Hyperloop Transportation Technologies (HTT) has licensed a passive magnetic levitation system from Lawrence Livermore National Labs (LLNL) for its Hyperloop project.

HTT describes passive magnetic levitation, which was developed by the late Dr. Richard Post at LLNL, as a "cheaper, safer alternative" to an active magnetic levitation system such as MagLev.

"Utilizing a passive levitation system will eliminate the need for power stations along the Hyperloop track, which makes this system the most suitable for the application and will keep construction costs low," says Bibop Gresta, COO of HTT. "From a safety aspect, the system has huge advantages. Levitation occurs purely through movement. Therefore, if any type of power failure occurs, Hyperloop pods would continue to levitate and only after reaching minimal speeds touch the ground."

Hyperloop pods are intended to travel at the speed of sound. Image credit: HTT. As described in LLNL's Science & Technology Review, the passive magnetic levitation system requires neither control currents to maintain stability nor externally supplied currents flowing in the tracks. Instead, only the motion of train cars above the track is needed to achieve stable levitation.

The system's two primary components are a special array of permanent, room-temperature magnets mounted on the vehicle and a track embedded with close-packed coils of insulated copper wire. The permanent magnets are arranged in configurations that concentrate the magnetic field on one side while canceling it on the opposite side. When mounted on the bottom of a rail car, the arrays generate a magnetic field that induces currents in the track coils below the moving car, lifting it by several centimeters and stably centering it.

When the train car is at rest (in a station), no levitation occurs and the car is supported by auxiliary wheels. As soon as the train exceeds a transitional speed of 1 to 2 kilometers per hour, which is achieved by means of a low-energy auxiliary power source, the arrays induce sufficient currents in the track's inductive coils to levitate the train.

The Hyperloop concept first gained significant public interest when Elon Musk published a detailed white paper in 2013 describing a futuristic mode of transport that would move people from Los Angeles to San Francisco in about 30 minutes. Musk handed the concept to the public asking for entrepreneurs to take over its development while he focused on his existing projects.

In addition to HTT, a separate company, Hyperloop One (formerly Hyperloop Technologies), is testing an air-cushion concept to propel passenger-carrying pods to near-sonic speeds.