Imagine a future full of impossibly amazing technology: holographic movie trailers, self-drying jackets and a weather service that actually controls weather patterns. Welcome to 2015—as perceived in 1989.
In Back to the Future Part II, Marty McFly time-travels 30 years into the future to find that his hometown is like a completely different world, complete with flying cars and hoverboards. Looking back from the reality of 2015 on the opening scene of the movie, we might laugh at the things they thought possible.
But commercial flying cars and hoverboards aren’t impossible. They’re just completely improbable.
If flying cars or hoverboards ever became available to the everyday person, one way to build them would be using magnetic levitation based on a special kind of material called a superconductor. Here’s how it works:
“The simplest way to generate magnetic levitation is with several magnets pointing in different directions,” said Argonne scientist Axel Hoffmann. “When you put a superconductor above these and cool it, it traps the magnetic field, and therefore is held in its original position. It can be pushed and pulled, and even turned upside down, but it is always strongly attracted back to where it was.”
The vehicles could hover about four inches off of the ground, Hoffmann said—as long as the superconductor is cooled to -320° Fahrenheit and there is a magnet underneath.
But if maglev cars were made, they would not be able to “fly” as shown in Back to the Future Part II. In one of the scenes in the movie, the cars ride up a ramp and fly about 30 feet above the ground, which would require an extremely powerful magnet.
There are two major problems, though. A maglev vehicle levitates as long as the superconductor stays cold and there is a magnet underneath. Without either of these factors, it stays on the ground.
The magnets are the hardest part to deal with. For maglev cars and hoverboards to work, entire towns would need magnets underneath the streets and sidewalks. Even then, it would be difficult to drive freely without a track. The superconductor would try to follow a definite path, so roaming around in a hoverboard—or something as simple as changing lanes in a flying car—would be very difficult.
DID YOU KNOW? Earlier this year, a Japanese superconductor-based maglev train set a new world record for train speed—375 miles per hour. So maybe we’re on our way?
Another factor is the cooling system. All superconductors need to be kept cold, and the most common coolants for this are liquid helium for conventional superconductors and liquid nitrogen for high-temperature superconductors. The second the coolant is gone, the levitating superconductor drops back down to the ground. Maglev cars and hoverboards would need cooling units and regularly available liquid helium or nitrogen, all of which are, for the moment, too expensive for widespread use.
This is not to say that companies aren’t working on them—just this year Lexus released a working prototype hoverboard that uses superconductors, and Hendo Hover is making its own with a different system. Meanwhile, Argonne scientists are working on superconductors and ways to make them easier to use for practical purposes.
So give it another 30 years—we might yet be hovering to school.
Science Behind the Fiction is a regular feature in Argonne’s free science magazine, Argonne Now. Click to subscribe, or check out previous stories: