wind-powered vehicle defies physics

http://www.bbc.com/future/story/20120727-the-wind-beneath-my-wheels




Rick Cavallaro must have thick skin. For more than four years he has been bombarded by naysayers who have ridiculed him and his work.

It all started when the software and hardware developer proposed a design for an unlikely-sounding, wind-powered car that he said would be able to travel faster than the wind blowing directly behind it.

Despite others having proposed similar ideas, skeptics immediately labeled it a hoax, putting it in the same category as perpetual motion machines. It defied physics, they said, and claimed Cavallaro was a charlatan. Searching through comments on any article that dared mention the design and you will find post after post that is openly hostile. Even respected bloggers and magazines waded in with some branding him a “bozo”.

“They have this problem that their intuition tells them that it’s not possible, because once there’s no wind over the vehicle [when it is travelling at wind speed] it can’t harness any energy from the wind” says Cavallaro. The vehemence of the response was a shock to him.

“The thing that was most surprising to me was how much even professional engineers and scientists will not only rely on their intuition, but accept their intuition over a straightforward rigorous analysis, and real world proof.”

But, Cavallaro remained undeterred, and with the backing of large firms – including Google – he built his machine. The result is Blackbird – a ground-hugging, three-wheeled racing car with what essentially looks like a 5m- (14ft-) high wind turbine stuck on the back. Over the last two years he has refined the design and in a series of tests has shown that it can not only run downwind faster than the wind, but it can run upwind too.

“The reason I think that most people find it counter-intuitive is that you get to a point going downwind, when you are going at exactly the same speed as the wind” says Cavallaro. To go faster, the machine would have to somehow pull ahead of the wind that’s pushing it. And, as most sailors know, that’s not possible... at least in a boat.

But by using a propeller instead of a conventional sail, Blackbird is able to overcome this limit. “We didn’t invent or discover any new physics, we just have a clever way of exploiting some basic physics,” he says.

Finish reading here: http://www.bbc.com/future/story/20120727-the-wind-beneath-my-wheels

I don't think you can defy physics.

Krispy said:

I don't think you can defy physics.

Just find new ways to exploit them.

Rather impressive.

I remember that a maritime rotating sail had already been presented, which also allowed travelling faster than the wind propelling it, but I'm too lazy to find a link. It was a giant column-like structure however, not a conventional vertical propeller.

And, as every aviation aficionado knows, there's a neat little function called "variable pitch", which allows propellers to "bite" more or less into the wind. First time I saw this on a land vehicle though.

Krispy said:

I don't think you can defy physics.

Details!

I defied the laws of physics to move my fingers -- against the crushing weight of gravity -- when I made this reply - TAKE THAT, NEWTON!

Seriously, though, this guy's invention is pretty cool.

Well, it's good to have a reminder that it's not our intuition and simple physical formulae that determine reality; reality sets it own rules, and it's up to us to figure them out. I'd still like to see a force diagram for this, though, because I find it mind-boggling. Somehow the propeller is still serving as a power source even when the car's moving faster than the wind itself. I guess that a "rotating sail" is somehow able to collect more power from the wind than a stationary sail - the propeller is, in effect, creating a 50 mph wind out of a 20 mph by pushing backwards against it, then using that 50 mph wind for thrust. I wonder if this thing is limited in principle to a certain speed:wind speed ratio, or if, without friction, it could actually accelerate indefinitely.

Another crude analogy: this thing isn't powered by wind, but by a velocity differential between the ground and the air. Heat on its own is useless except for raising another object to an ambient temperature, but a temperature differential can be used to generate the power to increase the temperature of a single object beyond ambient levels. The same kind of thing is happening here.

It's an impressive bending of physics. But in a world with land speed records and jet planes and spacecraft, it all seems a bit twee. Maybe it's just me being thick but I don't see any practical application for his cool little invention.

On another note, apparently BBC worldwide isn't available in the UK so the link doesn't work for me.

Here's an upwind drive: http://www.youtube.com/watch?v=F7PNSyAfCjk

I expect it would be useful if it could change from downwind to upwind mode on the fly (or be equipped with both setups on the back of 1 vehicle), so that on a zigzagging route, you can go both directions. I expect it won't be efficient enough to go uphill on average roads, though maybe after building up speed on flat stretches. Adding bicycle pedals may be the most logical step, to accelerate much more quickly and perhaps for hills.

Adapting it to boat rotors seems the most useful, though I wonder if too much efficiency would be lost compared to wheels to make it viable on water.

That's actually really neat, but what are the applications?

Krispy said:

That's actually really neat, but what are the applications?

Traversing a windy desert with no fuel? :-p

I love it when, in Britain, I get this message from the British Broadcasting Corporation:

We're sorry but this site is not accessible from the UK as it is part of our international service and is not funded by the licence fee.

Dear customer, please go fuck yourself.

It's not funded by the license fee? What is it funded by? The only two answers are ads or your taxes, in which case... fail.

They probably don't have very good intuition or at least aren't able to use it properly.

Well, they are British. Britain is known for having institutions that make no sense even to Britons. :D

True, true.

Aliotroph? said:

Well, they are British. Britain is known for having institutions that make no sense even to Britons. :D

Like this one:

The ministry of silly walks is the very epitome of a sensible organisation compared to some of the real ones here. :D

[edit]


What is it with me and videos posted in this thread? LOL