In August 2013, billionaire entrepreneur Elon Musk released a 57-page white paper concept for Hyperloop — a supersonic mass transit system between high-traffic cities that lie within short distances. The founder of Tesla Motors and SpaceX envisioned it to be a frictionless system where pods inside low-pressure, vacuum-sealed tubes would transport passengers and cargo at up to 760 miles an hour — approximately the speed of sound. Powered by solar energy, it would be strong enough to withstand extreme weather and earthquakes.