This may be a little esoteric for some but I've been following this for the last two years. It was originally posed as a brainteaser, thus:
"Can a vehicle powered only by the wind go faster than the wind, directly downwind, steady state?"
It has been shortened to DDWFTTW (Directly Downwind Faster Than The Wind). This brainteaser set off a tremendous flood of arguments in many sailing, science, and physics forums, with a Nobel laureate (Kammen) and physics profs weighing in on both sides of the question. The traffic generated by the discussions set records on those sites as the opposing views were hotly contested!
Small devices were built and tested (I have one) that indicated that the concept was in fact true and was not a violation of conservation of energy or perpetual motion or the 2nd Law of Thermodynamics, but the deniers claimed that the evidence was not conclusive and likely even faked. Without solid results, it looked like the question would never be settled.
But much to the consternation of the DDWFTTW deniers, a large scale version of the test models was built, large enough to carry a person and sufficient instrumentation to answer the question conclusively. That vehicle, dubbed the Blackbird, recently achieved 2.8 times the speed of the wind under very closely scrutinized conditions by NALSA(North American Land Sailing Association). NALSA is the same group that ratified the record held by the Greenbird, at just over 126 mph, powered only by the wind!
The Blackbird holds the newest land speed record of 2.8 times the speed of the wind (27.7 mph in a 10 mph wind). There were test runs that achieved as high as 3.7 times wind speed but the team that built the vehicle were after the most reliable and undisputable record rather than the fastest.
This vehicle has been featured in articles in Popular Science, Wired, and seen on Discovery's series Daily Planet. For those interested, here's a link to the blog covering the build, with links to those articles:
