regardless of the other mechanics, its claim to be able to create thrust while only consuming 10 watts is dubious, as that means that there is only 10 watts of power available to create forward motion.
That’s not very much. Your car, for instance, provides tens of thousands of watts of locomotive power.
I think that the idea is that they don’t understand “relativistic mass”, or at least, are pretending that they don’t. The idea that something that actually gains mass as you accelerate it and decreases mass when you decelerate it could be used for something like that. Unfortunately, that’s not actually how it works. It doesn’t actually gain or lose any mass, it only gains or loses momentum that acts like mass only to a naive observer. If something hits you with enough relative velocity that it has a Lorentz factor of 2, then it will seem as though delivered twice the punch that its rest mass times its velocity would indicate, making your naive assumption being that the object had doubled in mass.
This isn’t the case at all, as even the naive observer would note, should they choose to jog alongside the test particle. They reach out and weigh the particle, and find that it is equal to its rest mass, even though its moving. Of course, the naive observer could note that while they are doing their little jog, somehow or other the entire universe has doubled in mass. You can say that the energy to “double the mass” of the test particle comes from whatever you used to accelerate it. But where did the energy to double the mass of the universe come from? That’s where it really starts to break down that “relativistic mass” does not and can not have an actual meaning that can be used to describe or predict physical phenomena.
Anyway, that’s what I see them doing here, misusing relativistic mass to create a reaction-less drive and perpetual motion machine on paper. If it works, great, we’ve not only solved every energy crisis and space travel, but also revolutionized every idea we’ve ever had about the way the universe works. My money is on it not panning out.
I’m not sure that’s at the root of their confusion. Relativistic mass may be a dubious concept, but relativistic momentum is not, and that’s really all that matters here: a momentum transfer between some internally moving masses and the external device.
But relativistic momentum doesn’t change anything, because the only way to exchange momentum is via a force, and that force is exactly symmetrical forwards and back (yet another one of those pesky physical symmetries). So sure, accelerating those ions to relativistic speeds produces a greater momentum transfer than if Newton were correct. But to get those particles back to the front of the drive, you first have to cancel that backward velocity, and to do that you have to apply the same greater-than-Newtonian force to decelerate them.
In fact the nature of the function is irrelevant. The integral of a function f(x) from a to b is the negative of the integral from b to a. Whatever forces you had to apply to accelerate some particle from 0 to whatever are the exact negative of those needed to decelerate it from whatever to 0.
It’s the same problem with basically all perpetual motion machines. It’s like walking around a hilly landscape, eventually coming back to the origin, and hoping that somehow your altitude has changed. It’s obviously impossible, and the path you take and the shape of the landscape is utterly irrelevant.
I have a hard time believing it would be truly reactionless. Using some frame-dragging effect to push yourself off the black hole without propellant? Sure, I can believe that. But the black hole would then be pushed in the opposite direction. No different from jumping off a small asteroid.
This is obviously crank woo bullshit, and only deserves as much analysis as one finds entertaining, certainly not worth going into great detail about, but if you turn off your brain for a minute, then their misuse of “relativistic mass” makes sense if you don’t think about it too much.
You send the particles really fast in one direction. Because of how fast they are going, they have more mass. You send them in the other direction at a slower speed, so they have less mass. Therefore, you have more mass moving in one direction than the other, and bob’s your uncle, forward thrust!
That’s how I read the claims, anyway. There may one day be some great breakthrough that changes our view of physics, but this is not it.
This. They’re claiming that relativistic momentum introduces an asymmetry between the fast moving and slow moving parts of the cycle. I haven’t the math skills to prove it but almost certainly not true.
This only works for a rotating black hole. If you managed to remove all the charge and angular momentum from a black hole, you couldn’t get any more energy out by these methods.
Luckily most, or all, black holes are probably rotating quite fast, so this trick will normally be possible.
So does that mean that no propellant-less propulsion system is consistent with relativity? I guess you could have a system that somehow deflects exterior mass to push against but didn’t have to eject its own mass?
You could have a laser pointing out the back, and that would give you thrust. The “propellant” in this case is photons. Downside is that the power to thrust ratio is terrible, upside is the the specific impulse is effectively infinite.
It is possible for some of these proposed “reaction-less” drives to give thrust, but it would not be because they are revealing some new physics, but because they leak radiation preferentially in one direction. Of course, if that is what is giving the thrust, there are less complicated ways of doing so.
You could also use the magnetic field of the Earth or of the Sun (or other body with a magnetic field. Great for Jupiter too, but not so much for Venus or Mars.) to produce thrust, requiring only electricity to run, but in this case, the reaction mass is whatever is coupled to the other end of the magnetic field.
There is the possibility that someone will figure out how to interact with dark matter or neutrinos or some other fundamental aspect of space-time, and create a drive that does not use any conventional particle as reaction mass, but even in this case, it would be the dark matter or neutrinos or fundamental aspect of space-time that it is acting upon. A naive physicist with only contemporary tools at their disposal may well consider such a device to be reaction-less, but only because it is not fully understood.
Some proposed “Mach” drives supposedly use the entire background mass of the universe as the reaction mass; and/or equivalently decouple inertia from the rest of the universe.
Sometimes it’s hard to distinguish speculative physics from pure woo.
No, this is a real effect in general relativity, known as ‘spacetime swimming’. In a gravitational field, a body can perform a series of local deformations involving only internal forces, and undergo a positional translation as a result—see the original paper here and a discussion here.
Conservation of momentum, however, isn’t violated, as the ‘swimmer’ never has a nonzero net momentum.
Furthermore, the Alcubierre metric—better known as the ‘warp drive’—would also be an example of a ‘reactionless’ drive—although of course no thrust is really generated, as the ‘ship’ isn’t actually accelerated. But even for sublight speeds, such a configuration would need exotic forms of matter currently not known to exist.
The drive discussed here won’t work, though. If you correctly account for the four-momenta of the ions and the fields used to accelerate and decelerate them, you will not obtain a net momentum in any direction.
From your initial description, I thought “hmmm–sounds a bit like how a cat can change its orientation in space while maintaining zero angular momentum”, and I see from your second link that it’s a close analogy.
Of course the effect can’t be used for a drive that continuously accelerates, as is being posited here. You can only accelerate a very small amount before having to pull in your limbs and decelerate again.
Yes, that’s a great intuition! But one has to be (as always) careful with analogies—the other one Koelman suggests, of the ball thrown once around a closed universe, doesn’t actually quite work, as you could also do that on a torus with zero curvature. So this is actually a topological effect, not one of curvature!
Still, it illustrates a dilemma one sometimes faces in these debates: before knowing about spacetime swimming, I would have categorically denied that such a thing is possible. So, if I claim that this sort of drive discussed here is impossible (which it is), what’s to prohibit anybody from claiming, ‘well, you were wrong about spacetime swimming, so maybe you’re wrong about this, too!’.
It’s hard to conclusively argue that there’s no ‘wiggle room’ for the kind of thing proposed here—it’s two different levels of being wrong: being wrong about spacetime swimming involves being wrong about the consequences of established physical theory, while being wrong about the ‘helical drive’ would entail being wrong about its fundamental principles. The former is routine—even established theory may hold surprising and intriguing consequences (that’s what makes the whole thing fun). The latter, however, would essentially overturn vast swaths of our current scientific understanding—so being wrong about that would mean having to clear a much larger hurdle of empirical evidence and theoretical reasoning than being wrong about spacetime swimming does. To most laypeople, however, both just look like ‘being wrong’ in the same sense.
The whole universe is permeated by gravity fields that curve space - so it should (in theory) be possible to perform ‘space-time swimming’ anywhere. But the effect is so small that in most of the universe this effect would not be measurable.
One place where the effect would be noticeable would be close to the event horizon of the supermassive black hole at the centre of the galaxy. Space is so sharply curved there, that the circumference of a circle can be significantly greater than 2πr.
That’s not so hard; just divide the 52 cards into an infinite number of infinitely convoluted pieces, then put them back together slightly differently. Set Theory, it’s magic!
