Hyperloop: A to B Faster than Ever

Posted by Science Explored on September 05, 2013

Elon Musk is no stranger to pioneering new ideas.  He was the driving force behind PayPal and is the current CEO of Tesla Motors (which created the electric Tesla S, the highest-rated car in history) and Space X.  The South African native is a perpetual learner and tinkerer and as such,  no one was surprised when he recently revealed his latest idea:  the hyperloop, a new mode of transportation that could revolutionize how we travel long distances.  Glimpsing into Musk’s mind, we invite you to explore the creativity of Musk’s latest endeavor. 

Musk began by identifying a problem, as most inventors do.  Airplanes are expensive, trains and boats are generally slow, cars create clouds of pollution and result in thousands of deaths – what if there were a fifth mode of transportation that was cheap, reliable, safe, and amazingly fast?  That fifth form already has a name, according to Musk:  the hyperloop.  The hyperloop is, in its basic form, a huge drive-up bank deposit vacuum tube, but with a few key differences.  

Musk's concept art for the hyperloop is impressive and frightening.  The idea of riding a "missile" cushioned by air might have some travelers a little worried.

Passengers would enter a narrow capsule suspended on a cushion of air within a tube that connects two distant stations.  Using magnetic propulsion, the capsule would accelerate to 700 miles per hour.  At these speeds, a trip from Los Angeles to San Francisco (the region where the hyperloop might be built) would take a little over 30 minutes.  Even better, multiple capsules could be sent through the tube at the same time meaning that station wait time would be only minutes.  Sound too good to be true?  Musk has drawn out compelling plans to back his idea.

Musk’s plans describe the minutiae of the hyperloop’s parts and systems, but most intriguing is how he overcame a physical law:  the Kantrowitz Limit.  The Kantrowitz Limit describes a phenomenon that occurs when an object moves through an enclosed space, like a tube.  If the object is nearly as voluminous as a cross-section of the interior of the tube, the maximum speed it can travel through the tube will be relatively low.  The reasoning is that the air in front of the object needs to squeeze around it as the objects traverses the tube; if there’s less space on the edges of the object to squeeze around, the air ahead of the object acts like a wall, slowing or even stopping its movement.  The hyperloop’s capsule would travel inside a tube much like in the later example.  For safety, it would have to be nearly the size of the tube to prevent it from wildly bouncing around and smashing to pieces against the tube wall at high speeds. 

Determined in the face of this physical limitation, Musk devised an ingenious solution.  Using a fan-like rotor on the front end of the capsule, the capsule could redirect air in front of it to the back end using an internal duct system.  Taking a step further, Musk intends for the rotor to redirect air to the edges and sides of the capsule to create “air bearings” that would perform like ball bearings (small metallic spheres that allow two pieces to easily slide by one another like in a rotating tray).  The advantage of air bearings is that they do not wear down and create heat from friction.  By generating air bearings, the capsule would effectively glide on a cushion of air through the tube much like a puck on an air hockey table.  However, ordinary air is not dense enough to support the weight of heavy capsule and prevent it from grinding against the sides of the tube.  Musk’s plans include a series of air compressors to increase the density of the air and thus make the air bearings a reality.

Musk’s plans also call for the spine of the tube to be plated with solar panels, making the entire hyperloop, stations and all, self-powering.  In fact, using magnetic accelerators that attract and repel the capsule as it moves through the tube would require no fossil fuels to attain the incredible speeds of 700 mph Musk has promised.  Still, storing energy created by the hyperloop to power the magnetic accelerators, the capsule rotor, and station equipment is still a challenge, as batteries have difficulty storing large amounts of energy.  As funding begins to pour in for the project, we are likely to see more refinements along the way.  Regardless, should it work, planes, trainsz, and cars may soon be dated forms of transportation.

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