August 16, 2013 - Boston - Earlier this week, technology billionaire Elon Musk revealed his ideas for "hyperloop," a speculative new mode of high-speed transportation. The system would propel car-sized compartments through low-pressure tubes (like pneumatic tubes once used to move mail through office buildings) at 1,000 km/h. Musk says that connecting San Francisco and Los Angeles (through a proposed $20-fare, 35-minute ride) with the system would cost about $7 billion, or a tenth of the projected cost of California’s beleaguered high-speed rail system meant to connect those cities – and could be built in less than a decade.
Naturally, such a bold idea immediately attracted criticism, such as a USA Today article listing mundane reasons it won’t work like "you’d have to slow down for turns" and "the towers would have to be made safe." Of course, others fell over themselves praising the plan, reasoning that Musk's vision is so awesome that even if it doesn't quite turn out as planned, it would still be great, anyway. While it’s easy to get overly excited or overly skeptical about the concept, a dose of datapoints is useful:
- If Musk hadn’t proposed it, it wouldn’t be worth attention. Musk is a singularly successful entrepreneur, having quickly turned equally-futuristic ideas into successful businesses several times: electronic money (PayPal moves $150 billion a year), electric vehicles (Tesla is profitable and the cars, though expensive, are critically acclaimed), solar energy (SolarCity gets Lux's much-coveted "Strong Positive"), spaceflight (SpaceX, which developed a national-grade space program in seven years and makes a profit). Musk’s solid record lends credibility to an otherwise fanciful idea.
- The system requires no exotic new materials, properties of matter, or unproven technologies. Musk’s 57-page detailed explanation of the idea explains how the system might work using relatively off-the-shelf technologies. It acknowledges that there are many engineering problems to be solved, and offers the concept as an open-source blueprint – a starting point for something actually workable. As such, the many solid criticisms of the plan actually move it forward.
- Musk’s announcement should be seen as political commentary wrapped in an engineering design. The white paper opens not with a visionary problem statement, but by stating, "When the California ‘high speed’ rail was approved, I was quite disappointed, as I know many others were too. How could it be that the home of Silicon Valley and (NASA's Jet Propulsion Laboratory) – doing incredible things like indexing all the world’s knowledge and putting rovers on Mars – would build a bullet train that is both one of the most expensive per mile and one of the slowest in the world?" Like many California taxpayers, Musk is frustrated by the cost overruns, delays, and mediocre performance of the state’s high-speed rail program, and the political problem is arguably the one Musk aims to solve.
Of course, a tech entrepreneur's political commentary isn't newsworthy either, and there has been rampant speculation as to whether Musk – or anyone – could successfully build the contraption. Pneumatic transportation is not novel, and similar – if much slower – versions of pneumatically-propelled people pushers have been envisioned, and even deployed, long ago. Paris and New York had air-powered public transit in the 1870s. The vacuum-tube variation Musk is currently proposing has recently been explored in China and in Switzerland. So how does the concept stand up to technical scrutiny?
- Hyperloop's cost-per-kilometer would be as revolutionary as its speed. California high-speed rail's high cost per kilometer is as much a consequence of political and environmental issues as the technology, and those concerns would likely dog Hyperloop, too. Musk proposes an elevated, high-technology solution that would indeed address issues like land use, but such systems are if anything even more expensive: the Shanghai Pudong monorail cost $1.3 billion to build and is 30 km long ($40 million/km), while the Airtrain monorail in NYC cost $1.2 billion for just 12 km of track ($100 million/km). One way to defray the cost might be co-locating the route with other state-spanning infrastructure. Using the same right-of-way for a natural gas pipeline or energy transmission lines with PG&E, fiber-optic cable (which are routinely co-located inside city sewers) or water could be part of the calculus.
- The passenger pod's cousin, Tesla, could supply on-board power technology. On-board batteries are not a technological hurdle, because the initial acceleration (and subsequent boosts) needs would be met by external, stationary linear electric motors and their energy sources. The on-board batteries would then be used primarily for powering a large electric compressor fan at the front of the Hyperloop. The resulting battery would likely be on the order of 200 kWh – about three Tesla Model S's worth of energy storage capacity, which can be engineered using today's battery technology. Moreover, these batteries would contribute only a sliver – less than 0.1% – to the overall cost of the Hyperloop, being dwarfed by infrastructure like pylon construction and land permits.
- Even in sunny California, the solar-powered system would need backup storage. While Musk's plan assumes the energy requirements of the system could be met by solar energy – perhaps he is hoping that SolarCity will get the installation contract – solar panels would need grid storage to operate at the expected utilization rate. So while solar power will help, the larger energy storage opportunity would be in the stationary batteries required to operate the Hyperloop's linear electric motors at night or in poor weather.
- The open-source model is an open invitation to rail system manufacturers like Bombardier, Siemens, and ABB. Siemens test-drove crowdsourcing by opening up its engineering software to the Local Motors crowd, with the now-available Rally Fighter vehicle a testimony to its success. As with other "big innovations," the spinoffs of R&D on Hyperloop would benefit adjacent technologies, and advance the process of collaborative design. Manufacturers of other high-performance transport vehicles, such as automotive, aircraft, and spacecraft – like Musk's SpaceX or the NewSpace community – should join the Hyperloop crowd.