Why Don't We Have Hoverboards?

The year was 1989. The first GPS satellites were launched into orbit, Nintendo introduced its Game Boy to Japan, and Michael J. Fox brought us all back to the future, again. This time, however, it wasn't just the DeLorean time machine that captured techno-geek moviegoers' imaginations. It was the Mattel hoverboard.

In perhaps the most famous scene of Part II, Fox's Marty McFly jumps on a hoverboard?a pink floating skateboard without wheels?to flee from a pack of 2015 goons riding tougher-looking boards. After that scene, whether you were a skateboarder or not, you wanted a hoverboard. Bogus rumors even began to fly, encouraged by director Robert Zemeckis, that the hoverboards were real and not simply Hollywood smoke and mirrors.

Nearly a quarter-century has passed since the release of Back to the Future Part II, and we're only two years from finding out how much of the movie's idea of 2015 will match reality. Are we any closer to riding hoverboards around town than we were in 1989?

Hovercrafts, in some form or another, have been possible for decades. In 1997, to demonstrate how simple the project could be, research engineer William J. Beaty posted detailed, step-by-step instructions showing how easy it is for just about anyone to build an "ultra-simple hovercraft," using common items, tools, and hardware. Powered by a reversible vacuum cleaner or leaf blower, Beaty's hovercraft uses a circular wooden platform and a sheet of plastic (the same or similar to a shower curtain) to create a "ground-hugging skirt" of positively pressurized air. Because the air trapped inside this skirt is under more pressure than the air surrounding it, the platform hovers a few inches off the ground.

This is the basic design of most modern hovercraft, including the large ones you see on the water. But Marty McFly's board doesn't rely on a visible skirt to keep pressurized air trapped underneath. Nor is it like the Airboard, a disc that uses an engine and fan to get itself and its rider an inch or two off the ground. It's just a board that levitates.

Researchers at Universit? Paris Diderot in France introduced a product in 2011 that shows some promise toward developing a real McFly-style hoverboard by using magnetism to keep the board aloft. Called Mag Surf, this levitation device uses a liquid nitrogen?powered superconductor to propel a skateboard-size hoverboard across a magnetized track. The metal on the bottom of the board becomes a superconductor when treated with liquid nitrogen (to cool it to insane temperatures, near minus 200 degrees Centigrade) and placed atop the magnetic field in the track. The supercooled metal repels the magnetic track, levitating it. This force also pins the board to the track, allowing it to travel back and forth. Check out these photos and video of the Mag Surf.

Superconductivity may be the most practical way to achieve levitation, at least that engineers know about today. It doesn't allow for the freedom of the Back to the Future Mattel board, which can move freely in all directions (but, for whatever reason, levitates but lacks propulsion over water). To make that happen would probably require a breakthrough in superconductivity at more reasonable temperatures, as Slate points out.

But while we await a trackless, high-temperature-superconductor-powered hoverboard, we can rest assured that someone, somewhere, is working to propel us back to McFly's future. (Just don't settle for the nonhovering Mattel replica hoverboard, which we can all agree is $120 better spent elsewhere.)

Source: http://www.popularmechanics.com/technology/aviation/why-dont-we-have-hoverboards-15363707?src=rss

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