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Given that it has so far been detected as working by two independent organisations that tried very hard to get the test right, some new science has clearly been done here. We don't yet have clear evidence that it's a new propulsion technology, as it's possible that what has been discovered is an entirely new mechanism for confounding measurement instruments, but that does not lessen the scientific value of this discovery.

There is new knowledge here. Perhaps new physics. I slightly wish I was a physicist so that I could go and find out.

>two independent organisations

Sorry, but one of them being Chinese, I would say that there is only one reliable source, and the chances that they made a mistake are high.

Are you saying that no good science can be made in China purely because it's China? USSR sometimes lied about their results,but they had scientists just as good as the US did. I have little doubt that good science can be done in China too.

Nope, I am saying that Chinese science is not reliable. I'm not saying that they lie about all their science, or that no good science is done in China.

But when you have to go with your gut, and there are only two sources and one of them is Chinese, I would never reach a conclusion such as: "some new science has clearly been done here"

>>Nope, I am saying that Chinese science is not reliable

Why not?

From the Chinese graduate students and professors that I have talked to the problems seems to be that it is really is to commit fraud and get a way with it.

In particular in some fields you can get rich writing grants, getting a considerable amount of money and writing fake papers.

There is a heavy temptation for many to do the same when all of their colleges are able to buy multiple houses and live an extravagant life style. An example from ~5-9 years ago would be a Chinese professor flying to California and buying a multi million dollar vacation house in cash. This is an extreme example and was uncommon even at the time.

My understanding is that this is not the case in all fields, it is easier to get a way with fraud in the less hard sciences supposedly. I also have read about several efforts over the last several years to try and correct matters.

It is also the case that many papers written by non-native english speakers suffer from grammar and spelling errors. Unfortunately incorrect grammar and or spelling often has a negative halo effect for many on the scientific content of the paper.

There is plenty of good science that comes out of China, however it suffers from a negative halo effect from the above sources.

I know some phd's here in the states... it's not much better. Seriously.

Lots of back scratching that goes on behind closed doors and lots of bogus papers that re-use old results or "recombine" old data in order to get funding for an actual project... really a lot of hogwash and bad science.

Nothing directly to cause fraud where I am tho. Tho I'm sure some publications are better about that than others.

I don't know much about the physics field, but in economics all that davorak says applies [0]

[0] https://news.ycombinator.com/item?id=8115275

In economics, given things like the Reinhart and Rogoff paper on debt, that would seem to apply to places like Harvard as well.

There's cultural incentive to report results that are favorable even if they are wrong.

This has the unfortunate side effect that research coming out of China needs to be taken with a grain of salt and extra doubly carefully verified.

It's nothing the scientific method can't handle (we're seeing the start of the verification steps here), but knowing that lots of research coming out of China is misrepresented it introduces another layer of healthy skepticism that it needs to be verified before being accepted as a thing.

Suppose University of Shanghai produces a result, and the University of Beijing confirms it. Rather than accept the result, it's likely that before it's declared "SCIENCE!" a NASA or MIT or whoever is going to want to have verification from someplace that doesn't have a long history of misrepresenting scientific claims.

This is going to be treated differently than if the original work was done at say...CERN and the confirmation was done by CalTech.

"There's cultural incentive to report results that are favorable even if they are wrong."

Indeed, but unfortunately in western capitalism there is sometimes a financial incentive to report results that aren't favourable even if they are wrong. A bit like what happened with the banks, or with tobacco companies.

I don't think NASA has the same credibility as an MIT or Caltech. From their arsenic-based lifeforms [1] to their D-Wave "quantum computer," [2] NASA seems to work on a lot of fringe science.

[1] http://science.nasa.gov/science-news/science-at-nasa/2010/02...

[2] http://www.nas.nasa.gov/quantum/

Here is a great paper that shows that more than 99% of Chinese clinical trials show a positive result. Either null results are being suppressed or data is being fabricated.

http://www.dcscience.net/Vickers_1998_Controlled-Clinical-Tr...

Good science certainly comes out of China, but a lot bad science comes along too.

It should be noted that the paper (as I've read in the abstract) extrapolates from MEDICAL data. There's a huge prevalence of pseudomedicine and mysticism which receives incorrect confirmation (as evidenced by the aforementioned paper), but a poor publication record in medicine journals isn't necessarily a good predictor of physics journals.

US journals aren't big on publishing null results either.

The Chinese tests did not include testing in a VACUUM. Not a sealed chamber, but an actual, airless, gasless, box of some sort.

The power levels involved in these devices are 10-20 kW - that much power into anything is capable of heating air and producing currents from convection alone. A microwave cavity is exactly the sort of thing which would make a great make-shift reaction chamber for a very inefficient, very ordinary jet engine of some sort.

I note the Wired article here also makes no mention of whether they tested the device in a vacuum chamber. Its the only test which matters, and no one ever does it, meanwhile they're pumping enough wattage to flash boil water around things.

EDIT: From the NASA abstract as well - "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."

Given what this thing claims to do, and how you have to operate it (allegedly) and the scale of the forces involved (tiny), not testing in an actual, evacuated vacuum chamber is absurd.

If the microwave chamber is sealed air tight, they might need to construct a special one before they can test it in vacuum. But yes, they should get on that!

That much current would also create a magnetic field radiating out from the wiring. Maybe the force is that of the interaction between the earth's magnetic field and the microwave.

IANAP

They tested with an RF load to look for that kind of effect.

If it ain't tested in a vacuum, it's almost certainly simple coronal discharge.

Even if in a vacuum, you can get multiplication.

http://www.microwaves101.com/encyclopedias/470-multipaction

Except that they also tested a dummy unit with the resonance chamber futzed, so any gross physical effects from coronal discharge, convection etc, should have shown up on that as well.

According to the abstract of the paper they found a similar but smaller effect on the dummy unit.

I don't believe this means much of anything, other than, "the working unit probably had coronal discharge, and the dummy didn't."

That's certainly a lot easier to believe than the result they got. If, on the other hand, they observed the same sized effect in a decent vacuum, I would be more inclined to believe it. The fact that this test didn't take place in a vacuum, despite already being in a vacuum chamber ought to make people wonder a bit.

Having fed microwaves into vacuum chambers my own self: if the torsion pendulum was already in there, there is absolutely no reason this experiment wasn't run in at least a rough vacuum. I can understand not going to UHV if the cavity things are dirty or have crap which outgasses, but there is no excuse for not running this experiment in a rough vacuum.

There is actually a history of "antigravity" researchers measuring coronal discharge. http://blazelabs.com/l-intro.asp

It would alter our understanding of physics, so it would be both scientific and technological. From what I understand it would move our understanding of everything even further from classical Newtonian physics and deeper into the relativity/quantum dichotomy realm. This thing could only have a relativistic macroscopic explanation and a quantum mechanical microscopic one. Classically it's impossible.

One immediate consequence of a massless drive is that interstellar flight becomes far more "thinkable." It's not like we could build a starship tomorrow, but if this worked and if you could build a power plant (fusion?) capable of running a big one long enough, you could practically accelerate to meaningful fractions of the speed of light. Hell... I wonder if fission would be sufficient if you no longer had to take propellant? All that propellant mass could be plutonium instead, and you "burn" it slowly and jettison the spent fuel to progressively reduce your mass and increase your acceleration.

Side note: if this keeps getting confirmed, the Fermi paradox becomes even more paradoxical. "They should be here." The impracticality of interstellar flight disappears as an excuse. If this effect is possible, something is clearly wrong. Either life itself is edge-of-impossibility improbable and most of the cosmos is sterile, we are the most advanced/complex life in the galaxy, or they are here and they're not communicating with us, or something even weirder.

This engine does not change the energy needed for interstelar travel, only reaction mass, and reaction mass is often free with an energy generator, because all of them waste some mass. If this thing is confirmed, it will be a much more significative scientific breakthrough than a technological one.

That said, there is no reason for interestelar travel not to be viable. It's just too expensive for us with our current tech.

Reaction mass is definitely not free. You can get a lot of energy by a number of means, but the need to haul an ever increasing quantity of reaction mass for every bit of delta-v you want is the limiting factor.

If you did not have to haul any reaction mass, then delta-v is limited solely by energy. Which means you can take some solar panels and thrust indefinitely up to light speed, with a vessel weighing a couple of kilos as opposed to megatons.

That would not work for several reasons. The energy produced from the solar cells would be negligible compared to the force of photons hitting the panels. If you instead of an engine just used a very large thin sail with a proportionately small cargo then you could theoretically reach c, but only close to stars. If you instead removed the sail and used antimater as an energy source, that would also work. The problem with all ideas is the interstellar medium, particles, photons. Drag from interstellar medium would damage and slow down the ship, even at lower percentages of c. Close to c everything would behave as shot from a particle accelerator and even photons from background radiation would be blueshifted to high energy gamma rays.

I wasn't commenting on using photon reaction - I was commenting on using this hypothetical reactionless drive (which would, presumably, produce more thrust then photon force - which the claimed device does from relatively small amounts of power).

If you had a reactionless drive, then the solar sail force would be negligible compared to the drive.

Even if the thrust from reactionless drive would be higher, it cannot be higher than the pressure produced by the photons on the solar cell, which you use to power the drive. If the developers claim that it does, then you have basically infinite energy.

I wonder which speed should a spacecraft have so that cosmic microwave background will be as bright as Sun from earth.

This may explain "where is everybody", btw. Why do you need a Dyson sphere when there's free sunlight.

We have no technology for carrying energy that does not waste more than enough mass for using in reaction. Reaction mass is free with the carried energy.

Well, except for solar pannels, of course. But you can't move near lightspeed and stay near the Sun.

No, look up the rocket equation.

Let's say your rocket is a mass driver, throwing rocks out the back end with electromagnets. You need two things: one is an energy source to power the electromagnets, like some kind of nuclear reactor, and the other is a big pile of rocks.

The big problem for a rocket is that it's not just carrying the payload and reactor fuel, it's also carrying that big pile of rocks. For a given exhaust velocity, the faster you want to go, the bigger that rock pile has to be, which is even harder to push, and the challenge just multiplies. If you're trying to get to another star it's practically impossible.

A reactionless drive would still have the nuclear reactor, but it gets rid of the big pile of rocks. Now higher speed no longer means you need a bigger rock pile, it just means you run the nuclear reactor longer. You'll need more reactor fuel but with the mass driver you needed that plus the bigger rock pile. Now you just need more reactor fuel, and that's relatively minor.

So yeah, it'd be a huge technological breakthrough, if it actually works.

Once you get up to speed reaction mass might be effectively free with something like this: http://en.wikipedia.org/wiki/Bussard_ramjet

One thing I've wondered about with respect to bustard ramjets: they work by collecting hydrogen from the quite rarified interstellar medium and fusing it for energy release.

Collection of hydrogen for fusion means that collected hydrogen atoms need to be in close proximity with one another for fusion to occur.

This in turn means that interstellar hydrogen, essentially at rest with respect to the ramjet-equipped spaceship ploughing through the medium, has to be accelerated pretty much from the rest frame to the velocity of the ship as part of the collection process. This acceleration of hydrogen to ship velocity requires energy.

At what ship velocity would more energy be expended collecting hydrogen than it would yield in ship reference frame when fused? This would seem to be an upper limit for Bussard-type propulsion systems.

Assuming proton-proton fusion, the speed limit is about 12% c, relative to the interstellar medium (http://www.projectrho.com/public_html/rocket/slowerlight.php). That depends, however, on the assumption that the initial kinetic energy of the incoming hydrogen is completely wasted- that the ramjet does not have "regenerative braking", so to speak, that can recover some of the pre-existing kinetic energy. That's a pretty reasonable assumption from an engineering point of view, but physics theoretically allows us to do better.

It's the same with jet engines, for similar reasons. (Although in practice your maximum speed is largely dictated by "melting the engine is considered shortsighted".)

The theoretical upper-bound exhaust velocity of a Bussard ramjet is something like ~0.12c, assuming you start with 4 hydrogen and end with 1 helium. As such, the theoretical upper-bound speed limit relative to the interstellar medium of a Bussard ramjet is also ~0.12c. In actuality, it will be quite a bit lower, as quite a lot of the energy is carried off in the form of energetic photons and neutrinos.

Personally? A Bussard ramjet will never work, even assuming we get the scoop part figured out. The lower bound on how fast it has to go before it can start working and the upper bound on how fast it can go are too close. Not to mention the Lawson criterion for hydrogen burning (4xH -> He), or, alternatively, the problem of containment of the catalyst and the beta-decay steps of the CNO cycle.

If you crunch the numbers, it turns out the bad news is a Bussard ramjet won't work as an engine.

The good news is, it will work as a brake. That takes care of the deceleration half of your delta-V requirement, which is better news than it sounds: thanks to the rocket equation, it doesn't just halve your required mass fraction of fuel, it square-roots it.

I don't know where you got those numbers from. Momentum of an object is equal to mass times velocity. Change in momentum is equal to impulse, which is force times time. Therefore f * t = mv, and change in v = f * t / m. Plugging in the numbers, (0.00005 N) * (3600s/hour * 24 hours * 365 days) / (722 kg) = 2.18 m/s

Voyager used gravity assist to achieve its current velocity, so the comparison isn't 100% fair. A craft with this drive can certainly avail itself of that technique as well.

Oh, for sure. It's by no means an apples-to-apples comparison (just being in orbit around Earth before you start your journey out gives you a huge jump on that), just gives you a sense of scale.

Other deep-space spacecraft make use of non-trivial delta-v, around 200/300 m/s for some maneuvers: https://space.stackexchange.com/questions/4054/delta-v-of-de...

Let's not forget a similarly ellusive case which lasted quite long:

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

Although admitedly this thruster can undergo much more testing.

It's not a breakthrough in science at all, honestly. It is already well known that you can propel something just by generating photons (generally using nuclear power to heat an element, just like a light bulb). Microwaves are just a different wavelength. It is just too inefficient to matter at the moment. The only breakthroughs to be made are in efficiency. Photons still have energy and momentum, just no rest mass, and there is even such a thing as electromagnetic pressure created from photons transferring momentum.

Considering that photons have a force, I wonder if the force of the photos hitting a craft propelled by an EmDrive would be able to approach a star. The craft with an EmDrive would likely need solar panels to sustain the EmDrive which would increase the craft's surface area to encounter more photons and other energy particles.

There's no need of a solar panel for big spacecraft, US and USSR have designed compact enough nuclear reactor that can generate Mw of power for various submarines,like here http://en.wikipedia.org/wiki/Alfa_class_submarine. There has been time that a single US submarine was able to power the entire Hawai island after a natural disater http://news.google.com/newspapers?nid=1755&dat=19821128&id=E...

It's true you can generate thrust by throwing photons out one end, but that's not what this device does. It bounces microwaves around inside a closed, superconducting chamber, with one end wider than the other.

Exactly right. It's an apparent violation of Newton's Third Law, unless the photons are pushing against virtual particle pairs as suggested in the article.

It's not a violation from the reference frame of the rf - just yours.

Oh, it's that device? The one that was on the cover of New Scientist at some point? We (i.e. the lecturer) mocked that in physics lectures (mostly on a "look at the shit New Scientist publishes..." sidetrack). It may also have claimed perpetual motion, while it was at it.

If there really is some quantum interaction, then this becomes interesting, but from momentum alone the contributions from the sides of the box always exactly cancel the resultant from the mismatched plates (by definition of a closed box).

Argument from Authority is a thing.

indeed, my PhD supervisor is often wrong about stuff. I don't believe my lecturers per se, but rather I remember the argument about cancelling edge effects (which certainly seems to apply here.)

If you've got constant thrust from constant energy input, that pretty much implies perpetual motion, since energy input increases linearly with time and kinetic energy with the square of time.

If you want to say you get less thrust as velocity increases then you run into trouble with the principle of relativity.

So I'm skeptical too, though I think it's worth continuing experiments.

Wait, I get what you're saying (0.5mv^2), but isn't it relatively straightforward to get constant thrust from constant energy in other situations? Laser --> lightsail, for example.

To reply to myself, the thrust you'd get from a laser that shoots at you would in fact diminish as you accelerate away from it, as the light would redshift and thus carry less energy to you.

Sure, you can only find the mistake while repeating the experiments (perhaps, as someone else suggested, in a vacuum might be a plan).

I hadn't noticed the constant thrust problem you mention, I'm now recursing back through the equations I remember to try and work out why it costs more energy to push something that's already moving fast... wait, force applied was never anything to do with energy to start with, impulse/power were. Brain-fart resolved.

What if you had an ideal electric car driving on flat ground with no friction losses (i.e. if you turn off the motor, it coasts forever.)

If you draw constant power from the batteries, is it impossible to maintain constant acceleration?

Oh right, that makes sense; constant acceleration implies constant force, and work is force*distance. As the meters tick by more rapidly, the motor performs the same work in less time, and thus the required power increases.

Which means, "a reactionless drive is like a car in space" would be a nonsensical concept without a preferred reference frame.

It's already a kind of well known concept in SciFi to bounce the photon back and forth a lot, getting a little hit of momentum each time (and draining its energy, thus changing its wavelength). Keeping the reflecting pair on the rocket and trying to use asymmetry to pull more off on one side than the other seems a pretty straightforward thing to try.

Voyager is only traveling at 17km/s because of orbital maneuvers. These thrusters would probably not be used for delta-v. However, they would be great for reliable attitude control. Currently attitude is controlled with reaction wheels, small fuel based thrusters or magnetorquers or some combination. Reaction wheels fail, fuel based thrusters run out of fuel, and magnetorquers are weak.

NASA is running out of fuel (Plutonium) for RTG's and no new fuel is produced.

http://www.isciencetimes.com/articles/6087/20130919/nasa-plu...

The plutonium shortage in NASA really has nothing to do with technology or science, but just politics. We simply stopped producing the stuff, but we could start again at any time; as the article you linked mentions, we're planning on doing so.

There's enough plutonium to make 10,000 nukes stored in the Sellafield facility in Cumbria, England

http://www.independent.co.uk/news/uk/vaults-will-store-the-n...

So, there is no storage.

It isn't that simple:

http://en.wikipedia.org/wiki/Plutonium-238#Production

Of course a program could be spun up to actually do the separation, but I think it might be sort of expensive.

I've been there as a child, if I'd have known that, I probably wouldn't have gone.

It's impossible to run out of plutonium so long as uranium fuelled reactors are running. It's a common by-product of the fission process.

It maybe be harder or impractical for them to get it or process it, but saying "no new fuel is produced" is false

That's like saying we won't run out of oil because we are producing carbon and oxygen... if it's not in useful form, it's perfectly sensible to say that no new fuel is being produced.

Normal uranium reactors produce a mix of plutonium isotopes, which are hard to separate and end up as nuclear waste. NASA needs pure Pu-238, which has to be made in specialized reactors.

Iirc, all Canadian CANDU reactors produce large amounts of weapons-grade plutonium.

Which is exactly the problem. RTG needs Pu-238, and can't use weapons-grade plutonium, which is mainly Pu-239.

That design has also been altered by India to consume the plutonium by-product, using it as fuel.

I know I read an article about 2 years ago saying that more was being made. Now I have to find it.

EDIT Got it! http://www.spaceflightnow.com/news/n1303/20pu238/#.U9qX5fldX... The date is six before the other story.

"For the first time in 25 years, the United States is producing plutonium fuel to power spacecraft on missions beyond Earth, replenishing a dwindling stockpile to supply NASA's next Mars rover and other proposed probes."

Combining with the comments below, there is a note that the test worked even when they changed a vital configuration (seemed to be a control test).

When a control fails, the conclusion is that the experiment is buggy and you need to rethink things. Unfortunately, it seems from the article, the conclusion was that some new physics was at work here.

19 thousand years.

Woops, you're right! I was doing some ballpark math a couple orders of magnitude higher thrust, to see what would be practical if this were scaled up.

(For context, my original post said that matching Voyager's velocity would take 19 years.)

Your first explanation was my immediate thought -- but I assume they at least checked for this (if it's obvious to a high school physics type such as myself).

I would assume that an actual thruster would be a bit bigger than the test unit!

What happens after two, five and ten years?

It should increase linearly.

Keep in mind that a linear speed increase is still a non-linear distance increase over time.