You step inside the sleek silvery pod, settle back in your seat. There’s a slight shudder as the pod is loaded into the vactube – and you’re off. The pod catapults forward, then banks south to join the Hume Highway. You are skimming along at 1,220 kilometres per hour. Sydney to Melbourne in 48 minutes? Just take the tube.
Hyperloop was conceived by billionaire entrepreneur Elon Musk. The idea is for passengers to travel at near supersonic speeds in minivan-sized pods that are fired through a tube. It sounds wild, but Musk (co-founder of Paypal, and CEO of Tesla Motors and SpaceX) has a track record of turning the seemingly impossible into reality. Musk says Hyperloop would provide a faster, cheaper and more energy efficient means of high-speed travel. How would it do this?
In any vehicle, power is required to overcome air resistance – and the faster you go, the more power you need. For this reason aeroplanes climb to altitudes of around 10 kilometres, so they can travel through thinner air.
In a Hyperloop tube air would be pumped out to reduce the air resistance faced by the speeding pod. (Musk proposes that the density of air remaining in the tube would be equivalent to the air density at 50 kilometres above the Earth.)
“It’s a concept whose time has come,” says Dennis Levy, head
of the Australian engineering consortium.
The pods would not use wheels but would float on little jets of compressed air, further reducing friction. Electric motors, similar to those used on maglev trains, would be situated every 50 kilometres along the tube. Their super strong magnets would give each passing pod a kick along. Speed would be limited to 1,220 kilometres per hour – just below the speed of sound to avoid a sonic boom shockwave, which might reflect off the tube walls.
High-speed transport in a tube is not a new idea. Robert Goddard, the early 20th century pioneer rocket scientist, also came up with designs for what he called the “vactrain”. And in the past 20 years, an American company called ET3 (Evacuated Tube Transport Technologies) proposed a modern vactrain design, although they have not built a working model.
Musk is not developing the Hyperloop himself, but is promoting his proposal as “an open source transportation concept”. Several companies have taken up the challenge, including Hyperloop Transportation Technologies, a California-based start-up backed by Uber billionaire Shervin Pishevar. In August they announced a partnership with Oerlikon Leybold Vacuum, a European specialist engineering firm that supplied some of the high-vacuum systems used at the Large Hadron Collider.
Hyperloop Australia Design is working to adapt the idea to the Australian market. “It’s a concept whose time has come,” says Dennis Levy, head of the Australian engineering consortium.
Levy acknowledges that “some extremely difficult challenges still need to be solved” before a commercial Hyperloop could be built. For example, Musk’s concept describes how the pod would ride on “air bearings” – a cushion of air a fraction of a millimetre thick – created by jets. “Air bearings” have been used in other applications, such as shuttling crates around warehouse floors, but might not be viable to create the extremely smooth surface required inside the Hyperloop tube.
Reducing heat built up by air compressors at the front of the pods also poses a difficult problem. And the concept’s economic viability is unknown.
Musk’s initial vision was to service the San Francisco-Los Angeles route. Sydney to Melbourne, one of the world’s busiest air routes, would also be a good candidate, Levy says.
Musk’s company SpaceX is constructing a 1.6-kilometre test track at their California headquarters. In September, they launched a global competition for pod designs to encourage interest from universities and engineers. It will begin testing in June 2016.
Air pressure in the tube is lowered to about 1/1000th the pressure at sea level, or the equivalent to an altitude of 50 kilometres. This reduces drag, allowing the pod to travel at very high speeds while propelled by a relatively low amount of energy.
Linear induction motor magnets, similar to those already used on maglev trains, are placed at regular intervals along the tube and accelerate the pod by giving it an electromagnetic push. They also recover the pod’s kinetic energy using regenerative braking, much like a modern electric car.
The pod rides on a cushion of air pumped from 28 jets. The air cushion is only one millimetre thick yet creates an almost frictionless suspension.
The nose of the pod contains a compressor similar to the turbine on a jet aircraft. Its job is to pump the small amount of air remaining in the tube from the front of the pod to the rear. Otherwise, the speeding pod would quickly collect a pocket of air at its nose, and lose its low air pressure advantage.
Cruising speed: 1,220 kilometres per hour. Passengers per pod: 28. Estimated cost to construct: San Francisco to Los Angeles route US$6 billion (less than 1/10th the US$68 billion proposed for the California high-speed rail project). Trip time: 35 minutes (SF to LA). Estimated cost per passenger: per trip (SF to LA) US$20 plus operating costs per one-way ticket. Frequency of pod departures: Every 30 seconds during rush hour.
Estimated trip times for Australian routes: Sydney to Melbourne: 48 minutes. Sydney to Brisbane: 52 minutes. Sydney to Canberra: 19 minutes
Originally published by Cosmos as The hyperloop alternative to a very fast train
Cathal O'Connell is a science writer based in Melbourne.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.