Hyperloop One, one of several start-ups racing to make Elon Musk's vision for "super fast travel" a reality, is embroiled in a lawsuit that raises questions about its finances and direction.
The lawsuit calls into question Hyperloop One's ability to build the best-in-class technology required to stave off competition from rivals, such as Hyperlink Transportation Technologies.
But how exactly is this wildly futuristic idea supposed to work in real life?
Without getting too technical, here is how Musk in 2013 envisioned the technology that Hyperloop One and Hyperloop Transportation Technologies are now working on to shrink the travel time from San Francisco to Los Angeles, some 380 miles, to less than half an hour (in other words, faster than an airplane can make the journey).
An underground or above ground pylon-supported tube will create a "special environment" — a low pressure system — through which passenger pods will travel with very little air pressure to slow them down.
An electric air compressor fan on the front of the pod will transfer high air pressure from its front to the rear and sides of the vessel. This will reduce friction in front of the pod, help propel it and create an air cushion around it, so that the pod is suspended in the air within the tube. So-called air bearings — which work on the same basic principle as an air hockey table — will replace wheels that would not work at the required high speeds, said Musk.
The pod will be battery-powered and propelled by an external linear electric motor — an electric induction motor that produces motion in a straight line rather than rotational motion — similar to those used in the Tesla Model S. This motor would propel the pod to subsonic velocity — that is, slower than the speed of sound, and provide a reboost about every 70 miles, said Musk.
"The linear electric motor is needed for as little as 1 percent of the tube length, so is not particularly costly," he said.
Musk has said he believes the system could be built for as little as $6 billion, but experts have said that the real cost could be much higher. Building the tube on pylons above ground would have the benefit of saving money, providing protection from earthquakes and allowing solar panels to be placed on top, said Musk.
"By placing solar panels on top of the tube, the Hyperloop can generate far in excess of the energy needed to operate," said Musk. "This takes into account storing enough energy in battery packs to operate at night and for periods of extended cloudy weather."
The hyperloop could be built in prefabricated sections and dropped into place, and there would be no need to purchase a lot of expensive land. It could almost follow California Interstate 5 highway, he said.
By building the tube on pylons, it would not need to be rigidly fixed at any point, and could therefore withstand an earthquake by shifting with the ground. Inside each pylon, adjustable lateral and vertical dampers would absorb small changes between pylons caused by extremes of temperature or shifting ground.
Hyperloop One, which has raised $100 million, stressed that the lawsuit has no merit, and does nothing to stand in the way of the company's ambitions.
The company's lawyers on Tuesday called the lawsuit "unfortunate and delusional," dismissed the claims as "pure nonsense," and said the lawsuit was result of a failed coup among the plaintiffs.
"Hyperloop is on track, its board and team are united and today's bogus lawsuit will have no impact on its goal of becoming the first company to bring the Hyperloop to the world," attorney Orin Snyder said in the statement.
Rival start-up Hyperloop Transportation Technologies, whose funding is undisclosed, also issued a statement to quell fears that the lawsuit could have a chilling impact on fundraising and development of the technology.
"Hyperloop Transportation Technologies is in no way affected by developments at Hyperloop One, we wish them a speedy resolve to their recent issues," said Hyperloop Transportation Technologies CEO Dirk Ahlborn.
Correction: An earlier version of this story misstated the distance from Los Angeles to San Francisco.