For BMW, engineering the impossible comes naturally. The company's engineers heard that hydrogen will be the fuel of the future, so they took a 7-series sedan and converted it. Instead of the 10-plus years of development that's gone into other automakers hydrogen-powered fuel-cell vehicles, BMW needed only a couple of years to build the Hydrogen7, which it showed off at the Los Angeles Auto Show. But the Hydrogen7 uses a completely different approach than a fuel-cell vehicle. BMW Vice President Dr. Timm Kehler told us that electric motors could provide the performance that BMW demands, so the company worked out how to use hydrogen in an internal-combustion engine. The Hydrogen7 has hydrogen and gas tanks, and can switch between them, just in case you can't find any hydrogen refueling stations. BMW's 6-liter V-12 powers the Hydrogen7, but Dr. Kehler said that with further development, a 2-liter four-cylinder hydrogen-burning engine could pump out 300 horsepower. In another departure from the hydrogen mainstream, the Hydrogen7 uses liquid hydrogen, which is more compact than the gaseous form, but has to be kept at about minus 250 degrees Celsius. No problem for BMW engineers--they designed the tank like a giant thermos, so it keeps the hydrogen cold without resorting to any cooling systems.