Die-hard advocates of alternate energy might fantasize about cars that could one day run on water. But scientists in India have gone a step further. They’ve mathematically modeled an engine that should allow a motorcycle to run on air—compressed air, that is. Their design is described in the Journal of Renewable and Sustainable Energy. [Bharat Raj Singh and Onkar Singh, Fd3dO] The hunt is on for alternatives to fossil fuels. Internal combustion engines convert the energy in gasoline’s molecular bonds into motion. But what if there were another way to make engine parts move? Scientists in India were thinking of a well-directed wind. And after crunching the numbers on pressure and flow, they’ve concluded that a tank of compressed air could generate enough power to run a motorcycle for up to 40 minutes. The air would spin a turbine, which would then get things rolling. Of course they’d need to design a tank that could store enough air to fuel a long haul. Current cylinders would need changing or charging after about 20 miles. Which would still cover a lot of commutes and trips to the grocery store. And you’d still need to get air in the tank in a green way. Maybe a solar-powered, geothermal, wind-driven compressor?