EmDrive? More like BS drive: Physics-defying space engine flunks out The "impossible" EmDrive may be just that, though don't count it out just yet. A group of German physicists at TU Dresden has tested two proposed means of propellantless propulsion – the EmDrive and Mach Effect Thrusters – and found the act of testing is what makes these arguably physics-flouting technologies appear to work. …
Given that this is in direct contradiction of NASA's own previous experiments and the Chinese experiments (IIRC Chinese are actually sending a prototype into space on a satellite for orbital testing), I would take these results with a pinch of salt. It is not at all evident that the experimental hygiene applied here is more stringent than at NASA.
One side of me says "why is the physics community even entertaining this idea - it was obviously B0110cks from the start" and the other says well, where would physics be if we all discounted out-of-hand any ideas which at first glance, appeared to be utter bollocks.
But on balance, my suspicion is, it's bollocks.
It's probably bollocks, but it is theoretically possible that it's real. There's no way to know without testing it out -- so I think the various researchers are doing the right thing.
At this point, I think that anybody who says anything definitive about the effect are talking nonsense. There isn't enough data on which to base a conclusion either way.
If you were to tell someone the quantum physics / general relativity stuff without much context - if someone had discovered the physical effect before we'd derived the equations that helped us find it - that would have been called bollocks too.
It's only because we went the other way "Well, that leads to this... which can't be right... can it? My word, there it is..." that quantum physics "feels" right, everything else about it is completely counter-intuitive and contrary to so much of "ordinary" physics.
That said, it always felt dubious not because of some unknown effect being in play, but because said effect was so tiny, in such a huge and powerful piece of equipment, that it basically feel into the error margin. Don't you have to apply KW of electricity to see this effect, as per the original experiments? That's a hard thing to account for down to the tiny amount of thrust seen - the thrust is outweighed by things like losses in the cable (generating those magnetic fields!), the AC-DC conversion, etc.
But at least we didn't go silly. If we'd got into space and found out this thing didn't actually work, there'd be hell to pay. It's kind of expected that a few organisations would try to replicate the results with various success and that would throw up enough questions that we have to look deeper and doubt ourselves. And that's where we are.
Unfortunately, for the vast majority of papers written, this kind of reproduction just doesn't occur. Wasn't there a study once and something like 50% of academic papers had results that literally could not be reproduced even by experts?
Funny you should say that.
Because that's just about what current Ion thrusters need to generate milliNewton thursts from a big tank of (expensive) Xenon.
Until they run out of course.
IIRC Most people thought Shaylers explanation of how the thruster worked was BS.
However several teams claim to have demonstrated thrust is being generated. And if you don't understand how something works how do you know what it's safe to ignore (or just leave out) in the design? "I left the power transformer out of the amplifier I built but it should work fine anyway." WTF?
The really attractive part of a propellantless thruster is not that it could drive a probe out to Pluto (with a fission power source of some kind).
It could then bring it back afterward.
if someone had discovered the physical effect before we'd derived the equations that helped us find it - that would have been called bollocks too.
Um, we did do exactly that. The photoelectric effect, for instance, was known in the 19th century, and it makes no real sense in classical physics: Einstein didn't write the paper explaining how it worked until 1905, and we didn't have a really proper mathematical theory until the late 1920s. All of the development of QM was driven by experimental results which seemed insane classically: that's why there was, for instance, the old quantum theory (which explained some things but clearly made no real theoretical sense) and then two new quantum theories (matrix mechanics and wave mechanics) which explained much more, and then later turned out to be the same theory. It's worth reading the history of this stuff -- in particular if you read the letters people wrote each other in the 20s and 30s they're just full of 'this result makes no sense, and the theory which explains it makes even less sense': no-one wanted QM to be right (many people still don't!).
There are numerous occurrences of this in physics: in fact the cases where theory precedes experiment are pretty rare.
GR is, perhaps, a partial (but only a partial) exception to this. Special relativity was inevitable following experimental results which made no sense without it -- the Michelson-Morley experiment for instance. There is some evidence that Einstein came up with SR without really paying much attention to experiment, but he was working in an environment where everyone knew something was needed as a result of MM & similar things, and also the mathematical form of SR was already pretty much there: he 'just' provided a conceptual framework for it ('just' meaning 'this was a huge step'). General relativity is more nuanced: once you have SR it's immediate that Newtonian gravity makes no sense, but I don't think there were any really good experiments which showed that as the differences are pretty small on scales we could measure in the early 20th century: the precession of the orbit of Mercury was known to be an anomaly I think, but perhaps that's it. GR kind of should not have existed until the second half of the 20th century, and in a sense it really didn't: almost nothing happened with the theory until the GR renaissance in the 50s-70s, and that was driven substantially by experimental results in cosmology.
The most glaring exception is black holes: BHs were just clearly a bit of interesting maths which didn't correspond to anything in the real world until, much later, people started seeing things which only really made sense if BHs were actual physical objects. But BHs might be one of the very few exceptions.
Even things like neutrinos -- predicted in 1930 and not observed until 1956 -- come out of experimental results: Fermi predicted the neutrino because without it beta decay does not conserve energy.
Great comment on how science was, and should be, done. Unfortunately, it's rather outdated. Today, scientists put their assumptions into computer models that 'prove' that which is desired to be proved. When real data conflict with the models' output, they clearly must be wrong, and are adjusted until they conform properly to the models.
Don't expected significant scientific breakthroughs in several fields for a while.
> Today, scientists put their assumptions into computer models that 'prove' that which is desired to be proved.
There have always been bad scientists, and computers gave them another toy for doing bad science. Massaging data into shape or outright fake is possible without computers and has happened all the time when computers were not around.
I dare to say good and proper science still exists.
Would you like to give concrete examples rather than making vague accusations of malpractice?
I work somewhere where we run very large computer models of physical systems, and I can tell you that people spend a lot of time worrying about the agreement or otherwise between the models and the data.
I think there is definitely a problem with some theoretical physics because the experiments to test theories have become essentially impossible to do -- we have theories that work essentially perfectly in all the cases we can construct experiments to test even though we know those theories can't be completely correct. So we're kind of stuck -- I suspect the best hope is either that a theory will come along which is compellingly good at explaining various astronomical observations or that someone will think up experiments which can be done without spending absurd amounts of money, or that something completely unexpected will turn up in existing experiments. Any of these would clearly be really good. But that problem is not the same problem.
Science stops being science the moment a claim is dismissed purely on the basis that our current theories say it can't happen. Sure, there are definitely nuances concerning how much effort you might be inclined to invest in studying a specific claim, but ultimately the only thing that matters is multiple experiments confirming or disproving that claim, not what we think "ought to" happen.
I agree with this, in case it's not clear: I don't object at all to people testing these things, any more that I object to people doing experiments to see if antimatter experiences gravity backwards (which people are doing/have done). There must come a time where you stop, but it's not fir me to say when that is.
"I can tell you that people spend a lot of time worrying about the agreement or otherwise between the models and the data."
Most people. I work in a similar environment and we've caught people just inserting fudge factors to close the gap between observations and calculations instead of flagging it for further research.
Senior people were understandably furious when they found out as it meant that opportunities to improve the calculations were being lost.
On the other hand one of the more interesting discussions in the last few years was a result of 32 and 64 bit versions of the same software giving different answers. The original assumption was that one was "wrong", but the eventual answer was that they both were - the reason many generations of compounded rounding errors. Rewriting the software to not feed the results of the last orbital calculation as input to the next vastly improved accuracy and got both flavours of software giving vastly more stable solar system modelling.
Yes, I'm not arguing that some people don't fudge things: people have always fudged results, and one of the purposes of peer review & the rest of the scientific process is to find that (which it looks like you did!).
What I claim is that there is not a wholesale move to a state where people run models on computers and then adjust the experimental data to fit those models.
Indeed where I work we have a problem very like this: our models give results which are uncomfortable in various ways, and there is a lot of pressure to insert a fudge factor to make them more comfortable, which is being resisted: the models may be wrong (there is not good enough experimental data to know yet) but people want to understand why they're wrong in terms of the physics they're modelling ('oh, we've missed out this process, let's put that in and see if things are better') rather than just adjusting the results.
"
that's not how science is done in *my* field.
Yes, models exist, but the *models* are adjusted to match the data, not vice versa.
"
That's the difference between a scientist and an engineer. If asked what 2+2 equals, the scientist will reply "4" and the engineer would close the door and whisper, "What do you need it to equal?"
I recall reading an early paper claiming that the MM effect was caused by the earth dragging the ether along with it. So the experimenters did a series of experiments at various elevations and found that as you got higher the speed of light differed in different directions.
It is difficult to separate out the truth when there may be experimental error, experimenter bias etc. After the fact it seems so obvious.
Ether dragging was one possible explanation, of course, and as I said it;s not clear how much Einstein paid attention to the experiments (relativity was kind of an exception, which was my point really). I think if ether dragging was true you'd get some interesting results looking at light coming from other planets.
if someone had discovered the physical effect before we'd derived the equations that helped us find it - that would have been called bollocks too.
Actually try looking at the rotation of our galaxy, Vera Rubin did and what was measured didn't match what we thought we knew.
So we now have dark matter and dark energy as a book keeping exercise until we can actually work out what is going on.
May people consider dark matter and dark energy to be bollocks but so far nothing else fits and we don't appear to have a better explanation.
The experimenal results before QM were much cleaner and gave multiple "signals" that Newtonian machanics had problems. You couldn't accout for the black body radiation curve. Once the nucleus-orbiting electron model replaced the current-bun model for the atom, it was a classically impossible system as the electrons would radiate and spiral in, etc.
Unfortunately, for the vast majority of papers written, this kind of reproduction just doesn't occur. Wasn't there a study once and something like 50% of academic papers had results that literally could not be reproduced even by experts?
I'm not sure that's correct. Unfortunately I can't find a study which reproduces this study.
@Lee D:
I'm inclined to agree with much of what you say, and not just because of Relativistic vs Quantum theoretics debates (Okay - they shouldn't be vs debates anymore, they should be how do we get them to mate in that tree over there debates), but -- well -- if we look *out* from where we are and decide that the universe can give us some hints, the big one is that, well, when it comes to *stuff*, we really really really haven't made that much progress, and there is a *lot* of dark (matter/energy) that we cannot yet explain. Like, WAY more that we can't explain that we CAN explain.
So, if there's even a tiny ledge of theory that the bollocks can stand on we have to keep pushing them till they fall off that ledge. Then we can braise them in red wine and add some fungi and fava beans and have a fine meal.
Twice the Nobel Prize was awarded to people who demonstrated that accepted thoughts on the matter were completely wrong. I remember the professor giving us a stern lecture about assumptions. Scientists (the kind not on amusing TV shows) are now rightfully sceptical when the word "obviously" is used. In fact ever since Quantum Physics was established nobody should assume too much about anything that may appear obvious.
Just off the top of my head.. how big and how heavy is the device(s)? If gravity is throwing a curve ball into the works, make a mini-sat, launch it out into the void and see what happens. Probably not really ready to do that yet as apparently there's "design" issues. On the other hand, it might be bullocks like perpetual motion machines.
" For that they were getting a thrust that would counterbalance a desicated flea."
As long as the thrust is higher than the resisting forces holding it at rest, then you'll get acceleration and it (eventually) adds up to significant velocities.
Ion drives chew plenty of power. Their disadvantage is that they eventually run out of fuel.
>>...the power supply is similar to that required to run a single family house hold...
thought experiment -- edison accidentally discovers a form of led light but it takes the energy needed to power new york city to light a closet. pronounced as useless and unscientific rubbish on the spot.
point is that nobody knows what's going on or how it works. not claiming that the final design will run on a phone battery but IF IT WORKS AT ALL then the understanding of it would result in vast improvement in efficiency.
Still plenty of gravity out there, plus all kinds of poorly quantified and changing effects (outgassing from satellite, solar wind, radiation pressures like the Pioneer Anomaly). The effect has been hard to study this effect in a well-equipped lab here on Earth, being in space will just add to the fun.
Though if I were one of the researchers I'd certainly argue for its necessity, along with the need to budget for some site visits...
Legend has it that, when Thomas Edison had invented the light bulb, someone said to him something like "so it took you (let's say) 1480 tries to make it work ?", to which Edison replied "No, I invented 1479 ways not to make a light bulb".
This is Science. We don't just need to know that it doesn't work, we need to know why it doesn't work, in a mathmatically quantified way. Because maybe, one day, somebody will be able to revisit the maths and find a way to make it work. Or maybe the maths will give him an idea for something completely different.
In any case, some bloke on YouTube is not a scientific reference.
Except Edison didn't invent it. He was looking for a better way to make carbon filaments. Tungsten was too difficult to work with. Nor did he invent Cinema despite his patents. He was an entrepreneur, not a scientist.
I agree the EM drive and Mach drive are worth investigating (Photon propulsion does work), though the expectations of the proponents for space travel are overblown. Though you don't need reaction mass, unlike Ion drive, solar power is only good well within the orbit of Jupiter. Nuclear power needs fuel and if you had a fusion drive you can use the helium etc produced in a linear accelerator / Ion drive. Electrons can be accelerated separately and mixed with the Helium ions.
the problem with photon propulsion is that the energy required is highly inefficient. the existing ion drive using a heavy element gas is much better, since thrust = delta momentum = delta velocity * mass of propellant.
To double thrust you either double delta-velocity or double mass. If you double delta-velocity, then delta-kinetic-energy is QUADRUPLED.
So shooting photons has nearly zero mass times "speed of light squared" energy, as compared to something considerably less relativistic speed-wise, and the mass of a heavy nucleus. It may consume fuel, but the ion drive wins every thrusting contest this way.
Yeah the dream is sticking out your solar panel and having an electric no-fuel thruster, but it would be SO inefficient...
photon propulsion is the most efficient use of reaction mass possible, and reaction mass is what limits spacecraft, not energy.
Indeed, if you want to move around in the neighbourhood of a star you can just use a big mirror and rely on the photons the star is spitting at you. You use no fuel at all and expend no energy at all. You need a big mirror to get much thrust, OK (pressure from sunlight at earth's orbit is ~ 10^-6 Pa).
It may consume fuel, but the ion drive wins every thrusting contest this way.
The problem isn't consuming "fuel" - a photon drive will also consume fuel, after all, if it's not powered entirely by something external such as solar panels or fusing interstellar hydrogen or unicorn magic.
The problem is consuming reaction mass, which may or may not be a waste product of consuming fuel. Based on the rest of your post I assume that's what you meant, but calling it "fuel" is inaccurate.
The article makes the same error.
People are excited about propellantless drives for the same reason they're excited about photon drives: no reaction mass to haul around and run out of (or have to replace from somewhere). A photon drive isn't propellantless, but its propellant has zero rest mass and can be whipped up from just energy inputs, solving the same problem.
Personally I would be extremely surprised to see a working propellantless drive; conservation of momentum has always been good to me, and I plan on sticking by it as long as I can.
" Nor did he invent Cinema despite his patents."
Whilst the light bulb was the result of a lot of actual work making Swan and Priestly's inventions viable, the cinema was flat-out intellectual property theft.
He even stole complete movies made by the Lumiere Brothers and claimed copyright on them.
In any case, some bloke on YouTube is not a scientific reference.
That bloke on YouTube happens to be Phil Mason, PhD. One of his series of YouTube experiments ended up overturning the traditional explanation of why sodium dropped into water ends up exploding. So he's not a typical YouTube knowall who wibbles on about stuff in advanced Dunning-Kruger mode.
You did watch the video before commenting, right? Just enough to tell if he knew what he was talking about, right? Just to see if he raised any points that might discredit EMDrive, right? Just to see if he used empirical evidence and mathematics (as you insist are required) to substantiate his claims, right? Nah, wrong, you just wanted to mouth off.
Oh, and let's not forget that the Germans just confirmed what Mason figured out nearly two years ago, so your dismissal of him without even looking at what he had to say is even less justifiable.
I'm thrilled to learn that someone who is competent in physics had a good YouTube video of why something could not actually work.
Unfortunately, if I'm not mistaken, YouTube is not a recognized, peer-reviewed, scientific news platform.
So please point me to his published paper on why the EMDrive couldn't work, because if there isn't any, I fail to see why Science should take that into account.
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