THE INSTITUTEImagine traveling the 615-plus kilometers from Los Angeles to San Francisco on the ground in less than 40 minutes, instead of nearly 6 hours. That’s one of IEEE Honorary Member Elon Musk’s dreams. The founder and CEO of Tesla and SpaceX proposed the Hyperloop in 2013 after becoming irritated by the relative sluggish speed and US $68 billion price tag of California’s proposed high-speed rail project to link the two cities.
Passengers in Musk’s version of the Hyperloop would ride in pods—sealed vehicles propelled through an underground tube kept at a near-vacuum. The pods could theoretically travel at close to the speed of sound (about 1,200 km per hour), using a fairly low-energy propulsion system—propelled either by passive magnetic levitation or by air expelled from the pods themselves. The tube would be suspended off the ground to protect against weather and earthquakes.
Sound implausible? Maybe not. A test track has been built by SpaceX and teams of university students tested scale models of the pods there in January. And in August, they’re slated to race fully functional pods on the track in time trials. Most of the pods are expected to rely on magnetic levitation to raise them a slight distance above the track and move them forward.
Musk says he believes a one-tube Hyperloop system could be built for less than $6 billion. He calculates travel time between Los Angeles and San Francisco would be 36 minutes. California’s new rail system is expected to move passengers between the two cities in a little less than 3 hours. A plane ride takes a bit more than an hour.
The Hyperloop concept, or something like it, has been around since at least the 1860s, according to the British Postal Museum and Archive. The London Pneumatic Despatch Railway system, for example, was a pneumatic tube proposed to carry people and parcels beneath the streets of the capital.
Musk has inspired innovators to help bring the California Hyperloop to reality. And he’s lending them a big helping hand. SpaceX built an airtight one-track test tube at its headquarters in Hawthorne, Calif. The track is about 1.6 km long with an aluminum cover whose outer diameter is 2 meters.
In January 2016, SpaceX held its first Hyperloop Pod Competition, created to inspire college students to design and build subscale prototype pods. Student teams displayed their sketches, 3D models, and renderings to judges at Texas A&M University, in College Station. More than 100 teams participated, and judges selected 27 to build scale model pods. These are the ones tested on the SpaceX track this January. In August, new teams are expected to join the finalists from January in the Hyperloop Pod Competition II. The fastest vehicle wins.
A team of MIT students participated in the January competition. It was stocked with 35 aeronautics, mechanical engineering, electrical engineering, and business management students. IEEE Graduate Student Member Yiou He was on the team while she pursued a Ph.D. in electrical engineering.
“Building the pod was very rewarding because of its many challenging engineering problems,” He says. “We were stimulated to come up with ideas for how to solve them.”
The design rendering MIT entered in 2016 proposed a 250-kilogram pod with an exterior of carbon fiber and polycarbonate. Once up to a critical speed, the pod would be elevated by a passive magnetic levitation system along the test track composed of 40 neodymium magnets. The system would rely on the repelling magnetic field force generated by the fast-moving permanent magnets against the track to maintain a 15-millimeter gap above the tracks. The design includes an eddy-current braking system that automatically halts the pod when it reaches the end of the tube. The pod also has one low-speed drive wheel and four supportive wheels to get the pod moving on its two rails when it’s moving too slowly to levitate and when it slows to a stop.
MIT’s pod was judged to be the best overall design among the contestants last year. The school moved to the next phase, held this January: running a small-scale prototype on the test track.
At the competition, the MIT prototype levitated inside the near-vacuum of the Hyperloop test track. Sensors broadcast real-time telemetry data during the kilometer-plus run. The pod also had to accommodate the track’s mechanical pusher provided by SpaceX to get the pod up to speed before the maglev kicked in. The pusher accelerated each pod up to about 90 km/h, before releasing it to run on its own.
The 250-kg MIT pod is 0.6 meters wide, 0.6 m tall, and 2.5 m long. The team built a pod that demonstrated the high-speed, low-drag levitation technology and traveled at the maximum speed the pusher could provide, according to He. The team also emphasized the scalability, safety, and stability of the pod.
“The key feature of our pod is its passive magnetic levitation system,” He says. The vehicle has two 1.9-m skis beneath the pod, like a bobsled—each loaded with 20 permanent magnets. The pod levitates once it reaches a “lift-off” speed, He says.
Another key feature of the MIT pod is its eddy-current braking system. “Because the pod travels at very high speed, figuring out how to stop it fast was hard to do,” He says.
To be controlled safely the vehicle needed more than 30 sensors feeding a communications and computing system that made decisions based on the sensors’ data. The electronics and software team, which included He, developed the system
Program sponsors, including Draper, General Electric, and Hyperloop One, and other sponsors helped the MIT students in various ways, including donating parts to build the pod. MIT’s Edgerton Center, in Cambridge, provided work space, administrative support, and advisors.
Three teams, including MIT’s, were selected from the 27 to perform a vacuum run at the maximum pusher speed. The pods were placed in the tube in front of the pusher. The door to the tube was then sealed and in 30 to 45 minutes the air pumped out to reduce friction.
The MIT pod placed third overall in this phase of the competition. Delft University of the Netherlands got the highest overall score. The Technical University of Munich had the fastest pod. The judges considered safety and reliability; innovation; and design and construction. MIT’s pod won an award for safety and reliability.
Musk visited the competition. “It was very exciting to meet him,” He says. “He was impressed by the ideas from all the teams.”
The MIT team won’t be competing in next month’s competition; too many of its members have graduated. Several are working for startup companies building technology for a Hyperloop. He is considering joining one of those companies after she gets her Ph.D. next year.
Meanwhile she is working on recruiting younger MIT students to form another Hyperloop team. She expects that continuous competitions will be held in the future to encourage teams to come up with more mature technologies that achieve higher performance.
The MIT pod, currently in storage, is likely to have seen its last run. According to He, the MIT Museum plans to put it on display.