Welcome to tech Stuff, a production from iHeartRadio. Hey there, and welcome to tech Stuff. I'm your host, Jonathan Strickland. I'm an executive producer with iHeart Podcasts and how the tech are you? So y'all already know what this episode is about, because it's right there in the title for the episode. The title itself is a reference to a nineteen ninety five Jackie Chan film called Rumble in the Bronx. So in the climax of that film spoiler alert, there's a scene in which a hovercraft goes absolutely ape through the city. It crashes into cars, it absolutely destroys Lamborghini, and it interrupts a rock band that's playing outside on the street. And it's at this point in the film where the drummer of the rock band stops playing mid song, stands up, points and yells hover aft, which is my favorite part of the whole movie, even with all the amazing fight sequences taken into account. And this is the sort of stuff that inspires tech Stuff episodes, because that's how my brain works now anyway, Yeah, Jackie Chan films from the nineties really a source of inspiration. So I thought it would be fun to do an episode tracing the history of hovercraft and to talk a little bit about how they actually work. And I also think this is the type of topic where you have one concept in your head when you first hear about it, Like when you first hear the word hovercraft, you might have a vision in your head of what that might be, and then ultimately you could be disappointed when you see it in the real world. That was my reaction anyway, because as a kid, when I heard the word hovercraft, I thought of some sort of semi magical vehicle that could levitate above the ground, probably something closer to what drones are, but without the rotors, right, Like there's some unseen force that makes the thing floatt. So I was kind of thinking of something similar to like the hover boards that are featured in the documentary Back to the Future too, But of course that's not how your typical hovercraft works. Hovercraft, by the way, are also called air cushion vehicles, and that air cushion gives a huge indication of how these things work. And arguably my whole perception or misperception of hovercraft isn't really fair. I mean, it's not the hovercraft's fault that I had an overactive imagination and unrealistic expectations. It is a fascinating invention, and it traces its history really back to the nineteenth century, when you had people sort of theorizing about it, but effectively for talking about making something that actually works. It's more like the middle of the last century. And I was born in the last century, and saying that way hurts a little bit. But the inventor of the hovercraft, the person that we credit as the inventor, so so I guess you could say sort of inventor of the hovercraft was a gentleman by the name of Christopher Sidney Cockrell. Now I say sort of because, as we will find out later in this episode, there was another person who came up with the same concept a decade earlier, but due to a technicality, this person had no ownership of this idea. But we'll get back to why that happened. So Cockrell's parents were both distinguished members of English society. His mother was Florence Kingsford cockerl. She was known for her artistic talents in calligraphy, illumination, illustration, and costuming. When I say illumination, I mean manuscript illumination, think of the stuff that monks used to do back in the Middle Ages. So way back in my college days, I focused my studies in medieval literature and medieval history, and after looking at Florence's work, I'm really amazed at how her evokes those ancient texts. Cockrell's father was Sir Sidney Cockrell, who came from a coal mining family. Like it astonishes me. He came from a family that worked coal mines, but he found himself thrust into the social circles of influential people who were in the artistic and literature worlds in England. So Old sid served as a personal secretary to British author and artist William Morris, and Sydney eventually became the director of the Fitzwilliam Museum in Cambridge, England, where he had a bit of a reputation for having an incredibly effective method to convince hoity toity rich people to hand over some of their filthy lucre to support the museum. So Christopher Cockrell came from, if not blue blood, at least light blue blood Lemmelson Mit, which bills itself as the quote national leader in advancing in vention education in The quote says that Sidney Cockroll wasn't entirely sold on the idea of his son going into engineering, but that's exactly what young Christopher Cockroll wanted to do. And I find this notion rather like a money python sketch, because you have a man who comes from a coal mining family. He's defied the odds, he's become a director of a prestigious museum, and now he is concerned that his son wants to be an engineer. In fact, there is a money python sketch in which you have a family of It sounds like lower class English folk who are authors, who are a shame that their son wants to go into being a coal miner, flipping the old narrative on its head. So this is reminding me of that fictional sketch, you know, very silly stuff. But yeah, he didn't want Christopher to become an engineer. But whether he had reservations or not, ultimately Sydney agreed to support his son's pursuit of an education in engineering. In fact, according to the Guardian, Sydney offered Christopher the princely sum of ten pounds for every patent his boy would receive. This was back when old Chris was still a teenager. Sidney would call an end to that deal later on because it would get pretty deep, deep, pretty expensive. Christopher attended Petterhouse College at Cambridge University. In his obituary Cockrell passed away in nineteen ninety nine, by the way, in his obituary in The Guardian, Christopher Cockrell was said to have spent much of his spare time in college quote taking motorcycles to pieces or racing them end quote, and that this gave him the experience of practical background in basic mechanics and engineering, which is kind of cool, like the idea of learning by doing something you're already interested in. So that was already neat of course. Christopher by this point, by the time he was going to university, had already expressed a deep interest in engineering. Upon graduation, Christopher Cockerrell took a position with the Radio Research Company. This was in nineteen thirty five, so still relatively early in the days of radio. I mean radio had been around for a while, but still a fairly young science. And he joined the Marconi Wireless Telegraph Company and worked in an R and D department that largely focused on radar and he made numerous contributions to radio and radar technology. Many of those contributions were put to use by Allied forces during World War Two. Now, Christopher Cockrell made a career change in nineteen fifty, so the war hit was over. He continued to work in radio for a few years, but in nineteen fifty his father in law had left his wife a big sum of money, and together Christopher and his wife decided that they wanted to purchase a boat business in Norfolk, England, and Cockroll devoted his attention to managing this boat business. And it was to shift when I was reading up on his life that this actually gave me a little bit of whiplash, because here's someone who was instrumental in advancing technology and radio and radar, and now he's switching over to manage a boat business. But it was as a manager of this boat company that led him to start thinking about a solution to a really tricky problem and ultimately would lead him to inventing the hovercraft. So Cockrell got to thinking that there must be a way for heavy watercraft to travel much faster across bodies of water, and it would be possible if only you could get the boat out of the water. If you could remove it from contact with the water itself, if the craft could somehow float above the surface of the water, then that would eliminate all the friction that it otherwise would encounter as it moves through the water, and it would be able to move much more quickly than it could otherwise. But you just had to figure out a way to minimize or eliminate contact with the water. And if you could get it to lift up above the surface of the water entirely, technically you actually would have an aircraft, not water craft. But that was his starting point. He thought, how can I create a vessel that would minimize or eliminate contact with the water so that it can move much more quickly and efficiently. So Cockrell imagined a craft with a cushion of air underneath it. That cushion of air would provide a barrier between the vessel itself and the water or land underneath. If you could blow out enough air, it could skim right across the surface, whether it's water, land, or some mixture like mud or swamp or whatever, and it could potentially cut travel times significantly, at least as far as water goes maybe not with land, because as it turns out, if you're going across solid land and you've got yourself a road and you have a wheeled vehicle, you can zip along that pretty darn fast, and it would probably be difficult and very dangerous to operate a hovercraft at those speeds, because you've got to remember, hovercraft typically for propulsion's sake, is using wind power as well. Right, you've got a fan that points backward and you're blowing out airs and you know, obviously equal opposite reaction time. That means you're moving forward as a result with a proportional force, but that doesn't mean that you can easily do things like stop, and that turning is more of a gradual process as well. So moving at high speeds across land where you could occasionally encounter obstacles probably not the best idea. But anyway, in Cockrell's spare time, he started to tinker to see if this idea he had could be made practical. He wondered, first is it plausible and then is it practical? So early on, as a store where he goes, he used some tubes from an old vacuum cleaner as well as the vacuum cleaner's motor, and he used a pair of empty cans. The types of cans, it depends on which version you read. Like some say it was a couple of coffee cans. One was slightly smaller than the other. One was like, no, it's a coffee can, and then a cat food can. Some call them tin cans, some call them aluminum cans. I think what's important to know is he used a pair of cans. One was larger than the other one. He put the smaller one inside the larger one. He blew air so that it would go underneath the smaller one, which was turned face down I imagine, like open side down, and the air would create an air cushion, and the smaller one would end up hovering inside the larger one and just kind of bang around a little bit. So he saw that this was possible. It could create lyft, and that lift could be enough to counteract the weight of the vessel, in this case the little small can. So his concept had validity, and Cockrell got to work building on a prototype, an actual sort of small hovercraft that would be more substantial than just a pair of aluminum cans and some tubes. And it took him a while to build it, but by nineteen fifty five he had a working prototype, and he then had to decide what was he going to do with it. And he could have tried to create like a private business based off this, but the story goes that instead he thought, I'll show local officials, I'll see if I can get some investment in this and turn it into something viable. In that way, I'm not just sinking money into something that may never pan out. So he arranges a demonstration for his hovercraft prototype with some local officials, and the story goes that the local officials were astonished and more than a little frightened as Cockrell's prototype skimmed around inside an office that he had brought it into this office of the the local officials. He had fired up the engine that would drive the fan. So you got to remember, this is an internal combustion engine. It is burning fuel and letting out fumes, and it's very loud, and it's turning this fan, and the fan is making this hovercraft skim above the surface of the ground. And then there's not really a way of steering the hovercraft at this point. It's just showing a proof of concept. It's kind of bumping around like a bumper car all over the office. People are jumping up on chairs and desks and trying to get out of the way. And meanwhile, like I said, it's noisy and it's smelly. It made a real impression and it makes me think of that scene in Rumble in the Bronx where there's just a hovercraft gone wild. So the officials weren't quite ready to devote funding to Cockrell's invention at this point. There was this general perception in the nineteen fifties that England was not really that interested in investing in innovation. There was this perception that England was kind of backward at this point. They were focused more on things like, well, we're doing it this way because that's how we've always done it. Whether that was an accurate representation of what was going on in England, I can't say, but that was the perception. So consequently, the nation was starting to feel like it was falling behind some of the rest of the world. More than that, the officials who saw this demonstration decided, rather than fund Cockrell's idea, they would put it on a so called secret list, which effectively meant they were classifying his invention. They were putting it under classified information, and Cockrell would be legally prohibited from talking about it or finding some other means to fund his work that that would be against the law. Maybe he could find a way to fund it if he could somehow convince people to give him money without actually talking about the invention itself. But really it just meant that the officials were really hamstringing him. Now we're going to take a quick break, and when we come back, we'll talk about what happened next and how Cockroll was able to get some progress despite this initial setback. But first let's take a break to hear from our sponsors. Okay, we're back. So before the break, I talked about how Cockrell does this demonstration. Officials are taken aback and they decide to classify Cockroll's invention, which effectively makes it impossible for him to do any real work on it. This is despite the fact that Cockrell had demonstrated to them that his hovercraft could potentially solve a lot of problems like not only could it glide over water, it could go over land, it could go over lots of icky stuff that other vehicles actually have a lot of trouble with so marshes and muddy sections and stuff. You know, if you had a boat, you wouldn't be able to go through these because there's not enough water to keep the boat floating right. The boat would just get beached or mired. Same with vehicles that are on treads or wheels, they would eventually get stuck in really nasty muddy situations. But the hovercraft would float above all this. It could get you through to places that other vehicles couldn't unless you were using something like say a helicopter or an airplane. So Cockrel was really making a case for how this could be a really useful vehicle for all sorts of different applications, and none of that seemed to really matter to these officials. However, he did receive a patent for his invention in nineteen fifty six because he had filed for this patent before the officials had put the hovercraft on the secret list, so ironically, his invention was already public because patents are public, right, that's one of the elements of patents. When you file for a patent, your description of your invention is made public, but in return, you receive government protection for your idea, at least for a certain amount of time. So this is why we call him the inventor of the hovercraft, because Cockrell actually secured patents relating to his invention, although as I mentioned earlier in this episode, and we'll get back to it, there was someone else who had built something similar a decade before Cockroll did. In nineteen fifty eight, the UK government declassified his work and this gave Cockroll the chance to actually pursue funding. The UK's National Research and Development Agency or NRDA, was really impressed with his invention and they commissioned a company called Saunder's Row to build a test hovercraft based on Cockrell's design. So Sunder's Row was already an established business. It specialized in building boats, and they produced a vehicle that was called the SR in one. SR standing for Saunder's Row, and it was really only big enough to hold its own crew. It wasn't designed for passengers. But here's the thing. It did work, and on July twenty fifth, nineteen fifty nine, Saunder's Road demonstrated its capabilities by having the SR in one cross the English Channel. The hovercraft left Dover in England and landed in Calais in France. Ou La Lain. Cockrell himself was aboard of the hovercraft for this demonstration. According to The Guardian, he served as ballast very dignified. This demonstration convinced UK authorities to invest more heavily into the hovercraft technology, and the NRDA created a company called Hovercraft Development Limited with the purpose of creating hovercraft for commercial purposes such as ferrying cargo and passengers across various rivers and channels like the English Channel. The organization oversaw the work of five different companies that were all dedicated to this purpose, so there was five different boating companies that all began building hovercraft vehicles. Christopher Cockrell landed a gig as the director for Hovercraft Development Limited, and he was also the technical advisor to the company and he stayed on in that capacity until nineteen sixty six. Also in recognition of his contributions, he would ultimately receive a knighthood in nineteen sixty nine, just like his dear old dad. So you had Sir Sidney and now you had Sir Christopher. The first of the passenger hovercraft was the Vickers VA three, which was an experimental vehicle it wasn't meant to be built for full commercial use. It was more like, again a proof of concept. It launched in nineteen sixty two. British United Airways ran the service because again hovercraft were thought of as an aircraft not a boat, right, because these fans would end up creating this air cushion that made the vehicle hover, sometimes several feet above the surface that it traveled across. So as such it was more of an aircraft than a watercraft. So the initial route passed over an estuary between Liverpool and North Wales. The hovercraft would hold up to twenty four passengers per trip, and it was intended to take twelve trips per day. And like I said, this was kind of an experiment. It was a pilot program. And originally the concept was that it would go for fifty nine days and then they would evaluate does this make sense, like can we turn this into a reasonable and viable transportation option. But while it was meant to go for fifty nine days, it only made it to thirty six. The reason for that was not entirely the fault of the actual vehicle, although there were some engine problems that turned out to be a bit of an issue, and in fact that would become a thing for a lot of hovercraft. It's not that the design was bad, it's that sometimes the equipment that was being used wasn't the most reliable. The other issue was that there was a lot of bad weather during that stretch. Now I think that you should just anticipate that, because as far as I'm concerned, bad weather is kind of a constitutional requirement in the UK, at least every time I've been there. So anyway, because of this combination of issues, the experiment was cut short. The VA three would retire as a passenger vehicle, but the British government would continue to use the VA three vessel to conduct some other kinds of tests, including a very extreme one. Namely, the test they wanted to really check out was could a hovercraft pass safely over a zone in the sea that happened to be occupied by marine mines? Right? Like? These are those mines you see? You know, typically I almost only see them in things like cartoons, where it's the giant globe with lots of little pressure sensors on it that are connected by chains and anchor to the seafloor. And the ideas that a boat which will pierce the surface of the water. If it were to make contact with these would cause it to explode. Well, the thought was, well, hovercraft, they don't pierce the surface of the water, they hover above it. So is it possible that a hovercraft could safely glide over an area that is filled with marine mines and not trip them? And they tested it and the VA three done blowed up real good, which answered that question rather definitively. Passenger hovercraft would tackle the English Channels starting in nineteen sixty six, with one of the most famous being a class of hovercraft called the SRN four. Again back to the Saunders Row and this was also known as the mount Batten class of hovercraft, and the very first one that made the trip across the English Channel was called Princess Margaret. This was in nineteen sixty eight. These vessels could make the trip between England and France in about half an hour. Typically we're talking like Dover to Calais, but sometimes a different port in France. But the interesting thing is if you contrast this with the traditional ferries that were making this trip between England and France, that journey would typically take an hour and a half. So three times as long. So the fairies had some advantages, right, You could build a ferry large enough to carry much more cargo and many more passengers than your typical hovercraft could. You know, hovercraft was usually carrying around two dozen people, maybe a little bit more, and maybe like as many as twenty cars initially. With these larger hovercraft and fairies could carry much more than that. However, hovercraft could make three trips in the same amount of time that the ferry took to do one, so there was a way of you know, kind of figuring that out and balancing it between the two. For a while, hovercraft would factor into Britain's transportation infrastructure. In fact, some would call hovercraft a quintessentially British form of transportation because there were lots of places around Britain where you could grab a hovercraft to go from one port city to another, whether it was to cross a river or an estuary or a channel or whatever it might be. But as I mentioned earlier, there's some slight dispute as to whether we should even call Cockrell the father of hovercraft in the first place, and that maybe thinking of hovercraft as a really British type of technology is misleading because, as it turns out, a Yank came up with a very similar methodology a decade earlier. And again, the actual theory for hovercraft predated both of these guys by decades, like almost a century, so let's keep that in mind. But the Yank was a guy named Charles Joseph Fletcher who was born in nineteen twenty two in New jer the United States. So Cockrell was born in nineteen ten. Fletcher was born in nineteen twenty two, so he's twelve years younger than Cockrell. During World War Two he served as an officer in the US Navy, and while doing so, sometime around that same time period. The details, to me are are a little bit hazy because a lot of the sources just don't have things like specific dates, But sometime around then, he sketched out a design for a vessel that would use a cushion of air to glide. You know, you could almost say hover above the surface below, whether that was land or sea, which sounds pretty familiar right now. He called his invention a glide mobile, so he had hovercraft and glidemobiles. So the story goes that Fletcher actually built a prototype of his design and tested it in New Jersey and showed it off to the Navy, and the War Department said, say that can be useful and then swooped in to take charge. So the War Department classified the project, similar to what happened to Cockrell when he showed it off to those local officials over in the UK. By making it a classified project, it prevented Fletcher from being able to seek a patent for it. He did not file a patent before showing it off, so the Glidemobile didn't really go much further as a result, because it just became the property of the War Department, and the War Department apparently didn't do very much with it. However, eventually some British companies were making a patent claim against the glidemobile design. This is after World War Two, it's in the nineteen fifties, and the hovercraft companies are saying, hey, you are infringing upon a patented technology. And then Fletcher was able to defend the position of the glidemobile by pointing out that no his designs predated Cockrell's patent and that it served as sort of prior art and meant that they weren't infringing upon a patent because they were building upon a design that actually pre dated the patent. Presumably Fletcher was able to prove this concept predated Cockrell's patent and he was able to move forward. I don't know for sure, because again the details are pretty scarce. But anyway, you didn't see hovercraft become a favored form of transportation here in the United States, whereas again in the UK, particularly in like the sixties and seventies, it really was like it became a kind of common form of transportation for folks who were trying to get across bodies of water quickly. Now, even though they were really famous in those days, there's only one commercial hovercraft service that is still in business today in the world, and it happens to be in the UK. It's a route that goes between the city of Ride, which is on the Isle of Wight, and south Sea in Portsmouth. So you might wonder what the heck happened? Why did this form of transportation, which was fairly enthusiastically embraced in the sixties, why did it peter out by the time you get to modern day, to the point where now there's only one commercial route still in business. Well, I'll tell you, but before I do, we're gonna take another quick break to thank our sponsors. Before the break, I mentioned that, you know, for a while, hovercraft were enjoying a moment in the spotlight, but then a few decades later they have all but disappeared, at least as far as commercial travel goes. I don't want to say that there are no hovercraft anymore. There certainly are, and in fact, there are a lot of hovercraft that are meant for very specific purposes. It's just you don't see them as cargo and passenger travel solutions these days, not that much anyway. And there are a few reasons for this. And it is kind of crazy because even if you go back to like the nineteen seventies, there's a James Bond movie in which there's a big hovercraft sequence. And again there's the bit in the ninety five movie Rumble in the Bronx where there's a big hovercraft sequence. But there are reasons why it's no longer a reliable and widespread travel solution. One is that hovercraft, especially older hovercraft, are really really noisy. I mean they make a huge amount of noise. They use these massive engines to turn the fans. The mount Batten class that I mentioned earlier used these enormous turbo gas engines that were made by Rolls Royce, and these engines make a whole lot of noise. They also generate a lot of exhaust, but they're very, very loud. The fans also generate a good deal of noise as well. So if you were a company and you're proposing building out a hovercraft to run a route between two particular cities, chances are you're going to have residents of those cities say, come on, we don't want that. We do not want to have this kind of noise pollution in our communities. Most folks aren't keen to have their days punctuated with extremely loud traffic from all sorts of places. And as someone who lives right across from a freight train line, I can understand this is not thrilling to hear that freight train go by. So that made expansion a little tricky, right. It's a lot of not in my backyardism, but understandable because that noise pollution is serious stuff. But another issue is that while hovercraft can have a big advantage in that you don't have to use a peer or anything like that. Like, you don't need a peer or a dock in order to secure the craft. You can just drive the hovercraft from the water up to the land as long as the land is relatively clear. You still need a space where the hovercraft can go, right, you can't just plow through like woods or whatever. You can't go wreaking havoc through a marina. You need to have a dedicated space where the hovercraft can beach itself, like can go up onto the land and then descend so that people can get off the vehicle. So you do need to have some physical space available for the hovercraft, and not every place had that as an option. Then there's the issue of maintenance and repair. Hovercraft need these really big engines to work. Like if you're looking in the grand scheme of things the fans used in hovercraft, they don't need to generate the same amount of lift that a helicopter would, right, they don't have to work as hard as the rotors of a helicopter, but they still have to work. And these really really big hovercraft, while they can be very efficient, still need a great deal of power in order to generate that lift. So you need these really large engines. If those engines are in disrepair, then you're not going to go anywhere. And as I've already said, like some of the engines that were used in hovercraft, especially in the early days, weren't terribly reliable, and that meant that hovercraft could be down just as frequently as they could be in operation, and this gets expensive to do maintenance and repair all the time. There's also the matter of fuel. Those engines require a lot of fuel in order to operate, and fuel is expensive. And remember, in the nineteen seventies, the world went through an oil crisis and fuel prices skyrocketed in the nineteen seventies. This was due to a political crisis in the Middle East that spawned from some military conflicts in the Middle East. So this was not a natural oil crisis, it was a man made one. But it's still meant that fuel prices around the world, especially in the UK and the United States and in Japan, went crazy high, and so operating a transportation system that was fuel hungry was kind of a losing proposition as far as money goes. So eventually it just got to a point where the return on investment wasn't really that good. It became too expensive to operate a hovercraft service. Most hovercraft are fairly modest in size. They might carry a couple of dozen passengers at a time, maybe a few cars. The Mount Batten class was different by the time we get to its later refittings because of the Saunders Row would end up upgrading this class of hovercraft over and over again. By the end of it, they could carry more than four hundred passengers and around sixty cars at a time, which is pretty impressive, but I imagined that the profit margins were still fairly thin when you look at how expensive it was to keep the vehicles in operation versus how much you can make in ticket sales to customers. Because eventually you're going to get to a point where a customer is going to say, I'm not willing to spend that much money just to save an hour's worth of time while I'm crossing the English Channel, for example, Like I'll spend less money and it'll take me an hour and a half to get there, rather than spend five times as much in order to get there in half an hour. So it just meant that there really became fewer and fewer financial reasons to keep a hovercraft operation going. So by the year two thousand, most hovercraft services commercial ones had shut down, and as I said, the only one that remains now goes between the Isle of Wight and Portsmouth. Occasionally you will see hovercraft of various sizes doing other types of jobs. There are some military hovercraft, there are some other ones that are used for you know, recreation purposes, but when it comes to commercial transportation, it's really mostly a thing of the past. Now that we've covered the history of the craft, let's talk about what's actually making them hover because it's just a tiny bit more complicated than fan points down and air pushes hovercraft up, but only a tiny bit more complicated than that. Ultimately, that is what is making the hovercraft work. So you could just walk away with fan points down. It pushes air down, hovercraft goes up because equal and opposite reaction and whatnot. So the original hovercraft design used two layers of a shell or hull. Think of it like a channel, like it was a channel through which air could flow, and the underneath the hovercraft is a hollow section that would be called a plenum. In fact, the original version of a hovercraft that little ten can version. You could think of that as a plenum based hovercraft, where you're just pumping air through the plenum. That's enough to generate lift, but only generates a little left. You aren't able to get very much height using that. So this other version, the one that Cockroll had designed, used this channel of air that would direct air to flow down along the periphery of the hovercraft's bottom, So you have a vertically oriented fan it's blowing air downward. That air flows through this channel, which then is directed toward the outer section of the hovercraft. It creates a ring of air. That air is effectively flowing inward toward the inside of the hovercraft, that plenum, that hollows section underneath the hovercraft, and that ring of air also serves as a kind of curtain or barrier, so it's not allowing air to escape out the sides of the hovercraft, or at least not a lot there escaping out the sides of the hovercraft. And this creates the lift. It allows the hovercraft to levitate up, not levitate, but to hover up, and you can get a hover of around several inches up to a couple of feet, but you couldn't get much higher than that. However, later on, engineers developed a flexible skirt for hovercraft. So imagine that you have this flexible material, typically made out of rubber, that goes around the periphery of the hovercraft. So it's got a little skirt that goes all the way around. When you're directing air downward, perhaps in the same style as you were before, which was actually called a peripheral jet approach, maybe you're using a combination of the skirt and a peripheral jet. Then it keeps the air in more effectively than just the peripheral jet by itself. The rubber contains the air there. It creates this air cushion, and theft actually get much more height this way. You can get maybe up to like six or seven feet of height using this. So the skirt makes it look like the hovercraft is still keeping contact with the ground, but the actual bottom of the hovercraft itself is several feet above that, and this is how hovercraft typically work. A secondary fan is usually used to provide propulsion. I mentioned this earlier. You got a fan that points like backward from the hovercraft, and when you turn that on, it's shooting air. Out the back, and then you get the equal but opposite reaction. The hovercraft will move forward. You usually have a rudder or some other method to redirect that fan so that you can make turns. Those turns can be pretty gradual, and you still have momentum. You know, you have the loft conservation of motion. You're still moving. So that's why it's difficult to pilot these things. It's challenging. You can't just slam on brakes with a hovercraftft. You can stop the fan and you will come to a stop gradually, but you can't just slam the brakes, so tight turns and sharp stops are not really possible, which is why hovercraft are typically a little easier to operate on the water than they are on the land. If you come up to an obstacle on land, you might be bumping into something. One thing that Cockrell figured out was that, perhaps counterintuitively, the larger the hovercraft was, or more precisely, the larger the area of the air cushion or cushions that provide the lift, the more efficient the hovercraft became. Here's how he put it in his patent, and it does get technical. So here we go quote. In such vehicles, the lift or load carrying capacity is proportional to the plan area of the gas cushion or cushions. The energy required to contain the cushion or cushions is proportional to the peripheral dimension of the cushion or cushions. Thus, for an increase in size of a vehicle, the lift increases proportionally to the area of the cushion or cushions, whilst the energy requirements increase linearly with the periphery of the cushion or cushions. So, in other words, the larger the hovercraft is, or the larger the surface area of the air cushion is, the easier it is to achieve greater lift with only a smaller increase in actual power. So you're getting greater returns for just a smaller investment in power, and thus it's more efficient to build larger hovercraft than it is to build smaller hovercraft. I guess you could still just say that pointing a fan downward provides the lift needed to hover the vehicle, and you could just leave it at that, but you do need some other design elements to make the vehicle stable and useful, Like I said, hovercraft are still a thing, They're just not typically used for commercial transportation. They are not commonplace, but similar technologlogies related to hovercraft have found their way into designs since then. You might know that the original concept for the hyperloop train system included a train running through a tube where you had pumped out most of the air, and the train would hover above the floor of that tube through the use of air ball bearings. So Elon Musk described it as sort of like an air hockey table, only facing downward instead of facing upward. That's not that different from a hovercraft, or a glidemobile, or an air cushioned vehicle, however you want to call it. The methodology described in the hyperloop concept is a bit different from what you'd see in a hovercraft, but the gist is similar. As it would turn out, the various companies that sprung up in the wake of Musk's proposal would, by turns, choose a different approach. Some went with magnetic levitation, some would dispense with the idea of suspending the train above the track entirely and thus embrace a more traditional train design. But initially the hyperloop was meant to have an air cushion under it. Of course, you could argue that these days the hyperloop concept has been all but abandoned because several of the companies that pursued the goal of making it a reality have since gone out of business. You can, of course, build your own hovercraft. There are websites describing how to make a sample hovercraft using like a balloon and an old CD or a DVD. I would suggest use one you don't plan on ever playing again. Maybe maybe a kid rock album would be suitable. There are also kits to build an actual hovercraft. You know, you can kind of build a sort of personal pan pizza sized vehicle. I've seen diy hovercraft on YouTube of varying degrees of safety and reliability, and there are lots of ones for things like radio controlled hovercraft. Right. There are a lot of toy versions of hovercraft that work on the same principle, but they're obviously at a much smaller scale, and that way you can learn how challenging it is to direct a vehicle that works on momentum and has a lack of breaks. It can really be easy to get moving in a particular direction and a real challenge to you know, stop doing that. But that's our look at hovercraft, a technology that I think is pretty interesting, pretty cool. I have never written on one. I've never been on a hovercraft. I kind of wish that I had had that experience. Maybe one day I'll make a trip out to the Isle of Wight simply so that I could say I wrote on a hovercraft, which means that I'll be walking around Isle of Wight and probably lamenting how many places have closed down. I've watched some videos recently of that area of Isle of Wight and it was looking a little grim, although I should say that was also in the off season, so maybe that's it, you know, Maybe it's just that, Oh, these are things that are usually working in the more popular seasons. It's just in the off season they shut down because there's no sense in running it. Then maybe that's the case, I hope. So, but that is our look at hovercraft. I hope you enjoyed this episode. You learned a bit about Sir Christopher Cockrell and his mission to create a new form of transportation and to get past that irritating problem of friction that voting stuff encounters. Although Cockroll encountered more than a little friction just you know, in the political side, as opposed to as opposed to physical friction that you would encounter in the water. I hope you are all well. Thank you so much for listening, and I will talk to you again really soon. Tech Stuff is an iHeartRadio production. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.

Welcome to tech Stuff, a production from iHeartRadio. Hey there, and welcome to tech Stuff. I'm your host, Jonathan Strickland. I'm an executive producer with iHeart Podcasts and how the tech are you? So y'all already know what this episode is about, because it's right there in the title for the episode. The title itself is a reference to a nineteen ninety five Jackie Chan film called Rumble in the Bronx. So in the climax of that film spoiler alert, there's a scene in which a hovercraft goes absolutely ape through the city. It crashes into cars, it absolutely destroys Lamborghini, and it interrupts a rock band that's playing outside on the street. And it's at this point in the film where the drummer of the rock band stops playing mid song, stands up, points and yells hover aft, which is my favorite part of the whole movie, even with all the amazing fight sequences taken into account. And this is the sort of stuff that inspires tech Stuff episodes, because that's how my brain works now anyway, Yeah, Jackie Chan films from the nineties really a source of inspiration. So I thought it would be fun to do an episode tracing the history of hovercraft and to talk a little bit about how they actually work. And I also think this is the type of topic where you have one concept in your head when you first hear about it, Like when you first hear the word hovercraft, you might have a vision in your head of what that might be, and then ultimately you could be disappointed when you see it in the real world. That was my reaction anyway, because as a kid, when I heard the word hovercraft, I thought of some sort of semi magical vehicle that could levitate above the ground, probably something closer to what drones are, but without the rotors, right, Like there's some unseen force that makes the thing floatt. So I was kind of thinking of something similar to like the hover boards that are featured in the documentary Back to the Future too, But of course that's not how your typical hovercraft works. Hovercraft, by the way, are also called air cushion vehicles, and that air cushion gives a huge indication of how these things work. And arguably my whole perception or misperception of hovercraft isn't really fair. I mean, it's not the hovercraft's fault that I had an overactive imagination and unrealistic expectations. It is a fascinating invention, and it traces its history really back to the nineteenth century, when you had people sort of theorizing about it, but effectively for talking about making something that actually works. It's more like the middle of the last century. And I was born in the last century, and saying that way hurts a little bit. But the inventor of the hovercraft, the person that we credit as the inventor, so so I guess you could say sort of inventor of the hovercraft was a gentleman by the name of Christopher Sidney Cockrell. Now I say sort of because, as we will find out later in this episode, there was another person who came up with the same concept a decade earlier, but due to a technicality, this person had no ownership of this idea. But we'll get back to why that happened. So Cockrell's parents were both distinguished members of English society. His mother was Florence Kingsford cockerl. She was known for her artistic talents in calligraphy, illumination, illustration, and costuming. When I say illumination, I mean manuscript illumination, think of the stuff that monks used to do back in the Middle Ages. So way back in my college days, I focused my studies in medieval literature and medieval history, and after looking at Florence's work, I'm really amazed at how her evokes those ancient texts. Cockrell's father was Sir Sidney Cockrell, who came from a coal mining family. Like it astonishes me. He came from a family that worked coal mines, but he found himself thrust into the social circles of influential people who were in the artistic and literature worlds in England. So Old sid served as a personal secretary to British author and artist William Morris, and Sydney eventually became the director of the Fitzwilliam Museum in Cambridge, England, where he had a bit of a reputation for having an incredibly effective method to convince hoity toity rich people to hand over some of their filthy lucre to support the museum. So Christopher Cockrell came from, if not blue blood, at least light blue blood Lemmelson Mit, which bills itself as the quote national leader in advancing in vention education in The quote says that Sidney Cockroll wasn't entirely sold on the idea of his son going into engineering, but that's exactly what young Christopher Cockroll wanted to do. And I find this notion rather like a money python sketch, because you have a man who comes from a coal mining family. He's defied the odds, he's become a director of a prestigious museum, and now he is concerned that his son wants to be an engineer. In fact, there is a money python sketch in which you have a family of It sounds like lower class English folk who are authors, who are a shame that their son wants to go into being a coal miner, flipping the old narrative on its head. So this is reminding me of that fictional sketch, you know, very silly stuff. But yeah, he didn't want Christopher to become an engineer. But whether he had reservations or not, ultimately Sydney agreed to support his son's pursuit of an education in engineering. In fact, according to the Guardian, Sydney offered Christopher the princely sum of ten pounds for every patent his boy would receive. This was back when old Chris was still a teenager. Sidney would call an end to that deal later on because it would get pretty deep, deep, pretty expensive. Christopher attended Petterhouse College at Cambridge University. In his obituary Cockrell passed away in nineteen ninety nine, by the way, in his obituary in The Guardian, Christopher Cockrell was said to have spent much of his spare time in college quote taking motorcycles to pieces or racing them end quote, and that this gave him the experience of practical background in basic mechanics and engineering, which is kind of cool, like the idea of learning by doing something you're already interested in. So that was already neat of course. Christopher by this point, by the time he was going to university, had already expressed a deep interest in engineering. Upon graduation, Christopher Cockerrell took a position with the Radio Research Company. This was in nineteen thirty five, so still relatively early in the days of radio. I mean radio had been around for a while, but still a fairly young science. And he joined the Marconi Wireless Telegraph Company and worked in an R and D department that largely focused on radar and he made numerous contributions to radio and radar technology. Many of those contributions were put to use by Allied forces during World War Two. Now, Christopher Cockrell made a career change in nineteen fifty, so the war hit was over. He continued to work in radio for a few years, but in nineteen fifty his father in law had left his wife a big sum of money, and together Christopher and his wife decided that they wanted to purchase a boat business in Norfolk, England, and Cockroll devoted his attention to managing this boat business. And it was to shift when I was reading up on his life that this actually gave me a little bit of whiplash, because here's someone who was instrumental in advancing technology and radio and radar, and now he's switching over to manage a boat business. But it was as a manager of this boat company that led him to start thinking about a solution to a really tricky problem and ultimately would lead him to inventing the hovercraft. So Cockrell got to thinking that there must be a way for heavy watercraft to travel much faster across bodies of water, and it would be possible if only you could get the boat out of the water. If you could remove it from contact with the water itself, if the craft could somehow float above the surface of the water, then that would eliminate all the friction that it otherwise would encounter as it moves through the water, and it would be able to move much more quickly than it could otherwise. But you just had to figure out a way to minimize or eliminate contact with the water. And if you could get it to lift up above the surface of the water entirely, technically you actually would have an aircraft, not water craft. But that was his starting point. He thought, how can I create a vessel that would minimize or eliminate contact with the water so that it can move much more quickly and efficiently. So Cockrell imagined a craft with a cushion of air underneath it. That cushion of air would provide a barrier between the vessel itself and the water or land underneath. If you could blow out enough air, it could skim right across the surface, whether it's water, land, or some mixture like mud or swamp or whatever, and it could potentially cut travel times significantly, at least as far as water goes maybe not with land, because as it turns out, if you're going across solid land and you've got yourself a road and you have a wheeled vehicle, you can zip along that pretty darn fast, and it would probably be difficult and very dangerous to operate a hovercraft at those speeds, because you've got to remember, hovercraft typically for propulsion's sake, is using wind power as well. Right, you've got a fan that points backward and you're blowing out airs and you know, obviously equal opposite reaction time. That means you're moving forward as a result with a proportional force, but that doesn't mean that you can easily do things like stop, and that turning is more of a gradual process as well. So moving at high speeds across land where you could occasionally encounter obstacles probably not the best idea. But anyway, in Cockrell's spare time, he started to tinker to see if this idea he had could be made practical. He wondered, first is it plausible and then is it practical? So early on, as a store where he goes, he used some tubes from an old vacuum cleaner as well as the vacuum cleaner's motor, and he used a pair of empty cans. The types of cans, it depends on which version you read. Like some say it was a couple of coffee cans. One was slightly smaller than the other. One was like, no, it's a coffee can, and then a cat food can. Some call them tin cans, some call them aluminum cans. I think what's important to know is he used a pair of cans. One was larger than the other one. He put the smaller one inside the larger one. He blew air so that it would go underneath the smaller one, which was turned face down I imagine, like open side down, and the air would create an air cushion, and the smaller one would end up hovering inside the larger one and just kind of bang around a little bit. So he saw that this was possible. It could create lyft, and that lift could be enough to counteract the weight of the vessel, in this case the little small can. So his concept had validity, and Cockrell got to work building on a prototype, an actual sort of small hovercraft that would be more substantial than just a pair of aluminum cans and some tubes. And it took him a while to build it, but by nineteen fifty five he had a working prototype, and he then had to decide what was he going to do with it. And he could have tried to create like a private business based off this, but the story goes that instead he thought, I'll show local officials, I'll see if I can get some investment in this and turn it into something viable. In that way, I'm not just sinking money into something that may never pan out. So he arranges a demonstration for his hovercraft prototype with some local officials, and the story goes that the local officials were astonished and more than a little frightened as Cockrell's prototype skimmed around inside an office that he had brought it into this office of the the local officials. He had fired up the engine that would drive the fan. So you got to remember, this is an internal combustion engine. It is burning fuel and letting out fumes, and it's very loud, and it's turning this fan, and the fan is making this hovercraft skim above the surface of the ground. And then there's not really a way of steering the hovercraft at this point. It's just showing a proof of concept. It's kind of bumping around like a bumper car all over the office. People are jumping up on chairs and desks and trying to get out of the way. And meanwhile, like I said, it's noisy and it's smelly. It made a real impression and it makes me think of that scene in Rumble in the Bronx where there's just a hovercraft gone wild. So the officials weren't quite ready to devote funding to Cockrell's invention at this point. There was this general perception in the nineteen fifties that England was not really that interested in investing in innovation. There was this perception that England was kind of backward at this point. They were focused more on things like, well, we're doing it this way because that's how we've always done it. Whether that was an accurate representation of what was going on in England, I can't say, but that was the perception. So consequently, the nation was starting to feel like it was falling behind some of the rest of the world. More than that, the officials who saw this demonstration decided, rather than fund Cockrell's idea, they would put it on a so called secret list, which effectively meant they were classifying his invention. They were putting it under classified information, and Cockrell would be legally prohibited from talking about it or finding some other means to fund his work that that would be against the law. Maybe he could find a way to fund it if he could somehow convince people to give him money without actually talking about the invention itself. But really it just meant that the officials were really hamstringing him. Now we're going to take a quick break, and when we come back, we'll talk about what happened next and how Cockroll was able to get some progress despite this initial setback. But first let's take a break to hear from our sponsors. Okay, we're back. So before the break, I talked about how Cockrell does this demonstration. Officials are taken aback and they decide to classify Cockroll's invention, which effectively makes it impossible for him to do any real work on it. This is despite the fact that Cockrell had demonstrated to them that his hovercraft could potentially solve a lot of problems like not only could it glide over water, it could go over land, it could go over lots of icky stuff that other vehicles actually have a lot of trouble with so marshes and muddy sections and stuff. You know, if you had a boat, you wouldn't be able to go through these because there's not enough water to keep the boat floating right. The boat would just get beached or mired. Same with vehicles that are on treads or wheels, they would eventually get stuck in really nasty muddy situations. But the hovercraft would float above all this. It could get you through to places that other vehicles couldn't unless you were using something like say a helicopter or an airplane. So Cockrel was really making a case for how this could be a really useful vehicle for all sorts of different applications, and none of that seemed to really matter to these officials. However, he did receive a patent for his invention in nineteen fifty six because he had filed for this patent before the officials had put the hovercraft on the secret list, so ironically, his invention was already public because patents are public, right, that's one of the elements of patents. When you file for a patent, your description of your invention is made public, but in return, you receive government protection for your idea, at least for a certain amount of time. So this is why we call him the inventor of the hovercraft, because Cockrell actually secured patents relating to his invention, although as I mentioned earlier in this episode, and we'll get back to it, there was someone else who had built something similar a decade before Cockroll did. In nineteen fifty eight, the UK government declassified his work and this gave Cockroll the chance to actually pursue funding. The UK's National Research and Development Agency or NRDA, was really impressed with his invention and they commissioned a company called Saunder's Row to build a test hovercraft based on Cockrell's design. So Sunder's Row was already an established business. It specialized in building boats, and they produced a vehicle that was called the SR in one. SR standing for Saunder's Row, and it was really only big enough to hold its own crew. It wasn't designed for passengers. But here's the thing. It did work, and on July twenty fifth, nineteen fifty nine, Saunder's Road demonstrated its capabilities by having the SR in one cross the English Channel. The hovercraft left Dover in England and landed in Calais in France. Ou La Lain. Cockrell himself was aboard of the hovercraft for this demonstration. According to The Guardian, he served as ballast very dignified. This demonstration convinced UK authorities to invest more heavily into the hovercraft technology, and the NRDA created a company called Hovercraft Development Limited with the purpose of creating hovercraft for commercial purposes such as ferrying cargo and passengers across various rivers and channels like the English Channel. The organization oversaw the work of five different companies that were all dedicated to this purpose, so there was five different boating companies that all began building hovercraft vehicles. Christopher Cockrell landed a gig as the director for Hovercraft Development Limited, and he was also the technical advisor to the company and he stayed on in that capacity until nineteen sixty six. Also in recognition of his contributions, he would ultimately receive a knighthood in nineteen sixty nine, just like his dear old dad. So you had Sir Sidney and now you had Sir Christopher. The first of the passenger hovercraft was the Vickers VA three, which was an experimental vehicle it wasn't meant to be built for full commercial use. It was more like, again a proof of concept. It launched in nineteen sixty two. British United Airways ran the service because again hovercraft were thought of as an aircraft not a boat, right, because these fans would end up creating this air cushion that made the vehicle hover, sometimes several feet above the surface that it traveled across. So as such it was more of an aircraft than a watercraft. So the initial route passed over an estuary between Liverpool and North Wales. The hovercraft would hold up to twenty four passengers per trip, and it was intended to take twelve trips per day. And like I said, this was kind of an experiment. It was a pilot program. And originally the concept was that it would go for fifty nine days and then they would evaluate does this make sense, like can we turn this into a reasonable and viable transportation option. But while it was meant to go for fifty nine days, it only made it to thirty six. The reason for that was not entirely the fault of the actual vehicle, although there were some engine problems that turned out to be a bit of an issue, and in fact that would become a thing for a lot of hovercraft. It's not that the design was bad, it's that sometimes the equipment that was being used wasn't the most reliable. The other issue was that there was a lot of bad weather during that stretch. Now I think that you should just anticipate that, because as far as I'm concerned, bad weather is kind of a constitutional requirement in the UK, at least every time I've been there. So anyway, because of this combination of issues, the experiment was cut short. The VA three would retire as a passenger vehicle, but the British government would continue to use the VA three vessel to conduct some other kinds of tests, including a very extreme one. Namely, the test they wanted to really check out was could a hovercraft pass safely over a zone in the sea that happened to be occupied by marine mines? Right? Like? These are those mines you see? You know, typically I almost only see them in things like cartoons, where it's the giant globe with lots of little pressure sensors on it that are connected by chains and anchor to the seafloor. And the ideas that a boat which will pierce the surface of the water. If it were to make contact with these would cause it to explode. Well, the thought was, well, hovercraft, they don't pierce the surface of the water, they hover above it. So is it possible that a hovercraft could safely glide over an area that is filled with marine mines and not trip them? And they tested it and the VA three done blowed up real good, which answered that question rather definitively. Passenger hovercraft would tackle the English Channels starting in nineteen sixty six, with one of the most famous being a class of hovercraft called the SRN four. Again back to the Saunders Row and this was also known as the mount Batten class of hovercraft, and the very first one that made the trip across the English Channel was called Princess Margaret. This was in nineteen sixty eight. These vessels could make the trip between England and France in about half an hour. Typically we're talking like Dover to Calais, but sometimes a different port in France. But the interesting thing is if you contrast this with the traditional ferries that were making this trip between England and France, that journey would typically take an hour and a half. So three times as long. So the fairies had some advantages, right, You could build a ferry large enough to carry much more cargo and many more passengers than your typical hovercraft could. You know, hovercraft was usually carrying around two dozen people, maybe a little bit more, and maybe like as many as twenty cars initially. With these larger hovercraft and fairies could carry much more than that. However, hovercraft could make three trips in the same amount of time that the ferry took to do one, so there was a way of you know, kind of figuring that out and balancing it between the two. For a while, hovercraft would factor into Britain's transportation infrastructure. In fact, some would call hovercraft a quintessentially British form of transportation because there were lots of places around Britain where you could grab a hovercraft to go from one port city to another, whether it was to cross a river or an estuary or a channel or whatever it might be. But as I mentioned earlier, there's some slight dispute as to whether we should even call Cockrell the father of hovercraft in the first place, and that maybe thinking of hovercraft as a really British type of technology is misleading because, as it turns out, a Yank came up with a very similar methodology a decade earlier. And again, the actual theory for hovercraft predated both of these guys by decades, like almost a century, so let's keep that in mind. But the Yank was a guy named Charles Joseph Fletcher who was born in nineteen twenty two in New jer the United States. So Cockrell was born in nineteen ten. Fletcher was born in nineteen twenty two, so he's twelve years younger than Cockrell. During World War Two he served as an officer in the US Navy, and while doing so, sometime around that same time period. The details, to me are are a little bit hazy because a lot of the sources just don't have things like specific dates, But sometime around then, he sketched out a design for a vessel that would use a cushion of air to glide. You know, you could almost say hover above the surface below, whether that was land or sea, which sounds pretty familiar right now. He called his invention a glide mobile, so he had hovercraft and glidemobiles. So the story goes that Fletcher actually built a prototype of his design and tested it in New Jersey and showed it off to the Navy, and the War Department said, say that can be useful and then swooped in to take charge. So the War Department classified the project, similar to what happened to Cockrell when he showed it off to those local officials over in the UK. By making it a classified project, it prevented Fletcher from being able to seek a patent for it. He did not file a patent before showing it off, so the Glidemobile didn't really go much further as a result, because it just became the property of the War Department, and the War Department apparently didn't do very much with it. However, eventually some British companies were making a patent claim against the glidemobile design. This is after World War Two, it's in the nineteen fifties, and the hovercraft companies are saying, hey, you are infringing upon a patented technology. And then Fletcher was able to defend the position of the glidemobile by pointing out that no his designs predated Cockrell's patent and that it served as sort of prior art and meant that they weren't infringing upon a patent because they were building upon a design that actually pre dated the patent. Presumably Fletcher was able to prove this concept predated Cockrell's patent and he was able to move forward. I don't know for sure, because again the details are pretty scarce. But anyway, you didn't see hovercraft become a favored form of transportation here in the United States, whereas again in the UK, particularly in like the sixties and seventies, it really was like it became a kind of common form of transportation for folks who were trying to get across bodies of water quickly. Now, even though they were really famous in those days, there's only one commercial hovercraft service that is still in business today in the world, and it happens to be in the UK. It's a route that goes between the city of Ride, which is on the Isle of Wight, and south Sea in Portsmouth. So you might wonder what the heck happened? Why did this form of transportation, which was fairly enthusiastically embraced in the sixties, why did it peter out by the time you get to modern day, to the point where now there's only one commercial route still in business. Well, I'll tell you, but before I do, we're gonna take another quick break to thank our sponsors. Before the break, I mentioned that, you know, for a while, hovercraft were enjoying a moment in the spotlight, but then a few decades later they have all but disappeared, at least as far as commercial travel goes. I don't want to say that there are no hovercraft anymore. There certainly are, and in fact, there are a lot of hovercraft that are meant for very specific purposes. It's just you don't see them as cargo and passenger travel solutions these days, not that much anyway. And there are a few reasons for this. And it is kind of crazy because even if you go back to like the nineteen seventies, there's a James Bond movie in which there's a big hovercraft sequence. And again there's the bit in the ninety five movie Rumble in the Bronx where there's a big hovercraft sequence. But there are reasons why it's no longer a reliable and widespread travel solution. One is that hovercraft, especially older hovercraft, are really really noisy. I mean they make a huge amount of noise. They use these massive engines to turn the fans. The mount Batten class that I mentioned earlier used these enormous turbo gas engines that were made by Rolls Royce, and these engines make a whole lot of noise. They also generate a lot of exhaust, but they're very, very loud. The fans also generate a good deal of noise as well. So if you were a company and you're proposing building out a hovercraft to run a route between two particular cities, chances are you're going to have residents of those cities say, come on, we don't want that. We do not want to have this kind of noise pollution in our communities. Most folks aren't keen to have their days punctuated with extremely loud traffic from all sorts of places. And as someone who lives right across from a freight train line, I can understand this is not thrilling to hear that freight train go by. So that made expansion a little tricky, right. It's a lot of not in my backyardism, but understandable because that noise pollution is serious stuff. But another issue is that while hovercraft can have a big advantage in that you don't have to use a peer or anything like that. Like, you don't need a peer or a dock in order to secure the craft. You can just drive the hovercraft from the water up to the land as long as the land is relatively clear. You still need a space where the hovercraft can go, right, you can't just plow through like woods or whatever. You can't go wreaking havoc through a marina. You need to have a dedicated space where the hovercraft can beach itself, like can go up onto the land and then descend so that people can get off the vehicle. So you do need to have some physical space available for the hovercraft, and not every place had that as an option. Then there's the issue of maintenance and repair. Hovercraft need these really big engines to work. Like if you're looking in the grand scheme of things the fans used in hovercraft, they don't need to generate the same amount of lift that a helicopter would, right, they don't have to work as hard as the rotors of a helicopter, but they still have to work. And these really really big hovercraft, while they can be very efficient, still need a great deal of power in order to generate that lift. So you need these really large engines. If those engines are in disrepair, then you're not going to go anywhere. And as I've already said, like some of the engines that were used in hovercraft, especially in the early days, weren't terribly reliable, and that meant that hovercraft could be down just as frequently as they could be in operation, and this gets expensive to do maintenance and repair all the time. There's also the matter of fuel. Those engines require a lot of fuel in order to operate, and fuel is expensive. And remember, in the nineteen seventies, the world went through an oil crisis and fuel prices skyrocketed in the nineteen seventies. This was due to a political crisis in the Middle East that spawned from some military conflicts in the Middle East. So this was not a natural oil crisis, it was a man made one. But it's still meant that fuel prices around the world, especially in the UK and the United States and in Japan, went crazy high, and so operating a transportation system that was fuel hungry was kind of a losing proposition as far as money goes. So eventually it just got to a point where the return on investment wasn't really that good. It became too expensive to operate a hovercraft service. Most hovercraft are fairly modest in size. They might carry a couple of dozen passengers at a time, maybe a few cars. The Mount Batten class was different by the time we get to its later refittings because of the Saunders Row would end up upgrading this class of hovercraft over and over again. By the end of it, they could carry more than four hundred passengers and around sixty cars at a time, which is pretty impressive, but I imagined that the profit margins were still fairly thin when you look at how expensive it was to keep the vehicles in operation versus how much you can make in ticket sales to customers. Because eventually you're going to get to a point where a customer is going to say, I'm not willing to spend that much money just to save an hour's worth of time while I'm crossing the English Channel, for example, Like I'll spend less money and it'll take me an hour and a half to get there, rather than spend five times as much in order to get there in half an hour. So it just meant that there really became fewer and fewer financial reasons to keep a hovercraft operation going. So by the year two thousand, most hovercraft services commercial ones had shut down, and as I said, the only one that remains now goes between the Isle of Wight and Portsmouth. Occasionally you will see hovercraft of various sizes doing other types of jobs. There are some military hovercraft, there are some other ones that are used for you know, recreation purposes, but when it comes to commercial transportation, it's really mostly a thing of the past. Now that we've covered the history of the craft, let's talk about what's actually making them hover because it's just a tiny bit more complicated than fan points down and air pushes hovercraft up, but only a tiny bit more complicated than that. Ultimately, that is what is making the hovercraft work. So you could just walk away with fan points down. It pushes air down, hovercraft goes up because equal and opposite reaction and whatnot. So the original hovercraft design used two layers of a shell or hull. Think of it like a channel, like it was a channel through which air could flow, and the underneath the hovercraft is a hollow section that would be called a plenum. In fact, the original version of a hovercraft that little ten can version. You could think of that as a plenum based hovercraft, where you're just pumping air through the plenum. That's enough to generate lift, but only generates a little left. You aren't able to get very much height using that. So this other version, the one that Cockroll had designed, used this channel of air that would direct air to flow down along the periphery of the hovercraft's bottom, So you have a vertically oriented fan it's blowing air downward. That air flows through this channel, which then is directed toward the outer section of the hovercraft. It creates a ring of air. That air is effectively flowing inward toward the inside of the hovercraft, that plenum, that hollows section underneath the hovercraft, and that ring of air also serves as a kind of curtain or barrier, so it's not allowing air to escape out the sides of the hovercraft, or at least not a lot there escaping out the sides of the hovercraft. And this creates the lift. It allows the hovercraft to levitate up, not levitate, but to hover up, and you can get a hover of around several inches up to a couple of feet, but you couldn't get much higher than that. However, later on, engineers developed a flexible skirt for hovercraft. So imagine that you have this flexible material, typically made out of rubber, that goes around the periphery of the hovercraft. So it's got a little skirt that goes all the way around. When you're directing air downward, perhaps in the same style as you were before, which was actually called a peripheral jet approach, maybe you're using a combination of the skirt and a peripheral jet. Then it keeps the air in more effectively than just the peripheral jet by itself. The rubber contains the air there. It creates this air cushion, and theft actually get much more height this way. You can get maybe up to like six or seven feet of height using this. So the skirt makes it look like the hovercraft is still keeping contact with the ground, but the actual bottom of the hovercraft itself is several feet above that, and this is how hovercraft typically work. A secondary fan is usually used to provide propulsion. I mentioned this earlier. You got a fan that points like backward from the hovercraft, and when you turn that on, it's shooting air. Out the back, and then you get the equal but opposite reaction. The hovercraft will move forward. You usually have a rudder or some other method to redirect that fan so that you can make turns. Those turns can be pretty gradual, and you still have momentum. You know, you have the loft conservation of motion. You're still moving. So that's why it's difficult to pilot these things. It's challenging. You can't just slam on brakes with a hovercraftft. You can stop the fan and you will come to a stop gradually, but you can't just slam the brakes, so tight turns and sharp stops are not really possible, which is why hovercraft are typically a little easier to operate on the water than they are on the land. If you come up to an obstacle on land, you might be bumping into something. One thing that Cockrell figured out was that, perhaps counterintuitively, the larger the hovercraft was, or more precisely, the larger the area of the air cushion or cushions that provide the lift, the more efficient the hovercraft became. Here's how he put it in his patent, and it does get technical. So here we go quote. In such vehicles, the lift or load carrying capacity is proportional to the plan area of the gas cushion or cushions. The energy required to contain the cushion or cushions is proportional to the peripheral dimension of the cushion or cushions. Thus, for an increase in size of a vehicle, the lift increases proportionally to the area of the cushion or cushions, whilst the energy requirements increase linearly with the periphery of the cushion or cushions. So, in other words, the larger the hovercraft is, or the larger the surface area of the air cushion is, the easier it is to achieve greater lift with only a smaller increase in actual power. So you're getting greater returns for just a smaller investment in power, and thus it's more efficient to build larger hovercraft than it is to build smaller hovercraft. I guess you could still just say that pointing a fan downward provides the lift needed to hover the vehicle, and you could just leave it at that, but you do need some other design elements to make the vehicle stable and useful, Like I said, hovercraft are still a thing, They're just not typically used for commercial transportation. They are not commonplace, but similar technologlogies related to hovercraft have found their way into designs since then. You might know that the original concept for the hyperloop train system included a train running through a tube where you had pumped out most of the air, and the train would hover above the floor of that tube through the use of air ball bearings. So Elon Musk described it as sort of like an air hockey table, only facing downward instead of facing upward. That's not that different from a hovercraft, or a glidemobile, or an air cushioned vehicle, however you want to call it. The methodology described in the hyperloop concept is a bit different from what you'd see in a hovercraft, but the gist is similar. As it would turn out, the various companies that sprung up in the wake of Musk's proposal would, by turns, choose a different approach. Some went with magnetic levitation, some would dispense with the idea of suspending the train above the track entirely and thus embrace a more traditional train design. But initially the hyperloop was meant to have an air cushion under it. Of course, you could argue that these days the hyperloop concept has been all but abandoned because several of the companies that pursued the goal of making it a reality have since gone out of business. You can, of course, build your own hovercraft. There are websites describing how to make a sample hovercraft using like a balloon and an old CD or a DVD. I would suggest use one you don't plan on ever playing again. Maybe maybe a kid rock album would be suitable. There are also kits to build an actual hovercraft. You know, you can kind of build a sort of personal pan pizza sized vehicle. I've seen diy hovercraft on YouTube of varying degrees of safety and reliability, and there are lots of ones for things like radio controlled hovercraft. Right. There are a lot of toy versions of hovercraft that work on the same principle, but they're obviously at a much smaller scale, and that way you can learn how challenging it is to direct a vehicle that works on momentum and has a lack of breaks. It can really be easy to get moving in a particular direction and a real challenge to you know, stop doing that. But that's our look at hovercraft, a technology that I think is pretty interesting, pretty cool. I have never written on one. I've never been on a hovercraft. I kind of wish that I had had that experience. Maybe one day I'll make a trip out to the Isle of Wight simply so that I could say I wrote on a hovercraft, which means that I'll be walking around Isle of Wight and probably lamenting how many places have closed down. I've watched some videos recently of that area of Isle of Wight and it was looking a little grim, although I should say that was also in the off season, so maybe that's it, you know, Maybe it's just that, Oh, these are things that are usually working in the more popular seasons. It's just in the off season they shut down because there's no sense in running it. Then maybe that's the case, I hope. So, but that is our look at hovercraft. I hope you enjoyed this episode. You learned a bit about Sir Christopher Cockrell and his mission to create a new form of transportation and to get past that irritating problem of friction that voting stuff encounters. Although Cockroll encountered more than a little friction just you know, in the political side, as opposed to as opposed to physical friction that you would encounter in the water. I hope you are all well. Thank you so much for listening, and I will talk to you again really soon. Tech Stuff is an iHeartRadio production. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.