The Mojave Desert’s dry Ivanpah lake bed shimmers under a vicious solar glare,creating the illusion of water. Piercing the mirage are dozens of sails—a vast array of color streaking over a dusty ocean. It’s the last week in March, and Ivanpah is hosting the North American Land Sailing Association‘s annual dirt-boat championships, the America’s Cup. It may seem odd to give this competition the same name as the more famous ocean race, but truth be told, in a strictly technical sense the two America’s Cups are quite similar. Dirt sailing is sailing, after all: The tactics are the same; the maneuvers are the same. The main difference, as people who race on dirt are keen to point out, is speed. Sailing on a dry lake is about three times faster than sailing on water.

Then there are the competitors themselves. “There’s just something about the desert that attracts strange people,” longtime dirt sailor Richard Jenkins says. He would know: Jenkins is the current king of the Dirt Cup, as some call it, having set the world speed record at the competition in 2009, when his land yacht, Greenbird , hit 126.2 miles per hour. “Land sailors are a weird bunch. Oddballs. Alternative in every respect.”

Cavallaro knew that a sail on a tack and a spinning propeller blade were aerodynamically the same.

No one here is weirder or more alternative than a mustachioed man who has shown up this year with an exceptionally strange-looking dirt boat and an extraordinary claim. The man, a fast-talking inventor named Rick Cavallaro, says that his craft— Blackbird —can, while sailing directly downwind, go faster than the wind that is propelling it.

Jenkins, like other veterans of the Dirt Cup, thinks this is preposterous. There’s no doubt that a boat (dirt or otherwise) can go faster than the wind. That’s part of the magic of sailing: By running at an angle to take advantage of crosswind effects, a boat can outpace wind speed. But directly downwind? Impossible. In a best-case scenario, a sailing vessel headed directly downwind will move at the speed of the breeze that’s pushing it.

The problem with downwind sailing is that from the perspective of the craft, once it reaches wind speed there is no more wind. And if there is one thing every sailor knows, it’s that “you can’t power through zero wind,” as Jenkins says. Not only would the sailing craft have to somehow pull ahead of the wind that’s pushing it, but from the perspective of the sailors on board, it would face what feels like a headwind pushing it back. In sailing, zero wind—real or apparent—is considered an absolute barrier, like the speed of light in physics.

Yet Cavallaro claims that Blackbird can break this barrier. Not only that, he says, it will likely go downwind twice as fast as the wind. The boast is made all the more outlandish by the fact that Blackbird doesn’t have anything that looks even remotely like a sail.

The craft is a crude contraption of plywood, carbon fiber, bicycle parts, and pieces of go-cart. It’s low and relatively streamlined, except for the 14-foot-high tower mounted behind the cockpit. Attached to this is what can be called—for the sake of argument— Blackbird ‘s sail. Many will choose to call it a giant propeller, because it has two diametrically opposed 8-foot-long blades that rotate just like, well, a giant propeller. But propellers imply motors. Blackbird ‘s rotating propeller-shaped sail is the motor. Cavallaro has connected the prop to wheels via a drivetrain, so the faster the cart rolls, the faster the sail-prop spins, thereby creating a feedback loop that Cavallaro claims will accelerate the cart from a standstill through the zero-wind barrier and beyond.

To most people, Blackbird ‘s engineless drivetrain sounds like a perpetual-motion machine. “Cartoon physics” was typical of the barbs thrown at Cavallaro when he revealed his idea. But he remained undaunted. Blackbird is the result of a years-long quest—a personal attempt to prove something deeply counterintuitive to the world. A software and hardware developer with a degree in aerospace engineering, Cavallaro has done the math. He has made small models and run tests. His contraption will work, he says. Even if no one believes him, he is certain that he’s right.

But any sailor worth his salt—or dust, as the case may be—will tell you he’s wrong. So will many engineers and physicists. And they’re not shy about spelling it out. Since Cavallaro first proposed Blackbird ‘s design on the Internet, his concept has been ridiculed and lampooned in blogs and forums, and the idea has even been refuted in a national magazine. The debate recently reached a fever pitch among a certain type of geek, especially in Silicon Valley, so much so that some notable entrepreneurs, including Google’s Larry Page, forked over the cash to let Cavallaro finally build the vehicle. After four years of online arguments, explanations, and insults, Cavallaro has brought his vision here—to the Dirt Cup—to prove he can beat the wind.

This is where the Rube Goldberg rubber hits the hard, flat playa. Cavallaro is suited up in a helmet, goggles, and motorcycle pads. Now all he has to do is make the damn thing work.

He climbs into Blackbird ‘s coffinlike cockpit. His seat is just a hammock that hangs a few inches above the ground. A single front wheel from a BMX bike rests between his feet. There is a rudder in his right hand and a brake under his left foot. Every instrument—every GPS device, every anemometer, every radio—is double-checked to make sure Blackbird ‘s speed will be recorded accurately. The ground crew triple-checks that the craft is pointed directly downwind. When Blackbird is finally ready to roll, Cavallaro pops open the brake.

And nothing happens.

Blackbird started with a brainteaser: Al Alcorn, the Atari engineer famous for giving the world Pong, had a question for his friend Rick Cavallaro, who never met a logic challenge he didn’t like.

Could a sailboat outrun a balloon? Alcorn asked. The question is an old sailing stumper, but it was new to Cavallaro, and it pushed his buttons hard.

A Navy brat, Cavallaro was born in Cuba in 1962, the son of a flight surgeon. His father was soon posted to New Jersey, but by the time Rick was 12, the family had moved to Florida, where Cavallaro grew into a thrill-seeking teen. He owned a car before he could legally drive and would later sneak onto a yet-to-be-opened highway to push his Mazda RX-4 up to 135 mph. At 16, he got his pilot’s license and started flying Cessnas. Cavallaro was equally into science, largely because an assistant to one of his physics teachers had a Messerschmitt aerobatic plane and would take him up for loop de loops.

It was Borton who finally cracked over the controversy. “Screw it,” he said to Cavallaro. “Let’s build a big one.”

College was at Georgia Tech and grad school at UCLA. After a short stint in Southern California’s defense industry, Cavallaro left in 1989 for the more congenial climes of the San Francisco Bay Area. He quickly landed a job at a high tech startup, Etak, helping design a pre-GPS navigation system for cars. After Etak was purchased by News Corp., he joined Sportvision, home of the virtual first-down marker, where he now serves as the company’s chief scientist.

Cavallaro’s singular obsession, however, has long been the wind. In addition to aircraft, he pilots sailplanes and experimental hang gliders of such radical design that you wouldn’t recognize them as hang gliders. “Lately,” Cavallaro says, “I’ve taken up powered paragliding.”

This passion, plus a penchant for brainteasers, drew Cavallaro to John Borton, Sportvision’s director of manufacturing and a champion glider pilot. Their friendship started as an argument over an aerodynamics riddle that hinged on whether you could know the true direction of the wind while hang gliding without looking at the ground. (You can, though Cavallaro has never fully conceded the point.)

Alcorn’s balloon-versus-sailboat question was exactly the type of thing the two loved to mull over and argue about. Both understood that sailboats (and dirt boats and ice boats) can sail faster than the wind. What’s more, they understood the physical principles behind the phenomenon, which boil down to lift. Aerodynamically speaking, a sail with wind traveling across it acts like a vertical wing. It will pull a boat forward the same way an airplane wing will pull a fuselage right off a runway. Sails and wings both produce lift, as long as there is wind moving across them. That said, the two men realized that on a direct downwind heading, there is no wind moving across the sail. The sailing speed limit in that case is the speed of the wind.

So to beat a balloon, a sailor must navigate at an angle to the destination, then tack, or turn, the boat back toward the finish line. This downwind zigzag course—jibing, in sailing terminology—is often the fastest way to traverse between points A and B. But given that you have to cover more ground and take the time to turn, is it really fast enough to beat the wind itself (represented by the balloon)?

Answering that question requires factoring in things like drag and angle of attack and using racing-performance data to figure out wind speed multiples for every angle of sail.

Illustration: Mike Bain/based on animation by Heikki Anttila

Of course, you could just skip this and go right to Google. A little research reveals that Steve Fossett’s speed-record-smashing yacht, Cheyenne,has the capability—the wind speed multiples and attack angles—to beat a balloon in a downwind race. And Larry Ellison‘s even faster USA-17 actually jibed its way through a downwind leg of last year’s water-based America’s Cup with a faster-than-the-wind official time. So yes, Mr. Alcorn, some sailboats can outrun a balloon.

Cavallaro isn’t the kind of guy to Google an answer, though. He prefers thought experiments to web searches. And the balloon-versus-sailboat thought experiment he came up with took him to another planet: a cylindrical planet entirely covered by water, with a constant wind blowing down its length. Call it Planet 50-Gallon Barrel and visualize a balloon racing a sailboat from one end to the other.

The advantage of holding a race on this planet is that, because the boat can sail completely around the cylinder, it never has to zag to end up at the same end point as the balloon. Instead, the craft can stay on one continuous crosswind heading and spiral all the way around the barrel, ending up at the finish line. On Planet 50-Gallon Barrel, the math simplifies. But forget the math for a moment and concentrate on the visual picture.

What if the balloon-versus-sailboat race ran down cylindrical planets of smaller and smaller diameters: Planet Telephone Pole? Planet Sewer Line? Planet ABS Pipe? What if the cylindrical planet had no significant diameter: Planet Steel Rod? In that case, the boat would essentially be spinning around its own axis and its sail would suddenly look a lot like a turning propeller blade.

This is the point where a little Blackbird -shaped light bulb flickered on over Cavallaro’s head. With his background in aeronautics, he knew that a sail on a downwind tack and the blade of a spinning propeller are aerodynamically the same.

Blackbird ‘s sail-prop-driven design quickly coalesced in Cavallaro’s mind. Imagining it, he realized that the crosswind-only caveat to sailing faster than the wind didn’t apply to Blackbird . The lift the propellers provided would pull the cart forward, with the wind. That forward motion would feed back into the system through the wheels, which would turn the prop even faster, creating even more lift, or, as it’s usually called vis-é-vis a propeller, thrust. The propeller—on its continuous rotational “tack”—would then simply screw itself through the zero wind.





How Blackbird

Was Born The best sailing craft can go faster than the wind is blowing, as long as they sail at an angle to the wind. But sailing faster than the wind directly downwind? That was generally considered to be impossible—until Rick Cavallaro came up with a clever thought experiment involving a barrel-shaped planet.

The Basic Science

Thanks to aerodynamic lift—the same effect that lets airplanes fly—a fast boat sailing at an angle to the wind can beat the wind itself. In other words, the boat could outpace a balloon floating across the sky. The Thought Experiment

What if a boat sailed at an angle down the length of a planet shaped like a barrel? The craft could sail all the way around the planet, eliminating the need to waste time and energy charting a zigzag course. The Twist

What if you make the planet thinner—the width of a rod. The boat would complete revolutions faster, always staying ahead of the balloon. Of course, the thinner you make the planet, the faster the boat will spin, until… The Aha! Moment

…the boat essentially becomes a propeller. So, if back on earth you swap a sail for a propeller, a fast boat (OK, a land yacht) should be able to sail directly downwind faster than the wind.

Illustration: Mike Bain/based on animation by Heikki Anttila

Blackbird was Cavallaro’s best thought experiment yet! Forget about tacking and sail-efficiency tables and Cheyenne. Here was a wind-powered vehicle that could outrun a balloon in a straightforward race from point A to point B.

Cavallaro realized he had stumbled onto the perfect setup for a new brainteaser. And so, in spring 2006, he started a fresh thread on Runryder.com, a forum for model-helicopter enthusiasts. His post, with the subject line “Annoying Brain Teaser #1,” went like this: Can you make a vehicle that goes directly downwind, powered only by the wind, faster than the wind?

The world of brainteasers is a small one. Most people find the idea of being asked to think hard for no good reason to be annoying. But every few years a question tickles our collective smart bone and becomes a breakout hit. The most famous is likely the Monty Hall problem: Suppose you’re on a game show and you’re given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say Number 1. The host, who knows what’s behind all the doors, opens another, say Number 3, which he knows is hiding a goat. He then asks, “Do you want to pick door Number 2?” Is it to your advantage to switch your choice?

Yes. Switching your choice always raises your odds.1

The brainteaser making the rounds when Cavallaro had his sail-prop epiphany is known as the Airplane on a Treadmill. It goes like this: An airplane taxis in one direction on a moving conveyor belt going the opposite direction and matching the speed of the wheels. Can the plane take off?

Yes. The plane will take off normally.2

The observant will notice a pattern developing here. For a brainteaser to “work,” the right answer has to be counterintuitive. It has to seem like the wrong answer. Most people understand this, and they suffer through the I-feel-dumb setup to get to the punch line. In a sense, brainteasers are like knock-knock jokes for the brainy set.

In Cavallaro’s mind, his brainteaser, which quickly became known on the Internet as Directly Downwind Faster Than the Wind, or DDWFTTW for short, was no exception. The answer, as he saw it, was yes here, too. You can go DDWFTTW—if you build a Blackbird .

Considered as a brainteaser, however, DDWFTTW has a serious flaw: Almost no one gets it right. And the brain-tease is not truly over until its victims acknowledge that, yes, they were wrong and understand the counterintuitive truth.

When Cavallaro made his big reveal on Runryder and half a dozen other websites, he didn’t have Blackbird , or even a model of Blackbird . Instead, he showed everybody how wrong they were with a vehicle made of pure thought, beamed in from an imaginary planet shaped like a cylinder. At which point the Internet spat out a column of flame dozens of websites wide and thousands of comments long. Cavallaro, almost everyone concluded, was an idiot.

“It was a brainteaser,” Cavallaro says, shaking his head. “Of course I had the right answer!”

As it happens, others had previously considered making a vehicle with a propeller sail. There’s photographic evidence, for example, that a man named Andrew Bauer created a Blackbird -like craft in 1969. And the idea has bubbled up occasionally in sailing circles ever since (most notably in an obscure UK sailing publication called Catalyst ). But it wasn’t until Cavallaro’s fresh brainteaser that the debate roared to life across the broader Internet. And roar it did, with Cavallaro and his few supporters enduring a sustained onslaught by those who said the idea was hogwash.

Eventually the flame war settled into two camps: the proof-of-concept modelmakers versus the disproof-of-concept modelmakers.

Chief among the DDWFTTW debunkers was Make magazine writer (and former Wired contributor) Charles Platt. Responding to the online debates, Platt wrote a story for Make in summer 2007 entitled “The Little Cart That Couldn’t.” In the article, he detailed his experience piecing together a tabletop model of a DDWFTTW-type car. Total budget: less than $30. Platt shaped his own wooden propeller with a belt sander. A rubber belt connected the prop-shaft to the wheels. When he was done, he sprayed copious amounts of WD-40 on all the moving parts and turned on a powerful fan.

Nothing happened.

Well, almost nothing. After some tweaks, Platt got his cart to move downwind—at about 2 inches per second in a 30-foot-per-second tailwind. “Hopeless,” he concluded in Make‘s August 2007 issue, in which he called the DDWFTTW idea “delusionary.”

After reading this, a steamed Cavallaro, with the help of Borton, decided to build a model cart of his own. Unlike Platt, Borton and Cavallaro opted to splurge. They used real bearings to reduce friction on the moving parts and fabricated the rest from lightweight carbon fiber and aluminum. Their propeller was nylon, sourced from a website that specializes in remote-control-airplane parts. And instead of a belt-drive system, they opted for a long driveshaft to connect the wheels at the front end of the cart with the propeller, mounted in back. Despite the myriad differences from Platt’s design, the basic premise was the same. When the prop cranked, the wheels spun, and vice versa. All in all, they spent about $40.

Despite the superior construction, come test time even Borton had his doubts. “Truth be told,” he says, “I was skeptical we could get it to work. Friction is usually what kills stuff like this.” But work it did, and rather nicely. They ran their baby Blackbird on a treadmill to simulate the crucial zero-wind moment, as well as in real-world wind on the street. In both cases, they boasted, the cart broke through zero wind and kept accelerating. They uploaded the videos to YouTube in November 2008. “I was happy to stop right there,” Cavallaro says. “We had proven it.”

The majority of people who watched the videos, however, disagreed. Many criticized the treadmill test, insisting that the treadmill was propelling the cart. Others found fault in the nature of the real-world wind tests, saying that gusts and turbulence meant the cart wasn’t going directly downwind. Rhett Allain, a physicist at Southeastern Louisiana University and a blogger for ScienceBlogs, diagnosed what he called DDWFTTW’s “free energy” problem and concluded that “you can’t get something for nothing.”

The Internet consensus remained that DDWFTTW was not possible. “It wouldn’t have bothered me if 5 percent of the people didn’t accept our results,” Borton says. “But it was more like 99 percent.”

Borton finally cracked. A few months later, after stewing over the Platt-inspired drubbing that he and Cavallaro were getting online, Borton came into Cavallaro’s office and said, “All right, screw it. Let’s build a big one.” This time it wasn’t going to be a model. “It needed to be huge,” Borton decided, because it had to be big enough to carry Cavallaro through the zero-wind barrier.

The pair barnstormed the local universities and sailing clubs looking for free labor and official sponsorship. They made presentations at San Jose State University, Stanford, and the St. Francis Yacht Club in San Francisco. They were asked by a student to speak at UC Berkeley, too, but the head of the school’s Renewable and Appropriate Energy Laboratory, Daniel Kammen, rejected Borton and Cavallaro, explaining in an email that DDWFTTW was not possible “due to conservation of energy.” Yet their increasing notoriety was good for something: attention. Boing Boing covered the controversy, as did ScienceBlogs’ .dotphysics. And so, when Cavallaro began working the phones asking for money, a pair of Silicon Valley bigwigs decided they weren’t going to let two of their own be trashed online without a fight. JoeBen Bevirt, inventor of the Gorillapod, wrote out a check for $5,000. Larry Page threw down $10,000 from Google. Everyone wanted to see what Cavallaro and Borton would come up with.

1/ Originally, you had a 1 in 3 chance of guessing the correct door. When Monty shows you the goat behind a door you didn’t choose, the probability of a car being behind that door drops to zero and the chance that there’s a car behind the third door thus rises to 2 in 3. So your odds improve if you switch your choice.

2/ The plane moves because its engines push air, not because its wheels push against the ground. The wheels on a plane spin freely, so it doesn’t matter if the runway is moving against the direction of the plane. The plane will move forward relative to the ground and therefore be able to take off.

Construction took six months and about 2,000 person-hours. Even with the donations, “budget constraints meant that all of it was a hack,” Cavallaro says. He pounded together a frame from modified wooden joists, and Borton remachined and repurposed an odd assortment of mountain bike and go-cart parts into a drivetrain. The hardest part was shaping the sail-prop out of a pile of fiberglass cloth, foam, two old carbon-fiber windsurfing masts, two ski poles, and a vat of epoxy.

Blackbird ‘s first run, they decided, would take place at the 2010 Dirt Cup. Despite the excitement, Borton was preparing for disappointment. “If it doesn’t work,” he told himself “at least we’re showing up with something that makes it look like we’re serious.”

Back on the Mojave playa, it looks as if Borton’s nightmare has come true. Cavallaro is suited up and in the cockpit. And nothing is happening.

Well, almost nothing. After 10 excruciatingly long seconds, Blackbird starts to creak and trundle forward. Simultaneously, the craft’s outsize propeller starts ever so slowly to sweep a languorous arc, like the second hand of a clock.

Cavallaro’s voice crackles over the radio: “Two miles per hour… 3 miles per hour… 4 miles per hour.”

Thirty seconds into the speed trial and the handful of curious onlookers can walk faster than Blackbird is “sailing.”

“Six… seven… eight,” Cavallaro says.

A minute into the test and Blackbird is moving at a jogger’s pace.

“Ten… 12 miles per hour…” Cavallaro now has to raise his voice to be heard over the thwomp, thwomp of the propeller spinning ever faster behind him.

At 90 seconds, he has v-e-r-y s-l-o-w-l-y accelerated to 15 mph. That’s about sprinting speed, but more important, it’s the velocity of the wind today. Blackbird ‘s telltales—little pieces of orange flag tied to the vehicle’s various struts and antennas—go limp. The craft has reached the zero-wind barrier.

For a moment everyone holds their breath. Then Blackbird accelerates. Hard.

The telltales reverse direction: They start blowing back toward the rear of the cart. Blackbird has pushed itself past the wind.

On the far side of the mythical barrier, things get weird. Cavallaro feels wind blowing in his face—yet the wind is also propelling him forward at… Cavallaro glances at the GPS-enabled speedometer mounted in the cockpit. The numbers tick up faster than he can report them. “Twenty, no, 22!” He’s shouting into the transceiver: “30!”

Running out of playa, Cavallaro hits the brakes. The team immediately backs up Blackbird for another run.

It’s on the third run that things go wrong. Blackbird once again powers past the zero-wind point and reaches its highest speed yet. But the view from the chase car reveals an oddity: The dust that Blackbird is raising on its run is coming off of only one of the cart’s three wheels, the right rear one. Blackbird is starting to tilt. What’s going wrong?

Inside, Cavallaro has this same question, but Blackbird ‘s cockpit is not conducive to deep thought. The sail-prop is spinning so fast that it’s inflicting roughly 470 foot-pounds of torque—about the same as the V-8 in a new Corvette ZO6—on a drivetrain made of bicycle parts. The prop’s rapid thwop-ing has morphed into a beating, pulsing thwap! thwap! thwap! Everything is shaking.

Cavallaro feels his starboard wheel lift with every thwap! and realizes that he never properly considered the rotational effects of the propeller’s torque at these higher-than-expected speeds. That’s a problem, because if Blackbird flips, decapitation is a real possibility.

Crack!

Cavallaro, head still attached, leans on the brake. He’s alive, but the chain, rotating the prop faster than it was ever designed to go, has ripped the sprocket right out of the drivetrain. “Too much horsepower,” he says, laughing. Slowly he rolls to a stop from a top speed of 46 mph.

The sprocket is pretzeled, but there is no doubt about what Blackbird has achieved.

The Land Sailing Association doesn’t consider the run official—largely because it has no official DDWFTTW race category. But after repairing Blackbird , Cavallaro and Borton will return to log their feat in a newly created land-sailing category. Four months later, on July 2, 2010, the association officially documents Blackbird ‘s performance, recording 27.7 mph in a 10 mph wind. Not as quick as those first three runs, but conclusively faster than the wind.

Cavallaro and Borton did the “impossible” with Blackbird , and they did it in front of skeptics, whom they then asked to confirm and check their achievement. What started as a gotcha game that convinced almost no one turned into an arduous DIY demonstration that hewed to the scientific method. The reward for all their efforts? A new mark in the record book, sure. But even better: changing people’s minds.

The first skeptic to flip was land-sailor Richard Jenkins, who, after watching the official record-setting runs, was compelled to blog about Blackbird . “It works,” he wrote. “It starts from rest, trundles to true wind speed, then powers to a multiple of about three times the true wind speed.” Jenkins went so far as to call Cavallaro and Borton “sincere, genuine, technical people, who took a myth and made it real.”

Cavallaro and Borton’s victory tour took them to Science Foo Camp 2010, an invite-only “un-conference” by and for the geek elite. It’s held every summer at the Googleplex, Google’s headquarters in Mountain View. This is Cavallaro and Borton’s kind of crowd, and after the duo gave their DDWFTTW presentation, they were feted as heroes. Larry Page personally drew them aside for a tête-à-tête-à-tête about other possible uses for the technology. He noted that there have already been some promising experiments using traction kites on cargo ships. Why not a propeller? Cavallaro and Borton love the idea and have estimated that installing DDWFTTW technology on a cargo ship would save 7 to 10 percent of its fuel cost—or about $100,000—per Pacific crossing.

Even Make magazine came around. In November, editor in chief Mark Frauenfelder published a long mea culpa on the Make blog, which explained how Make got it wrong. Cavallaro was invited to write a piece entitled “The Little Cart That Did.” And with that, the tide of Internet opinion turned decisively.

To be sure, there are the stubborn few who aren’t convinced. As of this writing, Platt is still skeptical. “I think Rick Cavallaro is probably sincere,” Platt writes. “But sincere people may be victims of self-deception.” Another holdout is Allain, the Southeastern Louisiana physics professor (who, it should be noted, now blogs for Wired.com’s Wired Science network).

Platt still can’t see how what happened can be possible, so he won’t yet admit he got it wrong. Instead, Platt remains fixated on the discourtesy he feels that the pro-DDWFTTW crowd showed him on the Make blog after his original article called on them to “face facts and admit that it doesn’t work.” Allain, on the other hand, prefers to turn the tables, asking, “Why are all the downwinders so anxious for me to say it works? If it works, does it matter what I say?”

He’s got a point, and indeed Cavallaro and Borton have moved on. In fact, they’ve come up with a brand-new brainteaser for the world to chew on: Can you make a vehicle that goes directly upwind, powered only by the wind, faster than the wind?

Adam Fisher (adamcfisher@gmail.com) is a former Wired senior editor.