The Hyperloop's biggest questions are still unanswered

Less than two years after it was first announced, Elon Musk's Hyperloop seems to be making great progress. Two independent companies have now launched projects to build versions of the high-speed transportation system, drawing from Musk's open-source plans. And yesterday, Musk's own SpaceX announced it was building a test track that will host a "pod racing competition" in which groups will compete to design the most aerodynamic crafts. After a spectacularly unconventional development, the idea is closer to reality than it's ever been.

It's good news, real progress on an exciting idea. Even a 5-mile Hyperloop represents a significant challenge, and settling on a craft design will be an important part of any system. But by tackling these problems, the teams are side-stepping the Hyperloop’s harder problems and avoiding the technology’s most central questions. If you’re wondering how fast the hyperloop can go or how safe it will be at high speeds, a capsule design competition won’t do you much good, and a 5-mile test track will only give you the slightest glimpse of the important challenges ahead. As a result, what looks like a step forward may be more like a holding pattern.

DEPLOYMENT DETAILS ARE LIFE-OR-DEATH ISSUES FOR THE HYPERLOOP

The biggest issues are speed and scale. The Hyperloop was pitched as faster and cheaper than alternatives like cars and trains, but even small shifts in those numbers can dramatically change how it stacks up. It's easy to imagine safety concerns limiting Hyperloop speeds to just a fraction of its theoretical top speed or right-of-way issues keeping stations far from urban centers. Would we still be excited about the Hyperloop if a 30-minute trek became a three-hour one? What if it cost $60 billion instead the promised $6 billion? After enough setbacks, it might not be worth developing the technology at all. Those deployment details are life-or-death issues for the Hyperloop, but as long as the tests are focused on small-scale loops, it's not clear we'll ever get answers to them.

SpaceX's latest round of tests doesn't seem likely to change that. The test track is only 5 miles, nowhere near the distance it would take to reach 700 miles per hour. Another test track built by Hyperloop Test Technologies will have the same problem, aiming at a 200mph top speed. For the same reason, these test tracks can’t address the unique safety issues that come with near-supersonic travel. The result is just a tube-powered version of conventional transportation tech like maglev and rail. That doesn't mean that useful work can't be done on this round of test tracks, but it means the central question of the Hyperloop — whether it will be fast and cost-effective enough to replace airplanes and conventional rail at scale — is going to remain unanswered.

In part, the problem is how well Musk has sold the Hyperloop. What exists now — what we're talking about when we say "Hyperloop" — is basically just a technical sketch. Put together a lightweight pod with air rails and an enclosed maglev tube, and that's a Hyperloop. We're still feeling out the engineering challenges involved in combining those technologies and the limitations that pop up along the way. We can make estimates about how fast it could travel and how much power it might use, but they're still just guesses, and it's hard to know how they'll survive the rocky transition from the drafting table to the real world.

WOULD WE STILL BE EXCITED ABOUT THE HYPERLOOP IF A 30-MINUTE TREK BECAME A THREE-HOUR ONE?

It’s common for a technology to fall short of its initial hype once logistical realities set in — but the Hyperloop started with an extraordinary amount of hype. When Musk first announced the plans, he said a working hyperloop could travel from Los Angeles to San Francisco in 30 minutes, many times faster than any conventional mode of transport, all at a fraction of the traditional price. Those numbers were the source of the excitement, and we still don’t know how plausible they are. If the Hyperloop is running on anything but a perfectly straight track, then its speed will likely be determined by the sharpness of the curves, not the power of the accelerator. It's also unclear what it would be like to maintain a Hyperloop, which elements will break down, and how often. Safety equipment, particularly earthquake safety, would raise costs and friction even further.

Closing that gap has been particularly difficult because of the unusual development of the Hyperloop. Since the beginning, Musk has taken an impassive approach to the project, first open-sourcing the design with no plans to deploy it, now challenging other groups to build human-scale pods to his specifications. The open-source nature of the challenge is usually read as magnanimity, putting aside the profit motive to share his idea with the world, but it could just as easily be seen as caution. If the Hyperloop is a cool idea that's impossible to deploy, the caution makes perfect sense. Even now, we've seen three companies take up the idea (counting the current SpaceX challenge) and no plausible plans to realize the LA to San Francisco route Musk initially envisioned. Even after testing, the route may simply be unworkable at the speeds Musk first proposed.

It wouldn’t be the first technology to fail to make the leap. Monorails, maglev, and other high-speed rail systems started out as promising, only to be whittled down by some of the same right-of-way and top-speed challenges now faced by the Hyperloop. Musk may well succeed where those projects failed, but until we start to address the big questions, it’s still just a good idea.

That's not to say the Hyperloop will turn into a boondoggle, or that the latest round of testing won't be successful. It really is a promising idea, and more research is always a good thing — but the road to a fully functional Hyperloop isn’t getting any shorter.