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An article at NasaSpaceFlight.com is claiming that the superficially reactionless EmDrive has again been tested at NASA Eagleworks, this time in hard vacuum, and the anomalous thrust is still being detected:
A group at NASA's Johnson Space Center has successfully tested an electromagnetic (EM) propulsion drive in a vacuum – a major breakthrough for a multi-year international effort comprising several competing research teams. Thrust measurements of the EM Drive defy classical physics' expectations that such a closed (microwave) cavity should be unusable for space propulsion because of the law of conservation of momentum.
With the popular explanations of thermal convection or atmospheric ionization being ruled out by operation in vacuum, and thrust thousands of times greater than expected from a photon rocket, is it time to start taking the EM Drive seriously as a fundamentally new form of propulsion, and possibly a door to new physics?
Roger Shawyer, the inventor of the EmDrive, claims that the device's efficiency will scale even further with greater levels of power, potentially enabling fast interstellar travel powered by a radioisotope thermoelectric generator or nuclear fission.
Previously: NASA Validates "Impossible" Space Drive's Thrust
(Score: 3, Insightful) by tangomargarine on Friday May 01 2015, @08:53PM
Another smart post said that if the "efficiency" reaches a certain amount that the devices could be mounted on a wheel and then turn the wheel driving a electrical generator at the center that in turn would power the devices .. thus creating a "perpetuum mobile".
Yeah, that's called Perpetual Motion [wikipedia.org] and when you bring it up most self-respecting scientists laugh you out of the room.
It's a simple concept; the problem is that as far as we know it's impossible.
"Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"
(Score: 2, Disagree) by snick on Friday May 01 2015, @09:14PM
All true. But we are talking about a drive with properties which most self-respecting scientists laugh out of the room.
As long as you are getting laughed out of the room, why not go big? Perpetual motion ... time travel ... match all the socks in your laundry basket. (yeah, I know, that last one is't plausible)
(Score: 2, Insightful) by khallow on Friday May 01 2015, @09:31PM
(Score: 0) by Anonymous Coward on Friday May 01 2015, @10:19PM
That phenomenon could be manifesting itself as dark energy.
(Score: 3, Funny) by tangomargarine on Friday May 01 2015, @10:30PM
"And of course there's the time Rodney blew up a solar system."
"Quit exaggerating! It was only four-fifths of the system. And it was an accident."
"Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"
(Score: 0) by Anonymous Coward on Friday May 01 2015, @09:53PM
Yeah, that's called Perpetual Motion and when you bring it up most self-respecting scientists laugh you out of the room.
Obligatory Simpsons [youtube.com]
(Score: 2) by HiThere on Saturday May 02 2015, @01:54AM
The thing is that there are certain kinds of "perpetual motion" that happen. What you can't (usually) do is extract energy.
OTOH, there is a design for a nano-machine that should work as a perpetual motion where you can extract energy (though not much). Basically it's just a ratchet that's small enough that occasionally it will vibrate in a way that winds the ratchet. (But you can't have significant back pressure or it stops working, so you need to use the twist as you generate it.)
There are lots of "edge cases" that don't fit into the way we normally think about physics. Every once in awhile one of them becomes important enough to require a detailed explanation, and then you get something like quantum theory. (That said, the nano-machine I described doesn't break any actual law of physics, just the way we normally talk about it. When you get small enough thermodynamics stops working because you aren't dealing with a large enough collection of "pieces" to make treating it statistically a valid approach. But quantum uncertain continues to work.)
And *that* said, we know that the standard model of physics is incomplete. We just don't have a good idea of how to modify or extend it. Perhaps this will give us some clues. (And quite likely, if it proves out it will have limits that will restrict it's usefulness.)
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 3, Informative) by tangomargarine on Sunday May 03 2015, @05:32PM
Yes, it's called a Brownian ratchet [wikipedia.org] and, although it took them a long time to do so, scientists finally figured out why it wouldn't work.
The PM Wiki article is quite in-depth. It's a good read.
The other "gotcha" they mention is that things that *appear* to be perpetual motion machines (e.g. something that gets its input from tidal energy or radioactive decay) may work for an extremely long amount of time, but they will eventually fail because of entropy (plutonium will eventually be totally decayed in millions of years).
"Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"
(Score: 3, Interesting) by ancientt on Saturday May 02 2015, @02:10AM
Solar cells provide perpetual motion machines by old definitions. The idea of turning light into motion would have been shocking a few thousand years ago, but nobody is shocked today because the idea of turning radiation into motion is considered basic science and the definitions we use for perpetual motion are updated to reflect that. The idea that there could be something new we didn't understand a few years ago and understand tomorrow is basic science. When a scientist encounters something that doesn't do what is expected, a scientist tests to see if any of the possible understood explanations can be used to understand the new thing first. That's what phase we're in now.
From TFA:
That's ruling out, piece by piece, the understood explanations.
One of two things is happening here. Either we are encountering something new, or we're encountering something known in a new context. One is a breakthrough in physics, the other a breakthrough in engineering. Either is exciting and useful.
Consider a simplified version, that's probably more of an analogy than example: You turn on a flashlight and measure the propelling force of the light and it is greater than your theory predicted. Likely the explanation is that the extra force measured is demonstrating a failure of your theory's comprehensiveness, but the possibility exists that your flashlight is producing additional thrust due to something that any current knowledge would fail to include.
This is exciting news! The worst case scenario is that very smart people are going to learn to include an idea they hadn't previously considered. That means that engineers will be able to improve ideas and technology immediately. The better case is that there could be something new to learn and that means there are potentials to create whole new theories about how things work. Either scenario is great for science.
We use dams, solar cells, wind and geothermal energy right now and all of those are perpetual motion for the common man. Science can explain where the energy is coming from, but there is no limit any human can personally observe to how much energy can be eventually used. Even if this is a tiny breakthrough along the lines of "of course it turned out to be explained by theory X that everyone knows," it will be something that has new applications to existing systems. Of course we all hope it will turn out to be "this new thing we didn't know before" so that we can better understand our universe and so far... so good.
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(Score: 2) by tangomargarine on Sunday May 03 2015, @05:35PM
Technically solar power isn't perpetual because in billions of years (or whatever) the sun itself will burn out.
And isn't one problem with solar-powered space probes that they eventually get too holed up by bits of dust even in the "vacuum" of space.
"Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"