In August 2013, SpaceX and Tesla CEO Elon Musk published a white paper detailing a "Hyperloop," a super-fast passenger train that would overcome the usual friction by levitating above its track on air-bearings in an enclosed low-pressure tube. In the five years since, advancements have been incremental—a few interesting engineering choices have been swamped by announcements of feasibility studies for routes between populated cities.

Back in 2013, Musk declined to start a Hyperloop company himself (although he has not hesitated to start companies since then, perhaps suggesting that the extra work load was not the limiting factor). Instead, he made his work open to any startups that might want to tackle the challenge and started a contest series for engineering students to run their own test pods.

Two startups have since dominated the scene: Virgin Hyperloop One, which recently enjoyed a significant investment from Richard Branson's Virgin Group, and Hyperloop Transportation Technologies (HTT), which began as a collaboration among 800 engineers, designers, and other interested parties.

Both of these companies are years away from building a Hyperloop on any commercial scale, especially accounting for the inevitable land acquisition issues that traditional rail lines face as well.

On Wednesday, HTT released pictures of a commercial Hyperloop pod, a swanky-looking five-ton passenger cabin built by Spanish technology firm Airtificial. It has an outer length of 105 feet (32 m) and an inner length of 50 feet (15 m). The pod is designed to hold 30 to 40 passengers, HTT's spokesperson Ben Cooke said. It is also made of "dual-layer smart composite material," which Cooke said is "smart" owing to the fact that it's filled with sensors that theoretically send data back to HTT as the pod is traveling. Specifically, the sensors constantly measure the integrity of the system, Cooke added. Composite Manufacturing Magazine reports that the composite material is made by a Slovakian materials firm called c2i.

HTT's cofounder praised the sensor-packed pod as a high-water mark for vehicle safety. That's in theory, however. HTT doesn't have a test track yet, although one is being built in Toulouse, France. The company told Ars that the test track would be up and running by 2019.

HTT does have a number of agreements on the books for potential Hyperloops in the future. In July, the company signed an agreement to develop a Hyperloop in China's Guizhou Province. In July, the company signed an agreement in Ukraine. In April, the agreement was with the UAE. In February, HTT began a feasibility study for a Hyperloop between Cleveland and Chicago.

While HTT doesn't have a test track yet, its competitor, Virgin Hyperloop One, posted its top speed on its Nevada test track last December, with a top speed of 240mph. That's quite fast, but it's not a world record, despite the magnetic levitation that its test pod was on (magnetic levitation has been preferred by startups over Musk's air bearings).

Virgin Hyperloop One has also signed agreements and commissioned feasibility studies around the world. Dallas-Arlington-Ft. Worth has been pitched, as has a route between Chicago, Columbus, and Pittsburgh. A feasibility study for a Pune-Mumbai route is also reportedly in an advanced stage.

While the feasibility studies and passenger pods are good as public proof of work, hopefully the Hyperloop startup scene will start forming a more distinctive Hyperloop impression in the five years to come.