NASA paper on reactionless drive.

"NASA's long awaited paper, Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum, has passed peer review and been published the American Institute of Aeronautics and Astronautics (AIAA)'s Journal of Propulsion and Power. They consistently measured 1.2 millinewtons per kilowatt of thrust in a vacuum with no apparent reaction mass."

"If the vacuum is indeed mutable and degradable as was explored, then it might be possible to do/extract work on/from the vacuum, and thereby be possible to push off of the quantum vacuum and preserve the laws of conservation of energy and conservation of momentum. It is proposed that the tapered RF test article pushes off of quantum vacuum fluctuations, and the thruster generates a volumetric body force and moves in one direction while a wake is established in the quantum vacuum that moves in the other direction."

It's hard to describe to someone who doesn't have a good understanding of modern physics just how bizarre this effect would be.

First, it breaks conservation of momentum. That is so far beyond impossible that it's not clear how we would start building a new model of the universe.

Second, it means the universe is not translationally symmetric. We think the universe behaves the same wherever we are. The rules of physics appear to be the same everywhere. If this device works, that is no longer true.

It's also a free-energy device.


Nobody is saying that we're at the end of scientific discovery. But the current unknowns are at the extremes of scale, at the quantum level and at the galactic level. But in the realm of kilowatts and millinewtons, we are pretty damn sure we understand how things work. It seems incredible such an effect would not have shown up before as a confounding error source in many other scientific experiments and practical engineering.

I'd recommend putting your faith in witchcraft before EmDrive. It's kind of a toss-up as to whether witches or physicists throw better parties.

Is this a joke? Physicists throw terrible parties. You want to party with witches, hands down.

Also in the comments is a glowing example of absolutely everything that is wrong with Star Trek in just two sentences:

In this episode, a pair of sibling scientists show that warp drive propulsion is harming the very fabric of space. A sub-plot involves Data attempting to train his pet cat, Spot.

Previously, previously, previously, previously.

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20 Responses:

  1. CdrJameson says:

    Conservation of momentum doesn't need the thing that goes equal and opposite to be in the same place as the thruster. Could be the first time magic space thruster gets switched on we accidentally shove Mars into the sun.

    • tfb says:

      No, but locality does. Non-local effects are perhaps even more insane than non-conservation of momentum, as they lead trivially to causality violation which (outside of scifi) is bad.

      • pavel_lishin says:

        causality violation which (outside of scifi) is bad.


        • tfb says:

          Well, closed timelike curves, people eat their parents as children, the initial-value problem becomes intractable, tentacled horrors pour from the equations and devour everyone's minds and, dressing themselves in the husks of comedy fascists, frolic as the universe falls into the abyss. There is probably chittering, whatever that is. That sort of thing.

          Although a lot of that does seem to be happening, there is strong evidence that causality is not violated or, if it is, no-one knows how to construct systems that violate it. If I could make such a system, I could use it to send information into the past. If I can do that, even for fractions of a millisecond, I can win games of chance where bets take place on that timescale: in particular the financial markets. Shortly afterwards I have all the money there is. So there's no real upper bound on the value of a system which will do this, and no shortage of people willing to invest extravagently in technology which lets them win in the markets (witness HFT).

          This hasn't happened so no-one knows how to do it.

          There is probably a story by Borges where CV solutions are possible, and in which the many-worlds interpretation is also true: the branches of the universe in which CV solutions arise (or are discovered) terminate in horrible ways. So any branch which has not terminated is one in which CV solutions have not arisen. In this story there is an ancient organisation whose members know this, and whose purpose is to prevent the discovery of CV solutions in their branches of the universe. The logic is complicated. I can not comment as to whether I belong to this organisation.

  2. japh says:

    "I'm kinda fuzzy on the whole good/bad thing. Whad'ya mean, bad?"

    "Imagine all life as you know it stopping instantaneously and every molecule in your body exploding outward at the speed of light..."

    "Total protonic reversal..."

    "That's bad, okay. Important safety tip, thanks Egon."

  3. Nick Lamb says:

    "You want to party with witches, hands down". Sounds like somebody either got very lucky or hasn't actually met many witches.

    Even the witches I know don't want to party with witches. I live not so very far from where all that nonsense started (not physics, witchcraft) and essentially even the few people I know who'd describe themselves as witches or as believing in witchcraft will acknowledge that it attracts the worst possible tedious morons.

  4. Jake Nelson says:

    The last time this came up, I thought everyone agreed it was pushing off Earth's magnetic field in a way that would likely be useless in space. Did I hallucinate that?

    • jwz says:

      If everyone agreed with that, I imagine it would have been in the abstract of the paper.

      • Jake Nelson says:

        By "everyone", I suppose I meant the random Internet comment section armchair physicists, but yeah, fair point, one would think the authors would be aware. Ah well, if it somehow works anyhow, all for the better.

        I also think concerns about causality violations as a result of non-local effects are a little silly. Either it's no big deal or we're inevitably doomed anyway- in either case it's not worth worrying about it. Push the button, see what happens.

        • tfb says:

          My point wasn't actually that CV-could-happen-and-we'll-all-be-doomed, rather that CV isn't possible (at least not in flat spacetimes), nonlocality is equivalent to CV and therefore nonlocality isn't possible. This is just the conventional physics view.

          • Jake Nelson says:

            (I'll chase you down on this page yet!)

            I just have a personal belief that causality is not absolute in our universe and enjoy things that tweak overly prescriptive types about it. I am aware I lack the ability to argue for this scientifically, and don't intend to try, it's just a 'feel' thing.

            • tfb says:

              Oh, there are known CV situations: I just don't think they will crop up in flat spacetimes (and it is, or was 25 years ago) an open question as to whether such situations were physically plausible (ie could arise from reasonable initial conditions) or were censored if they were (I think the answers were assumed to be 'no' and 'doesn't matter since first answer is no').

              I'm not arguing for a 'we know all the answers' view, just that this particular thing is junk.

    • tfb says:

      I think it was previously clear that their experimental procedure was so poor that it could have been anything. This time they've presumably at least described the procedure well enough that someone else can repeat the experiment and show where the error is coming from. The whole thing is like FTL neutrinos, except that they seem to believe it while the FTL neutrino people, obviously, didn't.

      • Jake Nelson says:

        I assume the difference in belief is related to how much those in question want the result to be true. Magic free engines sure sound nice. Just-barely-FTL neutrinos are just problematic.

      • Jeremy Leader says:

        As far as I know, the FTL neutrino folks weren't looking for investors, unlike some of the proponents of the EM Drive.

        This whole EM Drive thing reminds me more of cold fusion.

  5. Mikester says:

    This is why Trump was elected, isn't it? Someone experimenting with a system that is twisting the fabric of the universe into knots, and now horrible monsters and inconceivable events are slowly crawling out of the abyss into our realm.

    And this is just the beginning – their device has so little power. What will happen when they scale it up?

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