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No, I don’t mean those stupid hands-free segways. Besides the flying car, (which seems precariously close to reality depending on whether your definition of flying car includes manned electric multicopters) hoverboards are the other main milestone that’s supposed to let us know it’s the future™
However despite being a mainstay of 2015 Hill Valley as depicted in Back to the Future II, 2015 has long since come and gone with nary a hoverboard in sight. What gives? Is a skateboard that hovers really such a difficult engineering problem?
In a nutshell, yes it is. Because what you’re asking for when you want a hoverboard is basically a very compact electric aircraft, just one that’s limited to an altitude of a few inches. As yet no technology exists that can emit a general purpose repulsion field that pushes against any material.
Magnets area different story though. Some years back, Lexus shot a viral promotional video with a fake hoverboard. Only nominally fake, in fact it used liquid nitrogen cooled superconducting magnets to hover along a magnetic “track”. This is among the only known ways to confine a magnetically levitated vehicle.
Therein lies the problem with the hoverboard. Even if you succeed in levitating the damn thing, how do you control it afterward? The directionality of skateboard wheels and how they’re mounted to the board are what keep it moving along a controllable forward trajectory. Not so if it hovers.
This was also the fundamental problem facing the Hendo Hoverboard, probably the closest thing to the Back to the Future II version covered in this article. It can only hover on magnetically reactive metal sheeting (copper usually) and generates a repulsive magnetic field in the sheet metal by way of spinning magnet pairs within each of the “hover engines”.
Setting aside the limitations inherent in a hoverboard that only works in skate parks that have been copper coated, it’s still exciting that we now live in a world where “hover engines” are a thing. The hoverboard is mainly promotional, their real bread and butter application will be warehouse robots.
This brings us to the second class of real life hoverboard. Some, like the Zapata Flyboard Air pictured above, utilize micro jet engines of the sort commonly sold to RC aircraft hobbyists with deep pockets. Others are basically just oversized drones you can stand on.
It may seem like overkill for the task of levitating the rider a few inches off the ground and it is. For that reason these are typically not used that way, instead being flown around for relatively short durations (you can only carry so much fuel in that backpack) at the same sort of public events jetpacks used to appear at.
In my mind this is cooler anyway. It’s a complete self contained (save for the fuel backpack) compact VTOL aircraft. That the technology needed for something like this exists now is more exciting in every respect than a hovering skateboard would be.
The same company also makes recreational “jetpacks” and “flyboards” that are basically just creatively mounted down-facing fire hoses driven by an internal combustion engine water pump floating on its own buoy below you.
These aren’t being seriously considered here because they only work on water. As we know from Back to the Future II, true hoverboards don’t work on water ( you bojo!) Unless you got power, that is.
They do highlight something of the design challenges facing any would-be hoverboard inventor though. Newtonian physics requires an equal and opposite reaction in order to move upward against Earth’s gravity, usually by throwing down reaction mass (excepting magnetics, which we discussed already).
In this case the reaction mass is water. In the case of ride-on drones it’s air, and in the case of jet engines the air is condensed and super-heated first.
What about a more literal approach to a hoverboard? A board shaped hovercraft, operating on the same principles of riding atop a cushion of air developed for the first hovercrafts back in 1955.
These are a perennial favorite DIY project of engineering students. I remember seeing ads for a hoverboard kit based on a vacuum cleaner motor in the back of comic books when I was a boy. None you could properly steer though, once again the fatal flaw of any hovering vehicle.
Military hovercrafts accomplish this by way of giant ducted fans on the rear of the vehicle with pivoting vanes to guide the airflow. Not really a practical solution for something the size of a skateboard, which ideally you’d steer by leaning. That’s to say nothing of the constant, ear-splitting noise of a small (probably 2 stroke) combustion engine sitting between your feet.
What’s needed is some sort of advance in electromagnetics or antigravity permitting a compact hover engine which both repels and grips the surface beneath it. This would allow it to levitate but not float frictionlessly out of control, similar to what we’ve seen from superconducting magnets.
Until such a technology is developed, the combination of features required for the consumer level hoverboard of our dreams will remain out of reach. Anybody brave enough to attempt learning to ride the Hendo hoverboard is welcome to finance a copper lined skate park to use it in. But be advised that Tony Hawk himself gave it a try, and couldn’t make the damn thing do what he wanted.
This is another case of futurists expecting too little, though. While we don’t have hovering skateboards, we do have skateboard sized aircraft which do a great deal more than hover. I doubt we’ll ever see these contraptions zipping along the sidewalks, for safety reasons, but they may yet become the basis for some new kind of sport.
This won’t satisfy everybody. Just like calling passenger drones “flying cars” elicits a grumpy scowl from a certain kind of person. But that’s just all the more reason to keep chipping away at the problems facing such a potential device.
Like the Moon landings, there was nothing immediately useful about them, but the technologies that needed to be developed to make it happen were spun off into products still in use today. Advances in computing, in materials, in telecommunications we’d never have gotten our hands on so soon otherwise.
It’s by chasing seemingly frivolous dreams, like flying cars, hoverboards, or walking on the Moon that the future happens. Many of our most important innovations are either accidental, or incidental: Things we weren’t specifically trying to invent, but had to in order to reach some greater goal.
Here’s to the hoverboard, then. That perpetually out of reach, yet seemingly always-imminent milestone of tomorrow.