NASA Tests Microwave Space Drive

schwit1 (797399) writes with news that NASA scientists have tested the EmDrive, which claims to use quantum vacuum plasma for propulsion. Theoretically improbable, but perhaps possible after all. If it does work, it would eliminate the need for expendable fuel (just add electricity). From the article:Either the results are completely wrong, or NASA has confirmed a major breakthrough in space propulsion. A working microwave thruster would radically cut the cost of satellites and space stations and extend their working life, drive deep-space missions, and take astronauts to Mars in weeks rather than months. ... [According to the researchers] "Test results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma." Skepticism is certainly warranted: NASA researchers were only able to produce about 1/1000th of the force the Chinese researchers reported. But they were careful to avoid false sensor readings, so something is going on. The paper declined to comment on what that could be, leaving the physics of the system an open problem.

Comments

KSP

[Thanshin]

Let's stick to the important consequences. When will this reach KSP? Is a patch/hotfix in development?

Re:KSP

[NotDrWho]

Let's stick to the important consequences.

How fast can it cook a potato?

Re:KSP

[Anonymous Coward]

It's already an end-stage upgrade to the plasma thruster in the KSP Interstellar mod.

Re:KSP

[gewalker]

No, the question is how fast can it accelerate the average potato. NASA reported 30-50 mN of thrust., call it 40. The average potato is about 375 grams, call is 400 even so math is real east. F=m*a or a = F / M or 1e-7 m/sec^2. So, accelerate for 1 year and you reach the break-neck speed of 31.5 meters per second or 70.5 mph

It is going to take a long time to get that potato to Alpha Centauri. Especially considering that you have to also accelerate the mass of the Q-drive unit itself and the energy source to supply the Q-drive.

Now if the effect is real and the efficiency and can be improved you still have something potentially useful in-deed for satellites. You could even maneuver asteroids if you had lots of patience.

Re:KSP

[jythie]

Even if the efficiency can not be improved much, the people who launch probes have impressive patience. Add a good solar panel or a nuclear source and you could get a nice constant acceleration over a long period.

Re:KSP

[gewalker]

Oops, off by a factor of 10. 1 year give 3.15 m/sec 7.05 m[h

Re:KSP

[gewalker]

You have to be more even more patient than they are for a probe. To accelerate from low earth orbit to escape velocity the 1e-7 m/s^2 will take 1080 years. Enough for orbit maintenance, probably. Enough for probes, no not really -- No one plans for missions spanning thousands of years.

Re:KSP

[green is the enemy]

Double-check your units. 0.4 kg will accelerate at 1e-4 m/s^2 under 40e-6 N of force. That's ~3000 m/s per year (3.15569e7 seconds in a year).

Re:KSP

[Anonymous Coward]

While we're at it, F=40 micro-Newton, m = 0.4 kg means 4*1e-5/4*1e-1 which in turns gives a = 1e-4 m/s^2, no?

Then one year would give a much more interesting 3155.7 m/s, or 11360km/h (about 7000mph I guess ?)

Re:KSP

[freeze128]

"All hands, prepare for burrito blast!"

Re:KSP

[FatLittleMonkey]

40mN is a 40 milliNewtons, or 0.04 Newtons.

40uN is 40 microNewtons. So up your final result by another three orders of magnitude.

Re:KSP

[Anonymous Coward]

It would be considered a Geneva potato convention violation if the potatoes used in the batteries to power the thing were cooked with it.

Re:KSP

[Anonymous Coward]

The key here though is that as far as we can tell it seems to *straight up violate conservation of momentum*, at least for things that aren't virtual particle plasmas. So if you put one on your ship, you're no longer bound by the rocket equation. You no longer need thousands of pounds of fuel for every pound of stuff you want to take somewhere.

That means you can actually go places.

Re: KSP

[SreeprakashNeelakant]

Escaping earth will use conventional rockets, but once in space 'such' a thing that can propel .. Hope it works

Bad summary

[Anonymous Coward]

Skepticism is certainly warranted: NASA researchers were only able to produce about 1/1000th of the force the Chinese researchers reported. But they were careful to avoid false sensor readings, so something is going on. The paper declined to comment on what that could be, leaving the physics of the system an open problem.

The physics of the system has two explanations, one relativistic relying on a classical radiation pressure, and one quantum relying on virtual particles, and is not an "open problem". These are things that were designed, not things that just work but we can't explain why. The EmDrive site will give you the relativistic model; the paywalled Chinese article presumably gives the quantum model. The NASA researchers produced 1/1000th of the force of the Chinese & English drives because they used a different design, which reduces the Q factor of the waveguide - again, this is explained on the EmDrive site. Now Chinese, English and American teams have all measured "anomalous" thrusts from this type of device, so skepticism is not really warranted on that basis, nor on the basis of a presumed anomaly in thrust magnitude when in fact that's all well understood.

Re:Bad summary

[Sockatume]

Unfortunately in this instance they measured the anomalous thrust on a version of the instrument designed and built by its own inventors in such a fashion as to not produce thrust at all. I'm inclined to believe that the anomalous thrust is some sort of weird ideomotor effect related to the fact that they had to manually control the frequency of the RF excitation as the test ran.

Re:Bad summary

[sillybilly]

Dude, they are getting impulse, momentum, mv, from the mass contained in the energy, mc2, which is pure light's mass. You could use that same energy to accelerate any particle, even an electron, to near speed of light velocities via a cyclotron first, then as relativistic mass takes over and cyclotron speeds get out of synch, so you take over with a coiled linear accelerator with correctly placed spacings along its path, a few miles long, then shoot it out into open space as a propulsion kickback conservation of impulse kind of thing, and get better bang, better kickback per energy invested, all you need is a simple piece of matter, like an electron to blow up in mass relativistically and generate a lot of impulse or momentum from this mass increase. As you invest into relativistic mass, you start wasting energy as mass, so there is probably some optimum point of say 0.8c or 0.9c, where the economic scarcity of matter mass dictates wasting energy as relativistic mass. The question is how difficult is it to come up with an electron from outer space, and shoot it back there. Or carry the electron fuel - bound to things like atomic nuclei, and then you can strip the nuclei completely of all electrons, or if that's too expensive energetically, of only a few electrons and the real kick and impulse you get then is of course from these much heavier ions, or stripped atoms, not the light weight electrons. In intergalactic travel you may not be able to filter enough hydrogen atoms or helium atoms (like a whale filters plankton) from the vacuum of space if the vacuum is too close to zero pressure, so then your economic option is using just light, or pure energy, gathered from starlight through massive solar panels, as a propulsion. Accelerating a very scarce electron to very close to speed of light, where the ratio of relativistic mass to rest mass is say, 100, that means 99 grams of 100 grams of stuff ejected as propulsion is energy-mass, then, then you might as well do 100 percent energy-mass, if the operation is simpler, and you don't need a funky cyclotron.

Re:Bad summary

[Anonymous Coward]

In that case the NASA result adds very little to the existing results. Shame. What I don't get is why they tested this Cannae drive instead of the EmDrive that's been knocking around for a while, and which the Chinese also tested. Seems to me that if the thrust output is 3 magnitudes less, your measurement errors are 3 magnitudes more important. Even if this experiment leads to NASA saying "hey guys, watch out for this unexpected source of errors in this kind of test", the errors are at most uN range so aren't important on a mN measurement.

Re:Bad summary

[dullertap]

Christ

Re:Bad summary

[Anonymous Coward]

And unfortunately as well, it is absolutely not clear for their one-page "publication" (press release ?) whether the thrust observed on the null apparatus is equal to the "with-thrust" instrument. If they're different (with the "null" being smaller than the "with"), that could explain their concluding remark:

Test results indicate that the RF resonant cavity thruster design, ..., is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma.

That or I'm a bit confused.

In any case, I'm old enough to remember the faster-than-light-neutrinos story ... wait and see.

Re:Bad summary

[Anonymous Coward]

I think the paper itself is being presented at a conference, so maybe it'll show up later.

I'm old enough to remember the faster-than-light-neutrinos story

So you're at least one year old :)

Re:Bad summary

[Anonymous Coward]

Technically, exactly correct. But what he didn't say is that he's old enough to remember (and put into practice the lessons from) the faster-than-light neutrinos story (which lessons are: wait and see). I don't know what that age is - could be 50 or 60 years old.

Re:Bad summary

[Immerman]

We have two competing theories being advanced by people who've built this family of thruster, both of which are also widely regarded as containing flawed physics (if not necessarily well-examined), and many other provisional theories having been advanced by scientists unconvinced that the effect is real. Meanwhile, NASA tests a related apparatus and does in fact detect thrust, but of a magnitude inconsistent with the theory upon which it is constructed.

By what stretch of logic do you propose they can responsibly claim either theory is accurate? The most that they can confirm is that they did in fact measure anomalous results. Addressing the specific physics in play was far beyond the scope of the experiment they performed, and thus would be pure speculation on their part. The proper response is to do exactly what they did: not endorse any specific explanation, but confirm that a repeatable phenomena unexplained by broadly accepted physics does appear to exist. That bolsters the legitimacy of anyone exploring the phenomena without endorsing a particular theory that they lack the data to confirm (aka making a statement of "faith" or "opinion").

Re:Bad summary

[almitydave]

Technically, exactly correct.

The best kind of correct.

Re:Bad summary

[Anonymous Coward]

http://en.wikipedia.org/wiki/Ideomotor_phenomenon

What?

Re: Bad summary

[fermion]

In 1989 Fleischmann and Pons published a paper showing evidence of cold fusion. No one, other than a team atmTexas AM, of course, was able to replicate. The lab where I worked had a preprint of he TAM paper andmeveryone unformly decides it was crapbduebto lack lack of experimental detailed procedure. I am told the FP paper had the same issues. Though millions was thrown t the problem in 1989 and 1990 nothing came of this discovery that gviolated all known science. Mather AM people denied fraud by claiming bad rods, but it seems likely there was some spiking. FP were so suspect the filed lawsuits against other scientists who disputed their results. The lesson bieng that one result is a best a guess and worse fraud, and while we want to test the current expectations of physics, a single result provides little information. It is not so much that cold fusion or virtual particles can't provide useful energy, but that the current theory does not show how such a thing is possible and experiment is inconclusive.

Re:Bad summary

[angel'o'sphere]

Well, if you want to teach the scientists something about science, get at least the magnitude thing correct.
They where not off by one magnitude, but by three :D

Re: Bad summary

[david_thornley]

Moreover, Fleischmann and Pons were getting energy out of what they were doing, so they did have experimental results. Some other people were confirming it as fusion, and were later exposed as people who had no clue how to use a neutron detector. Since then, I've been dubious about results like this (didn't stop me from trying to figure out how to put FTL neutrinos into Special Relativity, though).

Re:Bad summary

[Immerman]

It's perhaps an easy mistake to make if you're not well-versed in the terminology of the field, but you are describing order-of-magnitude, a term having nothing to do with magnitude itself, which (in this context) specifies the "length" or "absolute value" of a vector value such as displacement, velocity, force, etc.

For example speed is an always-positive scalar (single-number) value that specifies the magnitude of velocity, which is a vector (multi-number) value independently specifying the speed along each axis.

Re:Bad summary

[angel'o'sphere]

If we have X, and something is an(one) order of magnitude bigger than X, then it is 10x bigger than X.
If it is 100x bigger than X then this is two orders of magnitude and if we are talking about 1000x smaller or bigger, as in this case: it is three orders of magnitudes.

Re:Bad summary

[Anonymous Coward]

and there is talks of a resonance effect at 100 ghz which could allow maximum thrust.

would be funny if they try it and the test rig breaks the test arm.

Re:Bad summary

[Anonymous Coward]

Apparently the drive developed artificial intelligence, which in turn subconsciously willed itself to move...

Re:Bad summary

[Immerman]

Yes. That is what an order of magnitude means. But that is not what magnitude means - it has its own definition separate from that one particular usage: size. Try reading that in the context of what I wrote:

>Meanwhile, NASA tests a related apparatus and does in fact detect thrust, but of a -magnitude- size inconsistent with the theory upon which it is constructed.

I say nothing about orders of magnitude. I only refer to the size of the effect, and note that the size is inconsistent with the theory. The fact that the magnitude of the thrust is inconsistent with the predicted magnitude by three orders of magnitude is especially damning, but even if the actual magnitude was only 30% lower than predicted it would still indicate a likely problem with the theory. Legends are made by fixing smaller discrepancies than that with a completely new theory.

Just to reiterate

magnitude /magntood/ noun
the great size or extent of something.
"they may feel discouraged at the magnitude of the task before them"
synonyms: immensity, vastness, hugeness, enormity; size, extent, expanse, greatness, largeness, bigness
"the magnitude of the task"
antonyms: smallness, triviality

2.
size.
"electorates of less than average magnitude"

        a numerical quantity or value.
        plural noun: magnitudes
        "the magnitudes of all the economic variables could be determined"

3.
the degree of brightness of a star. The magnitude of an astronomical object is now reckoned as the negative logarithm of the brightness; a decrease of one magnitude represents an increase in brightness of 2.512 times.

Not that not one of those made any reference to a power of ten - the closest is the usage in astronomy where it represents a power of 2.512

Re:Bad summary

[angel'o'sphere]

We did not talk about magnitudes, we talked about orders of magnitudes.

I don't know why you wanted to bring that topic up :) So I corrected your previous post and pointed out that our parent was wrong with the orders of magnitudes ...

So, why do you bring up this topic? A sudden urge to educate strangers? Then perhaps tell me something I don't know?

Or don't we have a common parent and it was you I answered to? Then simply make your posts more clear :) instead of trying to weasel yourself out: " oh I never said 'order of' magnitude I only said magnitude ... " oops, did you? And that should make any sense to you? Only saying magnitude makes it even more wrong ... at least in german, or did you mean: "the measurement was off by a vastness from the expected result?" I mean: does that make sense in english?

Also I'm pretty sure the original post said a magnitude, where the 'a' is a synonym for 'one' ... not sure if you had the word 'order' in it ... and to lazy to travel up the parent chain to check something so mundane.

Re:Bad summary

[Immerman]

Perhaps your interpretations have been polluted by a set of sibling posts I never saw.

But you seem to have a problem with my specific usage of magnitude, despite explanations, so I think perhaps you are being willfully obtuse, I am doing a poor job of explaining it to you, or possibly you aren't as well-versed in english technological vernacular as you think - you do imply you speak German, perhaps you are in that uncomfortable situation where the similarities with your mother tongue are just enough to occasionally throw you for a real loop when they diverge.

And I do sometimes feel compelled to correct misunderstandings in people who seem to have some interest of the fields I'm skilled in (as you imply you do by flashing your knowledge of the meaning of orders of magnitude) - a small intervention against a flawed understanding can sometimes cast aside future obstacles to learning that might discourage a hungry mind. Especially if it's a correction for someone who is actively spreading their misunderstanding.

I just traced this conversation back to it's beginning, and you were the first to say anything about orders of magnitude. There were two prior uses of the word, both seemingly using the general mathematical meaning of "size" or "amount" of a potentially multi-dimensional quantity. Understand: this is common technical usage, at least in America - in the context of math and science "size" and "amount" can be potentially confusing as they have definite (if context sensitive) mathematical meanings, whereas "magnitude" has minimal common-language implications and has been assigned the very common-used meaning of "size of a potentially non-trivial value that may or may not have a geometric meaning". Try rereading the flow substituting "amount" for "magnitude", there are only three posts in this chain:

AC(top-level post):
The physics of the system has two explanations [...] and is not an "open problem". [...] so skepticism is not really warranted on that basis nor on the basis of a presumed anomaly in thrust [amount] when in fact that's all well understood.

Me:
We have two competing theories ... NASA ... does in fact detect thrust, but of a [amount] inconsistent with the theory upon which it is constructed.
By what stretch of logic do you propose they can responsibly claim either theory is accurate?

You:
Well, if you want to teach the scientists something about science, get at least the magnitude thing correct.
They where not off by one magnitude, but by three :D

On rereading I'll admit that the usage in AC's comment could have also been intended to convey the more specific sense of "amount within a power of ten", but then so could mine, and it works equally well with either interpretation with minimal change in meaning. So long as you recognize that both meanings exist any mutual misunderstanding rarely lasts more than a couple exchanges. Confusion on that front is rarely significant since if you're talking about specific orders of magnitude you always include the "orders of". Values may be off "by three orders of magnitude", but not by "three magnitudes" (except in astronomy, where "magnitude" is a precisely defined unit like "meter"). Nor is it common to speak of "a magnitude of difference" or "a difference in magnitude" in order to imply one order of magnitude.

Re:Bad summary

[angel'o'sphere]

Ah, so we did not talk about your post but about the ACs one ... so I'm not that Alzheimered as I feared.

Yes, we can agree that the word 'magnitude' has slightly different meanings, depending if other words like 'order' precede it.

Regarding english vs. german that is indeed a big problem, that is why I encourage you in any legal case regarding both languages to hire a professional interpreter (hint: the literal translation from german to english would not be interpreter but translator) e.g. words like eventually/eventuell and actually/aktuell have completely different meaning in those languages, you easy get tricked if you hear a 'similar' word.

Re: Bad summary

[qraal01]

It's not an "equipment fault" but a modified version that shouldn't work if Guido Fetta's Cannae QDrive explanation was the correct explanation. According to Sonny White's QVPT conjecture (and Shawyer's EMDrive theory) BOTH should work - and that is what they saw.

Re:Bad summary

[Anonymous Coward]

The null test that produced thrust was the result of a variable Q cavity with geometrical abberations thrown in. If you take the relativistic model (not sure about the quantum one) that would imply their variable-Q version was so lossy there weren't many reflections for the geometrical abberations to screw up to begin with as a variable Q where at least one side isn't a superconductive wall necessarily means massive losses to heat. The null test they did that just leaked microwaves out the side but kept the masses and vibrations the same produced no effect as expected and they did the test on a swing rather than a rotor so highly polarized Dean Effects (a flaw in the experimental setup that would give a false positive) weren't possible anyway.

Re:Bad summary

[Anonymous Coward]

by Anonymous Coward on Friday August 01, 2014 @08:13AM (#47580405)
Skepticism is certainly warranted: NASA researchers were only able to produce about 1/1000th of the force the Chinese researchers reported. But they were careful to avoid false sensor readings, so something is going on. The paper declined to comment on what that could be, leaving the physics of the system an open problem.

The physics of the system has two explanations, one relativistic relying on a classical radiation pressure, and one quantum relying on virtual particles, and is not an "open problem". These are things that were designed, not things that just work but we can't explain why. The EmDrive site will give you the relativistic model; the paywalled Chinese article presumably gives the quantum model. The NASA researchers produced 1/1000th of the force of the Chinese & English drives because they used a different design, which reduces the Q factor of the waveguide - again, this is explained on the EmDrive site. Now Chinese, English and American teams have all measured "anomalous" thrusts from this type of device, so skepticism is not really warranted on that basis, nor on the basis of a presumed anomaly in thrust magnitude when in fact that's all well understood.I

Re:Bad summary

[cbhacking]

Why do you say "a version of the instrument"? There were two (non-null) test devices: an EmDrive and a Cannae Drive. According to its inventor, the Cannae Drive requires radial slots in the chamber and won't work without them. The EmDrive doesn't need such slots. According to the inventor of the EmDrive, the Cannae Drive is basically an inefficient EmDrive and the slots are irrelevant. To test the Cannae Drive (NOT the EmDrive!), a null version without the slots was tested as well.

Experimental result: All three devices produced thrust. The EmDrive produced more than the Cannae drive, but the Cannae drive produced the *same amount* of thrust whether it had the slots or not. That means Guido P. Fetta (inventor of the Cannae Drive) is wrong. It does *NOT* mean that Roger J. Shawyer, who invented the EmDrive, is wrong - in fact, to a degree it supports his claim that the Cannae Drive is just an EmDrive - although his own math is called into question by the low output even of the tested EmDrive.

Seriously, stop talking as if the inventors of Cannae Drive and EmDrive are the same group of people and believe that they work the same way. Fetta was shown to be flat-out wrong when the Null drive produced thrust too. Shawyer was shown to possibly be at least partly right (not proven, but not disproven either) when all three devices produced at least some thrust, and his produced more.

Re:Bad summary

[cbhacking]

That's not (necessarily) an "unexplained fault in the test apparatus", you idiot (speaking both to the AC and to the people who modded em up). That is an unexplained experimental result. How the fuck did at least four people, at time of writing, manage to get that wrong?

There were *THREE* test devices. (Seriously people, the summary and linked TFA sucks but what the fuck do you expect from /. anyhow? Do some further reading.)

Device 1: EmDrive, designed by Roger J. Shawyer. This is the same drive tested by the Chinese, though NASA ran the experiment at 1/50th the power of the Chinese experiment. The thrust produced per energy put in was far less than the Chinese reported, but it was non-zero. NASA apparently plans to test with a more powerful version of the drive (closer to the Chinese experiment).

Device 2: Cannae Drive (test article, as designed by Guido P. Fetta). This drive produced less thrust than the EmDrive but did produce some. Fetta claims that the drive requires "radial slots engraved along the bottom rim of the resonant cavity interior" in order to produce thrust. Shawyer claims that the Cannae Drive is basically just an inefficient EmDrive.

Device 3: Null version of Cannae Drive (lacking the slots, which Fetta says should mean no thrust but which are irrelevant to the supposed mechanism of the EmDrive). This version produced the same amount of thrust as the "real" Cannae Drive test device.

Zaphod?

[fuzznutz]

Theoretically improbable, but perhaps possible after all.

Actually, it's infinitely improbable, therefore finitely probable. All they need is a heart of gold.

Re:Zaphod?

[Anonymous Coward]

and add a cup of tea

Re:Zaphod?

[Prof.Phreak]

``anything not explicitly forbidden, is mandatory!'' ---someone commenting on quantum mechanics.

Re:Zaphod?

[Anonymous Coward]

. The paper declined to comment on what that could be, leaving the physics of the system an open problem.

And a enthusiastic under-grad, willing to solve the open problem if it's in the text book.

Re:Zaphod?

[dowens81625]

A really hot cup of tea !

Re:Zaphod?

[dave420]

A nice hot cup of tea. Your hoopiness is fading ;)

Re:Zaphod?

[dowens81625]

I am all sorts of wrong while I do recall the nice cup I was referring to this passage.

"Then, one day, a student who had been left to sweep up after a particularly unsuccessful party found himself reasoning in this way: If, he thought to himself, such a machine is a virtual impossibility, it must have finite improbability. So all I have to do in order to make one is to work out how exactly improbable it is, feed that figure into the finite improbability generator, give it a fresh cup of really hot tea... and turn it on! "

Re:Zaphod?

[CaptnZilog]

Tea. Earl Grey.

Re:Zaphod?

[K. S. Kyosuke]

Apparently, TNG made the mistake of Picard, and not Geordi, ordering the beverage. ;)

Re:Zaphod?

[Anonymous Coward]

Or the heart of a small boy. Hold on, I think I have one on my desk.

Ugh

[Anonymous Coward]

Don't be deceived by vacuum chamber: the device was placed inside a chamber designed to be evacuated, but the experiments were conducted at atmospheric pressure. Ionization effects of air were not considered, and to demonstrate force at pressure and not in vacuum does nothing to establish the utility of such apparatus for extra-atmospheric purposes.

Re:Ugh

[queazocotal]

Nor were convection effects considered.
You don't need much airflow to generate 50 micronewtons.

Re:Ugh

[green is the enemy]

Yeah, that paper should be rejected. The results are totally useless. I wonder how many people went "WTF?" upon reading "...within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure."

Re:Ugh

[Anonymous Coward]

And the Slashdot Expert Speaks Again.

Really, these guys are NASA. I expect they know what they are doing. I expect they know way more than you do.

Re:Ugh

[cyberchondriac]

While you're more than likely right, some of the guys on here probably are from NASA themselves.

Re:Ugh

[joe_frisch]

Some NASA employees are experts, but that doesn't mean that all NASA employees are experts.

If the thrust is only proportional to the photon pressure from microwaves, then this is not particularly interesting.

If the thrust is from somehow accelerating ions, electrons, or ambient air molecules, this is not particularly interesting. (just a different type of ion drive)

If there is thrust with no exhaust, if it doesn't conserve momentum, then the device is impossible.
Yes, IMPOSSIBLE. Conservation of 4-momentum is among the best tested bits of physics. "quantum mumble" doesn't change that - quantum mechanics also conserves momentum.

Re:Ugh

[Anonymous Coward]

rtfa?

Re:Ugh

[queazocotal]

I read the actual abstract of the paper the article was based on. (the full text is not available)
'The tests were performed in a vacuum chamber, with the door closed, but at atmospheric pressure.'
Internal convection can move gas just fine and create anomalous torques.

Re:Ugh

[Neil Boekend]

If we assume the EM drive was setup vertically to provide thrust upwards.
The angle of the side walls to the EM source is steep. Most likely it is quite reflective at that angle.
The back end is flat. That means it is less reflective and thus will leak more EM energy.
More EM energy means more heat into the air below it. That air starts to rise, bumps against the flat bottom and provides a minute amount of thrust, evidently in the micronewton range.

Re:Ugh

[cbhacking]

Sure, but it can't produce *consistently asymmetric* ones. If convection was responsible, than the *net* torque should have been zero since the entire system was sealed. Or rather, if it can, then hey, just make sure the drive container is full of air at atmospheric pressure when you mount it on your spacecraft!

Re:Ugh

[cbhacking]

Actually, if it's proportional to the photon pressure, that's still pretty damn interesting... because the drive is *sealed*. There's nowhere for the photons to escape to. Light pressure is still an "equal and opposite reaction" deal. If microwave generation at one end of the chamber propels the drive one way, then microwaves impacting on the other end of the chamber ought to produce an equal propulsion the other way. Net thrust should be zero.

THE NET THRUST IS NOT ZERO! You appear to have completely misunderstood the design of the drive (not the supposed mechanism of it, the plain-English design). There's nowhere for photons, or ions, or electrons, or air molecules, or anything else to go. Either
A) point out where the exhaust of these things comes from
B) give a reason why they measured thrust when there actually wasn't any
C) stop calling things "IMPOSSIBLE" when they are, by multiple independently conducted experimental results, happening.

It wasn't that long ago that Newtonian mechanics were "among the best tested bits of physics". Relativity showed they were only an approximation of the truth, and that under previously-untested experimental conditions they were not accurate. I'm not saying that something similar is undoubtedly happening here, but I am saying that you're an idiot for claiming that it's impossible for "one of the best tested bits of physics" to be wrong under unusual situations.

Re:Ugh

[cbhacking]

Uh huh. Leaving aside the problems with everything you just said, what happens when you turn it over and get the same result? How about when you place it on its side and get the same result? Seriously, that's a pretty obvious null test. They thought of it.

Re:Ugh

[joe_frisch]

The test was done in air. There are a huge number of possible sources for thrust. Most notable are convection currents from temperature differences. Even if the test is done in vacuum, you need to be very careful. Temperature changes can cause out-gassing. Thermal radiation will generate force from photon pressure.

Newtonian physics was (and still is) extremely accurate in the range in which it was tested. The flaws were found under new conditions (relatively strong fields and fast motions of planets, and detailed measurements of the speed of light).

The amount of physics knowledge now is vastly greater than it was in 1900. My day job involves working with electrons at .99999999C. As I sit here I am looking at the energy of X-rays generated from scattering off of 12 GeV electrons - getting the correct energy relies on conservation of mass energy. Conservation of mass-energy is measured in everything from planetary orbits, to electron diffraction, to neutron star binaries, to high energy collisions.

This device is not operating in any new physical regime. The energies and length scales are quite modest.There is no physical explanation of what is going on (quantum mechanics conserves mass-energy). Its a very dirty experiment (done in air etc), so it is enormously more likely to be a mistake than the discovery of a new physical principal.

Re:Ugh

[queazocotal]

The net torque is zero - yes.
The problem is that because the 'vacuum' chamber wasn't part of the measured system, you can exert torques against it without issue. Convection can do this and distort the measurement.

A major reason why this can't be true - or if it is it's bigger than any Nobel Prize-winners discovery in history, and maybe all of them:
The reported thrust in the NASA paper is 0.4N/kW.
Power = force * velocity.
If you put this on a railway car going at 10m/s, then you get 0.4W*10m/s = 4W out for 1000W in.
If the car is going at 100m/s, it's 40W.
At 3000m/s, 1200W.
You take 1000W of this to run the engine, and you now have 200W of free energy.
This can be arbitrarily scaled up.

Is it mechanically awkward - sure.

Re:Ugh

[queazocotal]

Doh - in addition - the full article is available - http://www.libertariannews.org...

The reason given for not testing under vacuum is the unavailability of vacuum qualified amplifiers.
This is a very poor excuse - literally an hour is enough to make a vacuum sealed can into which you can put an amplifier.
You add a water-bottle and a fan, and you're good for some time.
Flushing the chamber with helium would have been a good and very fast step.
Turning the vacuum pump on, to pump out 1/3 of the air similarly.

Re:Ugh

[Neil Boekend]

I don't know. Things go wrong for the stupidest reasons. Remember the trouble with the Hubble? The malformed mirror that was caused by a piece of tape?
Everything can go wrong and a couple of micronewton is not much force.

free electricity!

[Anonymous Coward]

"it would eliminate the need for expendable fuel (just add electricity)"

And as plug-in electric car proponents everywhere will vigorously agree, electricity is free and abundant. It comes from nowhere, and no fuel is expended to create it.

Re:free electricity!

[kav2k]

In terms of thermonuclear fuel supply in the Sun, it's a good approximation. We're talking about space here.

Re:free electricity!

[bluefoxlucid]

Imagine a nuclear 747. The turbines spin, air moves through, and the plane moves. Great for a 50 pound brick of metal as a fuel source, eh?

Now imagine that 747 in space.

One of these things actually works. The other doesn't.

Re:free electricity!

[Anonymous Coward]

Sure, so as long as you're close enough to the Sun to allow for practical solar panels to work, whoopee, we're colonizing space now!!!

Re:free electricity!

[SJHillman]

It is possible to generate electricity without expendable fuel, whereas our current methods of chemical propulsion *must* use expendable fuel. Unless your religion doesn't believe in solar panels?

Re:free electricity!

[invid]

If you live near a star and you have solar panels, you won't need expendable fuel.

Re:free electricity!

[Anonymous Coward]

Compared to burning fossil fuels, electricity is easier to derive from multiple sources (solar panels, thermocoupled radioactive decay nuclear batteries, fuel cells), especially on a vehicle where refueling can be prohibitive.

For satellites, this is profound, as the life span of most satellites is determined by the amount of fuel they carry to correct orbital trajectories. Any time a satellite has to change orbit (i.e., retasked), it shortens it's service time significantly. Now, with reactionless propulsion, satellites are only limited by their ability to produce electricity. Of course, only when this technology proves out and it is able to be put into service.

For a Mars mission, for instance, it's a lot easier if all you need for propulsion is a fission reactor core and require no reactive fuel. Previously, you had to factor in this additional mass requirement. Now, all you have to worry about is breathable air and water for the crew.

Re:free electricity!

[NotDrWho]

Imagine a nuclear 747.

I'm already working on my pitch to Syfy.

Re:free electricity!

[Guspaz]

Luckily, there are existing electric propulsion technologies. They don't provide much thrust, but they're extraordinarily efficient (they require so little "fuel" as to effectively not be using any, with VASIMR producing roughly 10x-20x the fuel efficiency of chemical rockets, and the current VASIMR engine is very inefficient in terms of heat loss and such). The problem is that we've never had any large source of power in space, so while electric propulsion is great for getting your probe around the solar system with a minimum of fuel consumption, or perhaps automated cargo runs to some future colony that isn't time sensitive, they're not going to get you anywhere.

However, if you fit a nuclear reactor inside a 747, strap a bunch of if VASIMR thrusters to it, then that'd actually work. You wouldn't get much thrust, though... the 200 kW VASIMR engine produces only 5N of thrust. If you put a nuclear reactor on the thing similar to what you'd find in a submarine, you'd get 300N of thrust. Compare that to the "Draco" rockets used by a SpaceX dragon as manoeuvring thrusters... they have 400N of thrust.

Re:free electricity!

[PPH]

Imagine a nuclear 747.

OK

Re:free electricity!

[Anonymous Coward]

For comparison, you can accelerate a 747 to Earth escape velocity in half a year with 300N force, a=300N/450000kg, v=a*60*60*24*180s=~10km/s

Re:free electricity!

[jythie]

For that matter, a nuclear source on a probe or satellite can be treated as fuelless energy. Much better then having to expend propellent.

Re:free electricity!

[The Grim Reefer]

Now imagine that 747 in space.

I believe you meant a DC-8.

Re:free electricity!

[Shortguy881]

Problem being is all of these thrusters (VASIMR and the one above) only work in a vacuum. Good luck flying anything in atmo with one of these.

Re:free electricity!

[sycodon]

I expect that the vast majority of people reading that knew they were referring to the elimination of rocket fuel.

Re:free electricity!

[Guspaz]

What atmosphere would a 747 in space have to contend with? Of course it's absurd to have put a 747 in space to begin with, but then that was bluefoxlucid's example, not mine.

Re:free electricity!

[Guspaz]

I think your mass figures are off, that's above the maximum takeoff weight of a 747 (442mt), let alone the weight of the empty aircraft itself. Of course, somehow this 747 got into orbit, so the maximum takeoff weight is kind of meaningless.

An empty 747 weighs 178mt, and a submarine reactor weighs about 110mt. It's true that there are micro reactors that can produce about the same output at a fraction of the weight, but let's just say that we also need some radiators for cooling (since there's no active cooling in space) and call it as using up that extra weight. Some weight for the thrusters themselves, and perhaps 300 tons is a feasible weight for an unmanned spacefaring 747. Which is a totally insane phrase to say, I'll admit.

Re:free electricity!

[Immerman]

Well, technically you are still using expendable fuel - it's just in the form of the hydrogen being fused in the core of the sun with the power being beamed away as omnidirectional EM radiation. That you're operating a power antenna rather than a on-site reactor, or that the available fuel supply is projected to last for billions of years are incidental to the physics.

Of course, for most practical purposes on a human timescale, operating within range of a nigh-infinite near-constant power broadcaster is indeed functionally very similar to not needing expendable fuel.

Re:free electricity!

[bluefoxlucid]

Still wrong. VASIMR ejects ionized particles--mass--which is the same problem as a chemical rocket: eventually you run out of shit to eject.

We're looking for a technology that can take energy and turn it into movement without ejecting any mass. In other words: We're looking to keep going even when we have no mass to eject. You can't eject the control units, the ship's body, its atmosphere, or its crew, if you want it to keep functioning or support life; so your nuclear pile might remain hot longer than your mass resources hold out.

Re:free electricity!

[bluefoxlucid]

No, those are DC-8s with rocket engines.

Re:free electricity!

[fahrbot-bot]

Imagine a nuclear 747.

I'm already working on my pitch to Syfy.

Be sure to include sharks and tornadoes in your pitch as that seems to be what goes for SciFi at SyFy these days - sigh.

Re:free electricity!

[fahrbot-bot]

Imagine a nuclear 747.

I'm already working on my pitch to Syfy.

Be sure to include sharks and tornadoes in your pitch as that seems to be what goes for SciFi at SyFy these days - sigh.

Oops! Forgot. And WWE - double sigh.

Re:free electricity!

[Anonymous Coward]

http://mentalfloss.com/article/53184/brief-history-nuclear-airplanes

Re:free electricity!

[Anonymous Coward]

Pretty much anything that pushes something other than photons is actually a reaction-mass drive, VASIMR included.

My favourite zero-mass drive is a conveniently shaped heat-spreader. The impuse is too low, though... that heat spreader might end up doing more work because it acted as a solar sail :-p

Re:free electricity!

[mycroft16]

Technically, the solar energy comes from the Sun burning its expendable fuel, hydrogen, in a massive fusion reaction regulated by its the gravitational field of its fuel source.

Re:free electricity!

[david_thornley]

In Harrison's "Star Smashers of the Galaxy Rangers", the 747 was using a cheese-based drive for interplanetary and interstellar travel. None of this VASIMR nonsense.

Re:free electricity!

[CaptnZilog]

The aliens won't be happy when a box full of radioactive stuff collides with their spaceship and doses them with radiation 1000 years from now.

We might be extinct by then, of course... and if they don't have FTL travel it'll be another 1000 years+ after that for them to get here, to blow us all to extinction anyways for our negligence in launching toxic radioactive crap into space at them.

Re:free electricity!

[K. S. Kyosuke]

SLAM was much cooler, though. Or hotter, Geiger-wise...

Re:free electricity!

[TeknoHog]

I claim rights to the title "Eels on a Hovercraft".

Re:free electricity!

[Anonymous Coward]

That's a nuclear B-36, not a nuclear 747.

Re:free electricity!

[complete loony]

And your nuclear reactor is also turning mass into energy to drive it. Both the mass of the exhaust and it's velocity must take away mass from your craft.

Re:free electricity!

[Anonymous Coward]

Sharknado vs Nuclear 747: The end of the end

Re:free electricity!

[Anonymous Coward]

Now, with reactionless propulsion, satellites are only limited by their ability to produce electricity.

Hold on, there. The magnetrons currently available for space missions have a lifespan of about 15 years. Even you should know that if you kept your childhood microwave on for long enough, it would burn out. We don't have the eternal spacecraft here; parts still have a limited lifespan. Given that, the lifespan is increased drastically and fuel is not the bottleneck anymore

Re:free electricity!

[bluefoxlucid]

You get a lot more use out of a boat oar pushing against the water than you do hurling it like a javelin away from your boat.

From the pdf...

[Anonymous Coward]

Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce
thrust.

Re:From the pdf...

[SJHillman]

The best part of science is when we expect X to happen, but we get Y instead. And the very best of that is when X = nothing.

Re:From the pdf...

[Anonymous Coward]

No, the best part is that NASA were able to prove 1000 times more accurately than the Chinese that the "engine" produced NO thrust and that there are some inaccuracies that they haven't eliminated.

Re:From the pdf...

[SJHillman]

Why won't you let me have my magic space drive? Picard had one. Solo had one. Why can't I have one?

Re:From the pdf...

[tjmcgee]

You're right. "Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust. Specifically, one test article contained internal physical modifications that were designed to produce thrust, while the other did not (with the latter being referred to as the "null" test article)." Also: "within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure" I think maybe they made one of these: https://www.youtube.com/watch?...

Re:From the pdf...

[brambus]

Aside from the warp drive, which is currently from a physics stand point pure gobbledygook, the sub-luminal "impulse drive" of the Enterprise was a classical nuclear fusion plasma engine fueled by interstellar hydrogen gas (that's why those red things on the front of the Enterprise's warp drive nacelles were called Bussard collectors). It is technologically speaking far in excess of what we can do today, but nonetheless theoretically permitted by known laws of physics.

Re:From the pdf...

[ConceptJunkie]

which is currently from a physics stand point pure gobbledygook

Dr. Alcubierre would beg to differ.

http://en.wikipedia.org/wiki/A...

The warp drive in Star Trek was based an earlier incarnation of this theory, which is based on results from Einstein. Warp drive FTL travel might not be possible, but the idea is definitely not "pure gobbledygook".

Re:From the pdf...

[pla]

No, the best part is that NASA were able to prove 1000 times more accurately than the Chinese that the "engine" produced NO thrust and that there are some inaccuracies that they haven't eliminated.

...By arbitrarily ignoring the design used by not just the Chinese, but also the British, and coming up with their own entirely different and untested version. "Hah, we've proven that your Bugatti Veyron can't do 0-6 in under 2.5 seconds, because we tried it in our Ford Fiesta and it took over 9 seconds!".

Wee bit of "Not built here" syndrome, I wonder?

Re:From the pdf...

[brambus]

I'm aware of this idea and that it requires as yet purely hypothetical forms of matter that have negative mass. Just because you can contrive GR's equations to allow for all manner of things, such as wormholes and time-travel, does not mean that those things actually exist, or that there's any practical way for them to exist. Meanwhile, nuclear fusion of hydrogen nuclei is a very well known and observed process. A Bussard ramjet scoop, meanwhile, also doesn't require any kind of exotic new physics, just lots of large-scale engineering. That was my point.

Re:From the pdf...

[mycroft16]

Physics says moving an object faster than light relative to spacetime is impossible. However, physics does not say the same about moving spacetime faster than light relative to a stationary object. Seems like the same thing, but they are very different in physics. In fact inflation of the early universe was an expansion of spacetime itself, not the objects within spacetime moving apart, that occurred at speeds faster than light.

Re:From the pdf...

[brambus]

Wonderful! I await your complete theory of dark energy with baited breath. Or maybe I don't.

Re:From the pdf...

[Anonymous Coward]

Jealous again, Holmes?

Re:From the pdf...

[Anonymous Coward]

Actually the Chinese did produce a measurable thrust, but NASA for some odd reason used a different design from theirs and the original English inventor (Roger J. Shawyer) who came up with it. From the website of the guy who worked with NASA (Guido Fetta), he calls it the "cannae drive" instead of the EmDrive and it looks like a flying saucer instead of a rhomboid shaped metal chamber. This is quite different from the original design and likely why it doesn't work as well.

Now why they wouldn't try and replicate the original design is beyond me. Maybe NASA doesn't care much about revolutionary propulsion technologies.

Re:From the pdf...

[Anonymous Coward]

i guess they were trying to reproduce the physics with another version to see if the effect still happens. it still happens, and they have a vague idea of how it works. so less space magic and more "huh, that's not right..."

Re:From the pdf...

[Anonymous Coward]

'bated' breath. Held, hushed, a state of breathless anticipation. See also 'abate'. As grammar mistakes go, this is one of the dumber ones.

Re:From the pdf...

[Anonymous Coward]

Maybe he's saying his mouth smells like mealworms...

Re:From the pdf...

[Anonymous Coward]

physics does not say the same about moving spacetime faster than light relative to a stationary object.

er... I don't think that's exactly true. If the object is stationary than it isn't going anywhere or it wouldn't be considered stationary. At the hearty of relativity is the assumption that there are no 'special' frames of reference. An object can't be stationary in relation to something not of this universe so that the universe can move past it faster than the speed of light. Whether something is 'stationary' while the universe moves by or the universe is 'stationary' while the object moves through it is exactly the same from a physics stand point, it's the difference between the two states that generates the energy (and therefore the mass, which is what keeps the object from being able to accelerate to light speed).

On the other hand, the universe can appear to expand faster than the speed of light due to the cumulative effects of expansion. It's like this, If you were to line up 3 billion enormous balloons so that they were all touching and then arrange to have them all blown up, simultaneously, so that their diameters increased by 1 meter in 1 second, the outer edge of the farthest balloon would appear to be moving away from you faster than the speed of light . It's not a perfect analogy but it's the best I can come up with without invoking light cones or dark energy.

Also, I should point out, when the universe expands, by definition, the stuff in it moves farther apart, or there wouldn't be any way to tell it's expanding.

Re:From the pdf...

[Anonymous Coward]

Alcubierre generally works with 3+1 formalisms and numerical relativity. ("He wrote the book!") In particular, he is well known for finding software bugs in tools. The Alcubierre Drive exposes a couple of them and also a few problems in some popular 3+1 formalisms (BSSN and ADM in particular) that were easier to reason about than in one of his usual areas of application (corrections to Schwarzschild and Kerr black hole solutions).

The Alcubierre Drive thought experiment was that he could choose a "Final Value Surface", foliate a space-time in which there is a spacelike hypersurface corresponding with the FVS, and step backwards through the foliation and recover an initial value surface from one of the spacelike hypersurfaces closer to the early boundary of the model spacetime. This is roughly similar to demonstrating that a 3+1 formalism is time-symmetric. It turns out that with a careful foliation, ADM does allow for time symmetry in the Alcubierre metric, which was an interesting and useful result, the idea being that simulations involving black holes that are not eternal and which eventually evaporate. (Schwarzschild black holes are eternal; astrophysical ones form via gravitational collapse and are expected to evaporate due to Hawking radiation).

Additionally, the thought experiment when subjected to actual calculation exposed some issues in the process of recombining the foliated spacetime into a block universe. This now known to be a generic problem that 3+1 formalisms have to deal with.

There was never any idea that an Alcubierre Drive could actually be built -- Alcubierre did not propose any physical mechanism to generate the metric, he just drew a formal analogy between it and a collapsing shell of gas.

However, the metric is so simple that people have from time to time tried to grind out plausible mechanisms for generating it, and some of that isdescribed here:

http://www.sfu.ca/~adebened/fu...

Neat, and useful as a fun teaching tool, but absolutely a "gobbledygook" idea (see the last line of the link above).

Re:From the pdf...

[cytg.net]

this +1. Accidental scient for the win! However improbable(duh), I really hope there is something to this. Awsome-factor will be through the roof. Kind of like Hawking on the Higgs when he said something along the lines of; But the universe would be so much more interresting if you hadnt found it. Common, give us an interresting universe, please :).

Re:From the pdf...

[Anonymous Coward]

Impulse power required "inertial dampeners" to work. So that's gobbledygook too

Bad summary

[Anonymous Coward]

No. The NASA team have found unexplained faults in their test apparatus. The null experiment ALSO produced the tiny thrust.

Sensationalism at its worst

[MyLongNickName]

Fact 1: The NASA team has measured approximately 30-50 micronewtons of thrust in the experiment
Fact 2: The NASA team experienced a similar thrust on a test item that was NOT design to experience any force.

It is pretty obvious that there was a systematic error in NASA's experiment.

Re:Sensationalism at its worst

[Charliemopps]

Fact 1: The NASA team has measured approximately 30-50 micronewtons of thrust in the experiment
Fact 2: The NASA team experienced a similar thrust on a test item that was NOT design to experience any force.

It is pretty obvious that there was a systematic error in NASA's experiment.

Or the midichlorians were just screwing with them for fun.

Re:Sensationalism at its worst

[Sockatume]

The relevant quote:

Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust. Specifically, one test article contained internal physical modifications that were designed to produce thrust, while the other did not (with the latter being referred to as the “null” test article)

Re:Sensationalism at its worst

[meta-monkey]

The big problem I have with their "test" is that they did it at atmospheric pressure. So, they're supposing the force is pushing off quantum vacuum virtual plasma. That's one possibility. The other possibility is it's pushing off THE FREAKING AIR IN THE CHAMBER.

Don't get me wrong, I would love to see a reactionless drive. A reactionless drive could get us to the stars. But it generally involves violating conservation of momentum, and that's unlikely.

Re:Sensationalism at its worst

[minogully]

Fact 2: The NASA team experienced a similar thrust

[citation needed]

From the NASA article:

Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust.

and

Test results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma.

I don't read this as a "similar thrust" but rather as a non-zero but different thrust. So, yes, there's an error in the experiment causing the non-zero thrust, but there was still enough of a difference between the two experiments to lead them to the conclusion that something is going on.

Re:Sensationalism at its worst

[jschultz410]

Thank you! You beat me to posting this. From the summary:

"Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust. Specifically, one test article contained internal physical modifications that were designed to produce thrust, while the other did not (with the latter being referred to as the "null" test article)."

Re:Sensationalism at its worst

[jschultz410]

Nope, they did it in a vacuum chamber ...

Re:Sensationalism at its worst

[Ceriel Nosforit]

How do you explain the discrepancy between the two tests?

Re:Sensationalism at its worst

[fnj]

What part of this is hard to understand? "Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level, within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure." That's a direct quote from the abstract of the NASA paper.

It was in a vacuum chamber, but it was not in a vacuum.

Re:Sensationalism at its worst

[Anonymous Coward]

They did it in a vacuum chamber at atmospheric pressure. I don't really understand the point of that.

Re:Sensationalism at its worst

[angel'o'sphere]

Why do people always make such stupid claims: ... it generally involves violating conservation of momentum, and that's unlikely. Why would a drive using microwaves to utilize a quantum effect violate impulse conservation? Your ship gets a momentum in one direction ad said quantum effect thrust holds the other half of the momentum ... obviously!

Re:Sensationalism at its worst

[jschultz410]

Whoops! Mis-read that somehow. I thought it said ambient temperature. The fact that they were doing it an vacuum chamber threw me off. And, yes, I know temperature in a vacuum doesn't mean a whole lot. Just read too fast.

Re:Sensationalism at its worst

[sycodon]

What would be more likely?

1. They tested a quantum vacuum plasma thruster inside a vacuum chamber, which is probably cramped, difficult to run test instruments in, and costs more than a bench top and even closed the door but DIDN'T perform the test in an actual vacuum.

2. The did perform the test in a vacuum, but the abstract simply mischaracterizes what they did because the author of the abstract was some Public Relations flunky.

Re:Sensationalism at its worst

[ConceptJunkie]

If the thing works, it's not that it violates conservation of momentum, it's that it's doing something we don't understand, which appears to violate the conservation of momentum because we don't know how it works.

I'm sure many people would love to see this turn out to work because it would be a really cool real-world effect based on some of the the really bizarre and incredibly abstract physics going on these days. Like many people here I'm sure, I'm fascinated by the advances in modern physics in the last century, but a lot of it, especially in the past 30-40 years, seems to bear no connection to the world we see and experience. I know it explains how matter and energy work, but I'm talking about allowing us to do things we couldn't do before.

Plus, who isn't looking at this and wondering if it couldn't be the basis, assuming it can be improved umpty orders of magnitude, to Jetsons-style anti-gravity devices. Let a nerd dream...

Re:Sensationalism at its worst

[Anonymous Coward]

Depends... it could be correct that it is systematic or it could be that the force is being generated in some unknown way, by both objects. They should have run with a truly null test article - something like a house brick, and perhaps no test article too.

Re:Sensationalism at its worst

[K. S. Kyosuke]

They homeopathically used a smaller amount of vacuum to strengthen its effect.

Re:Sensationalism at its worst

[green is the enemy]

I haven't seen this vacuum issue addressed by anyone after some searching. To me it seems premature to speculate about quantum vacuum effects when interactions with air seem very likely. Perhaps they planned to perform these experiments in a vacuum, but didn't quite get to that point when the abstract was due? At this point, they may have finished the vacuum version of these experiments, so may have some results to present. If someone does know, please pitch in.

Re:Sensationalism at its worst

[cbhacking]

Fact 3: You're talking about the Cannae Drive, not the EmDrive.
Fact 4: They (NASA Eagleworks) *ALSO* tested the EmDrive, and found that it produced approximately 91 microNewtons of thrust.
Fact 5: According to the inventor of the EmDrive (who is NOT the inventor of the Cannae Drive), the Cannae Drive (in either normal or "null" variant) is just an inefficient EmDrive.

Now, I'm not saying that the EmDrive guy (Shawyer) is right. But *YOU* are wrong. There is no conclusive evidence of a systematic error in NASA's experiment.
Ockham's Razor time: which of the following is more likely correct?
1) The inventors of the EmDrive (Shawyer) and the Cannae Drive (Fetta) are both correct that their drives produce thrust, but Fetta is wrong that the radial grooves (which the null test was lacking) are required, and Shawyer is correct that his version is more efficient (though his understanding of why may still be wrong).
2) Both inventors are completely wrong, the Chinese experiment is wrong, and the fact that all of the test devices produce detectable thrust in the appropriate direction regardless of which way they are pointed is a "a systematic error in NASA's experiment".

Option 2 doesn't sound "obvious" at all.

Re:Sensationalism at its worst

[cbhacking]

Uh huh. That is a possibility.

So, where does "THE FREAKING AIR IN THE CHAMBER" go then, smart guy? What does it impart its momentum to? How does this produce a *net* thrust in one direction?

Actually, screw all that shit. Fine. This thing produces a thrust in one direction when placed in a sealed chamber containing air at 1 bar. Strap it to your spaceship or satellite - sealed air-containing surrounding chamber included - and go to town.

Why do people comment on physics when they have "NO FREAKING CLUE ABOUT BASIC DYNAMICS"? You just reveal yourself as an idiot.

Featured in a movie

[Anonymous Coward]

Brave Little Toaster goes to Mars

cool!

[silfen]

Let's power it with cold fusion! Alpha Centauri, here we come!

The paper...

[hAckz0r]

Is useless drivel. Its a one page abstract that reads like a news media comentatry of the test. There are not even graphs of measurments taken, no specifics on the test setup. Nothing. Its not even Science by my definition. Lets move along, nothing to see here.

Re:The paper...

[Anonymous Coward]

That's not the paper you utter fucking retard. It's the abstract.

A HowTo suggestion from a KSP discussion

[Paul Fernhout]

http://steamcommunity.com/app/...
"ishanda --- Kerbal Space Program Apr 17, 2013 @ 2:29am; If you REALLY want Star Trek Style impulse engines why not mod them yourself? All you really need is to make copies of the relevant part files, change the name of the Xenon Tank to "Deuterium" and change the Ion Engine to "Impulse Engine" and then change a few values to make them super efficient. Done."

Still looking forward to seeing how the real device pans out though... Just like I'm still wondering about all the claimed cold fusion results which may also be exploring new areas of physics and chemistry with the behavior of hydrogen atoms at the edges of metal lattices or in cracks in them perhaps in interaction with electro-magnetic pulses ...
http://www.extremetech.com/ext...

I'm still waiting on "Tom Swift and his Space Solartron" though: :-)
http://www.tomswift.info/homep...
"The main invention in this book is, of course, the Space Solartron. The Space Solartron was probably Tom Swift's most amazing -- and far-fetched -- invention. Its purpose was to make space travel practical by creating oxygen, water, and food from sunlight -- not a simple task, to be sure."

I've mused about even better tech that will extract energy and mass from zero point energy. Although we might then get a "tragedy of the commons" as so much mass and energy is created in nearby outer space as to collectively form a black hole? Now that might be another good mode for the multi-player version of Kerbal Space Program to see what happens politically as that "tragedy" plays out as the outer space equivalent of anthropogenic global warming? :-)
http://www.pcgamer.com/2013/11...

Perhaps that political problem might already be playing out at the core of out galaxy? :-)
http://science.slashdot.org/st...

Back to the EmDrive device, it would not surprise me if the impulse provided by the microwave device is much less than the impulse imparted by photons and/or solar wind on any satellite's solar panels to capture needed electricity. But that might be a non-issue if you have a small "Mr. Fusion" fusion reactor or cold fusion LENR device onboard the satellite? :-)

Of course, station keeping is even easier if you have a "HyperEdit" debugger hook into the simulation. :-)
http://www.pcgamer.com/2013/11...
"If you still think MechJeb is cheating, take a look at HyperEdit. It is cheating. Install it, tap Alt+H, and you're given a menu full of options that let you tweak and edit the game. With a few clicks, you can teleport your craft to the orbit of any planet on the solar system, then use the landing options to gracefully touch down. Alternatively, you can instantly replenish your fuel, obliterate a selected craft, or readjust Kerbin's gravity to make escaping its atmosphere unnaturally difficult. HyperEdit is a flexible toolbox that, when used without restriction, completely destroys the difficulty. With a little imagination, though, you can use it to create your own custom scenarios. It's as simple as popping an abandoned craft on a distant planet, and suddenly you've got the basis for a tricky retrieval mission."

See also:
http://www.simulation-argument...
"This paper argues that at least one of the following propositions is true: (1) the human species is very likely to go extinct

Not impossible just misunderstood

[epwpixieqneg1]

Everyone who has experimented with High Voltage 30-40KV+ will tell you that there is a thrust effect, observed. Clearly, this is due to the push against the dielectric particles of air, here on earth, but the same is true for the interplanetary space, just there the particle are fewer but of course the speeds they accelerate to a lot higher. If one reads Tesla's publications in "The Electrical Engineer" from June 10, 1892 ( and several others form the same train of publications), (s)he will realize the concepts and see that this is naturally possible phenomena, just requites clear understanding without common misconceptions.

Re:Not impossible just misunderstood

[CaptnZilog]

Everyone who has experimented with High Voltage 30-40KV+ will tell you that there is a thrust effect, observed. Clearly, this is due to the push against the dielectric particles of air, here on earth, but the same is true for the interplanetary space, just there the particle are fewer but of course the speeds they accelerate to a lot higher. If one reads Tesla's publications in "The Electrical Engineer" from June 10, 1892 ( and several others form the same train of publications), (s)he will realize the concepts and see that this is naturally possible phenomena, just requites clear understanding without common misconceptions.

That's called an ion drive, you're ionizing the free air around you (or in space perhaps a very thin amount of particles for much smaller thrust), You are still a 'reaction' drive, just not carrying the 'fuel' - not a 'reactionless' drive which this is claiming.

Carry the one

[FatLittleMonkey]

No, the question is how fast can it accelerate the average potato. NASA reported 30-50 mN of thrust., call it 40. The average potato is about 375 grams, call is 400 even so math is real east. F=m*a or a = F / M or 1e-7 m/sec^2.

40 mN is 0.04N

400g is 0.4kg

a = F/m = 0.04 / 0.4 = 0.1 m/s^2 not 0.0000001 m/s^2.

Therefore accelerating for 3e7 seconds (one year) results in a velocity of 3000 km/s. About 1% of lightspeed. And a distance of 330AU. You'll hit one lightyear in 19 years. Two lightyears in about 28 years, if you turn your potato around to decelerate, you'll deliver your potato to Alpha Century in 56 years. If you want to cook your potato by skimming one of the stars, it'll only take 38 years.

Re:Carry the one

[FatLittleMonkey]

[gewalker said "mN" so I used milliNewtons. I should have checked the paper, it's 30-50 microNewtons (30-50uN). So drop the velocities by 1000. And ignore the rest.]

Re:Carry the one

[Orleron]

You know, you can also strap two or three dozen of these thrusters to the back of of the potato to make it go faster. Accounting for the mass of the engines and the mass of the potato would still make a faster trip.

Re:Carry the one

[Anonymous Coward]

RTG on your potato? there is alot of kinetic energy in a chunk of plutonium the size of a football.

your potato is closer to a kinetic kill vehicle now, but still useful.

Re:Carry the one

[FatLittleMonkey]

Unfortunately, even though you wouldn't have to supply propellant, you would still need to supply the energy to accelerate it.

Actually you don't. Any reactionless thruster can be turned into a free energy machine. If force-produced is directly proportional to energy-input (eg, the device in TFA gets 31uN/W) regardless of position in the universe and direction of thrust (**), then the change of velocity per unit time is also proportional to energy-input. Linear. But the kinetic energy available is proportional to the square of total velocity. There's a cross over velocity where the increase in kinetic energy is greater than the energy input necessary to produce that change in velocity. Stick a set of reactionless thrusters on a flywheel, hook the hub to a generator, spin it up until the tip-velocity passes the cross-over, and from then on it's a free energy machine. So the potato would have one set of EMdrives powering a generator, and another set for propulsion powered by the generator.

At 31 microNewtons/Watt, the required tip velocity is over 30km/s, a wee bit past material limits. But as the "Q" increases in the EMdrive (predicted for the use superconducting cavities) the cross over velocity drops below 100m/s, well within the tip-velocity of a generator flywheel.

(** An anti-gravity drive that could only act in the direction of existing gravity, and lost efficiency moving out of a gravity well or at speed within a gravity well, wouldn't be a free energy machine. And the inventors of the EMdrive have indeed created some ad-hoc explanation for why theirs loses power at speed (to which every critic screams back "relative to what!") and can thus magically only be used to hover.)

Re:Carry the one

[Anonymous Coward]

But but but .. it isn't so important how long it takes to _cook_ your potato. It's how long it takes to _eat_ your potato! I suggest a close approach (cooking), loop around that sun (reverse direction), and then another 38 years for the return trip. Presuming the deceleration takes as long as the acceleration, you'll have your potato back, right where it started from (more or less) in 76 years.

Re:Carry the one

[SoftwareArtist]

Wow, that was wrong in so many ways.

1. There is no such thing as a "free energy machine".

2. No one is claiming this device is a "free energy machine". You have to put energy in as electricity, and you don't get more energy out than you put in.

3. No one is claiming this device is "reactionless". There's ongoing discussion about the exact mechanism (assuming it actually works). They suggest it may be pushing against space itself, somewhat analogously to how a swimmer pushes against the water they're swimming through. But if it actually does work, it almost certainly conserves momentum.

4. In any case, conservation of momentum and conservation of energy are independent conservation laws that come from different symmetries of the universe. If one turned out to be wrong, that wouldn't automatically mean the other was wrong too.

Re:Carry the one

[FatLittleMonkey]

1. There is no such thing as a "free energy machine".

And that's why skeptics are skeptical of the claims made for the EmDrive.

2. No one is claiming this device is a "free energy machine".

Skeptics are, because all reactionless drives are free energy machines.

You have to put energy in as electricity, and you don't get more energy out than you put in.

However, the power input is constant for the thrust out (Newtons-per-Watt), therefore power input is constant for acceleration (m/s^2-per-Watt), therefore energy input is constant for delta-V (m/s-per-Joule). But the energy out (kinetic energy) is proportional to the square of total velocity (Ek=1/2mv^2). Therefore energy-in increases more slowly than the energy-out. (Energy-in is linear, energy-out is exponential.) At a certain velocity, the energy-out exceeds the energy-in, and the device can be used to power a free energy machine.

It can be hard to get your head around, you may want to actually do the maths to convince yourself. (Fortunately the maths is simple. Basic Newtonian stuff. You get to skip all the GR stuff and just use the proponent's own figures for Newtons-per-Watt.)

3. No one is claiming this device is "reactionless".

Skeptics are. It's the class of device that the EmDrive belongs to. How it actually operates is largely irrelevant. All the proposed mechanisms have the same problem. For example...

it may be pushing against space itself, somewhat analogously to how a swimmer pushes against the water they're swimming through.

Space doesn't work that way.

Say the device interacts with virtual particles, a la Casimir Effect. The physics of virtual particles is not analogous to regular particles. The net velocity of virtual particles is zero, regardless of the velocity of the EmDrive. Hence it is still a "reactionless" drive, for the purposes of physics, even if people are waving their hands and saying it "reacts" with virtual particles. It's not the sort of "reaction" that Conservation of Energy or Momentum need to balance their books.

(The faster a swimmer goes, the more drag they experience, the more power they expend to overcome that drag, the less "efficient" the "device" (this loss of efficiency increases their free-energy transition velocity, so they never reach it.) But virtual particles are always at the same speed as a quantum "swimmer", the swimmer never experiences drag. A water-swimmer can't be used as a free energy machine because they can never reach the transition velocity due to drag. But a quantum-swimmer can. If free energy machines are impossible, then so is quantum swimming.)

The same is true of every proffered mechanism for the EmDrive.

Re:Carry the one

[SoftwareArtist]

2. No one is claiming this device is a "free energy machine".

Skeptics are, because all reactionless drives are free energy machines.

That's doublespeak. No one who believes in it claims it's a free energy machine. Ok, you are free to announce, "It's a free energy machine, therefore it can't exist!". But since you don't have any evidence to support your claim, that's meaningless. Either it works or it doesn't. If it does work, it almost certainly is not a free energy machine. No one has presented any evidence to indicate it doesn't conserve energy. If you make that claim anyway, it just shows you're making claims that aren't based on evidence. It tells us nothing about whether this device actually works or not.

It can be hard to get your head around, you may want to actually do the maths to convince yourself.

The only thing that's hard to get your head around is that you just made two assumptions that directly contradict each other. Conservation of momentum follows from Newton's laws of motion. If you assume momentum is not conserved, you aren't allowed to use Newton's laws anymore. But that's what you just did. You first assumed the existence of a phenomenon that violates Newton's laws, and then immediately started applying Newton's laws as if they were valid. If you make two assumptions that contradict each other, all your conclusions are invalid.

3. No one is claiming this device is "reactionless".

Skeptics are.

Same as above. Or to summarize:

Scientists: "Experiments indicate this device seems to work. We're not absolutely convinced yet, and we don't completely understand the mechanism. But if it really does work, we're pretty darn sure it must conserve energy and momentum."

You: "This device doesn't conserve energy or momentum. (Because, well, I just know it doesn't, even though I don't have any evidence to prove it.) Therefore it can't work."

Space doesn't work that way.

Say the device interacts with virtual particles, a la Casimir Effect. The physics of virtual particles is not analogous to regular particles. The net velocity of virtual particles is zero, regardless of the velocity of the EmDrive.

Now you're just making things up. There is no difference between "virtual" particles and "real" particles. They obey exactly the same physics. If a particle/antiparticle pair is created out of the vacuum and then is annihilated without ever being observed, we call them "virtual" particles. But while they exist, they can interact with other particles, and they interact in precisely the same way other particles do. Furthermore, that interaction can sometimes prevent them from annihilating each other, in which case we say they have become "real" particles that were created out of the vacuum by the energy of the interaction.

Actually, the whole concept of "virtual particles" is just an artifact of the mathematics: we don't know how to describe the true vacuum state, so we use perturbation theory to write an infinite series describing how it differs from another state we do know how to describe. And we call the terms in that infinite series "particles".

All of which is really completely irrelevant to the question at hand. A particle/antiparticle pair initially has zero momentum, but they absolutely can interact with other particles, and that interaction can impart momentum to them.

Re:Carry the one

[FatLittleMonkey]

you just made two assumptions that directly contradict each other. Conservation of momentum follows from Newton's laws of motion.

Newton's laws also fall out of GR at non-relativistic velocities. The inventors say their device is consistent with GR.

If you assume momentum is not conserved

I'm not assuming it, if the device works as advertised, it meets the standard criteria for "reactionless", and thus it can be used to create a free energy machine.

For it not to be able to be used as a free energy machine, it must break some other tenet of physics (such as mass/inertia equivalence, non-locality, no universal frame of reference, etc.) The explanations by the inventors have mostly involved ad-hoc efforts to let it break some tenet, but somehow in a way that doesn't actually break it. "It's exchanging momentum with the inertial state of the background universe, but not by violating non-locality", "it's interacting with virtual particles, but in a way that doesn't violate CoE", "it can't be used to accelerate, only to hover, but totally doesn't violate equivalence," and so on.

There is no difference between "virtual" particles and "real" particles. They obey exactly the same physics.

Virtual particles work in a different way to regular particles, because at the beginning of a reaction the virtual particles always have net zero initial velocity (net zero momentum) WRT the device, regardless of the acceleration of the device; that means the device will have a constant force-per-watt equation regardless of velocity. With regular particles, if you accelerate, you change their velocity relative to you, that changes the force-per-watt equation. The two are not analogous.

(Read my explanation using your "swimmer" analogy.)

And this is the same regardless of what explanation you have for the "fabric" of space, virtual particles, quantum foam, M-theory. They all must have this zero-net-velocity component in order to be consistent with, not just theoretical, but observed general relativity.

Re: Virtual particles becoming "real".
However, they steal that energy from something else. For example, when a virtual particle pair is split by the event horizon, the lost partner reduces the mass of the black hole. The net energy must be zero. And it must be uniform, there's no propulsive effect.

[In the case of a "drive", if you push against one partner in a virtual pair, you will be pulled back by the equal-and-opposite virtual partner. The net is zero. Even with Casimir, both sides of the gap are pulled equally. No net force.]

A particle/antiparticle pair initially has zero momentum, but they absolutely can interact with other particles, and that interaction can impart momentum to them.

But not net momentum. Not a force in a single direction.

--

Aside: Doesn't it make you curious that the more careful (and skeptical) the experimenters are with their test rigs, the smaller the measured effect gets?

Doesn't it make you curious that the supposed "null" device, designed by the same people not to produce a force, somehow produced a force on the same test rig? Isn't that what a null hypothesis is for? Doesn't Occam's razor suggest that the experimental protocol is missing an unusual but mundane effect and not a revolutionary unidirectional reactionless propulsion system?

Frankly the whole thing screams of a very technical version of those old perpetual motion devices made from magnets and moving weights and levers arranged on a wheel, which the inventor insists allows one side to experience more force than the other. No matter how many people explain why it can't work, they concoct increasingly elaborate explanations for how it must work. Look! It's turning! Oh it stopped. Well that just means it needs stronger magnets and axles with less friction. (Or in the case of EmDrive, superconducting cavities and higher-Q designs.) Or, in mathematics, like someone encountering the Monty Hall three door problem for the first time.

Re:Carry the one

[cbhacking]

Do we know how careful the Chinese experiments were, relative to the NASA ones? Serious question, because yes, the difference *is* curious... but it's not necessarily due to one result being inaccurate. The experiments were not identical. NASA used much lower input energy, and a non-identical apparatus.

The expressing of thrust in terms of input energy (linearly) is weird and questionable for all the reasons you state. If thrust/energy does indeed remain constant regardless of velocity, then yes, that would appear to be usable for free energy. What this means is one of three things: 1) It doesn't, and we misunderstand the mechanism involved (since the latter half of that statement is almost certainly true, the first could be as well); 2) It does, but this doesn't produce free energy because our understanding of the physics there is wrong (unlikely but possible, if there is a thrust then it's caused by something our previous models did not account for and they only appeared to be accurate because of approximations at near-zero levels of this activity); 3) Free energy is possible after all, and everything that says otherwise is itself not entirely accurate).

By the way, you seem to have forgotten (or misunderstood) that there are multiple drive candidates being tested here. The null device producing thrust anyway indicates that the supposed mechanism of the second drive (the Cannae drive, *NOT* the EmDrive) is wrong. However, according to the inventor of the EmDrive, the Cannae Drive (with or without the slotting distinguishing the experimental and null devices) is basically an inefficient EmDrive. If the Cannae Drive does, in fact, produce thrust for the same reason that the EmDrive does (this assumes, as the experiment supports, that both drives produce thrust) then the supposedly-null device doesn't (dis)prove anything at all and needs no further explanation. Note that this doesn't require that the theories behind the EmDrive be correct, merely that they be less incorrect than the ones behind the Cannae Drive.

Don't get me wrong, I'm as skeptical as the physics as you are... but at the end of the day, the experimental result is what matters. The experimental result appears to disagree with your theories. Therefore, your theories appear to be wrong, or at least incomplete. What you *should* be doing is proposing modifications of your theories and ways to test their correctness. Proposing explanations for the experimental results that are consistent with the current theories (and ways to account for the discrepancy in future experiments) would also be valid. Saying "Nope, the math doesn't check out so it can't happen and anybody who says otherwise is a crank" is just flat-out bad science. We have an experimental result. The result is closer to what the alternative theory predicts than what your theory predicts. The burden is on you to explain that, if you want to maintain the current theory.

Re:Carry the one

[FatLittleMonkey]

By the way, you seem to have forgotten (or misunderstood) that there are multiple drive candidates being tested here. The null device producing thrust anyway indicates that the supposed mechanism of the second drive (the Cannae drive, *NOT* the EmDrive) is wrong. However, according to the inventor of the EmDrive, [...] then the supposedly-null device doesn't (dis)prove anything at all and needs no further explanation.

And this is the sort of thing that happens with all these fringe-physics/alt-physics devices. (Also conspiracy theorists.) There's no negative finding that doesn't somehow still confirm their beliefs. See Dean Drive, GIT, or the anti-gravity disc for past examples.

The NASA tests picked up seismic effects of waves on a seashore 25 miles away. It would take a ridiculously small error to create a false positive. That's why you do null tests, to check you've eliminated noise and contamination. Faffing around afterwards saying "Oh, yeah, but but, ummm, the null article is actually not a null article. Yeah! Wait, that means this is confirmation! Woo! Theory confirmed! Suck it, skeptics!" is not science.

Which is more parsimonious? That the rig picked up noise (tiny unexpected thermal effects, say) in both the test and null articles, or that Shawyer accidentally produced a null article that also produced the magic force?

So how does that put the burden on skeptics?

oh great

[slashmydots]

If you believe Chinese test results then you probably are busy taking photos of the North Korean unicorn burial site as well. They lie about everything. Sometimes I think China is run by 5 year olds.

Re:oh great

[ConceptJunkie]

Sometimes I think China is run by 5 year olds.

As opposed to the U.S., which is clearly run by 6-year-olds...

Re:oh great

[CaptnZilog]

If you believe Chinese test results then you probably are busy taking photos of the North Korean unicorn burial site as well. They lie about everything. Sometimes I think China is run by 5 year olds.

NK is killing unicorns?!?! OMG those evil scumbags!! :P

Re:oh great

[slashmydots]

Don't you read Slashdot? They found an ancient cave with unicorn remains from a time long past, proving North Korea is the center of the universe or some crap like that.

I had a Crookes radiometer as a kid

[gestalt_n_pepper]

Can someone explain to me again why this couldn't be modified, scaled up and used as a micro thrust system for satellites and such? And why is a microwave resonant chamber "better?"

Re:I had a Crookes radiometer as a kid

[wonkey_monkey]

Can someone explain to me again why this couldn't be modified, scaled up and used as a micro thrust system for satellites and such?

Can you explain how it could be modified, scaled up, and used as a micro thrust system?

First problem: it goes round and round, but doesn't produce net thrust in any one direction.

Re:I had a Crookes radiometer as a kid

[ConceptJunkie]

If the effect is real, it could be. The question is whether the effect is real.

Re:I had a Crookes radiometer as a kid

[werepants]

Can someone explain to me again why this couldn't be modified, scaled up and used as a micro thrust system for satellites and such?

First problem: it goes round and round, but doesn't produce net thrust in any one direction.

Second problem: it doesn't work in a vacuum. Those bulbs are partially evacuated - too much atmosphere, and it doesn't work, too little, and it doesn't work. Which points to this being some kind of expansion-contraction thermal effect rather than some kind of spacey photon-momentum thing.

Point of interest: I've also heard that if you put one of these things in a freezer you can get them to run backwards...

Re:I had a Crookes radiometer as a kid

[wonkey_monkey]

I've also heard that if you put one of these things in a freezer you can get them to run backwards...

So that's what Cameron should've done with his dad's car!

Disregard, I suck cocks.

[FatLittleMonkey]

Oops, the paper said microNewtons, it was gewalker who turned that into "mN".

Re:Disregard, I suck cocks.

[Anonymous Coward]

yep, I read TFA (okay, I'll turn my geek card back) and only skimmed gewalker's post, so I didn't see the milliN / microN confusion, which explains the difference.

Interesting - quantum effects

[tbg58]

The Wired article speaks of Shawyer's EMDrive, which has been around for some time, and at first appears to confuse the EMDrive with a different technology Dr. Harold "Sonny" White of NASA has been working on for some time.

The tech report clears things up a bit. The test results are showing anomalous thrust, however NASA is reticent to attribute the thrust to Shawyer's theory of how it operates, which would violate conservation of momentum (hence the "impossible" in the title.

What the technical report says is something far more interesting. Dr. White has been working with several different test articles which use electromagnetic forces to increase the rate of virtual particle pair production in the quantum vacuum, then using the virtual particles during their very short time of existence as reaction mass. In other words, it is a reaction drive, but instead of carrying reaction mass in the tank, the investigators are trying to use mass borrowed from quantum vacuum plasma to generate a small, but measurable, amount of thrust.

The final sentence of the technical report contains the salient material:

"Test results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma. Future test plans include independent verification and validation at other test facilities."

Coypu

Re:Interesting - quantum effects

[Anonymous Coward]

hurray :) a sapient response to the article and exciting news.

Re:Interesting - quantum effects

[Anonymous Coward]

It's not fundamentally different technology, it's just that Shawyer has a relativistic theory of operation while White has a quantum theory of operation. Both explanations can be correct. The Chinese worked on an identical design to Shawyer but also came up with a quantum theory of operation, based on virtual pairs being the reaction mass, and their numbers agree with Shawyer's. Shawyer also claims to predict the uN range of the forces produced by White's design, which the NASA experiment bears out.

Re:Interesting - quantum effects

[Anonymous Coward]

I think you're right, this leads to bigger stuff. I read the Summary of the paper, and Sonny's appearance is quite interesting.

Re:Interesting - quantum effects

[angel'o'sphere]

attribute the thrust to Shawyer's theory of how it operates, which would violate conservation of momentum
No, it does not violate the law of conservation of momentum, why should it?
Hint: http://en.wikipedia.org/wiki/E...

Re:Interesting - quantum effects

[HiThere]

Well, if you threw away both halves of the virtual pair, you would transfer momentum to them. If they then recombined what would happen to the momentum?

Re:Interesting - quantum effects

[angel'o'sphere]

Nothing of course ... it is conserved obviously, but perhaps you lost me somewhere :D
Does the EMDrive create virtual pairs? Was not aware of that ...

Re:Interesting - quantum effects

[tbg58]

Neither did Shawyer suggest the EM drive created virtual pairs, but the last sentence from the technical report says that since no known electromagnetic phenomenon can account for the observed thrust, the EM drive may be demonstrating "an interaction with the quantum vacuum virtual plasma". The quantum vacuum virtual plasma is the reference to vacuum fluctuation, or virtual particle/anti-particle pairs. If I understand the report correctly I believe he is suggesting that virtual particles may be providing reaction mass, but at this point the key word is "may". The test observes thrust but the mechanism is not yet fully understood.

If the proposed mechanism is what is causing the thrust, then once the momentum has been transferred to the thruster by accelerating them (electromagnetically it seems) then it doesn't matter if they annihilate afterward. Once the reaction mass has left the thruster, it no longer has any connection to it, so what happens to it does not affect the original momentum transfer (or thrust). In the same way, with a water rocket, it doesn't matter what happens to the water once it leaves the nozzle of the rocket. It can fall to the ground or flash into steam by going onto hot metal or coals. It doesn't matter to the rocket what happens to it, as the water (the reaction mass) has already left and has no further connection to the rocket.

Re:Interesting - quantum effects

[CaptnZilog]

So now we're going to create virtual plasma from virtual particles to drive our virtual spacecraft to virtually anywhere?

Sensationalism at its worst

[Anonymous Coward]

It is pretty obvious that there was a systematic error in NASA's experiment.

Predicated on the assumption that science is never wrong. Therefore, unexpected behaviour are due to testing errors or chicanery of unethical scientists.

The alternative is that our knowledge is incomplete, and that as we increase our knowledge things that we assumed to be one way may in fact be different than what was accepted before.

Always left out...

[DerekLyons]

From TFS:

If it does work, it would eliminate the need for expendable fuel (just add electricity).

Always left out of these discussion is just how much electricity they need to produce useful thrust. While in theory, even a micro-Newton can eventually get you anywhere you want to go, practical considerations (E.G. the desire to not spend months in the Van Allen while spiraling outward, or the need to decelerate to enter planetary orbit) usually dictate a higher thrust level.

Power is, for example, a huge Achilles heel for the much vaunted VASIMIR - it requires much more than can currently be efficiently delivered in space.

Re:Always left out...

[joe_frisch]

People often miss that the problem with ion drives and other electrical drives is that the exhaust velocity is too HIGH, not too low.

The higher the exhaust velocity, the more power you need for the same thrust. Making high specific impulse drives is easy - a microwave source can be ~80% efficient and has an exhaust velocity of the speed of light. The problem is that the power requirements are enormous.

Sure, energy from the sun is "free", but the mass of the solar cells to collect that energy is not free. With a speed-of-light drive the thrust to weight ration is exceedingly small for conventional power sources (which includes nuclear and solar) so the acceleration is too small to be useful for most applications.

If you imagine a solar powered spacecraft, you need to be sure that over the lifetime of the mission you would get more total velocity change out of the solar cells and electrical drive than you would from the same weight of chemical rockets. For ion drives and long missions this is true, but for a photon drive (or any other propellant-free drive it is not true for any reasonable length mission).

The interstellar mod has microwave power.

[Anonymous Coward]

Along with an alcubierre drive. : )

won't this zero out?

[wes33]

the vacuum is electrically neutral; the virtual charged particles
created by quantum fluctuations will be in oppositely charged
pairs (e.g. electron / positron). Won't this drive send these pairs
in opposite directions? So the whole thing will have zero thrust

this thought is the product of complete ignorance of how this
drive is actually supposed to work however :)

Re:won't this zero out?

[HiThere]

I don't know the design, but couldn't you use the charge difference to separate them a bit, and then throw both away in the same direction? This seems implied by the comment that it violates conservation of momentum, because if the virtual pair then recombines momentum would seem to have disappeared.

A question is whether you could do this without using enough energy to stabilize the virtual pair as actual particles. It not then it would be extremely inefficient energetically.

OMG It's P rays!

[Anonymous Coward]

Sounds JUST like the infamous P ray demonstration, where the skeptic secretly removed a vital part of the apparatus, but the person promoting the effect still claimed to see the result.

no, just no.

[Anonymous Coward]

i do NOT want to be anywhere close to the buisness end of that engine, it'd be like standing with one hand in a microwave oven and the other one hanging of an us navy coastal radar station (antenna).

Re:no, just no.

[fisted]

Do not touch the operational end of the device.

Carry the one

[SoftwareArtist]

Unfortunately, even though you wouldn't have to supply propellant, you would still need to supply the energy to accelerate it. After accelerating for one year, your potato's kinetic energy is 1.8e12 Joules. That's a lot of energy. Initially you can stick a solar panel on it to power the drive, but once you're out of the inner solar system that won't work any more.

Captain Archer Pleez

[ChadSmith4920]

It's not your father's Warp 5 engine.

They used a vacuum, and a serious one at that.

[syukton]

It's probably #2. The paper, as presented at the 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, is available for purchase. I happened to have a spare $25 and a burning curiosity. The full paper isn't available on the NASA site, only the abstract can be gotten there for free. If you wanna read the details, you have to pay for 'em.

Anyhow, here's the relevant bit from the paper: "Two roughing pumps provide the vacuum required to lower the environment to approximately 10 Torr in less than 30 minutes. Then, two high-speed turbo pumps are used to complete the evacuation to 5x10E-6 Torr, which requires a few additional days. During this final evacuation, a large strip heater (mounted around most of the circumference of the cylindrical chamber) is used to heat the chamber interior sufficiently to emancipate volatile substances that typically coat the chamber interior walls whenever the chamber is at ambient pressure with the chamber door open. During test run data takes at vacuum, the turbo pumps continue to run to maintain the hard vacuum environment."

I'm not a physicist, but the paper is still an absolutely fascinating read, and contains a number of color photos of the test apparatus, the device itself, etc. The amount of detail they went into for the experiment is really impressive; seismically isolating the test chamber, using liquid metal (galinstan) electrical contacts to eliminate any forces due to a mechanical coupling to a wire, compensating for the magnetic field that is created by passing electricity through the device, and so on. This is NASA we're talking about here, the guys that do ROCKET SCIENCE. The idea that they wouldn't test this device in a vacuum is laughable.

Something spooky is going on inside this device, and I hope it doesn't take us too long to figure out what is really happening.

Re:They used a vacuum, and a serious one at that.

[green is the enemy]

Someone made this paper available for download. Their writeup makes it seem like they perform the experiment in a vacuum, except for one tidbit in the "Summary and Forward Work" section:

Vacuum compatible RF amplifiers with power ranges of up to 125 watts will allow testing at vacuum conditions which was not possible using our current RF amplifiers due to the presence of electrolytic capacitors.

This makes it sound as if these tests were not conducted in vacuum after all...

Re:They used a vacuum, and a serious one at that.

[syukton]

I think this is an error in grammar.

I believe what they're saying there is that with a higher-power RF amplifier that is purpose-built to operate in a vacuum, they could test in even higher vacuum than they were able to during this test. The section is Summary and Forward Work and I don't think they're saying that they did not test in a vacuum, but that their ability to test in a vacuum was limited and could be improved in future work. 5x10^-6 torr is not quite "vacuum of outer space"; it's a high vacuum, but not quite interstellar-space vacuum.

Re:They used a vacuum, and a serious one at that.

[green is the enemy]

There is another clue in the paper: In the lower right corner of Figure 22 it says "(In 750mm Air)". So at least the tapered cavity test article was not run in a vacuum. However, it is reasonable to read that that their earlier tests with a pillbox cavity were done in a vacuum. You'd have to agree that they were sloppy in specifying the exact conditions under which each test was performed. I'm looking forward to independent tests of this concept that are undoubtedly coming given the publicity this received.

Mod up - and thanks.

[drerwk]

Mod up - and thanks for dropping the $25 to inform the rest of us.

Thank you so much for answering the vacuum questio

[Anonymous Coward]

Thanks. I'll mod you up if I can.

I'm a complete ignoramus, but maybe..

[Anonymous Coward]

The energy input by the thrust system would increase the CHANCE of particles failing to annihilate. The momentum of those particles would be conserved, so that OVERALL the momentum balanced out. I'm thinking that on AVERAGE all the particles annihilate leaving a zero momentum, but IF the drive imparted energy to the particles SOME MIGHT survive. They could carry the "missing" momentum.

Anyone know?

More info on Q-Thrusters

[Anonymous Coward]

For those interested in learning more:

https://www.youtube.com/watch?v=vKTgNCGhq9Y

Skip to about 30 minutes in and hear Harold White of NASA explain the concepts behind this device. Much more info than the linked summary.

Bad summary

[Anonymous Coward]

No. The NASA team have found unexplained faults in their test apparatus. The null experiment ALSO produced the tiny thrust.

That isn't true.

They tested 2 thruster designs. Shawyer's and Cannae's. Both designs are basically a frustrum.

They tested a "null" version of Cannae's thruster (the frustum without some internal vanes that his theory said were necessary).

They tested a dummy RF load attached to the microwave source.

The dummy load produced no thrust.

All the frustum (frustrated cone) designs produced thrust with 17 Watts of input power. Shawyer's design produced about 3 times as much thrust (91.6 micronewtons average of 6 tests) as the Cannae design. Shawyer predicted he would produce more thrust because his chamber had a higher "Q" factor. The test applied only about 1/50th of the microwave energy the Shawyer thruster was designed use (it was a trivial test).

Shawyer seems to have a better grasp of the theory at this point. Cannae seems to be in "monkey see monkey do" mode.

The devices weren't actually tested in a vacuum due to component limitations in the power supply.

At some point the test may be repeated with an appropriate power supply to allow vacuum testing.

Since the dummy RF load produced no thrust ... looks like this might be the real deal.
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