in no way a "perpetual motion machine."

But it can be used to construct a perpetual motion machine. Here's how.
posted by ryanrs at 3:06 PM on April 30, 2015 [2 favorites]


I'd like to announce my new Kickstarter project for a personal space fighter based on this drive. We'll change the world forever if we meet our funding goal of 300k. Who's in?
posted by cosmic.osmo at 3:15 PM on April 30, 2015


4 Reasons Why the EM Drive is Probably Bullshit

The most profound is number 4. Note: you can't propel your '78 Corvette through space by just pressing hard on the dash. That's what the EM drive claims to do.

I feel like this may turn out to be a case of extended "Engineers Disease" -- the intellectual failing that causes otherwise brilliant Engineers to assume competence in areas far beyond their understanding -- among the Eagleworks people, especially since they went ahead and made up non-existent quantum forces to try and explain things.
posted by Avenger at 3:15 PM on April 30, 2015 [1 favorite]


I'm having flashbacks to 1989, to the same kind of tone, articles and point/counterpoint stuff on Web 0.1 (ie, Usenet) about the Pons and Fleischmann cold fusion claims. People want to believe - Mulder proved that.
posted by meehawl at 3:16 PM on April 30, 2015 [7 favorites]


Note that Avenger's link is from before the latest results.
posted by Justinian at 3:18 PM on April 30, 2015 [3 favorites]


I'm not knowledgeable so please bear with me.

Why are they only focusing on space travel with this? Could this not be used to propel a closed-circuit constant-speed delivery train over a wide route (offloading and loading by matching speed)? Or is the thrust so small that it would be ruined by atmospheric friction?

Or is the microwave chamber open and therefore an environmental risk?
posted by swimming naked when the tide goes out at 3:19 PM on April 30, 2015


Note that Avenger's link is from before the latest results.
posted by Justinian at 3:18 PM on April 30 [+] [!]


Note that it doesn't matter, because conservation of momentum is still a law.
posted by Avenger at 3:19 PM on April 30, 2015 [2 favorites]


you can't propel your '78 Corvette through space by just pressing hard on the dash. That's what the EM drive claims to do.

You also can't noticeably slow down time by running really fast. Does that mean relativity is bunk?
posted by ymgve at 3:20 PM on April 30, 2015 [3 favorites]


Also note that the EM-drive can't use more power the faster it goes because that would violate relativity (i.e.: you could measure its power consumption to determine its velocity in the 'preferred' reference frame).
posted by Pyry at 3:21 PM on April 30, 2015


Note that it doesn't matter, because conservation of momentum is still a law

Sure, but that's only 1 of the objections in your link. Some of the others were somewhat addressed by the new results.

I think the problem may be that you said that #4 was the most important objection. But I think you meant #1 (conservation of momentum).
posted by Justinian at 3:23 PM on April 30, 2015


If technical limitations stood in the way of perpetual motion with this you could still slap em drives on solar power satellites that wirelessly transmit energy to wherever you need it, and park them closer to the sun. And as a bonus, other em drive vehicles could go wherever those satellites transmitted power, and it would be trivial for the satellites to maneuver to direct it wherever it needs to go... so basically you'd have a free energy utopia with interplanetary highways of energy and em drive robots soaking up power generated half a solar system away to mine the asteroids and build our future in massive space factories AND you'd have a horrifying dystopia where an unbelievably powerful cloud of death ray satellites hung above our heads! Fun times!
posted by jason_steakums at 3:25 PM on April 30, 2015 [8 favorites]


Two questions:

Chemical rockets don't know how fast their going either, so they can't spend more energy to accelerate when they're already moving. Why doesn't this same reasoning apply to them?

Solar sails work, because photons have mass and momentum. Doesn't that mean sticking a flashlight in your butt will make you go accelerate forwards without spending any mass to do so? Why is this different from that?
posted by aubilenon at 3:29 PM on April 30, 2015 [2 favorites]


If technical limitations stood in the way of perpetual motion with this you could still slap em drives on solar power satellites that wirelessly transmit energy to wherever you need it, and park them closer to the sun. And as a bonus, other em drive vehicles could go wherever those satellites transmitted power, and it would be trivial for the satellites to maneuver to direct it wherever it needs to go... so basically you'd have a free energy utopia with interplanetary highways of energy and em drive robots soaking up power generated half a solar system away to mine the asteroids and build our future in massive space factories AND you'd have a horrifying dystopia where an unbelievably powerful cloud of death ray satellites hung above our heads! Fun times!

Isn't the sun already wirelessly transmitting energy to wherever you need it?
posted by dng at 3:30 PM on April 30, 2015 [2 favorites]


Damn. I just read that NASA page, and here it is linked on Metafilter! Got to go right now, but this is definitely an FPP to come back to.
posted by Kevin Street at 3:31 PM on April 30, 2015


you can't propel your '78 Corvette through space by just pressing hard on the dash. That's what the EM drive claims to do.

You also can't noticeably slow down time by running really fast. Does that mean relativity is bunk?
posted by ymgve at 3:20 PM on April 30 [+] [!]


Of course not, but relativity doesn't violate the known laws of physics. Actually, it bolsters them: the lack of preferred reference frames demands a universal conservation of momentum. Einstein updated Newton. He didn't cancel or abolish Newton.

Eventually we'll have a theory of physics which reveals that our understanding of general and special relativity were only partially correct, or only correct under certain conditions.

What we won't have is somebody inventing a God-Drive in their garage which disproves the last 500 years of scientific research in a single flip of it's switch.
posted by Avenger at 3:31 PM on April 30, 2015 [5 favorites]


Chemical rockets don't know how fast their going either, so they can't spend more energy to accelerate when they're already moving. Why doesn't this same reasoning apply to them?

Because they had to accelerate their propellant to their current speed before they could burn it and poop the byproducts out their nozzle. This means that the longer they want to operate, the more mass they have to start out with, and therefore the more they need to burn to accelerate that larger starting mass, etc. Basically this is the bane of rocket scientists and why a reactionless drive would be so cool. See Tsiolkovsky rocket equation.
posted by ryanrs at 3:36 PM on April 30, 2015 [4 favorites]


Doesn't that mean sticking a flashlight in your butt will make you go accelerate forwards without spending any mass to do so?

of course not - you have to put the hamster in first
posted by pyramid termite at 3:38 PM on April 30, 2015 [10 favorites]


I agree with Avenger but I secretly hope this drive actually works just so we can point to his comments mockingly in future history books.
posted by Justinian at 3:38 PM on April 30, 2015 [5 favorites]


btw, everyone be sure to favorite my comments so you can mock me later
posted by ryanrs at 3:40 PM on April 30, 2015 [19 favorites]


Justinian, if it works, there won't be any history books in the future. We'll just be able to re-create the past in new universes from our limitless supply of mass and energy and mock my comments from our interdimensional living rooms.
posted by Avenger at 3:41 PM on April 30, 2015 [8 favorites]


Of course not, but relativity doesn't violate the known laws of physics. Actually, it bolsters them: the lack of preferred reference frames demands a universal conservation of momentum. Einstein updated Newton. He didn't cancel or abolish Newton.


My point was more that you don't disprove high level physics effects by comparing them to what you can't do with your two hands in a car.
posted by ymgve at 3:41 PM on April 30, 2015 [2 favorites]


Chemical rockets don't know how fast their going either, so they can't spend more energy to accelerate when they're already moving. Why doesn't this same reasoning apply to them?

In addition to the chemical energy, kinetic energy is transferred from the propellant (reaction mass) to the payload.

As an example, imagine two 1kg boxes with a compressed spring between them that can be released (so one box is the 'payload' and the other is the 'reaction mass'). Let's say that the spring contains enough energy to accelerate both to 1m/s (one going left, the other right) when released if they start out stationary. In that case, the right box would end up with 1/2mv^2 = (1/2)(1)(1^2) = 1/2J of kinetic energy. But what if the boxes were moving at 10m/s before the spring was released? Then the right box would end up going 11m/s and gain (1/2)(1)(11^2)-(1/2)(1)(10^2) = 10.5 J of energy. But this isn't a violation of energy conservation because the left box slowed down from 10m/s to 9/ms.

Stationary starting situation:
[0m/s][0m/s] --> [-1m/s][1m/s]
KE: 0J --> (1/2)(1)(-1^2) + (1/2)(1)(1^2) = 1J
so the system gained +1J of energy (which came from the spring)

Moving at 10m/s to the right:
[10m/s][10m/s] --> [9m/s][11m/s]
KE: 100J --> (1/2)(81) + (1/2)(121) = 101J
so the *system* gained 1J (from the spring), the right box gained +10.5J and the left box lost 9.5J.
posted by Pyry at 3:44 PM on April 30, 2015 [2 favorites]


I thought the mechanics of it were obvious. The microwaves are used to make a cup of tea into which you place an atomic vector plotter hooked to the logic circuits of a Bambleweeny 57 Sub-Meson Brain.
posted by nathan_teske at 3:44 PM on April 30, 2015 [15 favorites]


Isn't the sun already wirelessly transmitting energy to wherever you need it?

Yeah but solar panels are large, and they have to be. They take up space and weight and provide a greater surface area for stuff like micrometeoroid impacts. You could move smaller and lighter and more durable things around on em drives if the solar power generation was done somewhere else and picked up by microwave receivers much smaller than solar panels, and you could concentrate the power gathered by many solar power satellites.
posted by jason_steakums at 3:45 PM on April 30, 2015 [1 favorite]


I'm not a physicist but sticking a flashlight in your ass will provide thrust, 300MW/N worth. The EM drive shenanigans are just (!) saying they can do this 2 orders of magnitude more efficiently (1 N/W is some guy's prediction).

It's still a gigantic claim (and worthy of as-yet unseen gigantic evidence).
posted by Skorgu at 3:50 PM on April 30, 2015 [1 favorite]



Yes, it's really easy to wave General Relativity at this and say this is not a reactionless drive.

Here, I'll do it too.

*waves GR*

This is not a reactionless drive.

That doesn't me *something* isn't going on here to produce force in an as-yet understood way that may in fact be useful.

A few things that are pushing this out of the crank zone.

1) This thing works in multiple places.

2) This thing works *as described*.

3) This thing works when someone other than the describer builds it, and works pretty much identically between copies.

So, now that you've all waved GR at it and declared it "not a reactionless drive" because "that's impossible" now start asking yourself this: What the heck is it? Because this is not the typical crankery, or at least, it is in no way behaving like a typical crank device. Note -- nobody has any idea *in theory* why it does what it does, so saying that theory says that it cannot do what is does is sort of dismissible outright, because it is doing something that theory is not, at first cut, explaining.

We'll just be able to re-create new universes from our limitless supply of mass and energy and mock my comments from our interdimensional living rooms.

That's assuming that it's a not-able-to-exist reactionless drive and not, say, a particularly efficient copper ion drive (because the microwaves are knocking copper off the back at very high velocities) which *can* exist, of course, and that thrust range would have a spectacular Isp which would make it a fantastically useful drive, but not one that in fact destroys the laws of physics. Of course, I would expect someone to have noticed this, but if the vacuum chambers were made of copper and well grounded, maybe they didn't. But that's just one possible way that this could produce a real thrust without being a magical GR violating device.

Or, in fact, though this is really really really really unlikely, GR is *wrong*. Would not be the first time that a beloved theory of the universe got shot down by a recent discovery. Now, I really doubt this, GR has been basically bulletproof ever since we could build things that could really test it. But it is not impossible --- you can't prove it will *never* be disproven.
posted by eriko at 3:51 PM on April 30, 2015 [29 favorites]


I'm not a physicist but sticking a flashlight in your ass will provide thrust, 300MW/N worth. The EM drive shenanigans are just (!) saying they can do this 2 orders of magnitude more efficiently (1 N/W is some guy's prediction).

It's still a gigantic claim (and worthy of as-yet unseen gigantic evidence).
posted by Skorgu at 3:50 PM on April 30 [+] [!]


They're saying that you can stick a flashlight in your butt, shine that flash light against the inside of your opaque underwear, and you will begin accelerating forever.
posted by Avenger at 3:52 PM on April 30, 2015 [5 favorites]


This does seem to be moving past "bullshit" into "huh, that's weird" territory, which, as we know, is the most exciting phrase a scientist can utter.

Also, early indications are that this drive will let you drive straight through Toll gates.

Immunology humour! I'm here all week!
posted by metaBugs at 3:53 PM on April 30, 2015


Doesn't the proposed mechanism involve expelling stuff? Which is not a reactionless drive but does avoid carrying fuel with you.
posted by squinty at 3:57 PM on April 30, 2015 [1 favorite]


Serious talk: my bet is on experimental error of some kind, or possibly, maybe, some curious new phenomenon that will be forever constrained to tiny forces at small speeds and never be useful for space flight.
posted by ryanrs at 3:57 PM on April 30, 2015 [5 favorites]


I agree with Avenger but I secretly hope this drive actually works just so we can point to his comments mockingly in future history books.

I've been mocking Avenger for these comments for centuries!

-It's Raining Time Travelling Hipsters
posted by It's Raining Florence Henderson at 3:59 PM on April 30, 2015 [5 favorites]


Pffft, I was time traveling before you were even a twinkle in you and your grandmother's eyes.
posted by ryanrs at 4:07 PM on April 30, 2015 [2 favorites]


Choke on that, causality!
posted by Steely-eyed Missile Man at 4:10 PM on April 30, 2015 [5 favorites]


fwiw, here's another article on the 'cannae drive' :P

IANAP, but in the theory section: "the paper describing the Eagleworks test of the Cannae drive referred to a possible interaction with a so-called 'quantum vacuum virtual plasma'. This reference has been criticized by mathematical physicists John Baez and Sean M. Carroll because in the standard description of vacuum fluctuations, virtual particles do not behave as a plasma."

oh and here's greg egan on past new scientist em drive coverage...

also btw!
-No Warp Drive for NASA: But Here's the Next-Best Thing
-NASA Announces New Partnerships with U.S. Industry for Key Deep-Space Capabilities
posted by kliuless at 4:20 PM on April 30, 2015


'm having flashbacks to 1989, to the same kind of tone, articles and point/counterpoint stuff on Web 0.1 (ie, Usenet) about the Pons and Fleischmann cold fusion claims. People want to believe - Mulder proved that.

I'm still skeptical, but the major difference between this and the cf debacle is that nobody other than pons and fleischmann were ever able to reproduce their results. Now we have two independent labs building this device themselves and claiming a result.

That's not nothing. It's probably not a warp drive, but it's not nothing.
posted by lumpenprole at 4:21 PM on April 30, 2015 [2 favorites]


you can't propel your '78 Corvette through space by just pressing hard on the dash.
That's pretty much Star Wars.
posted by condour75 at 4:26 PM on April 30, 2015 [3 favorites]


I must admit I don't understand the "thus perpetual motion" argument, because I don't see how linearly accelerating a flywheel gets past some magical point where it gains more kinetic energy than is put in.

I remember cold fusion, and the Dean Drive, and things you people wouldn't believe. I've debunked a few in print (and that's something I enjoy doing, once it seems that the perpetrators are not acting in good faith), and I've closed down a couple after the first press release (particularly proud of those!). But I always try to go back to square one and assume that this one - this time - could be something significant. Just as soon as we've got past the standard stuff that science does to make sure we're not fooling ourselves.

I can't speak for Shawyer's claims of having developed this thing over many years, but he claims quite a lot of interesting things (to the point that his government funded work was given to Boeing) and has videos of stuff happening (put emdrive into Youtube and have a poke around). But his stuff has been convincing enough for the Chinese to replicate - and they claim that they have - and for the Eagleworks people to get to the point where they're talking about building sets of experimental rigs and shipping them off to multiple independent labs. And as far as I can tell, they really are trying to do (on a shoestring) the standard stuff that science does in order to make sure, etc.

The question is: if you put microwaves into the right shaped chamber, do you get thrust? Saying "Im-POSSIBLE!" is understandable, but shouldn't really get in the way of putting the waves in the box. Lots of things are impossible - for really very good reasons - until they're done. I don't know whether Shawyer's theory of differential radiation pressure or White's theory of virtual particle interactions are 'correct' (one of the things about EM is that you can have quite different theories that arrive at the same result through very different assumptions), and anyway, that can wait until well after we're a lot further down the road.

I have absolutely no idea what the laser interferometry measurements mean, that seem to show superluminous possibilities.

But I do think that enough variations on the device have been tested - assuming reports are accurate - in enough configurations that there isn't a systematic instrumentation error. The numbers reported seem to tally too well for that.

Is there real new physics? Too early by far. I want it badly, so I don't trust my instincts. But if something is going to demonstrate something new, this is sorta how I expect it to happen.

(Oh, and really? The Cannae drive? As in "Cannae change the laws of physics, Captain"? Really?)
posted by Devonian at 4:31 PM on April 30, 2015 [18 favorites]


you can't propel your '78 Corvette through space by just pressing hard on the dash.

Truly the 3rd gen Corvette is the worst Corvette.
posted by ROU_Xenophobe at 4:33 PM on April 30, 2015 [1 favorite]


For what it's worth, those bogus 'quantum vacuum' explanations are the attempts to explain a stumbled-upon phenomenon, not the way they came up with it in the first place. The phenomenon isn't necessarily invalidated by a bad explanation.

My guess is it's a real but conventional physical phenomenon; some kind of quirk of the materials and the situation that is resulting in some unusual conventional thrust. Kind of like the lifter.

I will note, however, it's very slightly possible that someone could make a drive that appears reactionless without actually being so. You could push against something that's normally undetectable. For instance, if you found a way to interact with dark matter, you could push that for thrust and have something that looked awfully like a reactionless drive, but wouldn't violate conservation of momentum.
posted by Mitrovarr at 4:34 PM on April 30, 2015 [5 favorites]


Re Pons and Fleischman, there is also the little detail that if their own theories had been correct as to what their experiment did they should have been dead from the neutron flux, and they were alive enough to publish papers.
posted by localroger at 4:40 PM on April 30, 2015 [1 favorite]


So, now that you've all waved GR at it and declared it "not a reactionless drive" because "that's impossible" now start asking yourself this: What the heck is it? Because this is not the typical crankery, or at least, it is in no way behaving like a typical crank device. Note -- nobody has any idea *in theory* why it does what it does, so saying that theory says that it cannot do what is does is sort of dismissible outright, because it is doing something that theory is not, at first cut, explaining.

Perhaps we are on the verge of a Thomas Kuhn level paradigm shift.
posted by rankfreudlite at 4:41 PM on April 30, 2015


sticking a flashlight in your ass will provide thrust

I learn the damndest things on this website.
posted by emjaybee at 4:41 PM on April 30, 2015 [18 favorites]


For instance, if you found a way to interact with dark matter, you could push that for thrust and have something that looked awfully like a reactionless drive, but wouldn't violate conservation of momentum.

And yet it would have all the practical advantages (except for the conversion to perpetual motion thing) of an actual reactionless drive.
posted by localroger at 4:43 PM on April 30, 2015


I'm not a physicist but sticking a flashlight in your ass will provide thrust, 300MW/N worth.

Yawn. Get back to me when you've invented something that will create a USEFUL amount of thrust in my ass.
posted by Greg Nog at 4:43 PM on April 30, 2015 [16 favorites]


For instance, if you found a way to interact with dark matter, you could push that for thrust and have something that looked awfully like a reactionless drive, but wouldn't violate conservation of momentum.

I would agree with this, but only if you define "dark matter" in a way other than my current understanding of it.

I was just discussing this with my coworker, and we are both huge science dilettantes (don't actually work in science, but loves science in school, and still love reading about it *when it is written about well*). What it the quantum vacuum thing is sort of what is happening, but it's not quite that? We know a lot of things about physics, and quantum physics that we don't quite really understand (hence the whole LHC and searching for the Higgs Boson). What if the way this device is wired up, it actually is interacting with some part of the sub-quantum medium of space that we just never bothered to figure out how to interact with on a macro scale before? Or maybe things interact with it all the time, but we haven't had a way to measure the effect?

We don't know what we don't know, until someone stumbles upon something and decides to look more closely. I really hope that is the case.
posted by daq at 4:43 PM on April 30, 2015


I'm not a physicist but sticking a flashlight in your ass will provide thrust, 300MW/N worth.

Goatse will be the Yuri Gargarin of the analphotonic rocket age.
posted by stinkfoot at 4:45 PM on April 30, 2015 [8 favorites]


Also the perpetual motion thing is utterly wrong, even with the flywheel theory. Friction and the logarithmic increase in energy required to continue acceleration would almost always keep that threshold required to create more energy than you put into it out of reach, no matter how you build it. Not to mention the materials problem; if you are required to build your EM drive of particular materials in order for it to work, you are limited by how you can transfer that energy to your fly-wheel. If your acceleration was higher than the deformation threshold of the material, then the drive would smash itself to pieces well before you got anywhere near the speeds needed to get the flywheel into a high enough rpm to generate energy greater than being put into the system.

Yes, perpetual energy/motion machines are impossible.
Reactionless drives might not be.
posted by daq at 4:49 PM on April 30, 2015 [2 favorites]


Also, early indications are that this drive will let you drive straight through Toll gates.

No, that's the Donegan-Freburg drive.

Perhaps we are on the verge of a Thomas Kuhn level paradigm shift.

Perhaps we are on the verge of a Iain Banks level paradigm shift.
posted by snuffleupagus at 4:56 PM on April 30, 2015 [3 favorites]


Yawn. Get back to me when you've invented something that will create a USEFUL amount of thrust in my ass.

Call me.
posted by It's Raining Florence Henderson at 4:56 PM on April 30, 2015 [26 favorites]


Friction

Frictionless bearings are the easy part. We've already got those (magnetic bearings in a vacuum). And this so-called reactionless drive doesn't even need moving parts, so I'm sure we could make one sturdy enough to put on a turntable.
posted by ryanrs at 5:02 PM on April 30, 2015 [1 favorite]


Clearly we're not going to know for sure what thing is capable of until the Mythbusters build one of these out of a dozen magnetrons and some sheet copper.
posted by Mr.Encyclopedia at 5:03 PM on April 30, 2015 [2 favorites]


Frictionless bearings are the easy part. We've already got those (magnetic bearings in a vacuum). And this so-called reactionless drive doesn't even need moving parts, so I'm sure we could make one sturdy enough to put on a turntable.

https://www.youtube.com/watch?v=8KvRe4hJyjU
posted by jason_steakums at 5:07 PM on April 30, 2015 [2 favorites]


ryanrs,
I wasn't talking about the friction of the bearings. I was talking about the friction of the flywheel against your means of generating electricity. If you are going for a traditional DC current, you need your flywheel to transfer it's force to the dynamo of your generator, which creates friction. You would also have the Lorentz force of the magnets on your dynamo creating another EM field and another point of resistance, stealing kinetic energy from your flywheel at a constant rate.

Unless you know of another way to transfer the kinetic energy to something to produce electric power (which I will admit, I am unaware of any other mechanical method to generate electricity through kinetic transference).
posted by daq at 5:08 PM on April 30, 2015 [1 favorite]


also what jason_steakums just demonstrated. the flywheel would have to be able to withstand the rotational force trying to cause the material to fly apart.
posted by daq at 5:09 PM on April 30, 2015 [1 favorite]


Note: This is still a joke in progress:

IANAP, but in the theory section: "the paper describing the Eagleworks test of the Cannae drive referred to a possible interaction with a so-called 'quantum vacuum virtual plasma'. This reference has been criticized by mathematical physicists John Baez and Sean M. Carroll because in the standard description of vacuum fluctuations, virtual particles do not behave as a plasma."

Would not it be ironic if, when this technology is perfected, the commercials produced by the patent holders hired Joan Baez to record the songs?
posted by rankfreudlite at 5:10 PM on April 30, 2015


Daq, embed permanent magnets in the flywheel, and place stationary coils around it. Job done.

(I can't believe people are making up limitations on boring everyday engineering to account for the possibility of new, impossible physics.)
posted by ryanrs at 5:12 PM on April 30, 2015 [5 favorites]


Frictionless bearings are the easy part. We've already got those (magnetic bearings in a vacuum). And this so-called reactionless drive doesn't even need moving parts, so I'm sure we could make one sturdy enough to put on a turntable.

https://www.youtube.com/watch?v=ge6FiI3JCW8
posted by snuffleupagus at 5:13 PM on April 30, 2015 [4 favorites]


I mean, why are we even arguing about friction when we have infinite energy. Just bump the speed to 1.5x the break-even rpm and use the surplus to make up for your shitty ball bearings or whatever.
posted by ryanrs at 5:14 PM on April 30, 2015 [2 favorites]


physicsmatt
PHYSICSMATT
PHYSICSMATT

*looks expectantly into highly polished parabolic space mirror*
posted by snuffleupagus at 5:17 PM on April 30, 2015 [16 favorites]


This em drive hype was so bad he closed his account.
posted by ryanrs at 5:20 PM on April 30, 2015


As in "Cannae change the laws of physics, Captain"? Really?

If you only knew the truth about NASA's secret Carthaginian past...
posted by feloniousmonk at 5:26 PM on April 30, 2015 [3 favorites]


This "drive" is making a truly astonishing claim. It breaks a fundamental symmetry of the universe.

If you do an experiment in one place, then move it to another place with otherwise identical properties, do you expect to get the same result? If this drive works, this translational symmetry is no longer true.

A reactionless drive unquestionably violates the law of conservation of momentum. It's tempting to think that maybe conservation of momentum is (like Newton's laws) not universally valid, but that is not true.

Noether's theorem proves that conservation laws are consequences of symmetries. Conservation of momentum is a direct consequence of spatial symmetry (Lorentz invariance.)

This drive would prove that the universe is not spatially symmetric, which is far, far weirder than the perpetual motion that it also implies.
posted by Combat Wombat at 5:29 PM on April 30, 2015 [3 favorites]


Sorry, ryanrs, but I just don't think that your model of a perpetual motion machine would be a valid application of this kind of drive. All the other various forces that would be fighting against the mechanics would keep the system from ever reaching break-even. Even with frictionless bearings, and embedded permanent magnets, you have the rotational forces, the electromotive resistance, the the material fail points. It might be a nifty way to generate power, though, even at a loss (or ig you could get the EM drive to run entirely on solar power). That is still not perpetual motion, as you have an outside source of power providing the energy for thrust. That could work, but would still essentially be the same thing as existing power generation.

Actually, let's just do that. Hook these up in the desert and let the spin spin spin to generate terrestrial power. That would work.
posted by daq at 5:36 PM on April 30, 2015


As Shawmer says, when you turn this thing on you can feel it press against your hand.

G Harry Stine said exactly the same thing about the Dean Drive, although I don't recall whether he said he had felt it himself or whether a trusted witness had felt it. The real test for a reactionless drive is whether it will dangle at an angle; it's hard to finagle.
posted by Joe in Australia at 5:40 PM on April 30, 2015 [1 favorite]


Jesus, you are actually going to make me do the math to show that 1 N/W provides infinite energy with normal mechanical components I can buy off granger.com, aren't you? OK fine, but not right now, maybe tomorrow.
posted by ryanrs at 5:41 PM on April 30, 2015 [3 favorites]


(which is fair, btw. for all the shit-talking I've been doing, I ought to put up some math to back it up)
posted by ryanrs at 5:46 PM on April 30, 2015 [7 favorites]


which is fair, btw. for all the shit-talking I've been doing, I ought to put up some math to back it up

NERD FIGHT! Blackboards at dawn.
posted by nathan_teske at 5:50 PM on April 30, 2015 [7 favorites]


Electrical generators are typically 80-90% efficient at converting mechanical power into electrical power. Mechanical power is given by P = Fv, and the emdrive claims it could get 1.2N for 3kW, so to break even the emdrive has to be traveling faster than about 3000m/s. Making a literal flywheel where the edge was traveling faster than 3km/s would indeed be an engineering challenge.

However, 3km/s is child's play in terms of orbital velocities: for example, low earth orbit is about 7km/s. So put two rings of emdrive satellites in low earth orbit, each orbiting in the opposite direction, and have the satellites harvest energy off each other with linear generators (losing speed in the process, but using their em-drives to regain that speed to maintain their orbit).
posted by Pyry at 5:57 PM on April 30, 2015 [2 favorites]


However, 3km/s is child's play in terms of orbital velocities: for example, low earth orbit is about 7km/s. So put two rings of emdrive satellites in low earth orbit, each orbiting in the opposite direction, and have the satellites harvest energy off each other with linear generators (losing speed in the process, but using their em-drives to regain that speed to maintain their orbit).

Where were you and your fancy ideas when KSP came out of early access?
posted by RolandOfEld at 6:03 PM on April 30, 2015 [6 favorites]


Eye eye Captain. Is this drive just a fractally small version of a galaxy, not the Ford, I mean. Stepping out of the thread, but fascinating. They must have the alien driver at Guantanamo.
posted by Oyéah at 6:03 PM on April 30, 2015


The MeFi standard that new technologies must now meet: does it provide thrust in your ass?
posted by Salvor Hardin at 6:13 PM on April 30, 2015 [11 favorites]


If it is indeed proven to have real-world spaceflight applications, I will happily give the inventor of this device one testicle of their choosing.
posted by Falling_Saint at 6:21 PM on April 30, 2015 [1 favorite]


>>Isn't the sun already wirelessly transmitting energy to wherever you need it?

>Yeah but solar panels are large, and they have to be.


Still, this is a concept that doesn't appear to be widely appreciated.
posted by sneebler at 6:43 PM on April 30, 2015


My point was more that you don't disprove high level physics effects by comparing them to what you can't do with your two hands in a car.

Why not? You really can "slow down time by running really fast". It works as an analogy or as the literal truth. It may seem equally weird as the EM Drive to some people, but the theory of special relativity was as easily understood as it was hard to believe. It's not just because it didn't directly contradict known physics that it's a bad comparison. The theory made sense, and explained previously-existing widely-studied mysteries both mathematical and experimental, which had been around for decades.

The EM Drive premise is exactly that you can sit in a car and push on the dashboard to make it go, except you use microwaves instead of your hands. The theory as to why it should work contradicts the experimental results that are the only reason to look for such a theory in the first place, and appears to be as incomprehensible to physicists as it is to everyone else. There doesn't seem to be any great obstacle to building one, and the idea from reddit that Boeing, Lockheed Martin, or SpaceX haven't bothered trying largely because the inventor has a patent is just absurd. If they really haven't, it's because there's no real reason to think it would work. To non-physicists who aren't deeply offended by it, the violation of conservation of momentum is just one more nail in the coffin. Nothing wrong with a little digging through the festering contents by NASA, maybe they'll learn something. I wouldn't expect too much.
posted by sfenders at 6:54 PM on April 30, 2015 [2 favorites]


ryanrs, if your perpetual motion argument were correct, it would be equally true for an ion thruster. Both the EM drive (assuming it works) and ion thrusters convert electrical energy into thrust. The only difference is that one requires reaction mass. You could strap either to a flywheel; both will provide constant acceleration in a vacuum. And if you hooked a generator to that flywheel, you could convert the rotational kinetic energy of the flywheel back into electricity. And then, if you wanted to, you could feed that electricity back into the engine. But in both cases, you couldn't harvest more energy than what you put in. Assuming perfect conversion efficiency, the best you could do is break even. The issue of reaction mass is irrelevant to the thermodynamics of the system. Both engines are just converting energy from one form to another. The ion thruster is limited by energy and reaction mass. The EM drive is limited by energy. They are both limited by energy. Neither engine can produce energy from the aether.
posted by dephlogisticated at 7:03 PM on April 30, 2015 [2 favorites]


Metafilter: stick a flashlight in your butt, shine that flash light against the inside of your opaque underwear, and you will begin accelerating forever.
posted by CynicalKnight at 7:20 PM on April 30, 2015 [1 favorite]


Very interesting. Very doubtful that conservation laws are being broken but there isn't an obvious explanation yet.

ryanrs's proof isn't really a proof:

> If you bolt this magic device to the edge of a flywheel and apply constant power, then it should produce a constant force that accelerates the flywheel at a constant rate

There's a huge assumption in there: "constant force" - you don't know that's true. In fact, working backwards from the conservation of energy, you'd expect the force in your system to decrease as the square root of the velocity.

You can say, "The force has to be constant - how does the device know that it's moving" - to which I reply, "How does it work in the first place?"

(To which my answer is, "Probably it doesn't." But it's still very interesting.)
posted by lupus_yonderboy at 7:50 PM on April 30, 2015 [2 favorites]


Serious question:

I'm just a slob with username derived from a football team, but has an interaction with the earth's (or other) magnetic fields been ruled out as a possible source of the experimental effect? Is such an interaction even possible?
posted by eagles123 at 7:53 PM on April 30, 2015


> ryanrs, if your perpetual motion argument were correct, it would be equally true for an ion thruster.

This is not so.

The ion drive is actually sending mass backward, and in this case ryanrs's argument is accurate - you have to accelerate the reaction mass as your rocket accelerates before you finally send it out the back, so diminishing returns.

All "drives" that use Newton's Third Law - i.e. all "rockets" - behave similarly. The thing about this supposed drive is that it doesn't - it seems to get thrust without reaction mass. So if it could keep generating a constant thrust, then he's right that it would be a free energy generator. This only proves that it can't generate a constant thrust, however...
posted by lupus_yonderboy at 7:55 PM on April 30, 2015 [3 favorites]


> I'm just a slob with username derived from a football team, but has an interaction with the earth's (or other) magnetic fields been ruled out as a possible source of the experimental effect? Is such an interaction even possible?

Sure it's possible - why not? We're seeing force - magnetism is a possible cause of force - sure.

I'm sure the gross effects of magnetism have been considered, but there might well be something that hasn't been taken into account.

These are subtle results. This force would literally not accelerate a dime as fast as a snail could.

If you recall, the Pioneer Anomaly, a previous subtle effect, was finally shown to be thermal radiation pressure - something that had been initially ruled out.

My bet is on some electrostatic effect. You heard it here first. ;-)

But yes, it's very likely that it's something known like magnetism that hasn't fully been taken into account.
posted by lupus_yonderboy at 8:01 PM on April 30, 2015 [1 favorite]


Better explanation of why breaking conservation of momentum breaks conservation of energy...

Say you are riding one of these things and say it weighs 2 metric tons. You have enough energy in a battery to increase your speed by 1 m/s, so you do this. Great, you just accelerated to 1 m/s from your previous position. Kinetic energy (energy from moving objects) is defined as (1/2)*mass*velocity^2, so that means you must have used up 1 kJ of energy to pick up that speed.

But wait, say someone was watching who was going 1 m/s slower than you were originally. They see your speed increase from 1 m/s to 2 m/s. They calculate that you started out at 1 kJ of kinetic energy and then went up to 4 kJ, because it's velocity *squared*. They see you using 1 kJ of chemical energy in your battery to get 3 kJ of energy in velocity, in kinetic energy.

It's not just that it lets you make an infinite energy machine, it's that if you accept a violation of conservation of momentum, energy ceases to have meaning as a useful concept. Which is clearly wrong...

There are scientific discoveries that revolutionize our concept of reality, yes. But they fill in the cracks, they change things radically around the edges where previous theories start to make no sense. A claim like this, is claiming something that unravels every single observation we make about every day reality and says we can ignore all that because magic quantum something mumble mumble.

Look. You're dealing with electric charges and currents in a lab with plenty of other charges and currents to push off of and create a tiny, tiny force. Magnetize the object and the vacuum vessel slightly on accident, there's your force, build up a charge on something relative to something else, there's a force. Have a net current running through your device in a magnetic field you didn't expect, you're getting a force that puts an equal and opposite reaction on whatever's making that field. There are so many ways to get a tiny force like this without breaking laws of physics and making a magical propulsion device.
posted by Zalzidrax at 8:03 PM on April 30, 2015 [8 favorites]


Oh and if you want a crazy idea for flitting about the solar system with no reaction mass that is perfectly physical and might actually work, think about an electric solar sail.
posted by Zalzidrax at 8:07 PM on April 30, 2015 [1 favorite]


The best thing about ion thrusters is that they actually look like futuristic space drives.
posted by ryanrs at 8:32 PM on April 30, 2015 [1 favorite]


It would be pretty hilarious if Star Trek were actually quite accurate about alien species, and if the Vulcans and Klingons all had their own versions of it where humans were portrayed very differently.

That planet run by mobsters? That's the real Earth.
posted by zippy at 8:33 PM on April 30, 2015 [1 favorite]


*sigh*

Everyone knows you can't break the rules of physics. But you can work around them
posted by tigrrrlily at 8:37 PM on April 30, 2015 [2 favorites]


The best thing about ion thrusters is that they actually look like futuristic space drives.

While I know you're actually a certified mathemagician engineer, I'm beginning to think you might need a wee break from EVE online before you end up actually mining real asteroids.

Wait, no, that doesn't actually suck. Carry on.

But these experimental ion/plasma drives basically look exactly like Sci Fi movie spaceship drives to the point it's kind of surreal.

Complicated flanges and bells? Check. Shiny, wormy plumbing plugged in all over? Check. Hazy blue glow that isn't chemical fire rocket thrust? Check. Wait, is that a prop from 2001 or Red Dwarf? It can't be real.

They just need to make pulsing, thrumming noises (in space!) like something out of the Star Wars prequels and bolt them on to some heavily-greebled rust bucket of a smuggling ship with some laser turrets and we're basically almost there.

All we'll need is an actual warp drive and/or hibernation chambers and the next thing we know we'll be blasting freaky blue forest elves into wibbly bits for their unobtanium.
posted by loquacious at 8:49 PM on April 30, 2015 [2 favorites]


re: dark matter...
Science Is Closing in on Dark Matter, But Beware the Hype - "The past few weeks have brought a bevy of dark matter announcements. Some of the observations and claims have been genuinely thrilling, but some have been dubious."
posted by kliuless at 9:04 PM on April 30, 2015 [1 favorite]


Why does a reactionless drive necessarily violate conservation of energy as well as conservation of momentum? Read on...

Let's say you have a 1 kg spaceship is flying past you at 1 m/s. This spaceship then engages its "reactionless" drive, increasing its speed to 2 m/s.

Now let's say the spaceship starts at rest relative to you. It engages its reactionless drive, and speeds up from 0 m/s to 1 m/s.

In each case, we should expect the drive to require the same input of energy to accomplish the same delta v, since as viewed in the spaceship's initial rest frame, the two situations are identical. So let's examine the change in kinetic energy in each case:

In the first situation, the spaceship begins with a kinetic energy of 0.5*1*1^2 = 0.5 J, and ends with a kinetic energy of 0.5*1*2^2 = 2 J. This indicates that the drive must have expended 1.5 J of energy to accomplish this acceleration (assuming for simplicity that the drive is perfectly efficient).

In the second situation, the spaceship begins with a kinetic energy of 0.5*1*0^2 = 0 J, and ends with a kinetic energy of 0.5*1*1^2 = 0.5 J. This indicates that the drive must have expended 0.5 J of energy to accomplish this acceleration.

But wait...in the rest frame that the spaceship starts in, the two situations are identical! How can the drive expend different amounts of energy in each situation, when the pilot of that spaceship wouldn't be able to tell the difference? Well, let's wave aside that apparent violation of the relativity of inertial frames, and think about free energy. Does this violate conservation of energy so that we can extract free energy from it?

Yes! Let's assume that relativity is not violated, and that the drive in fact, somehow expends 0.5 J in both situations, despite the anomalous gain of 1.5 J in the first situation.

Let's set up a situation where we accelerate from 0 m/s to 1 m/s, expending 0.5 J, then from 1 m/s to 2 m/s, expending 0.5 J. Our ship miraculously has 0.5*1*2^2 = 2 J of kinetic energy, even though we've only expended 1 J. Now, all we have to do is run the ship (with a magnet bolted to the nosecone) through a series of wire coils, converting its 2 J kinetic energy into 2 J of electrical energy, which we can use to recharge the ship's batteries. Luckily, to repeat the process, we need only recharge the ship with 1 J, and we're free to use the other 1 J to do with as we please! 1 J in, 2 J out - It's free energy!

You might wonder how this paradox is resolved with a good old conservation-of-momentum-fearing drive. The paradox is resolved because the energy that a reaction drive spends is partly used to accelerate the ship, and partly to accelerate the propellant! Using conservation of momentum, one can show that the amount of kinetic energy that the propellant possesses in each situation exactly makes up for the discrepancy we observed here.

So, as much as I am a sci-fi nerd, and am currently making space-zooming and pew-pew noises in excitement over a drive that could make personal spaceflight, interstellar travel, and infinite energy all available in my lifetime...I don't see this panning out, at least not as advertised.
posted by Salvor Hardin at 9:04 PM on April 30, 2015 [13 favorites]


The article didn't say anything about it being a reactionless drive. It specifically mentions virtual particles of the Quantum Vacuum acting like propellant ions.

So, in my mind, the criticism has to be 'what the heck are virtual particles of the Quantum Vacuum, and can they be propelled, causing a reaction?'
posted by eye of newt at 9:36 PM on April 30, 2015 [1 favorite]


Virtual Particles of the Quantum Vacuum is Walternate's favorite prog rock band.
posted by It's Raining Florence Henderson at 11:02 PM on April 30, 2015 [9 favorites]


Dubious dark matter declarations are making a mess of this perception of cosmic space, someone get the quantum vacuum and don't forget the gigalightyear long power cord. The mega cluster roomba was mistaken for an out of galaxy invader and returned to sub quantum intention coupla weeks ago. Like I have time for this too.
posted by Oyéah at 11:14 PM on April 30, 2015 [1 favorite]


I know that this thing - whatever it does and however it does it - is probably not changing or violating any of the laws we know and love. There's an error somewhere, almost certainly. And, sigh, any utility it ultimately displays will probably be trivial.

But let's not pretend that we live in some Great Age of Epistemic Privilege. It is possible that our system of knowledge, as reliable as it has been, is simply wrong about something or explains it incompletely. Just because the scientific method scales FAR better than any other method/model doesn't mean there isn't some fundamental flaw in its current predictions.

Historically, it's only relatively recently that discovery has usually proceeded from prediction rather than from accident or wild experiment. I think because this is the case, we tend to feel we live in a some ahistorical era when it comes to science with a capital "S."

As a thought experiment, let's say we somehow developed GPS satellites before we had a working theory of special relativity. We'd eventually notice something weird was happening with time, seriously improbably observations for which we had no good explanation. Hope against hope, maybe something similar is happening here?

tl;dr: let's just give one of these EM things to Elon Musk.
posted by digitalprimate at 12:36 AM on May 1, 2015 [6 favorites]


Greg Nog: "I'm not a physicist but sticking a flashlight in your ass will provide thrust, 300MW/N worth.

Yawn. Get back to me when you've invented something that will create a USEFUL amount of thrust in my ass.
"

I am all about advanced anal navigational technologies. I figure once we have that down, then we move on to the limited AI friend/lover bots...
posted by Samizdata at 1:26 AM on May 1, 2015


And, note, I said limited.
posted by Samizdata at 1:39 AM on May 1, 2015


Yawn. Get back to me when you've invented something that will create a USEFUL amount of thrust in my ass.

It's a tyranny of capitalism that scientific research into ass-thrusting technology must be USEFUL rather than beautiful or fun.
posted by CBrachyrhynchos at 5:00 AM on May 1, 2015 [6 favorites]


I figure this science is suspect because I could understand a lot of it.
posted by From Bklyn at 5:50 AM on May 1, 2015 [3 favorites]


Is the result interesting? Maybe. But the experiments find less and less force each time they are more and more careful. And on the one hand we have the more plausible explanation of experimental error vs. the less plausible explanations involving exotic and apparently wrong physics The extraordinary claims are not yet being backed by extraordinary evidence. So, while there's a chance something interesting might be happening here, the chance is very slim. And so it is not unreasonable to proceed extremely skeptically and say "Get back to me when you've eliminated more potential sources of error. Don't show me sketches of your new space craft with this as the engine."

Maybe a more mundane analogy would be helpful here.

Imagine an article was published saying that after a very specific setup a chef observed that adding a small amount of water to a bowl and whisking it in a certain way and cooking the resulting liquid resulted in scrambled eggs.

You would probably, rightly, say that there's probably something silly going on with the setup like a small amount of egg residue is on the bowl or whisk or something.

If somebody then came to you and said "Why are you so skeptical! They tested the whisk and found no residue! Sure, the chef's explanation that egg particles are drawn from the refrigerator across the room might be poor, but there could be new cutting edge cooking here that could be very valuable! Why are you so closed minded!" would it really be so incredible to think they were being overenthusiastic about the result? And that it's more likely that looking for egg contamination somewhere is going to be more fruitful than worrying about "new cooking".
posted by delicious-luncheon at 8:10 AM on May 1, 2015


None of the other proofs of "reactionless drive == free energy" of this are correct. They all rely on the "reactionless drive" being able to put out constant force as the speed changes - but we have zero idea if it does behave this was. Instead, they are all proofs that IF a reactionless drive exists, then the amount of force it generates decreases as its speed increases, if the law of conservation of energy is to hold.

Speed relative to what, you might ask? Mach's "fixed stars", I'd suspect... yes, there are relativity issues there, but better than breaking the laws of thermodynamics...!

Again, it's probably a measurement error or the like, but we have to keep honest with our rebuttals.
posted by lupus_yonderboy at 8:11 AM on May 1, 2015 [1 favorite]


Yeah, nope. Still not convinced. One more of these reports, though, and someone will have to seriously roll up their sleeves and reproduce the setup and show why it's wrong.
posted by RedOrGreen at 8:42 AM on May 1, 2015 [1 favorite]


I am all about advanced anal navigational technologies

The Universe is Your Oyster with AANTs™ in Your Pants!
posted by CynicalKnight at 8:48 AM on May 1, 2015 [2 favorites]


Speed relative to what, you might ask? Mach's "fixed stars", I'd suspect...

Not the luminiferous aether? Still, that means it should be good enough for free kinetic energy up to at least 900 miles per hour, plus 19 miles a second, when it's in season.
posted by sfenders at 9:32 AM on May 1, 2015 [1 favorite]


Mach's "fixed stars", I'd suspect...

So although I joked about it above, I doubt this device is going to help us discover a universal preferred frame of reference.

Now, there are of course relativistic effects where a hypothetical reactionless spaceship gains mass as it accelerates but as sfenders points out, there's plenty of space at "low" speeds to still make it a great perpetual motion machine.

The only way out for this thing is for there to be some dark matter getting spat out the ass end that we don't yet detect.
posted by GuyZero at 9:53 AM on May 1, 2015


You all keep forgetting that we're living in bad screen-writer's universe now. International terrorists, eccentric billionaires building their own rocket ships, omni-present surveillance dystopia, etc.

Of course you're going to get mysterious drives built in a garage that violate the fundamental laws of physics, that's just part of the package. My advice is to relax and try to act surprised when the robot uprising comes.
posted by Eddie Mars at 10:08 AM on May 1, 2015 [10 favorites]


While specific examples had to be fairly simple, they are the consequence of much more powerful theories that would require calculus and more time and skill to explain clearly and succinctly than I possess - see Combat Wombat's mention of Noether's theorem above.

The upshot is that these conservation laws are the direct result of time, position, and mass being meaningful quantities. You can't get rid of conservation of momentum without unravelling literally everything - to get something to literally move without changing the momentum of something else, the very definition of either 'momentum' or 'moving' has to be changing. If those change, then the definition of energy has to change, and so on. You don't get to throw away just the momentum it and keep anything that looks remotely like energy in any form - thermodynamics when you get down to the details also relies on mass and positions, so that's out, too. When scientists speak of relativity in this context, this is Galilean relativity. That you can add velocities, distances, and masses and get the no matter where you are or how you look at them.

Now we've gone beyond classical laws of motion. They actually aren't quite conserved - they are just very good approximations at the scales we're used to. They are solutions to the cracks in the classical theories that we found when having to deal with high mass/energy scales or very tiny scales. And that is important. At very high energies, you have to use the definitions of General Relativity, but at human scales, those definitions approximate nearly exactly to the classical ones, plus some gravitational acceleration. At really tiny scales, you have to throw away your definition of particles and motion and think of probability and probability currents. But, at the human scale, these average out to particles and motion. At high energies and really tiny scales, well there's a reason that we have giant supercolliders running tiny bits of matter into each there at very high energies, because there are still obvious cracks at the edges of the theories where high energies run into tiny scales, and the theory isn't sorted out yet.

But one thing neither general relativity nor quantum theory does is argue that things should be significantly different at the scales we're used to using classical theory to describe. Saying that you used a perfectly ordinary amount of energy in a perfectly ordinarily sized place and get a result that violates these classical laws is patently ridiculous because to accept it would unravel literally everything. At all scales. Even the ones we can see, hear, and touch. For something to blatantly violate something like the conservation of momentum at those scales would require the laws of physics to be discontinuous at its surface, because the changes necessary to allow that would also be significant and almost certainly lethal to anyone nearby. Every single process in your body depends on a physical reality that would no longer apply. And that's just a fancy way of saying it's not science, it's magic.
posted by Zalzidrax at 11:01 AM on May 1, 2015


You all keep forgetting that we're living in bad screen-writer's universe now.

I'll bet the split occurred when Redshirts was published.
posted by Steely-eyed Missile Man at 11:47 AM on May 1, 2015


I could be wrong, the Pioneer Anomaly has been largely explained by "reactionless" photon pressure from their RTGs. I suspect the objection here is that the reported forces are much higher than one would expect from that effect.
posted by CBrachyrhynchos at 12:24 PM on May 1, 2015


There's nothing reactionless about the Pioneer photo pressure. The heat is lost by radiation (infrared photons) being emitted mostly in one direction. The photons have momentum. There's nothing mysterious there.
posted by delicious-luncheon at 1:46 PM on May 1, 2015 [1 favorite]


I've seen this one before. If you turn it upside down, it becomes a transmogrifier; flip it on its side, it's a replicator. And if you stand on its other end? Time machine.
posted by kcds at 4:16 PM on May 1, 2015 [1 favorite]


It opens a small gateway to hell and is moved by the screams of the damned.
posted by humanfont at 4:43 PM on May 1, 2015 [2 favorites]


It opens a small gateway to hell and is moved by the screams of the damned.

Well then this is nothing new, we've had PT Cruisers for a while now.
posted by jason_steakums at 4:58 PM on May 1, 2015 [3 favorites]


The problem with these "discoveries" -- always, always -- is not that people poo-poo them, but that their supporters fail to recognize the actual implications of truly breaking the laws of physics. It's not that their imaginations are too big .... they're actually too small.
Indeed. Framing this as a tool one could use to make orbital adjustments to the ISS is like pointing out that your newly discovered time machine could be used to enable faster taxi cab dispatch.

The universe is an interesting place, and I'd bet a lot there are still entirely unexpected, very strange, and possibly useful things waiting to be discovered. The chances that they'll be discovered by someone who sets out with the goal of inventing seemingly impossible technology and first published in bits and pieces on a space enthusiast discussion board seem remote.
posted by eotvos at 5:02 PM on May 1, 2015 [1 favorite]


I understand so little of this.

Being stupid is really irritating.
posted by aramaic at 5:03 PM on May 1, 2015 [5 favorites]


At this point no one understands what is going on. There are a number of proposed explanations, but nothing confirmed in the lab. We have a currently unexplained result.
posted by humanfont at 5:19 PM on May 1, 2015 [1 favorite]


/u/JordanLeDoux has a nice summary up on Reddit, complete with sources: The FACTS as we currently know them about the EmDrive and Cannae Drive.
posted by um at 7:14 PM on May 1, 2015 [1 favorite]


Being stupid is really irritating.

This is the smartest thing anyone has said in this thread.
posted by It's Raining Florence Henderson at 7:41 PM on May 1, 2015 [2 favorites]




Homemade independent test of EM drive

Unmentioned is the fact that this guy also microwaved several cats in the testing process. THAT SETUP.
posted by GuyZero at 4:09 PM on May 18, 2015


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