Pragmatic 81: Boring Loops

30 June, 2017


Elon Musk is considered by many to be a technological visionary. In this, the first in a series of shows about Elons projects, we look at Hyperloop and The Boring Company and the practicalities of what Elon’s trying to achieve.

Transcript available
Welcome to Pragmatic. [Music] Pragmatic is a discussion show contemplating the practical application of technology. By exploring the real-world trade-offs, we look at how great ideas are transformed into products and services that can change our lives. Nothing is as simple as it seems. Pragmatic is part of the Engineered Network. network. To support our shows, including this one, head over to our Patreon page. And for other great shows, visit today. This episode is brought to you by ManyTricks, makers of helpful apps for the Mac. Visit for more information about their amazingly useful apps. We'll talk more about them during the show. I'm your host, John Chidjie. And today I'm joined by Vic Hudson. How's it going, Vic? Good, John. How are you? doing better. How much do you know about Elon Musk and some of his side projects? Mainly, just the highlights that reach the news. I don't follow him too closely or anything. Do you follow him on Twitter at all? I don't think so. I can check real quick if you'd like. No, I was just curious. One of the things is I thought it would be interesting to do a couple of episodes that focus on some of the different things that Elon Musk is working on, because I feel like in a world where Steve Jobs is no longer with us, entrepreneurially speaking, I think Elon Musk is one of the big names of people that are, you know, stepping outside the box, doing stuff that's a bit out there. And there's a whole bunch to talk about, but I wanted to kick off with two of his more recent and unusual side projects. So I mean obviously Elon Musk is the man behind Tesla and SpaceX. But more recently he's been messing around with tubes and boring stuff. So not vacuum tubes? No no no no no. So have you ever heard of this thing called Hyperloop. I have. So how would you describe Hyperloop exactly? Um well from what I understand which is probably very little because I haven't dug too deep into it I've just heard a few casual conversations about it. It's going to be sort of like a an enclosed little bullet train system. Yeah pretty much bullet train in a tube. Yeah. So, it is a vacuum tube. That's true, actually. You're right. I'm sorry. Silly me. Quite right. So, in July of 2012, Elon Musk mentioned in a Pando Daily event, he was thinking about a fifth mode of transport and later he called that Hyperloop. And the idea is that you build a hollow tube, most likely made out of steel, deal. And then you remove as much of the air as you can from the tube and it creates a partial vacuum. It's not a full vacuum, it's a partial vacuum. So then you get a capsule. The idea is so it doesn't provide any resistance against the carriage, right? Yeah, exactly. So the idea, exactly right. Because drag is one of the biggest things you're fighting when you're trying to go really fast in Earth's atmosphere unless you're you know well even if you're a plane right because in a plane it's one of those dichotomies on the one hand you need the air to give you lift on the other hand the air slowing you down so yeah it's frustrating it's a never ending argument that the planes having with the sky but never mind that yeah yes so that is a general idea and you have a capsule or a pod or whatever the hell you want to call it you load that into the tube and you propel that along at high speed it all seems very cool but Elon Musk originally suggested that it would sit on a bed of air but if you think about it if you're already sucking all the air out that's gonna be pretty hard to achieve. Yeah, there's a little problem with that design. Yes. I had a toy when I was a child that sounds kind of like this thing. Really? Yeah it was called a rocket tube. You put it together, think of a racetrack, you know you had pieces of track that you put together and like an oval. But it was an enclosed tube, the top of it was clear plastic, the bottom of it was dark colored. At one end of the loop, so you had like an entrance into the loop, kind of like a pinball where you know you have the thing that shoots the ball in. So you got a loop with an appendage. At the end of appendage was this big blower fan and you had these little carriages that looked like a coffin shape and you put that in the tube and then you fire that thing up and it had this really noisy fan but that little tube would shoot or that little carriage would shoot around that tube. Wow cool. It was called it was called a rocket tube. Cool man that sounds really awesome actually I didn't have anything like that I don't even think I've ever seen anything quite like that but that sounds really cool. Well I don't know we had asked for a racetrack and that's what we got. Well fair enough then. Well that's pretty cool. So this is like a bigger... But the next year we got the... the next year we did get the racetrack so that was okay. Oh okay fine. So you forgave the... yes. Nice. Alright cool. I'm googling the rocket tube now to see if I... oh my goodness. Don't google rocket tube. Okay. Well then. Yeah. Okay. So, throw me a link, I can chuck that in the show notes, and if you find what it was. If I find the real thing. Yes, not the other stuff you might be accidentally finding. Anyhow. Yeah. So, when he gave up on the idea of a bed of air, it's probably going to be maglev, right? So, magnetic levitation kind of thing. And the idea is that you get a linear induction motor, and that's going to accelerate at one end and decelerate the pod at the other end and maybe have a couple of boosters along the way if you need it to keep the momentum going. Because even at a very low air pressure you will still get a build up in front of the pod that's going to slow you down. So the other concept was that you would have a high speed inlet suction fan at the front and some tubing to take that air to the back and then basically a fan at the back to, or air compressor sorry, at the back to help. So that will alleviate any pressure build up in the front and provide additional potentially propulsion I suppose, probably not much. Anyway, but the idea is that you wouldn't have a big motor on board so you don't have to carry around fuel, you don't have to carry around an engine, you know, it'd probably be battery-powered and so on. So technically it wouldn't be self-propelled exactly. Anyway, so the original concept was that you'd have these passenger-only pods and the original dimensions in the original concept design was something that would be 7'4" which is about 2.23m in diameter and a projected top speed of a pod was about 760mph which is 1220 km/h which is pretty zippy the maximum acceleration is about half a G which is not too bad not as much as your favourite roller coaster but certainly you'd notice now you compare that with the fastest passenger trains in the world, they're the TGVs and they run at 357 miles an hour, that's 575 km/h which is very fast but you know that's like half the speed of this thing the fastest maglev train if you want to because that's steel rails right but if you get a maglev you can go faster the problem with maglev is there's not many passenger trains around the world that are maglev that are that fast there are a couple of experimental ones on that run on experimental tracks that's like proof of concept and the japanese maglevs at the moment the l0 series hold the record at 375 miles an hour which is 603 kilometers an hour which is still half the speed of the proposed Hyperloop pods. But that was the original design. Anyway, there's three major companies building Hyperloop technology and none of them are really affiliated with Elon Musk or SpaceX. And SpaceX built a test track but they aren't actually developing the technology much beyond that. So these three companies are just just sort of doing our own things for their own reasons. But anyway, so that's the idea anyway. And the idea is that it would be, according to Elon Musk, quicker and cheaper than building a high-speed train, which is what he was trying to get around. It's like, "Yeah, this is the way to go. This is the future. This is the fifth mode of transportation." But the funny thing is, I was digging into this, I was sort of thinking about, "Okay, let's think about some of the problems," because it's not actually a new idea. was actually a pneumatic, very short, short distance railway kind of subway system actually in London there for a little while. And there was one in the US as well back in the 19th century. It's actually not a new idea. Mind you, not very fast and not very far. But anyway, it's not a new idea exactly. But anyway, so if we think it through, right, the pods, you're stuck in a steel tube and It's got to be a strong steel tube, which means no windows. So, no windows on your pod, no windows in the tunnel you're in. So, you'd be in a cylinder, a steel cylinder. So, you're not going to see much. Now, you'd be subjected inside that cylinder to a, I would say, not insignificant amount of noise and vibration, because that high speed airflow that's going around the pod and the air compressor and the inlet fan, that's going to be going to create some vibration and some noise, even in a partial vacuum, you know. So that's going to be interesting. So how you deal with evacuations, that's going to be a little bit problematic because you'd need to build emergency escape hatches and along the length of the tube every so many hundred feet or whatever. And every single connection, every one of them, every hatch, every join in those tubes needs to be very well sealed. Otherwise, give vacuum, partial vacuum is not going to last. It'll just leak like a sieve. Because I kind of thought about it. It's kind of like a jumping castle in reverse. So, in a jumping castle, we gave up on the idea that you could seal every hole or every seam against every potential like little leak. If you accept it's always going to leak no matter what you do, you just continuously pump new air into the jumping castle to keep it inflated. When someone jumps on it, you might get a rush of air leak out of it because of the extra pressure, but generally speaking, have you seen a jumping castle when it gets wet like in the rain? Have you ever seen that, all the little air bubbles coming up? Yes. Yes. So these things are always leaking because it's really really hard to keep them fully sealed So Hyperloop I figure would sort of be that same problem in reverse, which is you'd need to have dozens and dozens of air removal or extraction fans to try and keep that near vacuum maintained because if you didn't eventually air from the outside would would be drawn into the tube and you would just get a lot of air in there a lot Of friction and it would just negate the whole value of it And I also think that given the distributed nature of the pipe work, it's a huge volume. You've got to evacuate all of the time of air. So, you're going to need a lot of these extraction fans across the entire length of it. Yeah. So, that's potentially problematic because all of those will need power and so on. Anyway, so ignoring those common issues of a mechanical failure, right. So, you know, the most likely failure of a pod would basically be rapid deceleration. If the tube was broken or kinked or bent or damaged, there's no derailment 'cause there's no rails. But if you do have a rapid deceleration, which you could get on a high-speed rail, high-speed train if it went off the tracks, I suppose, and hit something, I guess that's a positive 'cause it can't go off rails, but still. So if it does actually get stuck or the pod gets damaged, what would happen if there's a depressurization of the pod? Because if you think about it, outside the steel tube is atmospheric pressure. Inside the tube is a vacuum, but inside the pod is atmospheric pressure. So if you actually got a leak in the pod and the pods inside the tube, then the pod would want to- You're going to have an experience like if your shuttle, Your space shuttle sprung a leak, aren't you? Yeah, exactly. So, if it lost its air supply, you're stuck in a steel tube without a breathable atmosphere. And the pressure of the design was one millibar, which is 100 pascals of pressure. That's nothing, because standard atmospheric is 101.325 kilopascals, which is a thousand and thirteen millibars, right? Yeah. And a person can survive, a human being can survive down as low as 61.8 millibars, which is 6.18 kilopascals. So that's like 6,180 pascals. And this is only 100 pascals. So there's no way a human could survive because at that level, the water in your blood starts to boil. Yeah. That's generally considered to be bad, painful, bad and lethal as well. So all three. And that limits... You just recently told me about that low boiling point. Cool. The funny thing is it's actually called the Armstrong limit. And for the longest time, I thought that was named after Neil Armstrong because like he had something to do with space and walking on the moon and stuff, depending on who you speak to. But the point is, it actually wasn't. It was named after Harry George Armstrong. Whoa, whoa, whoa, whoa, wait, wait, wait, wait, wait. Go back, go back. Depending on who you speak to. There are certain people. You're not one of those, are you? one of those what crazy people that say we didn't go to the moon. Hell, we went to the moon, man. I love the photos of that lunar reconnaissance orbiter with I think it was a lunar reconnaissance orbiter. And they took photos, high risk photos of the surface. And it's like. I will allow this to continue. Oh, did we go to the moon? Yes or no? Come on. I believe we did. Yes, same here. So this is the thing. But it's like you could see the tracks from the rovers that they, that the different landing sites had made. Yeah. And you could see the rover and you could see the flag just. And it's like all of the conspiracy theorists is like, oh, no, they faked that. I'm like, oh, man. Yeah. Yeah. The world isn't real. We're on the matrix anyway. So. Well, I just, if it had been a hoax and it was fake, I just don't think they could have really, truly kept it secret all this time. I guess obviously with lots of people out there that don't believe it and speculate and postulate that we didn't, then there's definitely some doubt about it, but it just seems like we'd have some concrete evidence by now if it had been faked. Some incontrovertible evidence that would prove it had been faked. I think the truth of it is that when it comes to faking stuff, people are really bad at it. Yeah. - And they do a lot faster. - Well, and in this day and age, you plain and simply couldn't fake it. - No, no, you just, you couldn't. But anyway, so not wishing to debate that exactly, but in any case, good old Armstrong limit, okay? So this is the problem, and it was discovered in the early days of the space program, right? So bottom line, if a human was exposed to the pressure inside a hyperloop tube without the pod to protect them, they die pretty quickly, you know, and pretty convincingly. So if there was a deep depressurization of the pod, you'd need to stop it, isolate the section of the tube that it was in, open an inward kind of airlock thing, like not like a blowout valve, but a blow in valve, I guess, to let air in from the outside into that section of the tube. And you'd have to do it really, really, really, really quickly. Otherwise you'd have quite a few, you'd have multiple fatalities. That's not so good. Anyway. So, it gets better. So, where do you put the tubes then? You've got a couple of options really. Well, I got three options above the ground, below the ground or along the ground. So, if you go along the ground. - In the ground seems safest to me. - Yeah, and that is actually one of the things we'll get to in a second actually. But going along the ground doesn't make the construction costs much different from roads, except you technically wouldn't need to make them as wide, but you know, or railway trot line, I guess. But you've got to deal with cuttings. So, I've got to cut into the ground and, you know, try and keep it level. But anyway, so that wasn't originally Musk's suggestion. He originally envisaged an elevated tube above the ground on pylons. But the problem with that is that elevated tubes are still expensive. And when the analysts first looked into it, they compared it and they said, well, elevated roads and elevated railways are more expensive than those along the ground. Therefore, so too would an elevated tube. But I think that's what it seems like kind of a vulnerable position for such a volatile system, too. Yeah, that's also true. But I also think on the costing side of things, I don't necessarily agree with the analysis originally, because these steel tubes should not be as heavy as a rail line with all of the sleepers and the ballast and, you know, all the concrete and so on. So I think, yeah, maybe it's not quite, you wouldn't need as big pylons and it'd be as strong pylons. I would think you could probably save a bit of money there on foundations and stuff. But irrespective, I think probably under the ground is more what they had in mind. And yeah. So with that in mind, if Hyperloop was going to go under the ground, there is one problem, and that is tunnelling is really expensive and it's really slow. And that brings us to Elon Musk's next little venture, which is really boring. So, before we do talk about that though, I just want to talk a little bit about our response for this episode, and that's ManyTricks. And they're makers of helpful apps for the Mac. Who can do, you guessed it, many tricks. And their apps include Butler, Kimo, Leech, Desktop Curtain, TimeSync, Moom, Name Mangler, Resolutionator, and Witch. And there's a lot to talk about for each app, so we're going to touch on the highlights for five of them. Witch, you should think about Witch as a supercharger for your command tab app switcher. If you've got three or four documents open at once in any one app, then Wiches beautifully simple pop-up quickly lets you pick exactly the one you're looking for. It was recently updated so you can now also switch between tabs as well as apps as well as app windows with horizontal, vertical or menu bar switching panels, text-based search for switching between windows and much much more. Name Mangler. Now let's say you've got a whole bunch of files you want to rename them quickly, efficiently in a really big numbers. 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Resolutionator is so simple, it's a drop down menu from the menu bar and you can change the resolution of whatever display you like that's currently connected to your Mac. The best part though, you can even set your resolution to fit more pixels than are actually physically there and that's very handy when you're stuck on your laptop and you need more screen real estate. And that's just 5 of their great apps. And that's only half of them, all these apps have free trials that you can download from many tricks all one word dot com slash pragmatic and you can easily try them out before you buy them. They're all available from their website or through the Mac App Store if you prefer to buy your apps that way. However if you visit that URL you can take advantage of a special discount off their very helpful apps exclusively for Engineered Network listeners. Simply use the code pragmatic17 that's pragmatic the word and one seven the numbers in the discount code box in the shopping and you'll receive 25% off. Now this offer is only available to Engineered Network listeners for a limited time. So take advantage of it while you can. Thank you to ManyTricks for sponsoring the Engineered Network. So I said the next bit was gonna be a bit boring, Vic. - Uh-huh. - Do you get what I mean yet? - I think maybe. - Tunnel boring machines. - Mm-hmm. - Oh yeah. Now this is one of the things that I love. - Who doesn't love to drill a good hole? Damn straight, man. Get out of shovel, let's get cracking. I mean, the thing is, I love this about Elon Musk, right? And I also think it's scary at the same time. It's a little bit millionaire syndrome, where like where every random thought becomes something they sink millions of dollars into just 'cause they can. And here we go. So, stuck in traffic, this is the what happened literally. In LA one day, an annoyed Elon Musk sent the following tweets. "Traffic is driving me nuts. I am going to build a tunnel boring machine and just start digging. Now, I'm assuming he wasn't driving at this point because that tweet went out at 11.05pm on the 17th of December. Yeah. He then- This is 2016. This is literally only five, six months ago. He then follows it up about an hour and 10 minutes later, and he says, yeah, it shall be called The Boring Company. And I'm like, I love this guy. And then of course, he's got the budget to make this happen. Yes, he does. So a few more hours later, 2/17, he says, I am actually going to do this. So those were the three tweets that were the beginning of the boring company, which is just like I'm flabbergasted, right? It's like that's the stream of consciousness that comes out of Elon Musk's brain. And he's like, you know what, I'm a bit pissed with traffic. Let's just start a company to build tunnels. Why not? So. As you do. As you do, right? Yes, of course you do. So, in February this year, the Boring Company had been formed and they actually began digging out the back of the SpaceX offices in Los Angeles Because they could without a permit. Do you really need a better reason? Apparently not. So, they started with a nine metre wide by 15 metre long by four and a half metre deep testing trench. And then by April, they bought a second hand tunnel boring machine so they could study the dynamics of how TBMs worked. Oh, man. So, they intend to build a new class of tunnel. By that, I just mean it's a tunnel, but it's different dimensions and it's smaller. And the idea goes that if you make it smaller, then it's quicker to drill it, which is obvious, and therefore, it'll be cheaper to cut through the ground, which may or may not be true. But we'll just run with that for the minute. Now, I watched the TED talk that Musk was interviewed. It wasn't more of a talk as much as it was an interview. And that was in April. And it was a great watch. The link in the show notes, really, really good. And you can also get through the TED Talk app, which I've also got some really good stuff in there. There's a lot of dribble in there too, but there's some good stuff. You know, filter out the dribble. Anyway, and in April, he said that current road tunnels were required by legislation in America, at least, to be between 26 to 28 feet, which is eight and a half metres in diameter. And that's pretty reasonable. But the reason for that is because you need to have emergency response. You want to have more than one lane. And he also said you needed ventilation for combustion engine vehicles. I like to think you need ventilation for the humans so they don't suffocate too. Just a thought. Anyway, you know. It's just a detail. Minor detail. That's it. Anyhow, he then went on to say that the boring company were instead looking to build a 12 foot or three and a half metre diameter tunnel instead. So, that's not that big, you know. Yeah. So, if you halve the diameter, and this is the rough back of the napkin calculations that he's doing during the TED talk. So, halve the diameter leads to a quarter of the cross section that you have to cut through. roughly correct. So good enough, which therefore means you should be able to cut four times faster. Well, that assumes that your cutting rate is linear, which it isn't, but it's probably close enough. So let's say maybe about four, maybe it's only three and a half times. It all depends. It depends on a lot of things, right? It depends on the kind of material you're cutting through. It also, there's the assumption that the material you cut through is consistent from the top to the bottom of the cutting face. So in any case, so another assumption, but that's okay. He then goes on about loading concrete segments behind the TBM to reinforce the tunnel wall. And he said that he, you could do that more efficiently, um, and increase this by a factor of two. I don't know about that one. That's an interesting one. So, um, how much do you actually, how much do do you know about TBMs, Vic? - Not much. - Okay, well, the basic concept is you have, in the front of it, you have a round wheel that's called the cutting head. And then behind that, connecting that on, you've got a series of hydraulic rams. And then behind that, you've got basically a casing section that expands and essentially is your anchor or gripping point on the tunnel, on the tunnel itself, the tunnel wall. So behind that, you then have the car and the car itself is just like a long chain of rooms that's really got like electrical switch room, your motors, gearboxes, all that other rubbish. And then behind that, you will have your reinforcing handling section and then you've got your trailing cables and your trailing cables go back to give you your electricity Because it's all electric. Well, these days it is, 'cause it's too dangerous to run the diesel. It's much cleaner to run it on electric. And the basic idea is that, so the car moves forward and stops in position where the hydraulic rams are fully retracted. It then puts, then the hydraulics then drive the grips out onto the actual outside wall of the tunnel. And then they start the cutting head turning, and then they start very, very slowly driving that cutting head into the rock and dirt. And inside the cutting head, there's several flutes and the flutes basically direct all of that rubble down towards a central chute. And that central chute goes onto a conveyor, conveyor goes down through the car, out the back and out to the surface where the rubble is stockpiled or carried away by trucks. - So I saw a documentary about them building a big tunnel somewhere I think in Europe. Yeah. TBMs are really, really cool and I had the great fortune to work on a tunnel here in Brisbane about a decade ago. At the time it was called the North-South Bypass Tunnel but it was renamed the Clem 7 and this particular tunnel was 4.6km long and it goes down under the Brisbane River. There were two tunnels and two TBMs, northbound and southbound lanes. It was quite an education going through there because you basically go through all the mining regulations when you're building them. You got to have all the usual things, like you got to have self-contained breathing apparatus training. There's these mining rescue rooms, all sorts of stuff you got to go. Ventilation is everything. The stuff that they do in there because of tunnel construction is quite amazing really because they've got to extend the conveyor belt to take out all the rubble and they also have to have a supply chain of trucks feeding in all the concrete segments that they put in place after the tunnel is built to shore up the walls. So that's what he was talking about when he was saying, "Oh yeah, well you can get these concrete sections that reinforce the tunnel wall and he reckons he could cut that by a factor of two. I suppose what he might have been referring to is the fact that those concrete segments usually come in quarters or halves and the quarters are going to be obviously as heavy as like the size of the wall they're trying to reinforce. So, if it's a smaller wall area then it's going to be lighter and then maybe that means you can move them around more nimbly and that'll reduce the amount of time it takes to fill. fit them that could be what he meant it's also if you have less arc then I suppose the concrete itself would be thinner so anyway bottom line is factor two I think is a bit presumptuous but hey you know let's run with it he also claimed you could run TBMs harder than they already are I have no idea if that actually makes any sense but that's what he said anyway so he'll find out yeah I I guess so. But the funny thing is he compared the speed of tunnelling to how fast a snail moves. Yeah. Have you ever seen SpongeBob SquarePants? Very few times. I don't know that I've ever seen an entire episode. So, there's a pet snail called Gary, right? Okay. Okay. And what they've got is they've got a pet snail. They've got a pet snail where they've dug the hole and they've called him Gary, and their goal is to make a TBM that can go faster than Gary, because right now TBMs, the fastest TBM in the world, is 14 times slower than Gary. Okay. I love this guy. Anyway, so. So, so let me, let me, let me make sure I understand this correctly. Yeah. Is, is Spongebob they want to build the tunnel faster than Gary or is Elon Musk actually competing with Gary? Um, Elon Musk and his tunnel boring machine are trying to compete with a fictional character. Yes. Okay. It makes sense. Okay. Yeah. Anyway. Sure. Yeah, of course. I mean, why not, right? As you do. Who doesn't love a good eccentric billionaire? Damn straight, man. Damn straight. So anyway, bring on the Elon. Okay, so the goal, I think, is to then use these tunnels that they would build with the smaller diameter tubes for two kinds of transportation. The first one would be a dedicated mass transit car of sorts. They only really just revealed this last week or week before that. and it's kind of like a bus but it's not a bus and it's kind of like a tram but it's not a tram and it's all just very yeah okay you can't tell much from the renders other than it's they're thinking just yeah okay whatever i don't know how else to describe it think of it like a rectangular room with a couple of little knobby wheel things on the bottom and it goes into the tube and away it goes and it's like all right interesting but the one that he actually talked about in the ted talk wasn't that. He said, I was still working on it. They need to work on it some more. But anyway, the idea is that they have a sled and you drive a normal car onto the sled and the sled latches onto the vehicle. And rather than the vehicle propelling itself through the tunnel, the sled takes the car on a ride through the tunnel. So, the sled does all the work. It does the propulsion. And that way you don't have any issues regarding how fast a car is capable of going. So, yeah, and the idea was he said about 125 miles per hour or 200 kilometers an hour because obviously you're only restricted by the speed of the sled and the amount of air pressure in the tunnel that you're trying to overcome as opposed to the ability of the vehicle that it's carrying. It's an interesting idea but then of course it comes back to Hyperloop. You could also use the tunnels for Hyperloop because the tunnels could be operated in a partial vacuum because if you build a tunnel to survive the water table, you can build a tunnel to survive a partial vacuum because the amount of pressure from a partial vacuum is in fact less than that that's required to survive the water pressure from the water table. Yeah. Yeah. So all of that kind of makes sense and you can see how Hyperloop can fit together with the whole tunnel boring thing. And I actually, yeah, Before I get to my opinion on that though, I want to talk a little bit about the sled idea which is the one he went on about the TED talk. Now, if you take a car and let's just take a Tesla Model S, right, because well, that's Alan's car. Anyway, it's about 2 meters wide, it's quite a wide car, 5 meters long, 1.5 meters high and that puts about a gap of about 75 centimeters or 30 inches on each side of the vehicle to of the tunnel wall, but if you assume that you lose nine or 10 centimeters on each side of the sled, because you've got to have the car encapsulated within the sled, you've got wing mirrors, you've got to make sure that it's capable of fitting different width vehicles. Assume you're going to have a couple of guardrails on the side to prevent people from opening their doors accidentally during high speed travel, a whole bunch of other safety things and such. You're probably going to lose a bit of clearance there. So, I'd say you're probably looking at about 55 centimetres. That's about 21 inches on each side. So, about two feet max, you know, maximum. Yeah. However, you've got to then take into account wall curvature and you really actually, if you take that wall curvature out, then it's less than that again. So, maybe 18 inches. It's like- It's a tight squeeze. Yeah. So, you really don't have that much space to walk up and down as an escape route. So, the other thing is with tunnels is that TBMs make tunnels that are round because, well, they just do. If anyone can come up with a square cutting head, let me know. But anyway, so these tunnels, they typically will have a culvert in the bottom, which is, you know, basically just like they'll flatten the bottom and create a space underneath that flat spot. They'll do the same at the top sometimes and they'll have that for like smoke extraction. So you imagine your round circle and it's sort of like clipped with a flat spot on the top and a flat spot on the bottom and your car sits in the middle on a sled you got a bit of space either side with a slightly curved wall and that would be the design but the idea is that the the culvert at the bottom you could put cabling, you could put the sled or guide system for the sled, whatever it might be, the acceleration technology, whatever it might be, if it's cable, if it's maglev or magnetic or whatever the hell it is, right? I vote for the maglev. Everyone wants the maglev. Anyway, so yes, I totally want one. Anyway, so the thing is he did say, Musk also said that you needed to extract the exhaust from combustion engine vehicles. But obviously you still got to evacuate people, you've got to evacuate smoke in the case of fires, and even in the case of a normal vehicle, you still need it, the car, people in the car to be able to breathe air. So by cutting the size of that tunnel down, you don't eliminate the requirement for having airflow. You might reduce some of it, but unless you're going to restrict those tunnels to being used by by electric vehicles only that don't create exhaust, which that could be an option, maybe that'll be the rule. But if you're gonna have combustion engine cars in there, you would have to tell them to turn their engines off while they're on the sled, so they didn't produce exhaust. 'Cause you've cut back the amount of ventilation you've got. So I don't know, that one's a bit iffy. You'd need to think that one through and how you would enforce that if you were gonna let combustion vehicles in there. Anyway. So the other thing is when tunnels for vehicles are built these days, typically why have one when you can have two twice the price? So what they'll do, government. (laughs) Government spending, right? Hey, do you know what movie I pulled that one out of? - I do not. - I was out of contact. 'Cause anyway, nevermind. So yeah, why have two when you have two twice the price? So they typically will dig two tunnels, next to each other. And in the case of the North-South Bypass Tunnel, one was the Northbound Tunnel, one was the Southbound Tunnel. And each of the tunnels are built as a parallel pair, and you have a cut-through between the tunnels every however many hundreds of feet. And they have these machines called a roadheader. And the roadheader is kind of like, I don't know how to describe it, it's got one or two or three spinning knuckles on the end of an extendable arm, kind of like a crane but more maneuverable and it basically just punches into the dirt and rock wall and just pulverizes it and gouges holes in it. So they'll use a road header to dig these between them and then they'll do quick set shotcrete or whatever onto it and that'll basically solidify and hey presto you've got an emergency escape now so you can now go from the northbound to the southbound tunnel via these emergency exit ways. In some cases they will actually have a mini boring machine that runs a third tunnel between the two major road tunnels as an escape route. So the other option might of course be that if you know Musk has a bunch of these tunnel boring machines maybe the answer is we're not allowing for too much pedestrian access because you only need to get to the escape tunnel and they'll just bore two or three or four tunnels next to each other. So maybe that's maybe that's their intention. I don't know. But all I do know is that I think it's sort of conflating when he said, "Oh, yeah, you don't have to ... You got to have all this extra room for escape, emergency vehicle access and all this other stuff." I'm like, "Well, I'm not sure that making the tunnel smaller is really the right solution because you're going to end up building more tunnels in parallel at the same time." So I'm not sure it's a net win. Yeah. But anyway. It might be more efficient to just build one larger tunnel. Well, maybe that's the point. Right. No, I'm not sold on that. Anyway, it certainly should be quicker to go with multiple tunnels in parallel, but in a sense, is that the right answer? Is that cheating? I'm not sure, but anyway. Bottom line though, with the size of these tunnels, there's no way you can fit two vehicles in the same tunnel side by side. They're just too small. So it's one vehicle, which means there's no bidirectional tunnels. There's no overtaking, no bypass line for your sleds. If you, you know, so when you get on, it's like, how do you get on? How do you get off? It has to, almost has to be point to point. So it's not like you can have like a network that you can switch between. It's like, you gotta pick this tunnel to go from point A to point B and you just can't go off anywhere else in between. Things get complicated if you wanna do that. Anyway, other problems are the side rails for the safety for the doors. And you don't want people opening doors when they're moving. How do you enforce that? anyway. But they also, if you did have restraints like that around the vehicle to keep the vehicle in place, they have to be retractable so that people can open the doors if they do need to escape if there's an issue. So, you know, other than that, it's like climb out the window. I don't know. Yeah, that's a problem. Yeah. So I've talked about banning combustion engines. The sleds would need to be maintained and flexible for the different lengths of different So the vehicles are, you know, like a Hummer might be quite longer. Maybe they won't. Yeah. Maybe stretch limos are out probably, but that's probably not a big problem unless you're in Los Angeles anyway. Then there's the loading mechanism. And that's the other thing I thought was really bizarre. They had this demo. It's like it was a render, you know, 3D rendered video kind of thing, you know, like computer CGI. And it showed a car driving onto a platform that looked like it was a car park on the side of the road. So literally a car space. And you drive onto this thing and then it would sink majestically into the ground and disappear from view. And I'm like, that's really dangerous. Like everyone in the audience is probably thinking, oh, that's so cool. And all I'm thinking is the engineer in me, that is so dangerous because- That's not what I was expecting. I was expecting you to describe something kind of like a ferry loading ramp or something. Well, that would actually make more sense and be safer, because if it's a hole in the ground, what's going to stop people from falling in when the elevator is going down. Yeah. What happens when some idiot drives onto it with a car that's too big and the elevator goes down and the car's beached? What happens if the car's too far to the front or the back and it gets stuck? Car elevators aren't popular for a very good reason because they tend to get stuck. I mean, there's a simplicity to having a whole... Some bonehead forgets to put his car in park. Exactly. I like the simplicity of a hole in the ground and a road that slopes slowly down into that hole. You can fence the sides, you can fence the top, there's no moving parts and there's nothing that can break. And it's like, if the car gets stuck in a small tunnel, how do you get the car out? Like, imagine the sleds halfway along the tunnel. How do you get the car out? You can get the people out through a parallel tunnel, but how are you going to get the car out? That's a good question. So, I've talked about clean air and the thing with tunnels is tunnels, tunnels don't have clean air in them. You get free clean air. Well, at least for the moment you do, it's not taxed. I'm waiting for that at some point in the future. But anyhow, like in Druidia. Anyway. But seriously, though, like you're walking around the street, you drive around the street, you haven't got a problem with ventilation, right. You're out in the open air, there's not a problem. As soon as you dig a tunnel, there is a risk of engulfment, the risk of collapse, there's increased risk of fire. And you've got the issue of clean air because it's confined space. So, anyway, digging a network of underground tunnels from a greenfield point of view, like as in there's no tunnels there yet, there's nothing under there yet, it's a walk in the park, no problem. But once you've done it and it's locked in place and built, it's really hard to modify it. See, because you can widen roads, but you can't easily widen tunnels. Because, I mean, think about it, you've got to take away your tunnel reinforcing. What are you going to do? Like, point the tunnel, the bigger tunnel boring machine in the same hole? No, you're not. You can't cross the tunnel without destroying the tunnel. You can't get too close to the sides of an existing tunnel or it might collapse. So what are you going to do? No, you really got to think that through ahead of time. Yeah, you do. And of course, they won't because town planners are still town planners and it's hard to get it right because you can't tell the future. You don't know what you're going to want to do in 50 or 100 years. You can guess, but you won't always get it right. In fact, I pretty much guarantee you'll never get it all right. So anyway, the only advantage I can think of is the one that he actually did cite in there, which is basically, you can build in three dimensions without any trouble. You don't need to worry about pylons and anything else. You're not restricted to two dimensions like you are the road on the surface. But that's pretty much it. And the more I think about it, tunnelling for Hyperloop makes more sense to me than a sled with a car on it that has a bazillion things that could go wrong with it. it, like more wrong with it than Hyperloop. So I don't know. I do think, to be honest, I do think it's actually is a great idea to develop tunneling technology that's faster and more efficient. Absolutely, yes. But I'm not sure at the expense of tunnel size and rescue, rescue ability, I don't know if that's a word, but anyway, being able to rescue people, that's not a compromise you should be making, you know. And having worked in tunnels, like I said, with the North-South Bypass, I mean, when they're being built, they are hot, they're noisy, they're humid, they're dangerous, you know. It's not a pleasant working environment building these things, believe me. And I don't know, and their cost at the moment, I guess, drives down their commonality. So, because they're so expensive, they don't make many of them. It's very much a specialist occupation. Because when I was working on the on the Clem 7 under construction, I was there, there were people from Germany, there were people from the Netherlands, people from Sweden, and you know, they were all tunnellers. They'd done tunnels their entire career. And there's one guy who said, "Oh, this is a baby tunnel." I'm not going to try and do his accent, but Yeah, he said, "This tunnel is a baby tunnel." Oh, hang on, I said I wasn't gonna do his accent. Anyway, so he told me it was a baby tunnel because his record tunnel was like 20 kilometers long and this one was 4.6 kilometers, so this is a baby tunnel. It's always about the size. - I take this tunnel in my sleep. - Always about the size for some people. Anyway, all right. The point is- - I take this tunnel in my sleep. - Well, the funny thing is, I was speaking to another guy who was younger though, he was like late 20s, and we were all getting in the go-karts 'cause they had, you know, like, there were electric go-karts and then there were the work, the gas-powered ones. And 'cause you didn't wanna drive utility vehicles, pickup trucks down there as often as you wanted because of the width constraints. 'Cause when the tunnel's done, you've got the conveyor along the side that conveyor takes up a lot of space. And the right-hand side, so the left-hand side was the conveyor, the right-hand side, you had a whole bunch of electrical wiring and patching and stuff. So the actual culvert, once it went down, you could drive on it, of course, but if you drove a ute down there, it was quite wide as a vehicle and there wasn't very much room. If you had to get a car out in the other direction while the tunnel's under construction, it was really, really narrow and quite dangerous and difficult. So they had a lot of those stop, You know those automatic stop and traffic lights? You know, like the portable ones on the side of the road for roadworks. They had like three or four of these checkpoints in the tunnel, 'cause it was just too narrow. So a lot of people preferred the little worker mule kind of things and little golf carts. So anyway, we got on this golf cart to go down into the tunnel, down towards the TBM, just past the low point. And he was started walking and I sort of said to him, don't you want to take one of these? It's like it's a three kilometre walk. And he said in all the years he'd been building tunnels, he preferred to walk because when you walk, you can see the problems. When you're in a vehicle, you don't see problems as well. So, he said every single- You go by too quick. Sorry? Because you go by too quick. Yeah, exactly. And you're not going fast. The speed limit's 10 kilometres an hour. So, what's that? Seven miles an hour. Yeah, but it's still, you really, you can stop and look around when you're walking. Yeah, exactly. And that was his point. So, every single day he walked the tunnel twice. And I said, when it gets closer to being done, that's a long walk. He said, no, not well. So, anyway, so building tunnels, I think the more they make, the numbers are going to push up the exposure to the risk because digging tunnels is dangerous And you can dig through pretty much anything, but you can't dig through everything and expect a clean result. You know what I mean? Like digging through a layer of soft peat and mud and slush is a very different proposition to drilling, trying to drill through bedrock or trying to drill through a layer of chalk. Yeah, rather famously, I think the channel, so the channel tunnel between the United Kingdom and France, they actually very specifically drilled through the chalk layer. And the chalk layer went all over the place. It went up and down and up and down, you know, just it's like geological fault lines or something. Electrical engineer, not geologist, but anyway, the liney bits of the chalk under the ground, them bits. They followed them bits. And they did that because it was so much faster to drill and tunnel through chalk than it was to try and go through anything harder, you know, like granite or basalt or God knows what else, right. So, you can't just- It's easy to say, yeah, you can drill in three dimensions. Well, yeah, you can and no, you can't. Yeah. And there are many, many cases where these TBMs get stuck and they got to back them up and do micro blasting around the hard boulders in order to break them up so the TBM can get through. You know, it's not all plain sailing. So I do think that the more that they drill, if they do pull this off and they do come up with a high speed, small diameter TBM, I think the problem's gonna then become a lot about how accurately you can point them, how well you can plan them, and during construction, how much more exposure, if you've got hundreds of these going off at once, how many more injuries and fatalities are they going to be telling through stuff that they shouldn't? Because once you can go faster, people deploy faster and then there's a higher exposure to that safety risk. So I guess I'm just not sold on it. I think I'm interested to see what they actually build. I think it's a fascinating idea. I think it's an interesting idea. I also question though, how many people would actually be like to use their sled and trust their vehicle on a sled, you know, in a tunnel, confined space. I don't know. What do you reckon? - I think that there will be people that are skeptical of it. - Yeah. - I think there'll be a lot of people that'll enjoy it though. - Yeah, I don't know. I think there's the novelty and there's the practicality, you know? And I mean, flying cars is just a stupid idea because of all the extra energy that it takes to keep something off of the ground. And in addition, gravity sucks or more accurately attracts. But anyway. And that's a problem, right? So, if you're on ground level, you can't fall. If you're in the air and you're above the ground, you can fall. Well, that's not entirely accurate, but. - Well, you can fall just not as far. - Yeah. - But you know, although some of those overpasses, geez, like that Dallas five ways thing, yikes, that's high. But anyway, generally speaking, you're on the ground, you can't fall far. But you know, with tunnels, you can't fall for the same rationale, but you can work in three dimensions. But the other problem is the opposite, which is how do you get up to the surface in an emergency? If you're on the surface, you're already there, no problem. So I don't know, I guess I'm just not sold on it. I think it's a fascinating idea. I also think it's kind of crazy, the fact that Elon Musk just has this random thought how he's pissed off about traffic one day, and then he tweets he's gonna start a company to solve the drilling problem, and then he does. And now they bought a TBM and they're playing with it, and that's like, okay. - As you do. - As you do when you're rich, I guess, but I don't know. from a pragmatic point of view, I think that tunnels aren't the answer. And I don't think they're the best answer either. I think that tunnels have got a lot of compromises and. And I love the name of the company, the Boring Company, that's so funny. It's not boring at all. It's absolutely fascinating. But whether or not it actually helps a hell of a lot or whether or not it's just a very small slither of a piece of the puzzle. Well, I guess we'll see. But anyway. Alrighty. Well, if you'd like to... If you want to talk more about this, you can reach me on mastodon@[email protected] or you can follow engineered_net on Twitter to see announcements about all the shows on the Engineered Network and you can find that at Causality has really taken off recently. It's a solo podcast that I do that looks at cause and effect of major events and disasters in history. So if you're a fan of this show, you might like it too, so be sure to check that out. If you'd like to get in touch with Vic, what's the best way for them to get in touch with you, mate? - They can find me on Twitter @vighudson1. - Awesome, that's the way. And if you'd like to send any feedback about the show or the network, please use the feedback form on the website. That's on the little email icon, the letter icon. That's if you're ever wondering what that is, that's what that is. And that's where you'll also find show notes for this episode. This episode was also brought to you by Many Tricks, and I'd like to thank them for sponsoring the Engineered Network. If you're looking for some Mac software that can do many tricks, remember, specifically visit this URL, manytricks,, for more information about their amazingly useful apps. They're awesome, make sure you check them out. Now, if you're enjoying Pragmatic and you wanna support the show, you can. Like some of our backers, Ivan, Daniel Dudley, and Chris Stone. They and many others are patrons of the show via Patreon, and you can find that at, all one word. So if you'd like to contribute something, anything at all, whatever you like, it's all very much appreciated. So a special thank you to our patrons, a big thank you to everyone for listening, and as always, thank you, Vic. Thank you for having me, Chuck. Anytime. Now let's start digging. 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Vic Hudson

Vic Hudson

Vic is the host of the App Story Podcast and is the developer behind Money Pilot for iOS.

John Chidgey

John Chidgey

John is an Electrical, Instrumentation and Control Systems Engineer, software developer, podcaster, vocal actor and runs TechDistortion and the Engineered Network. John is a Chartered Professional Engineer in both Electrical Engineering and Information, Telecommunications and Electronics Engineering (ITEE) and a semi-regular conference speaker.

John has produced and appeared on many podcasts including Pragmatic and Causality and is available for hire for Vocal Acting or advertising. He has experience and interest in HMI Design, Alarm Management, Cyber-security and Root Cause Analysis.

You can find him on the Fediverse and on Twitter.