Musk knows the commute well, reportedly shuttling by air twice each week between SpaceX in Hawthorne, near L.A. International Airport, and Tesla Motors headquarters in Palo Alto, Calif.
The concept was borne of Musk's frustration with California's plans for bullet-train service, which he argues would be slower, less safe, and, if unsubsidized, more expensive than flying. Given the enormous intellectual horsepower in places like Silicon Valley and Pasadena, home to Caltech and NASA's Jet Propulsion Laboratory, he argues, California could have devised an approach that represents a less expensive, more weather-resistant, and more environmentally sustainable way to operate.
Others have proposed variations on Musk's Hyperloop. Some envisioned capsules hurtling through an oversize pneumatic tube – the main delivery system for documents in office buildings in the days before e-mail. Others have proposed running capsules through a tube void of any air, which would eliminate air resistance and allow passenger capsules to reach high speeds. But each comes with its own set of engineering and safety challenges.
The Hyperloop splits the difference. To reduce air resistance as the aerodynamic capsule races through elevated steel tubes, air pressure would be reduced to levels equivalent to flying at 150,000 feet, while air pressure inside the capsules would be kept at normal levels – a concept familiar to anyone flying in commercial airliners.
The system relies on linear motors some 2.5 miles long to accelerate the capsules to top speed, and then decelerate them, at the appropriate locations along the route.
The design leaves little room between the capsule and the tube walls for air to flow along the capsule's length, which would allow pressure to build up ahead of the capsule and introduce drag. To keep air moving, the capsule sports a compressor in front that operates much like the compressor in a jet engine. In this case, the compressed air flows out through exhaust ports to keep the capsule levitated and provide additional push.