on the supposed Warp Drive

on

When people find out I’m an astronomer, one of the first questions I’m usually asked is if I want to be an astronaut. I always say no, because human spaceflight has been stuck in Low Earth Orbit since before I was born. I don’t want that; I want to go to distant worlds hundreds of light years away, that would take thousands of years to get to. I want to duck into one of the Pillars of Creation and see the chaotic mess of young star systems that exist therein, and, if possible, visit Planet Zog and see the three moons setting while a tumbleweed-shaped alien rolls around in a gelatinous sea. Basically, I want the Starship Enterprise. So having an actual warp drive would be really cool. Unfortunately, what’s going around in the news is definitely not a warp drive, and most likely not real.

This is actually a story I wrote about before, during an earlier flurry of Eagleworks stories. So, at the risk of repeating myself, here are the basic facts:

1. There are actually two (if not more) very similar devices being tested. The EM drive, which claims to move by generating microwaves in a closed cavity – the microwaves aren’t emitted, but the device moves anyway, and the Cannae drive, which claims to push against the fabric of spacetime itself. The claims are heavily disputed by physicists as basically nonsense.

2. The devices are supposed to create thrust without propellant. This is an obvious violation of Newton’s second law: for every action, there is an equal and opposite reaction. If you want to move something, a force must act on it. In the absence of anything to push on (say, a rocketship in deep space), you have to chuck something out the back. These engines claim to move without any propulsion. These devices would violate the conservation of momentum, and their supposed mechanisms would also violate conservation of energy. All of this is impossible on the level of the Lorax pulling himself up by the hairs on his head and floating up into the sky.

3. They do seem to move, albeit an extremely tiny (and variable) amount. This is surprising, but tests are still underway to determine if this is some amazing hitherto-unknown force of nature or, more likely, the devices pushing against something in the test chamber – the air, the table, magnetic fields from the power cables. One telling feature is that how much the EM drive moves isn’t the same between different tests at different laboratories, which is bad. Imagine pressing down on the gas pedal in your car and not being sure if you’re going to move half an inch a second or 600 miles an hour. This suggests that the drive itself isn’t what’s doing the moving.

4. In my previous post I suggested that the drives were “already proven to not work” because a test article (of the Cannae drive, specifically) with a supposedly critical component missing also produced thrust. That was unfair on my part. That test proved the device didn’t work the way the inventor claimed; it didn’t prove the device did not work at all. Still, as I mentioned above, there are plenty of good scientific reasons to expect that Eagleworks (or one of the other labs) will eventually prove the devices don’t work.

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These things aren’t warp drive, though: what they offered was basically unlimited (if slow) propulsion. Sure, if you could accelerate forever, you would eventually get quite CLOSE to the speed of light, but even in the inventor’s wildest dreams, they can’t break the speed of light.

Where did this get conflated with a warp drive? I’m not sure, but I have a few ideas:

  • People may be confusing this project with the other one Eagleworks’ leader (Harold “Sonny” White) is famous for: An improvement on the Alcubierre Warp Drive formula. Alcubierre’s warp drive, first proposed in 1994, gets around the limitation that matter can’t travel faster than light, by having a bubble of spacetime itself travel faster than light. Inside the bubble, there’s a pocket of normal space for a spaceship to park itself and be carried along for the ride. Unfortunately, while the math is valid according to General Relativity, it requires crazy and possibly non-existant things like negative energy. It’s not even clear you could survive inside the pocket anyway. And it would effectively make time travel possible, which opens the door to all manner of paradoxes.
  • Some of the explanations about how these drives work involves physics (distortion of space-time) that, if true, might make the Alcubierre warp drive possible.
  • Press releases have claimed that this drive would open up the exploration of the solar system in a big way. It’s possible that people have replaced “solar system” with “space”; exploring THAT efficiently would require a warp drive. Then again, that hasn’t happened to the Yuri Milner Breakthrough Starshot project, which aims to use powerful lasers to accelerate postage-stamp-sized space probes to 20% of the speed of light, at which point a trip to alpha Centauri would only take 20 years. There, at least, there’s a solid, well-understood method of propulsion: Light exerts pressure, which is force per unit area. That’s the mechanism by which the star eta Carina shot off its outer layers into space, and that’s the mechanism by which solar sails work. Of course, the breakthrough starshot won’t work until we can figure out how to shrink entire space probes to something the size of postage stamps with all the necessary components to take observations and communicate them to us over 4 light years away, AND build lasers that large, AND aim them at postage stamp sized objects in space, AND have the postage stamps not melt when blasted with powerful lasers. But there’s nothing in the laws of physics that say we can’t do that. There just need to be a lot of technological breakthroughs.

I want warp drive as much as (probably more than) the next guy, but this isn’t warp drive. It’s not a faster-than-light propulsion, and it’s not even reliable propulsion when repeated experiments give differing thrusts. It works, in a sense, but every test demonstrates it moving with close to zero thrust… and a really precise experiment will probably demonstrate ACTUAL zero thrust. But Eagleworks (and other labs testing these devices) aren’t done yet. Speculation is rampant, but it’s still all just speculation. Reports will follow, eventually. Unfortunately, given that this is all fringe science, nobody’s spending all that much time on the experiments.

 

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2 Comments Add yours

  1. The problem with these exotic reactionless drives is they’re basically science fiction, irrespective of the apparent science invoked to explain them. Heinlein envisaged one – ‘Horst-Conrad’ drive, which ‘clutched at the fabric of space’, for Starman Jones in 1953. Nonsense, of course, as Heinlein well knew. The issue, I think, is that the nature of space-time is counter-intuitive in many ways relative to what we see around us every day on Earth, and that gets our imaginations working – so that theoretical possibilities (which may well work out mathematically) become physical plausibilities, whether they actually are or not.

    That said, I wouldn’t mind if somebody DID come up with an exotic drive and/or a ‘warp’ system (really, we’d need both). I’d certainly want to go exploring, and the solar system ain’t big enough…

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  2. Bob Ludwick says:

    Hello Starguy,

    I’m pretty much where you are on this one: I really WANT it to be true, but I have seen no convincing evidence that it is and until I do, if I were voting with my dollars instead of my wishes, I would vote that it is not.

    That said I would like to quibble a bit re your point #3. Specifically this: “One telling feature is that how much the EM drive moves isn’t the same between different tests at different laboratories, which is bad. ”

    You are right. Variable response to constant stimulus is bad.

    In reality no two labs have conducted the same, or even closely similar tests, beyond the basic ‘Pump a bunch of power into a frustum and see what happens.’ level.

    Shawyer’s premise, which instigated this whole flap, was that a frustum fed microwave power at resonance would produce a thrust without ejecting anything out the end. The thrust was postulated to be proportional to the Q of the frustum and the power injected.

    I have been following the internet traffic since I first got all excited about Shawyer’s ‘EmDrive’ and as near as I can figure the folks doing the tests are all using the same approach: Build a frustum with dimensions that they predict will resonate at or near the frequency of a microwave oven magnetron, hook a microwave magnetron to it, torch it off, and look for thrust.

    There are several problems with this:

    The spectral output of an oven magnetron is wide and contains multiple spectral components. The frequency of each line and the power it contains varies widely from unit to unit, from test run to test run, and from second to second during the test run. It is entirely possible that a magnetron feeding a high Q frustum could have its output centered at the resonant frequency of the frustum and that little or no power would be injected at the actual frequency of resonance. Or that during a test run, one or more of the spectral components would drift through the resonant frequency. My point is, postulating for the moment that EmDrive thrust is actually possible and that the various experimenters were using frustums constructed to the same mechanical specifications and using the same make and model magnetron, there is no reason to believe that they would obtain the same test results. They aren’t and they didn’t. None of the various tests produce the same results, even if the EmDrive phenomenon IS real, because none of the various experiments have used the same frustum design OR the same drive source OR test under the same conditions.

    There is also the problem of excitation mode. The response of each frustum as viewed on a network analyzer reveals multiple resonant frequencies, some very close together. NONE of the testing done to date has used a stable, narrow band source that can be tuned exactly to each resonant mode and varied in small increments to track the resonance as the frustum heats up OR varied in power to see if any thrust actually measured varies with injected power and/or frequency. There is no reason to believe, again postulating the reality of EmDrive thrust, that all resonant modes would have identical Q OR that for a given Q and excitation level all modes would produce the same thrust. Or that more than one of the multiple modes would produce ANY thrust.

    There are other problems with EmDrive testing that guarantee that even if the principle IS valid, it would be EXPECTED that the results of the testing to date would be all over the place.

    In other words, while I agree with you that the chance that ‘EmDrives’ are real is somewhere between slim and none, the spotty results of the testing to date should not be considered a ‘show stopper’.

    Bob Ludwick

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