Ladies and Gentlemen… This is the topic that Technically Speaking was made for…
This… Is the Hyperloop.
Let’s start with some numbers:
- 20 – Dollars per one-way ticket
- 35 – Minutes to travel between San Francisco and Los Angeles
- 72 – Pounds of Drag Force on the Vehicle
- 760 – Miles Per Hour top speed
- 10 Million – Cost of vacuum pumps
- 6 Billion – Total cost of the Hyperloop System
In this episode of Technically Speaking, Jacob and Joe give the Internet’s most in-depth technical analysis of Elon Musk’s “Hyperloop” design, with the help of Metallurgical Engineer Mark Miller. Everything from propulsion to construction to user-experience is discussed and analyzed. Figures are checked! Numbers are calculated! Minds are blown! (It’s pretty much a Michael Bay movie, except replace explosions with equations, and sexy women with Microsoft Excel)
We answer the questions that no other show can answer, like: How far along is this design? How realistic is the design concept? How serious have the designers considered Safety? And what kind of TV Shows will I be able to watch while riding the Hyperloop? All that and more will be answered when you listen!
And YES, we did throw a Brainstorm into this episode! (We knew you missed it)
Do yourself a favor: listen to this episode, then go check out the Design PDF, then go rate us on iTunes to tell the world how much you enjoyed the show! Email us with questions or Hyperloop design ideas, or maybe start up a discussion on Facebook or Twitter with the rest of the Techies (…that’s what I’ve decided to call you all from now on… Techies, get it?)
Music: “Hyper Music” – Muse
Podcast: Play in new window | Download
Digging this except for the 20$ price tag. That seems too good to be true.
Seriously? For a half-hour ride, you’re worried about scenic videos and onboard entertainment? Millions of people have daily one-way commutes longer than this on the NYC subway and the London tube, and they get along fine without television screens at their seats. Bring along a freaking book, for Pete’s sake, or talk to the person next to you. At the most, maybe it would make sense for them to provide a WiFi connection, and if you can’t survive for 30 minutes without moving pictures, you can use that to watch lolcats on YouTube.
The difference, I think, between the Hyperloop and the things you mention is how very closed off the Hyperloop is. While scenery on a subway is limited, there are still stops every few minutes, plus you are able to walk around, and even though you’re in a tunnel, there are still windows through which you can see the walls and lights moving by.
With the Hyperloop you have no windows, and you are restrained to a chair. There’s only one person next to you, and maybe they aren’t particularly interested in talking.
I think the possibility of claustrophobia is very real in this scenario, and considering there would be no way to help a person suffering a claustrophobic panic attack, I think it would be worth while to attempt to trick the brain into thinking you aren’t trapped in a pod in a tube moving at the speed of sound (761 mph at sea level… outside. Not in the tube).
Most people would likely be able to handle it, but some wouldn’t. Better, I think, to eliminate as much chance as possible. One freak out could lead to bad PR for a very new transit idea.
Re: Green in summer
Most of California has two seasons. In winter, it rains a bit and things turn green briefly. The rest of the year, everything not irrigated is brown.
I have to take issue with one of the points in the hyperloop proposal, and with your agreement, and that’s about the security checkpoints on either end. First of all, those TSA checkpoints are “security theater”, and are very unlikely to stop determined terrorists. When tested, those TSA checkpoints have repeatedly failed to find serious threats. The real purpose of those checkpoints (aside from political pork) is to give travelers warm and fuzzy feelings of safety, not to actually improve safety.
But let’s put that aside for a moment and assume they’re effective. They rely on the fact that checking passengers and cargo at boarding time protects the entire flight. After all, surface-to-air missiles are hard to come by. But with hyperloop, screening passengers and cargo won’t protect the hundreds of miles of ground level pylons and tubes. If terrorists want to blow up a hyperloop pod, they’re going to drive to the middle of nowhere on I5 and destroy one of the pylons. Securing the entire length of the system would be roughly as difficult as the failed attempts to secure the border with Mexico. In other words, it’s not going to happen.
I also have a couple questions that are more relevant to mechanical engineering.
What about noise? Here in the San Francisco Bay Area we have BART, which is an excellent regional rail system, but it has the loudest rail wheels I’ve ever heard. They echo across the landscape. So what kind of noise will hyperloop pods make when they’re shooting through a steel tube at over 700 mph?
And what about wind currents in the tubes? As the pods go one way, and their ducts blow the low-pressure air the other way, I expect that this will lead to air currents going through the tube in one direction or the other. If the air moves with the pods, they will find it more difficult to take in enough air to blow outward and backward. If the air moves against the pods, they will have more wind to resist, and the system will get less efficient. So is this something that must be overcome somehow, or would it not matter?
Wow, thanks for your comment Bob! Get ready for a long response!
While your points about the TSA are well-noted, we decided to try to stay out of the politically-sensitive area of criticizing the TSA’s methods, and instead simply point out that security would have to be very serious for the Hyperloop, simply because the tracks are exposed and not underground. A secondary point is that the security of the system is also closely related to Quality of Service (QoS) within the Hyperloop system. If there is a security threat, 100% of the product is shut down and taken off the market, there is no alternative route, no sister-product to keep those customers. Security then becomes not just a safety concern, but also a product quality concern.
Regarding targeting the pylons, you’re absolutely correct – that’s all it would take. I would imagine that the pylons themselves would be protected by high fences and active security systems. Electrified fences, cameras, and alarms at least, would be necessary. It’s not crazy to think that this could present a market opportunity for someone who invents an automated less-than-lethal security system to be mounted on each pylon. Beanbags? Acoustic weapons? Who knows?
OK so your question about noise is a VERY good one. I don’t think I have a great answer for it, but I can make a few guesses:
1) The major sources of noise for trains is A) Mechanical friction noise (wheels, axles, etc…) and B) displaced air. Since the number of moving parts is very small, and the pressure in the tube is very low (meaning there is very little air inside the tube), I suspect that the major sources of noise will be greatly minimized. (Maglev trains already benefit from the elimination of Mechanical friction noise) The vehicle itself may make a lot of noise with it’s compressor motor and fan blades, but this feeds into my next point…
2) Because the inside of the tube is kept at such a low pressure, the air density inside the tube is very low. The low density of air inside the tube, contrasted with the high density both inside the vehicle and outside the tube means that any acoustic energy transferred from the low-density air to the high-density air will be quickly dissipated. Think of it like yelling at someone who is swimming underwater: they can probably hear you yelling at them, but you’re not very loud, and your words are muffled. That’s what a high density differential will do to sound waves when they attempt to cross from one medium to another. The frequency change will actually follow Snell’s Law (http://en.wikipedia.org/wiki/Snells_law), and the sound intensity (decibels) will change proportionally with density change of the fluid (http://en.wikipedia.org/wiki/Sound_intensity < - acoustic impedence is proportional to density). This makes sense when you think of the air densities as different weights of balls - If you're shaking two light dumbbells at 2 shakes per second, and then you trade them out for two heavy dumbbells, you won't be able to shake them at the same rate, because it takes more energy to accelerate and decelerate the heavy dumbbells for each change in direction during the shake. This is exactly what happens when the acoustic waves from the low-density air impinge upon the higher-density air (or, more accurately, the steel tube, and THEN the high-density air). 3) The fact that the vehicles are INSIDE a tube is going to make a huge difference. Think about how much of a difference a concrete wall makes when blocking highway noise, and I'm sure residents of Hong Kong could tell you how valuable the Glass Tubes in certain areas of the Metro are. Not to mention, these are very fast, point-sources of sound, which will travel into and out-of your field of hearing within a single second. So they won't be making noise very long. Lastly, another great question about the wind currents in the tubes. Once the system is in full operation, with vehicles travelling through the tube every 2 minutes, it's not crazy to think that the car in front may disturb the air for the incoming car behind it. Top Gun popularized this concept with the fictional "Jet Wash" that brought down Maverick and Goose's F-14. Luckily, it was a fictional phenomenon, and in the case of the Hyperloop, we're not going to have accelerated exhaust anyway. You see, the key point is that the compressor onboard the vehicle DOES NOT ACCELERATE the vehicle. It only provides enough propulsive force to overcome drag, and that's it. In Jet Engine design, this is what we call "Steady State Thrust", and it is the most fuel-efficient portion of the flight profile. The basic idea is that you suck-in incoming air at whatever speed you're traveling, accelerate it through the vehicle, and exhaust the air at the exact same speed. If you exhausted the air at a HIGHER speed, you would accelerate - if you exhausted it at a LOWER speed, you would decelerate. You get the idea. For steady state travel, you are sucking it in and spitting it out at the same speed, such that there is no "wind" being created in your wake. The only thing that's created in your wake is... well, your wake. The turbulent, localized eddy currents that quickly dissipate when left alone. Somewhat equivalent to the wake left by a boat when it's travelling at a constant speed - the motor doesn't create a water current in the opposite direction of the travel EXCEPT during the transition from zero-speed to constant-speed. THEREFORE (sorry this is getting long), since the compressor motors onboard the Hyperloop vehicles do not accelerate the vehicle (acceleration comes from linear induction motors every once in a while), there is little reason to believe that wind-currents will develop inside the tubes. (I guess an easier way to explain this would be to use Newton's 2nd Law to say that Nature abhors a vacuum, and nature tends towards a more disordered system. As some of the air moves with the vehicle, this would create lower-pressure zones behind the vehicle, which would then suck more air into those zones, eliminating the overall movement of air. Check this out for an example of how this happens – look at the animation and note how the deflected air gets sucked back into the middle of the airstream, behind the shadow of the sphere. That’s the low-pressure zone “sucking” air back in.)
Great questions, and I hope my answer wasn’t too long winded! For more information on how jet engines work (because it’s similar to the way the compressor motor works on the Hyperloop vehicle), check out my old blog post on the Paleocave!
Thanks for the detailed reply!
I thought you mentioned in the podcast episode that they would use the output as a gentle boost to help maintain speed, which would require forcing the air backwards. I’ll be impressed if they can perfectly balance the speed of the air intake and output at 700+ MPH so that in 3 minutes it’s back to roughly still, especially in a contained tube. But it does sound plausible.
Oh, and regarding sound, would there be any generation of sound via the air cushion? It still must be exerting a momentary force of at least the weight of the pod on the structure, which would at least cause the tube to flex. I also expect that the sections where the pod is on its wheels while accelerating or decelerating could be quite noisy.