From flying cars to living on the moon, the future has always been full of promises it doesn't keep. The latest example of this occured to me as I watched Back To The Future a couple nights ago during my long, boring no-customer haul from 8-10pm at Da Shack.
BTTF is a particularly grevious offender in the "promising us things the future will never deliver." For starters we have time travel, small-scale fusion reactors AND flying cars in one prop:
(Rather BladeRunner-esque, that shot...)
And then to make things worse, in BTTF 2, they introduced hoverboards:
What BTTF director Robert Zemeckis jokingly said to the press to the contrary, hoverboards were not real. They were entirely the creation of clever SFX teams in Hollywood. Unfortunately, the SFX guys did such an incredible job on them that they looked unbelievably real in the movies! Yet another piece of technology that the movies promised us we'd have in the future but we'll never see - except in some version that's really weak, lame and misses the whole point. Bah, the future is a constant disappointment!
Or is it?
You know that we have maglev trains now, don't you? Yes, they're out of the lab and already a reality in Germany and Japan. Maybe we can't have hoverboards that work everywhere, but how about a hoverboard park? You know, just take a couple of acres and carpet it with the same stuff that maglev train track is made of?
It's a simple idea that seems clever until you start looking at what really goes into making maglev train tracks. It turns out it's superconducting magnets that need to be cooled with liquid helium. At a cost of something along the lines of $10-30 million dollars per mile of track.
However, there is a better way. One Klaus Halbach of LBNL discovered that if you put a series of magnets together like so:
The field above the magnets almost entirely cancels out, and the field below becomes much stronger:
(Diagrams from http://www.wondermagnet.com/halbach.html)
This field is so strong, it turns out, that if you put a Halbach array with the strong field side facing down on the bottom of a box, and then move the box around above some coils, the magnets induce electrical current in the coils. And a coil with a current flowing through it is, you guessed it, an electromagent! Which produces a magentic field. Which in turn pushes back up against the Halbach array rather powerfully and levitates the box. Theoretically, a 50:1 magnet to cargo weight ratio is achievable. But the really cool thing about this system is it requires no external source of electrical power! Only permanent magnets and ordinary copper coils, plus some way to get the cart up to speed and keep it moving, since all the energy for levitation is provided by the movement of the magnets over the coils.
This system is called "Inductrack" and is much more efficient and inherently stable than conventional superconducting maglevs. Read http://www.alienbaby.com/levitron.html and all three pages of http://www.skytran.net/press/sciam02.htm for more about this very cool technology. Apparently, it's even possible to replace the coils with layered sheets of aluminium with slots cut in them, which is probably a lot more workable and cost effective in the long run.
So, making pratical hoverboards seems a lot clearer now. The only problem left is how do we get the boards going fast enough to be stably levitating and keep them going fast enough so they stay that way? This too, I have an idea on. Yes, you could put some kind of small jet engine on the board, but it would have to carry its own fuel making the board a lot heavier, and small turbines don't produce a lot of thrust, etc, etc...
Have you ever been to the "alpine slide" in Breckenridge, Colorado? It's a three foot wide, semi-circular cross section concrete trench that winds its way down a ski slope. You get a wheeled sled, ride to the top of the ski slope on the chair lift, and then "luge" down the slide on your sled. It's fun - if you get a chance to go to Breck in the summer I recommend it.
Well, you can probably see where this is going already... All we need to do is make a similiar arrangement of coils going down the ski slope, and we can have an hoverboard track that goes down the ski slopes! All the energy to keep the board moving will come from gravity pulling the rider down the slope. And you don't need to make the track just 3 feet wide, either. It can be much wider. I have visions of a 20 or 30 foot wide, shallow "half-pipe" with people tearing down it at 30 or 40 mph with nothing but an inch of thin air and an invisible magnetic field beneath them. The hoverboard made a reality at last...