The proposed design for the “Hyperloop,” an ultra-fast transit system that would run between San Francisco and Los Angeles, was revealed today in a 56-page PDF document on Elon Musk’s Tesla Motors website. Musk, the founder of SpaceX and Tesla Motors, describes a system that moves pods under low pressure through a tube between the two cities following the I-5 freeway.

The Hyperloop would consist of aluminum pods inside a set of two steel tubes, one for each direction of travel and connected at each terminus. The tubes would be positioned on top of pylons spaced 100 feet apart holding the tube 20 feet in the air, and the tube would be covered by solar arrays to generate its own power.

Inside the tubes, the pods would carry people at speeds of up to 760 miles per hour. The pods would each carry 28 passengers and depart every two minutes from either location (or every 30 seconds at peak times). So each pod would have about 23 miles between one another while traversing the tube. The transport capacity would therefore be about 840 passengers per hour.



The capsules’ speed would rely in large part on a low-pressure environment, about “1/6 that of the pressure of the atmosphere on Mars” or a fraction of a percent of that on Earth, maintained by vacuum pumps. This would reduce drag by 1,000 times, the document says.

The tubes would not use a “hard vacuum” because they are “expensive and difficult to maintain compared with low pressure solutions.” A pneumatic tube is fine for your bank, but it does not make an attainable, sophisticated transport solution.

The passenger capsules would be 4.43 feet at their widest point and 6.11 feet at their tallest. They would each weigh about 7,700 pounds and cost $275,000 to make ($1.35 million including all the onboard equipment, mechanical parts, and support systems). Musk envisions the passengers sitting in reclined chairs in rows of two with their feet elevated, as if relaxing in a chaise longue.

Each of the pods would have 28 attached “air bearing” skis that would “[float] on a pressurized cushion of air” a fraction of an inch away from the surface of the tube. The skis would be lifted off the surface by injecting air into the gap, a method that the document says is effective either when the capsules are stationary or moving very fast.



Inlets on the two noses of the capsules would serve as air intake sources, reducing the “choking flow” of air around the capsule as it moves through the tube. Removing air in the tube would not only smooth the capsule’s journey, it would feed the skis that the capsule needs to skate along on.

The air from the inlets would be processed by a compressor and then stored in a reservoir onboard the capsule. The capsule would then eject this air through grooves on the bottom of the skis, generating enough lift to support it that fraction of an inch away from the surface.

As for actually moving the capsules, acceleration in an environment like this is a huge concern. While human beings don’t care that much about being transported at supersonic speeds in enclosed environments, how they arrive at those speeds can be a huge problem. Generally, more than an extra g of force is extremely uncomfortable. So the design here takes care not to accelerate people too quickly.

The Hyperloop's capsules would be propelled by linear induction motors spaced throughout the tube. Magnets on the tube’s internal surface would function as the stator, with an electric current supplied to them to generate a magnetic field. Magnets on the capsule would function as the rotor, spurred on by those in the tube. Those accelerators would also have two inverters that would push outgoing capsules along while capturing energy from incoming capsules that are slowing down (while there is one tube for each direction of travel, this means the directions for either could be reversed).

The capsules would travel at a “relatively low speed” between 0 and 300 miles per hour while entering and exiting urban areas and maintain at about 300 mph while crossing mountainous areas. Once they reach the flatter I-5 stretch, they could be sped up by the linear accelerators to up to 760 mph to coast at roughly that speed for the bulk of the journey.



The document points out that a Hyperloop tube covered in solar arrays could generate about 52MW of power, a vast amount more than the estimated 6MW that would be needed to operate the Hyperloop itself.

Musk addresses some of the disaster scenarios that the Hyperloop tube might encounter. Since the Hyperloop capsules spend the most time coasting, the proposal states that they don’t need much power to travel, but everything needing power would be supplemented by lithium ion batteries. If a capsule depressurized, the control system would use the onboard pressurized air to maintain the environment until the capsule reached its destination. Worst case, oxygen masks would drop for the passengers.

The proposal states that it would be hard for a capsule to become stranded within the tube given that it spends most of its time coasting at a high speed (“no propulsion required for more than 90 percent of the journey). If a capsule was truly rendered immobile by its normal means of travel, however, it would use “small onboard electric motors” to power “deployed wheels” so the cabin could roll itself to safety.

It’s difficult not to imagine a partial loss of sanity among passengers who, thinking they’re in for a half-hour journey, suddenly find themselves taking 10 times as long to get there. Hopefully it wouldn’t be a frequent occurrence. The document makes special note that all capsules would be supplied with enough air to support the passengers even for this failure scenario of a suddenly-normal-length trip.

The alpha proposal still pegs the cost at $6 billion: $54 million to construct the 40 passenger capsules and $5.41 billion for the tube and propulsion system construction.

Even more ambitiously, the Hyperloop document suggests that not only people could benefit from a transportation upgrade. A “cargo capsule” system that could also transport vehicles would cost another $30.5 million for 20 capsules, plus another $1.5 billion for a more robust tube system—a total of $7.5 billion. But in this kind of futuristic world, who’s going to need cars anymore?