Features, Future Please

Future, Please: Hoverboards!

January 31, 2014

Everyone wants a hoverboard, and anyone who says they don’t is lying.

Transformers: The Movie is where I saw my first hoverboard

Credit: Hasbro

In many technicolor futures, everything flies. Bikes are jet bikes, VTOL is standard in passenger cars, and skateboards… ah, the hoverboard. I’ve wanted one for 28 years.

As a child of the 1980s – old enough for the Transformers and Back to the Future, not quite ready for Neuromancer – I saw my first hoverboard when Daniel wrecked his in the first few minutes of Transformers: The Movie. Daniel’s board got no love, and is mostly forgotten today. If my own memory serves, he rode it on screen, fell off, and caught a ride in a self-aware hot rod… hardly the best demo for hoverboard technology.

That was three years before Back to the Future II, the movie I am required to mention under Article III, Section I of the UN Convention on Cliches in Short Form Journalism. Today, Marty McFly’s creators are almost exclusively credited with popularizing the hoverboard, and rightly so; that hoverboard sequence is what encouraged me to take up skateboarding.

(Friction burns encouraged me to put it down.)

This is where the world learned about hoverboards

Credit: Universal Pictures

I grew up to be a writer, but many other kids in those same theaters became engineers. Some of them, in turn, have almost invented the hoverboard.

Airboards Are Not Hoverboards

The most common homebrew hoverboards are ACVs – air-cushion vehicles. These are more personal hovercraft than hoverboards, but they have the operational advantage of existing.

ACVs are awesome in their own right: by creating a volume of high-pressure air under the hull of the vehicle, an ACV “floats” into the lower-pressure air of the atmosphere. The concept is nearly a century old, though hovercraft didn’t come into their own as commercial vehicles until the ’60s.

ACV hoverboards are relatively easy to make. Most builders use leaf blowers to pressurize the air envelope and adapt some version of the Latimer-Needham skirting system from larger craft for speed and stability.

While ACV hoverboards look like a blast to build and ride, they’re not quite hoverboards. The skirting system is a deal breaker, almost as much as straddling a gas-powered leaf blower. For the real thing, we need a slicker, low-profile means of levitation.

Magnetic Propulsion Hoverboards: Almost, but Not Quite

Mag Surf Hoverboard

Credit: Eric Descarpentri

One option is to use electromagnetic suspension (pdf) to repel the board from a designated track, as with one system of maglev trains. This gives us the streamlined look of fictional hoverboards, though not their mobility.

 

The Mag Surf, one of the coolest hoverboards along these lines, came out of the University of Paris Diderot. The Mag Surf exploits a property of superconducting materials to repel magnetic fields from a track, below, providing smooth lift and a frictionless ride.

While incredible to look at and apparently a joy to ride, the Mag Surf doesn’t cut it as a full hoverboard. It’s tied to a magnetized track and requires expensive materials and engineering to assemble – remember, our Back to the Future hoverboards were cheap enough to ship in Mattel-branded lines for girls under 12.

In the everyday world, this simply isn’t workable. I can see something like it taking off in constructed environments, perhaps, like the floating cities of the Jetsons; though the engineers in that timeline had clearly solved the hovering problem in a cheaper and more versatile way. Everything in the Jetsons universe either hovers independently or rests on something that does.

I wouldn’t ride a hoverboard there, though. There are no safety rails anywhere, and it’s a long way down… More of a jet pack town, really.

Is the Hoverboard an Ionocraft?

A simple lifter, possible hoverboard technology

Credit: Timothy P. Szczykutowicz

One thing we do know about the Back to the Future timeline is that their engineers had a tremendous amount of power at their disposal. Are those hoverboards based on electrohydrodynamic lifters?

These lifters – named ionocraft by Alexander Nikolaievich Prokofiev de Seversky, who contributed much to the understanding of possible applications of EHD lifters in heavier-than-air vessels – use the flow of ionized air between asymmetrical conductors to generate thrust without moving parts. They’re fairly easy to build at a small scale, but hobbyists should exercise caution; these units can deliver a non-trivial shock if handled when powered.

To forestall any association with the kookier elements of the EHD hobbyist community, I need to make a series of filtering statements:

  • EHD thrusters are not anti-gravity units.
  • EHD thrusters do not generate ‘free energy.’
  • There is more evidence that UFOs are propelled by LSD than EHD.
  • Leave Tesla out of this, please.
  • EHD propulsion is a real thing, and it’s awesome. Don’t make it weird, okay?

Electrohydrodynamic propulsion was first modeled centuries ago, but practical engineering didn’t begin until the ’20s – Thomas Townsend Brown, of the infamous Biefeld-Brown Effect – and again in the ’60s, with de Seversky’s numerous contributions. While attempts to use EHD thrusters to power heavier-than-air vessels in atmosphere haven’t gotten very far to date, there’s always hope. It doesn’t hurt that they’re just plain fascinating to watch.

Lifters would fit the bill for hoverboard propulsion, with sufficient power and in the right configuration. They’re streamlined, contain no moving parts, and are just plausible enough to capture an engineer’s attention… if unworkable to propel an untethered, skateboard-sized vehicle with available energy storage technology.

Still, if you can knock together a prototype and live close enough to New York… I’ll happily be your test monkey.