Science
Related: About this forumIs EmDrive Real? NASA Paper On Impossible Propulsion System Passes Peer Review
Can you drive a car by getting on the front seat and pushing the windshield? The answer, as anyone familiar with high-school level physics would tell you, is no. Newtons third law of motion for every action has an equal and opposite reaction explicitly prohibits this.
However, after months of rumors, speculation and criticism, a peer-reviewed study published last week in the Journal of Propulsion and Power claims to have shown a propulsion system that, to all appearances violates this cardinal law, actually seems to work.
Electromagnetic drive, or EmDrive, is a proposed fuel-free propulsion system that putatively works by bouncing microwaves around a closed chamber. The problem with this kind of propulsion system is that its impossible. A system cannot produce thrust without pushing something in the opposite direction.
http://www.ibtimes.com/emdrive-real-nasa-paper-impossible-propulsion-system-passes-peer-review-2448992
longship
(40,416 posts)You cannot jump start a car by pushing on the steering wheel and making vroom vroom noises.
If you think you can, you are cuckoo for Cocoa Puffs.
Warpy
(111,267 posts)Oh, there's not a hell of a lot of thrust but it's there and it works in a hard vacuum as well as it does in ambient air. Next step is to test it in orbit.
While it probably won't get any sort of a payload (or even its own weight) off the ground, it looks to be useful for getting things from orbit farther out into space and for slowing the orbital decay of important gear put up there by conventional means.
It works. The challenge is to find out how and why it works, not pretending it's all fairy dust and unicorn farts.
http://arc.aiaa.org/doi/10.2514/1.B36120
longship
(40,416 posts)Also, I would expect more than a tiny itty bitty thrust to be anything practical. This is precisely the type of outcome one would expect if these results were due not to the EM drive working, but due to an effect of the data analysis, or noise in the data gathering.
Even if it does work as claimed, which I maintain it doesn't, what good is so itty bitty thrust?
If one is going to rewrite the physics textbooks, one has to have something better than this. Extraordinary claims require extraordinary evidence. EM drive is moonshine.
NickB79
(19,246 posts)For example, one article I read stated that the level of thrust they documented was something like 10X that of a solar sail, which is a promising tech in itself for interplanetary travel.
You don't need a lot of thrust in a vacuum, especially if that thrust is maintained over a long period of time.
longship
(40,416 posts)That would violate conservation of momentum, a pretty firmly substantiated principle of physics.
It has itty bitty thrust, mainly zero thrust, just on general principles.
This is physics 101 stuff.
And who in the Sam Hell is repeating this experiment? Anybody? Without replication these findings are utterly worthless.
I'll stand by this.
NickB79
(19,246 posts)IF it's replicated, it would be more powerful than a solar sail, based on their findings.
But I too am going to wait to see if this can be replicated before getting too excited about it, because we still can't explain why they got thrust readings in the first place.
longship
(40,416 posts)Or there are no findings. Certainly this is true given that the EM drive, from all appearances, violates the fucking conservation of momentum.
I am done here.
Warpy
(111,267 posts)Chinese scientists were the first to tune out the scoffers and test this thing in air. JPL built one and checked it in a hard vacuum and measured a small amount of thrust, which is what this paper is all about.
longship
(40,416 posts)I hope they aren't the same ones who falsified their stem cell research.
You're going to have to do better.
hueymahl
(2,497 posts)Dismissal without investigation is not.
eppur_se_muova
(36,264 posts)Warpy
(111,267 posts)After they figure it all out, physics textbooks will undoubtedly be rewritten.
Either that or it will be found to be eating its own capsule wall and spitting out ultra high energy particles, something that will be discovered if it's deployed in space and eventually fails and is recovered.
You can beat your head against Newton's pedestal or you can sit back and wait for wiser people who are familiar with the apparatus to tell us what's really going on. I'll do the latter.
If chemical propulsion is all there is, I will be enormously disappointed.
longship
(40,416 posts)There is no why it works until it is demonstrated why it does not violate the fucking conservation of moment!!!
If one is going to rewrite first semester college physics -- on principle -- one had better have more than one experiment from one lab. If it isn't replicated the research is worthless, especially if it violates the fucking conservation of momentum.
That's the way science works.
Warpy
(111,267 posts)Do continue to batter your head against a brick wall while shouting to the skies between blows that everybody else is wrong.
The rest of us will await the results of what might be a long investigation of this thing.
HAB911
(8,902 posts)NASAs Sonny White and his collaborators have published experimental confirmation that the so-called EM drive produces thrust. If this technology fulfills its promise, it will transform public and private space exploration and may have even broader implications for terrestrial power and energy.
Their paper explains why this work is important with typically understated academic language: For missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements. Let me say it another way for everyone else: wouldnt it be great to travel in space as fast as you want without even using fuel?
The what-ifs that these questions inspire in us are why we find technology at the edge of science fiction so appealing. I suspect that they also inspire the engineers at Eagleworks. Narratives about our future break us free from the tyranny of everyday life and give us permission to imagine a better future for ourselves and the world, if only briefly. Thats part of the appeal of Star Trek and other optimistic takes on the future. Its little wonder that Whites advanced propulsion research provided the real-world basis for the spacecraft in the current Star Trek reboot.
This paper isnt classified. Its in the public domain. This knowledge is for everyone, thanks to the democratic principles on which our nation was founded and that continue to enable the U.S. to lead the world in research in science and technology. And they make NASA the extraordinary agency it is. Public funding is central to any effort like space exploration. We have to pull togetheryes, pay our taxesto support work where theres no short-term profit to be had and yet so much long-term benefit to be realized.
We want a NASA that pushes the limits, rejects staid ideas, and is immune from cynical pork-barrel politics. Thats not always what we get, but more often than not, NASAs technology innovations change the game. If a warp drive or anything else from the world of science fiction ever becomes real, it will likely be thanks to NASA-sponsored research.
Is the EM drive one of these? I suppose that as an academic, I am expected to counsel everyone to proceed with caution. We dont know exactly why this strange device appears to propel itself by bouncing electromagnetic waves around inside a closed cavity. I should remind people that the basic idea of the EM drive violates the fundamental principle of conservation of momentum. I should point out that Whites speculation that the radio-frequency energy in the EM drive interacts with the quantum vacuum has not been confirmed in peer-reviewed research. In response to their claim that there is no experimental reason why this should not work, I should say something like, absence of proof is not proof of absence.
And I should point out that weve been burned before. Remember cold fusion from the 1980s? Remember more recently, in 2011, when CERN startled the world by announcing that its scientists had detected a particle traveling faster than light? The internet exploded with enthusiastic designs for faster-than-light spacecraft. It turned out that CERNs measurements werent perfect, and the fiber-optic timing system had just enough unexpected error to lead them to this false conclusion. So, we dont have faster-than-light technologyyet.
But Im just not that kind of academic. In my own research, I much prefer yes if to no because. In other words, incremental advances of mature technology are all well and good. Theyre essential. But like so many other engineers, Im also interested in revolutionary discoveries. If we dont bother to look, we wont make those discoveries.
To ensure that were not fooling ourselves, we check and double-check one anothers work. Only when theres undeniable evidence through repeated, independent, experimental observations do we conclude that we know the truth. The Eagleworks folks are fully aware of this practice. In response to earlier criticisms, their paper offers a detailed assessment of where experimental errors may lurk. They reason away each one of them.
There may well be more reasons that they havent thought of, but thats why we have a process of peer review. Carl Sagan would remind us that extraordinary claims require extraordinary evidence. I hope that other researchers try to replicate this result. After all, it took the world a long time to understand that the Earth is round, that it orbits the Sun, that species evolve, that microbes cause disease, that the speed of light is constant, and that our human activities are warming Earths climate. But we know all of that now, thanks to the continuous, rigorous grind of scientific inquiry.
The need for rigorous technology development despite the likelihood of failure is one the reasons that I supported the advanced-technology work of NASA during my time as the agencys chief technologist a few years ago. That advocacy was particularly difficult during the sequestration-related budgetary conflicts between the White House and Congress. Its too easy to sacrifice the long term to solve short-term problems. But were fortunate that NASA has kept this sort of work going.
Through its Space Technology Mission Directorate, Advanced Exploration Systems program, and myriad technology programs focused on science instrumentation, NASA continues to push the limits. If we dont fail from time to time, were not pushing hard enough. We owe it to our future to support NASA as it keeps up the pace of discovery despite how rare these revolutionary successes may be.
Mason Peck is an associate professor at Cornell University and NASAs former chief technologist.
caraher
(6,278 posts)It's not impossible for textbook science to need revision, but it's also a bad bet to take one anomalous research report as more credible than basic principles that have been confirmed repeatedly for generations.
What peer review mostly means is that the reviewers found no obvious blunders and together with the editor consider the report something worth letting other researchers know about. This is worth knowing about, like the Pioneer anomaly or superluminal neutrinos... something that could point to exciting new physics but most likely has a mundane explanation that simply hasn't yet emerged.
I should add that I've seen some extremely shoddy research come out of NASA's more speculative programs (though here I'm thinking more of NASA publications than peer-reviewed literature). My favorite example related to my own expertise was a paper speculating that sunlight could be used to generate ultrafast light pulses, based on little more than the observation that both sunlight and ultrafast lasers have large bandwidths. The concept of coherence seemed not to be in this author's vocabulary!