Hyperloop, Maglev, and related transport systems

This post will be the first in a series of posts about my thoughts on the latest technological and engineering developments.


So I read through Elon Musk’s entire hyper loop  proposal, accessible here, at 58 pages it’s certainly not light reading but I was intrigued by several news articles talking about the Hyperloop. First off it’s an incredible idea but not quite as revolutionary as the media portray it to be, there have been other proposals of tube trains, maglevs (magnetically levitating trains using linear motors for propulsion, the same propulsion system as the hyper loop), and even evacuated atmosphere maglevs in tunnels, such as a proposed floating undersea tunnel cross-Atlantic system. (which in itself is a fascinating topic)

Image from maglev.net Image from maglev.net

And it is being a bit disingenuous to say that a partial atmosphere transport system has never been proposed before. For example the aforementioned fully evacuated maglev system is only in a hard vacuum because of the enormous hypersonic (Mach 5+) design speeds envisioned so the same design could also be used  as a partially evacuated high subsonic transport system and the only difference would be adjusting the air pressure and increasing the propulsion power. There are other examples of smaller proposed systems, similar in scale to the Hyperloop, running in hard vacuums but again the fundamental design would be the same for a partial atmosphere.

Now that’s out of the way, I can clearly see why the Hyperloop is so attractive, compared to high speed rail it’s faster, cheaper, more energy efficient, more convenient, and can reach more places economically, I’m assuming that a Hyperloop station would be cheaper to build than a conventional HSR (high speed rail) station.

Conceptual rendering of a Hyperloop station Serge Roux. Conceptual rendering of a Hyperloop station Serge Roux.

The cost estimate given for a single way ticket at $20 is incredibly low but achievable, however not at the volumes given in the report. The report’s estimate depends on a $6 billion price, everything included, without interest rates on debt, nor maintenance and staffing costs, or any profit considerations. Needless to say the actual cost per passenger would be higher. Being generous and assuming the $6 billion figure is realistic and low maintenance costs with minimal staffing requirements:

R&D expenditure: ~$400 million

Estimated construction cost for passenger Hyperloop: $6 billion

Interest & Amortization (assuming 20 year government bonds): ~$1 billion

Maintenance and staffing costs per annum: ~100 million

Total sunk costs: $7.4 billion + $100 million per annum

Over a 20 year period this would represent a total, non inflation adjusted, cost of $9.4 billion after inflation this would be closer to $10.5 billion in 2015 dollars.

At 7.4 million passengers each way per year that’s $36.50 per ticket. Still very cheap. Of course the infrastructure, equipment, buildings, and R&D would still be worth something after 20 years of operation so the entirety of the value is not captured by the ticket price, but this would be roughly equivalent to the profits that still need to be made.

Assuming a linear growth in maintenance and staffing cost of $7 per passenger, a $20 ticket price would need about 26 million passengers annually.

I love the compression and air ski ideas, individually their great, it’s truly genius to combine them into one system that solves two problems in one. Overcoming the pressure effects by passing the incoming air, essentially, through the vehicle while simultaneously using this air to supply external pressure to the skis vastly reduces the size of the capsules. A lot of more conservative designers ,who only incrementally improve and at most introduces one revolutionary idea, might not have considered this to be an option as it takes both revolutionary ideas in conjunction for a Hyperloop like concept to be economically feasible.

However there some hidden downsides to selecting a Hyperloop over HSR, obviously doing both would be ideal but it’s highly doubtful that there is sufficient political and public will in California to construct two major transport systems. I will only cover the major issues that I see that is fixable.

First of all there’s public sentiment, people know what trains are, most everyone have ridden in a train or know someone who has, virtually everyone in the industrialized world has heard of HSR, or seen pictures of a high speed train (Shinkansen, TGV, ICE, etc). In general people would be comfortable, or at least would be easy to convince, in riding a high speed train, not so for the Hyperloop where you would essentially be climbing into a tiny, windowless, pod that can barely fit two adults side by side. Sure Hyperloop would be vastly more mass, energy, and volume efficient but the general public always seek the most familiar solution.

As can be seen through the success of Apple’s design ethos, many, if not most, people value the experience of something as much as the actual thing, Hyperloop is a distinctly more utilitarian approach compared to the romanticism of open air rail travel. The report briefly covers this mentioning videos of scenery to be shown on the interior walls of the passenger capsule, however I believe that fundamentally the vehicles need to be enlarged (or windows to be integrated in the tunnel) because the sense of space, real or perceived, is vital for the comfort of transportation.

Secondly the safety or lack thereof. At 760 MPH any sort of crash would be instantly fatal to all passengers, and Hyperloop doesn’t even have the redundancy of permanent magnets in maglevs. Any sort of failure of a sufficient number of the onboard air bearing skis or of the air supply system to the skis at 760 mph would result in a catastrophic loss of stability and collision with the tunnel wall. This can be mitigated by a backup suspension system, such as a secondary air supply system  or onboard emergency air tanks to supply the air skis. This comes with  additional weight, volume, and most importantly cost.

The air pressure of the tubes, at 100 Pascals while far higher than a hard vacuum, is still very low, it’s equivalent in density to the Earth’s atmosphere at 150 000 feet. Exposure for longer than a couple of seconds at this level would be fatal, or at the very least cause major organ damage. A breach in the tunnel wall would not be a big issue but a breach in the capsule itself would, again, be catastrophic, even if everyone was wearing pressure suits, the  1000:1 pressure differential would cause everything in the capsule to be sucked out the breach at high velocity. A solution could potentially be air tight doors mounted at intervals in the tunnel with emergency air release valves that would very rapidly equalize the tunnel with atmospheric air pressure. In case of a hull breach emergency the emergency braking system would activate and the doors would close and pressure normalized, to allow for a safe deceleration (higher pressure also increases deceleration so the braking system could be smaller) of the capsule until rescue crews could respond. The doors are placed so that a single accident wouldn’t depressurize the entire system reducing the cost and time it would take to start the system back up.

Well that’s it for my thoughts today, more will be coming in the future.