The Hyperloop is a proposed new form of transportation involving capsules that carry people in a low-pressure tube at high speeds using little energy. Elon Musk first proposed the concept as an alternative to costly high-speed rail projects. The Hyperloop would use solar power, travel at over 700 mph, and cost an estimated $6 billion to build a route between Los Angeles and San Francisco - far less than the projected $68 billion cost of a high-speed rail for the same route.