Can someone please explain to me what allows this board to actually hover?
Here’s a YouTube video of the new Lexus Hoverboardbeing ridden by a skateboarder. It clearly defies gravity. Apparently it’s fueled with liquid nitrogen and somehow super-cooling something makes this hover. What’s the science behind this?
Thanks in advance.
In a word, magnets. That’s the short version. The long version means steeling yourself for a light dose of physics.
According to Lexus, its hoverboard relies on superconductors and magnets, which combine to repel the force of gravity and lift an object—like, say, a fancy skateboard and its rider—above the ground.
The liquid nitrogen super-cooling is for an extremely powerful magnet. However, if this clip is indeed real then that skate park must have been specifically built for it, because it would have to have a metallic surface underneath it for the magnet to repel and hover.
And its not really ‘repelling gravity’ as in countering the fundamental gravitational force (which we don’t even completely understand to begin with), it is strictly in the realm of the electromagnetic force…
It has to run over a track of permanent magnets. The liquid nitrogen is supposed to be cooling superconducting magnetic coils. It’s so big I don’t understand why they need superconducting magnets instead of permanent magnets in the board.
It seems they’ve figured out you’ll need a half pipe or bowl shaped surface to do anything with it except to go in a straight line. There’s no way to steer with magnetic levitation.
To expand on this, the magnets are hidden in a track underneath the concrete in the skate park. It wouldn’t work in a normal environment, just a custom built area.
This seems like totally the opposite way of accomplishing hoverboard riding when you need a magnetic surface to ride on. Without fancy technology the service can be an array of tightly packed conventional electromagnets each activated by a Hall Effect switch and some interconnecting logic. A hoverboard with permanent magnet Halback arrays would move over the surface and the electromagnets would be switched on under the board and in it’s path based on velocity and direction. The electromagnet array would be covered with a thin, durable, and smooth material. Just enough to keep falling riders from damaging the electromagnets. A half pipe shouldn’t be that hard to construct, a kidney shaped pool type thing would be even more fun.
Should I try a kickstarter campaign for that?
My understanding is that conventional magnets wouldn’t work because of Earnshaw’s Theorem. Maglev trains use mechanical mechanisms or dynamic adjustment of the magnetic field to accomplish it. Superconductors on the other hand can stably levitate due to the Meissner Effect.
Edit: Oh I just noticed that you are proposing dynamic adjustment of the field. Seems a lot more expensive than a track of permanent magnets though.
–Mark
I think what Tripolar is saying is that you should put the dynamic magnets in the track, where there’s plenty of room for power, cryogenics, and controls, instead of on the small skateboard.
But there aren’t any dynamic magnets in the board, as I understand how this works. It’s just a superconductor (not even a superconducting magnet), with no control circuitry at all. It levitates due to the Meissner effect and flux pinning. Tripolar’s proposal would add a bunch of new control logic, sensors, etc. which don’t exist anywhere in the current design.
–Mark
But I don’t think it will need any superconductors, or even any cooling unless someone just hovers in place. A hoverboard that needs liquid nitrogen to operate isn’t going to be very practical.
Would the Lexus board wouldn’t need any dynamic magnets as longs as it’s moving at fair rate of speed?
There’s now a slick "making of" video (slash advertisement). Yes, there’s a single, hidden track. Still very nifty, IMO…
Yes, permanent magnets in the track and high temperature superconductors in the board.
If you use classical physics to work out what happens if you place a perfect conductor in a magnetic field, you find that a current will flow in just such a way as to exclude any magnetic flux from the the interior of the superconductor. This is a direct result of Maxwell’s theory of electromagnetism. The net result of this is that the currents in the perfect conductor create an electromagnet with exactly the opposite magnetic flux, thus two north or south poles adjacent to each, which causes repulsion.
Superconductors are perfect conductors with an additional effect and with some limitations. The additional effect is the Meissner effect, which is not really essential to the operation of the hoverboard. When you cool a superconductive material down, it becomes a superconductor at a characteristic temperature. As this transition occurs the flux is actually excluded (or approximately so). This is not a property of a perfect conductor, which would simply lock in the field that is present at the transition temperature. The limitation is that the high temperature superconductor used in the hoverboard does not exhibit a full Meissner or perfect conductor effect, but traps some flux when it is placed in the magnetic field. This is beneficial because it adds some stability that would otherwise make the hoverboard very unstable. Altogether this makes the physics much more complex than if there was a perfect conductor instead of a real-world superconductor.