Almost a year after Elon Musk, chief executive of Tesla Motors (TSLA) and SpaceX, first floated the idea of a superfast mode of transportation, he has finally revealed the details: a solar-powered, city-to-city elevated transit system that could take passengers and cars from Los Angeles to San Francisco in 30 minutes. In typical Musk fashion, the Hyperloop, as he calls it, immediately poses a challenge to the status quo—in this case, California's $70 billion high-speed train that has been knocked by Musk and others as too expensive, too slow, and too impractical..