Welcome to Stuff to Blow Your Mind production of My Heart Radio. Hey you welcome to Stuff to Blow Your Mind. My name is Robert Lamb and I'm Joe McCormick. And in today's episode, we're going to be looking at a spectacular bit of hypothetical air travel that has intrigued us for centuries. The vacuum airship or knull ship as I've seen it referred, and that's such a cool name for something that I think I had to front loaded on this episode, but usually it's just referred to as a vacuum airship. And the basic principle, as we'll discuss, is pretty simple. Hydrogen, helium or hot air filled balloons allow an airship to traverse the skies because these gases are lighter than the surrounding air, and even lighter gas is the absence of any gas at all, the vacuum. If one could create a vacuum chamber or bladder that was itself light enough, then this could be used to provide lift for airships on Earth or even on other planets. I mean, it's such an obvious extension of the idea underlying balloons indirigibles all lighter than air flight craft. You would have to assume that if if you don't see things like this being used all the time, there must be a pretty good reason. And I guess we'll get to that in a little bit. But yeah, it's it's like an obvious place to take the idea. Yeah, yeah, And and so it's ultimately such a fascinating topic because yeah, there's the basic underlying science of the principles of it are pretty sound. There are material challenges in place, but then the history of the concept is pretty interesting as well. Thus far, however, the main place you'll see these vacuum airships deployed are going to be within the pages of science fiction and fantasy. And one of the main examples of this and this and you'll see this why le Cited is a novel that was serialized between nine thirty by Edgar Rice Burrows titled Tarzan at the Earth's Core, not to be confused with At the Earth's Core, which was his nineteen fourteen novel that established the hollow Earth world of Pellucidar, which is this, like it sounds, it's like a world within our world. It it has a race of intelligent and I think psychic terra Saar overlords called the Mahar or the Mahar and the that novel prominently features a subderine. So we've actually mentioned that book on the show before in our episode about subderines, which is another sort of fantastic um hypothetical, uh, means of traversing the natural environment. But this Tarzan at the Earth score is a crossover novel which features Tarzan traveling to the inner world v a vacuum airship. And I had to dive into this in a little bit. I assume you haven't read this one either. No, I haven't read it. I do remember it was mentioned in that earlier episode. But also it just got me thinking about, like, wait, where do all of these science fiction books about a hollow earth with like a different biosphere or or some kind of archaic state. Uh, where does all that come from? Because this isn't the first one. This is in what thirty, but like as far back as the eighteen sixties you had Jules Verne with Journey to the Center of the Earth, which is very similar concept. I don't think it has like psychic pterosaurs, but it does have a hollow earth with like essentially a mirror biosphere on the inside that has dinosaurs and other prehistoric creatures. Well, it makes me think we should come back into a proper episode on the concept of the hollow Earth. You know why why it it wouldn't work A quiet individuals thought that it could have worked, and why it has uh, you know why it has captivated people's imagination for so long. Yeah, I don't know of anything older than than Jules Verne, but but there may be. So I had not read this book either. I think the only Edgar Rice Burrows novel that I have read is one called The Monster Men, which memory serves is largely it seems very inspired by the Island of Dr Moreau, but it was it was pretty fun, as I remember it, And so I went ahead and and dove into this one, and I was like reading through it trying to find some good examples of them talking about vacuum airships. And I think I wasted a good, uh like minutes just scanning through the book trying to do some searches. And then I realized that I was looking at the wrong one. I was looking at the Earth's Core instead of Tarzan at the Earth's Core. But I switched to the correct book, and they talk about the vacuum airship a lot in that one, So I can't just find like the one spot where they're talking about it there. It's a frequent topic of conversation. But I do want to read just a fragment here from it where they touch on it. Uh. So this is Edgar Rice Burrows from Tarzan at the Earth Score again from ninety. The greatest risk that we would have to face would be a possible inability to return to the outer crust owing to the depletion of our helium gas that might be made necessary by the maneuvering of the ship. But that is only the same chance of life or death that every explorer and scientific investigator must be willing to assume in the prosecution of his labors. If it were but possible to build a whole sufficiently light and at the same time sufficiently strong to withstand atmospheric pressure, we could dispense with both the dangerous hydrogen gas and the rare and expensive helium gas, and have the assurance of the utmost safety and maximum of buoyancy in a ship supported entirely by vacuum tanks. Perhaps even that is possible, said Tarzan, who was now evincing increasing interest in Gridley's proposition, the Americans shook his head. It may be possible someday, he said, but not at present with any known material. Any receptacle having sufficient strength to withstand the atmospheric pressure upon a vacuum would have a weight far too great for the vacuum to lift. Okay, so first of all, I am definitely picturing this as the Kristoff Lambart Tarzan from from gray Stoke. This has got to be it, right, Yes, yes, it's it's a gentleman Tarzan here. Mild spoiler for the for the book. Obviously they figure it out. I believe some sort of rare element or metal is introduced that it makes the impossible possible, because otherwise, how are you gonna get Tarzan to the Inner Earth to battle psychic terra stars. I mean, it's funny how this Psychic Terrastar book does uh correctly diagnose some of the problems with existing lighter than air craft. So one problem is needing to have continued access to your lighter than air gas so that so that you can like refill the balloon or the tank do because there's always going to be some kind of leakage or potentially even damage that would allow the gas to escape. You'd have to have a way to get more helium in there. If it's helium. Of course, if it's hydrogen, you run into a whole uh raft of other problems, as one can see with the history of the henden Bergens and fourth hydrogen very flammable and having the same uh you know, fixed access problems as helium. But yeah, with with a vacuum like, you don't need to carry vacuum around with you. All you would need to do is find a way to pump out the chamber. Yeah, so you can see why it's such an attractive option. And this this passage kind of encapsulates all that I was looking around too. I noticed that it's It's been noted that at least two other authors that we've mentioned on the show before have also employed vacuum airship principles. Peter Wattson makes use of them in his Rifters books as a means of enabling flying machines. I totally forgotten about this, and then Ian in Banks invoked them in at least three different novels, including at least one that I definitely read, but I also don't remember mentioned of them. I guess I just wasn't My mind wasn't as open of the idea of vacuum airships when I was reading these books. And I've also read that they factor into Neil Stevens since The Diamond Age, which I have not read, but I've heard good things about. So wait a minute, I actually know almost nothing about Tarzan. Where old does Tarzan go? Is he like the lepre Con or like he goes to space, he goes to the to the ocean, he goes to the Hollow Earth? Does he does he go to Las Vegas at some point? What? What? What are all his adventures? Well, Joe, there are twenty four Tarzan novels by bar Rice Burrow, so you know he he ultimately gets around. I have not read any of them, but you can just when you when you start scanning the titles, you realize that he maybe starts running out of jungle and he has to has to go to lost Empires in the Earth's core, in a city of gold, forbidden City. Uh. Looks like he may join the Foreign Legion at one point, so, uh, you know, he's got to get out there and travel around and and explore the outer world. But I think generally speaking, he's always going to battle or befriends some sort of the large animal. Thank you for correcting my tarzan ignorance. Now I know, all right, But I guess before we go any further exploring the history of proposals for vacuum airships, it would be worth briefly explaining the underlying reasoning, and that is that, whether you're talking about a lighter than air gas inside a balloon or a rigid chamber containing a vacuum, the physics phenomenon that would cause this, uh, this balloon or or chamber to fly is what's known as Archimedes principle, named after the ancient Greek inventor and mathematician. And I think the core idea you really need to understand in order to grasp Archimedes principle at a gut level is the idea of fluid displacement. Fluid displacement so a few extreme experimental conditions aside. Basically, if you are on Earth, you are submerged within a fluid. So if you're a barracuda or a jellyfish, that fluid is going to be water. If you are a human standing in line at King that fluid is the atmosphere. Both gases and liquids are fluids because they both flow to fill containing environments. And when you occupy space within a mass of either kind of fluid, whether it's liquid or gas, you are taking up space that this fluid would otherwise fill, would otherwise rush in to fill, So, in other words, you are displacing gas or liquid. The inside about physics that our comedes had is that objects submerged within a fluid are pushed upward, meaning in the opposite direction of gravity, by a force that is equal to the weight of the fluid displaced by that object. And this is why boats float. I mean, humans have been making boats for a long time, but uh, it took us a while to figure out what is the exact physics principle governing the flotation of boats. So a boat, for example, may have a steel hull, and steel is very dense, So you would think that a steel boat should sink, right, I remember wondering about this when I was a little kid. How does you know metal sink? So how does a metal boat float? A metal boat floats because the hull of the boat displaces a lot of water. An amount of water that is as heavy as the boat itself. So when a boat gets launched out into the ocean, it sinks down in the water until the amount of water it displaces is the same as the weight of the boat overall. And then after it reaches this equilibrium, it's held up on the surface of the water by that buoyancy, that force pushing upward on the boat equivalent to the weight of the water it displaces. And this, of course is also why a ship sinks when water leaks into its hull. It's water that is denser than air filling that void that was otherwise filled with with air. So kind of weird, but I think accurate. Way to think of a ship on the ocean is a rigid balloon filled with air. Now, the same principles that apply in water also hold true in the fluid of the atmosphere. Is a force pushing up on an object that is equivalent to the weight of the air that that object displaces. Now, for most objects around us, the the atmospheric buoyancy is negligible because objects are way more dense than the atmosphere that they're displacing. Uh. Though technically it is true that your body has a measurable buoyancy within the air. It's not enough to make you float up off the ground, because you know, human bodies are are pretty massive. But based on some rough calculations I looked up, it seems like it's probably a fraction of a pound at sea level for the typical range of human body weight. It's one estimate I saw was that it's like zero point two pounds for a hundred and seventy pound adult. So how can you change an object in order to take advantage of that atmospheric buoyancy and make it float up in the atmosphere like a boat floats on the water. Well, as demonstrated by balloons and dirigibles, what you can do is make that object take up a lot of space, mostly with material that is lighter than the atmosphere itself, which is usually going to be a lighter than air gas like hydrogen or helium. But of course it could also be a chamber that has no gas in it at all, nothing in it at all, which would be the lightest possible way of taking up space. Now here's a weird fact. I was just wondering about which of the fundamental forces actually causes the force of buoyancy. Where is that force pushing up on a boat or pushing up on a balloon coming from? Counterintuitively, that force originates with gravity, which is kind of strange because the force of buoyancy is going in the opposite direction of gravity. Right, Why would gravity cause something to rise up from the ground instead of sinking down? But you have to think about a sort of chain of causes here. So, whether you're talking about the atmosphere or the ocean, gravity is pulling all that fluid toward the Earth's center of mass. It's pull ling all the water or the gas down. So gravity is the cause of air pressure and water pressure, and it is the downward pressure of the surrounding fluid that causes buoyant objects within that fluid to rise. So, to use some kind of approximate and anthropomorphic terms, when a balloon floats, it's because the heavier gas of the atmosphere around it is all rushing down to get to the surface, and it has to push the balloon out of the way to get there. And it can push the balloon out of the way because the balloon is less dense than it is. It's kind of like if asking, well, hey, I'm why if everybody's trying to get to the TV section of the big box store on Black Friday, everybody's trying to get there, then why is the four Why am I being pushed out of the store because everybody else is pushing harder than you are. Thank But to come to real world proposals for vacuum airships. Uh. One thing I was shocked about was how far back this idea goes. I would have imagined it was something dreamed up in the nineteenth century. Yeah, I was very much the same. But then I started looking into it, and sure enough, the roots go all the way back to the seventeenth century. So our story here begins with an Italian Jesuit priest by the name of Francesco Lana Detersi, who lived sixty one through six seven, sometimes called the father of arionnautics. His groundbreaking book from sixteen seventy, titled Prodromo de larte Mastra, was apparently the first to discuss the possibility of human flight via mathematical calculations and an understanding of physics. Uh. These were no mere loss speculations either. This was a work that was translated and then circulated throughout Europe, and subsequent advancements in ballooning, for example, are are often directly linked to this work, namely thinking of the month Gaffier Brothers a flight in seventeen eighty three, which was an unmanned balloon flight lasting about ten minutes. Now, I want to stress we're largely talking with with the Western and European sphere of of exploration here. If you get into the Eastern accounts, there are some some older accounts of possible you know, unmanned hot air balloon experimentation in China for example, going back you know to I think like the third century see wow, but again unmanned. Now, in this particular book, Lana covered many subjects uh here and I was reading about this in a paper titled the Jesuit Contribution to Written Art Technological Sources in the seventeen and eighteen centuries by Karina Gramatki from sixteen. Apparently the topics include invention itself, drawing, design, pigments, chemistry, medicine, arithmetic, the production of telescopes, microscopes, and finally aeronautics. Pick a lane. I mean, this was an age where yeah, if you were if you were into stuff, you were you were into everything. Yeah, so, um a particular interest to Lana here though we were recent advancements in the creation of the vacuum pump. This would of course been a continuation of suction pump technology. Uh. The idea of the vacuum pump. The first vacuum pump was invented in sixteen fifty by the German scientists Otto von Garrick and subsequently experimented on by others. Oh. Yeah, we've talked about Otto von guerricky before in I think in an episode that we did about atmospheric pressure, specifically reference to his experiments with the so called Magdeburg hemispheres, which was a really interesting experiment that took place in the sixteen fifties, I believe, And uh, it's been while since we talked about it, so I may be forgetting some of the details, but basically, from what I recall, they took two brass hemispheres half spheres, and then greased the edges of them with lard and then pressed them together and then used the invention of the air pump to remove air from inside these two hemispheres, creating a vacuum within of course, a partial vacuum. You know, they're not going to get every single molecule out, but yeah, they're getting getting most of the gas out of them. And then they hooked these hemispheres up to horses and had the horses pull in opposite directions to try to pull them apart, and they couldn't. Like that, even horses could not separate them. What they were demonstrating there was how heavy the atmosphere is. That when you take all of the atmosphere out of the inside of these two two half spheres, you create such a disequilibrium that the you know, the atmosphere is essentially reaching down and and uh clutching these two things and pressing them together so that even great force cannot pull them apart. Yeah. There there are a couple of papers on this topic that I was reading from New Scientists actually, like I was kind of getting the impression that maybe the editor at New Scientists is like pounding the desk that I need more vacuum airship stories. But one of them was from two thousand and nine by Paul Collins titled The Rise and Fall of the Metal Airship, which is ultimately about metal airships in general and not just the vacuum airship concept, but he mentions, uh this this experiment, writing uh quote Otto von Gerriki had drawn together small copper hemispheres with such a strong vacuum that teams of horses could not pull them apart. But he mentioned some other things of note here. Collins also writes that the concept of a vacuum airship appears in a German interplanetary travelog of seventy four, envisioning trips to Mars. So another example of something ultimately far earlier than I would have had, oh guessed it. If I was to guess, well, when when we were people first thinking about vacuum airships in the atmosphere of Mars, I would not have gone with the mid Uh. Now is a brief detour. I want to touch on another thing that Collins mentions here um to get to the title of his paper, there actually was eventually a metal non vacuum airship, and this was in the first one was a thirty eight meter airship designed by David Schwartz and helped into the sky by the Prussian airship Battalion. And it was a It was blimp shaped, but its skin was riveted aluminum plates, and it traveled about six kilometers total before it stopped. They put the brakes on and it caused the thing to crumble due to its rigid construction. But the advantage of a fully functional metal airship would be speed. Though so uh the the idea didn't go completely away, and in good years, original airship designer Ralph Ubson quote formed the Metal Clad Airship Corporation to build an aluminum clad helium airship, the z m C two for the U. S. Navy. Although notoriously difficult to handle, the quote unquote tin bubble, as it was dubbed, could reach a speed of a hundred kilometers an hour, and it put in twenty two hundred flight hours before it was decommissioned in n and that was it for metal airships. That was the last one that took to the skies here on Earth. And yet that was the Detroit z m C two Angel. I include a picture of it here for you. If one was looking at you might not guess that what you're looking at is is a metal structure, aluminum clad helium airship. That I mean, if I've ever seen a tin bubble, that is the tin bubble. But to clarify again, the one the actual examples we've just been talking about, the people got up in the air flying even if they were even if they failed early on, these were not vacuum airships. These were airships that you even though they had rigid out or hulls, they did use some form of gas inside. Yeah. Yeah, So ultimately, as as we'll discuss, the vacuum airship is still a concept that individuals are still chasing today. Now coming back to Lana's book here, another important connection here would be to Robert Boyle's work proving that air has weight. Essentially, it was proven that all of the atmosphere could be mechanically drawn out of a volume. Maybe the nature didn't abhor a vacuum quite as much as previously supposed, and Lana has taken the next step by speculating one exciting way that such a vacuum could be made to work for us. So what Lana does here is he basically applies what was known at the time regarding the nature of air, vacuum and cylinders to devise a means by which first vacuum spheres would be made that would float up through the air, and secondly that with enough vacuum you could also float a vessel. So he proposed a vessel consisting of a basket with a say ill and rudder, held aloft by four large twenty five ft spheres made of thin copper sheeting and bound together by rigging. Uh. This was of course never actually built, but there have been various illustrations of what this would have looked like. I included one here for you, Joe. It looks positively whimsical. Why does it? Does it have an oar? I guess that's some kind of rudder. Actually, yeah, this is some sort of rudder device to steer it. Though it really does look like a paddle for the air. Now again, now again, Atlanta was a very serious individual, so it is he's not just dreaming here. He's applying what was known about about the atmosphere and you know, current understanding of physics, and so he was. He was serious about the underlying principles at work here. So he discusses not only how this concept might work, but he also gets into some of the objections to it. For instance, do you might ask, well, wouldn't this just float up into outer space until the people aboard died and it would just be completely uncontrollable. Well, he describes how controlling the air vacuum levels would allow you to make adjustments and keep yourself from just floating up to heights altitudes beyond which you had intention of traveling to. Right, So, I guess the fear is that, you know, if the vacuum is potent enough that it would just float you up to the top of the atmosphere and you'd sit on it like a boat floats on top of the water. Now, of course, you have to remember that even though a vacuum chamber would have buoyancy within the atmosphere, it also again there is weight, you know, there is weight made up of the shell surrounding the chamber and the boat and all that. So that would counterbalance that to some extent. But then also, yeah, the other thing is that you could control altitude just by allowing some amount of gas back into these partial vacuum chambers, and then so that would help you sink back down and then if you want to float up again, you would once again pump that gas out. Yeah. Now, the big problem here, of course, is the notion of containing that vacuum um. The big question would be wouldn't it crush the copper spheres that are contained that vacuum, or you know, that are allowing the whole system to supposedly float to begin with. And the correct answer we know now is yes, it would have just crushed those spears. But at the time Lanta contended that, now, this is the perfect shape of the sphere would hold up to the equal pressure of the vacuum within it. Again, we know now this wouldn't work, but his hypothesis was that it could possibly function. Right, So I guess here you're you're getting into the idea of a balancing act, right, so that you can, of course create a pretty pretty strong vacuum within a sealed chamber without the weight of the atmosphere crushing it, just you know, turn smashing that chamber like a tin can. But in order to do that, you have to make the outsides of the chamber pretty darn strong. And in order to make them that strong, you have to add more and more weight to the chamber, thus counteracting the buoyancy effect of the vacuum within. Right, So you're chasing the buoyancy here, and can you achieve it without adding so much metal that you lose any buoyancy? You might be seeking after and can you can you make the materials thin enough without just causing it to collapse anyway, And this will remain important when we get into subsequent attempts to make this hypothesis and a reality. But here's another little bit of of interesting, ultimately speculation by Atlanta on the use of aerial technology, because he ends up concluding in the book that God would never allow such a vessel to actually be built, as it could then be used to attack cities and towns from above, and that there would be absolutely no stopping such vessels. So you know, God would just shut that down. It would be like a tower of of battle situation. Oh, this theological prediction must have been very well vindicated then when when later people came along, I think Leibniz was one of them, uh, showing that like no materials we know about are strong enough to make this work. Yeah. But but but again this idea of of of aerial dominance say that would be possible in a military a situation. To a large extent line, it was correct here about just how devastating this would be. Because, of course, during War War one, Zeppelin served as the world's first long range bombers, though their dominance would be short lived due to their their weakness versus interceptor aircraft, but aerial bombardment would indeed be a defining factor of warfare from the twentieth century onward. Yeah, the invention of air power, I guess I'd say air power, along with like long range artillery, completely changed war in the twentieth century. Now, on that note, let's move to the next chapter in our history of of the vacuum airship or our pursuit of the vacuum airship, because this will take us to the late nineteenth century right up until the dawn of the twentieth century. Because there was at least one spirited individual who thought, yes, the vacuum airship can work, and it will work. And that is one author, Debase set Uh. And this is detailed in Balloons to Jets, A Century of Aeronautics and Illinois by one Howard L. Scame Horn. So author debossit here was a Chicago doctor who quote designed and electrically powered vacuum tub balloon which he intended to use for transporting passengers and freight over vast distances at high speeds. And this is described as an air tight tube cone shaped at either end, and it was going to be made of thin steel sheets and it would stay aloft when all of the air had been pumped out of it. And again it would be used for high speed transportation of passengers and freight presumably, uh, you know, from Chicago to two other important cities. I mean, if you can create that without the atmosphere crushing it, good on you. But I am doubtful. Yeah. But and so at this point you might think, Okay, Chicago doctor daydreaming about his airships. Well know, h he went a step further or uh, the good doctor actually organized a company with three associates, the Aerial Navigation Company of Chicago, and they raised a hundred and thirty thousand dollars at the time through the sale of stock to construct one of the ships. So already it's sounding a bit more like a legitimate effort now, right. And there's more. Uh, When they hadn't produced anything with it with these funds, they turned to Congress for more funds, and funding bills were introduced in both houses of Congress by then a representative Ransom W. Dunham of Chicago, And it was apparently some traction or momentum here, but both bills failed to pass. Why does this sound like something that should be associated with the Chicago World's Fair. I know I was thinking the same thing, you know, and I guess to a certain extent, we are talking about, you know, some of the same sort of you know, futuristic, technological, um optimistic ideas that were circulating at the time. You know that, like, well, we have the technology, but we can do this. We can make these airships a reality, and they're gonna fundamentally change the way we travel and the way we move cargo. It's this is great, Let's do it. Let's get the funding. Okay, well maybe we need a little more funding. Let's get Congress on the Horn. Uh yeah, it really it sounds like there should be a chapter about the Vacuum airship and Devil in the White City. Yeah, so skame Horn rights that The fight for the Chicago Void vessel here went on for a good twenty years up until the dawn of the New century, with the Debausit trying in vain to raise enough money to build one of these ships, all the while dealing with scientific critics that he had just insisted would be proved wrong if they would just let him build one. He was like, look, just just fund it. Just let me build one, and then you'll see you'll see that this this is possible. Um, but it sounds like the real nail in the coffin. Was that one of a couple of leading US aeronautical authorities of the time, Octave Channeux and uh Alvary France's zomb quote publicly denounced and mathematically prove the fallacy of the vacuum principle. Now, I don't know the basis of the fallacy they're talking about there, but I would have to assume that again, it's going to be, uh, it's going to be rooted in the lack of a material strong enough and light enough to create this kind of vacuum shell. That if you're going to create a rigid shell to contain a vacuum, the atmosphere is always going to crush it unless you make it so thick and so heavy that it that it again out does the buoyancy effect of the vacuum and makes it unable to fly. Right. Yeah, I mean that's that has always been and still is largely the achilles heel of the whole concept. Um by the way. The same book also reveals that during this same time period there was at least one other Illinois based inventor trying to raise funds for an airship. It wasn't a vacuum airship, but still airships were very much on the brain. And it does sound like, yeah, the people of the White City at the time, Uh, we're sharing some of the same dreams for what the future of air travel looked like. What if H. H. Holmes, instead of operating like a a murder hotel, had operated a murder airship. Well, now you've got a good movie, pitch. We haven't had a I don't think we've had a good airship movie recently, right, it could be all like a haunted airship or yeah, a murder airship. I can't think of one. I think of that scene in Indiana Jones and the Last Cersae. That's about it. Yeah, yeah, there was there was another one. Or when he when he punches the Nazi out of the window no ticket, Yeah, yeah, yeah, there's a and that had some some very neat scenes with with the Zeppelin there there was also a movie called Zeppelin that had Michael Yorke in it. This would have come out and I remember seeing bits of it. I don't think I've watched it in its entirety, but I remember catching bits of it. I'm like American movie Classics or something, and and being impressed by some of the scenes of people aboard these these airships. Than all right, well, let's take things into the twenty one century. Another New Scientist article. Again, New Scientist is your go to place for articles about vacuum airships. Uh. Noted science writer Philip Ball discussed this in in a New Scientist article titled flying on Empty from and as Ball discusses, yeah, this idea has never quite gone away, in part because if it could be pulled off again, you don't need hot air or flammable hydrogen or precious helium to keep the ship afloat. It's not about pump putting something in. It's about just taking atmosphere out. And if you could only figure out the materials problem, then you know the world is your oyster. And again, the materials problem is designing an outer shell that would be strong enough to withstand the atmospheric pressure trying to crush it in, but also light enough to stay afloat. Right, And of course, as we get into the modern era. We're in this age of of of special you know, nanomaterials and new ways of looking at how these materials can be put together. And of course this is this has led to a number of ideas that haven't been possible yet. We've been able to look to the future and say, well, what what might we be able to do If we can just create something that's strong and flexible enough, you know, space elevators can become a reality then, as well as things potentially like the vacuum airship. And so Ball mentions an individual by the name of Ben Jenet, who at the time of publication was working on his doctorate at the Massachusetts Institute of Technologies Center for Bits and Atoms, and Jenet devised the use of lightweight quote unquote lattice materials to make the shell of a vacuum ship possible. So Ball points out, the Genet calculated that even with currently available materials, a shell with a thickness one tenth of the radius of the sphere it contains will be able to withstand the air pressure without buckling, and this would then have to be covered with a thin, impermetable skin. Uh Genet's idea would also involves creating the vacuum at a higher altitude, which I thought was interesting where air pressure is lower, and so you would have some I think what it was discussed here is solar powered hot air would be used to allow the vessel to rise up to that initial altitude, and then you would begin the vacuum process when it's easier to pull that off, and then you would have would have a theoretical operating altitude of something like twenty meters or sixty thousand, six sixteen feet. Okay, so that makes sense. Up at a higher altitude, the air pressure is going to be reduced, which means there's less crushing force on the outside of the chamber. Yeah. Yeah, that's that's my understanding here. So Ball points out the Genet and his collaborators here were in at least we're in prep still are in contact with Boeing, so Aurora Flight Sciences on the concept, and then an Italian company called oh Boot was also looking into vacuum ship ideas. Ball reported that while most of the emphasis was on shipping with these modern concepts, the idea of at least some level of human travel wasn't beyond possibilities as well. At least for short jaunts. And again you come back to this sort of the the romanticism of airships. I can imagine where this would be the case. Well, one thing you mentioned that operating altitude you said, twenty thousand meters or like sixty feet, is well above the normal operating altitude of fixed wing aircraft. So so I wonder what, what does what does it look like once you get up that high? Are you starting to get into like looking at seeing the curve of the Earth territory? I don't know. Yeah, it sounds like a situation where you you could easily get into this area where you're pretty selling the tickets to celebrities and so forth, kind of like we've seen with with these other high altitude flight near space travel scenarios. So I don't know. It would be interesting to see where where things go in the decades ahead. But I wouldn't be surprised at all, uh to see one of these concepts sort of come to fruition in at least in that uh, that scenario. But I know when it happens, I'll be able to turn to New Scientist to read an article about it for all your null ship needs. Yes, So One thing I looked into is that vacuum airships have also been proposed in various ways for exploring other planets, particularly Mars. I think there have been a few ideas along these lines, but the main one I was reading about was linked to a U T. Austin aerospace engineering professor named John Paul Clark, who I think until just recently was here in town at Georgia Tech. But Clark and colleagues UH submitted a paper that I saw published under the NASA Innovative Advanced Concepts Program, or in i a C. This was a Phase one proposal called Evacuated Airship for Mars missions. And I was reading about this in another summary that Clarke had prepared that's hosted on the NASA website, and he makes some interesting points. One funny thing is that advanced project briefs like this always have the obligatory section where they rag on whatever technology we're currently using. So this one takes a few good wax at ground based rovers on Mars. It's like, you know, we're over with wheels, can fall in a ditch, get stuck, you know, and it's got limited line of sight, can't see over mountains, a lot of problems with with ground based rovers. You know what would be better a rover that could fly, But of course it's going to be very hard to fly on Mars. And here's where a vacuum airship could come in. Obviously, a vacuum airship would be useful in planetary explorations for some of the same reasons it would be useful on Earth. You get the general transportation efficiency benefits of air travel without having to rely lie on a fixed supply of low density gas like hydrogen or helium. To keep a vacuum airship afloat, you don't need a supply of gas. Technically, all you need is power power like electricity to operate a pump that will continuously evacuate gas particles from the inner void. Now, Clark points out that there is a good reason what we've never developed a vacuum airship for use on Earth. It's the same reason we've been talking about already. There is no homogeneous material yet discovered that is strong enough to be completely evacuated and withstand the crushing pressure of Earth's atmosphere, at least not without the structure becoming too heavy to float Earth's There is cruel to vacuum airships. But Clark argues that, based on his team's calculations, not only is this not true on Mars, the atmosphere of Mars is kind of an ideal environment for a vacuum airship. Now this immediately went against my into sans because before I really reasoned it through and read the argument here, I would have thought, well, okay, the atmosphere of Mars is much less dense than Earth's atmosphere. Uh, the average surface density is something like zero point zero two kilograms per cubic meter. Compare that to Earth's, which is more like one point two kilograms per cubic meter. So Earth's is a couple of orders of magnitude greater in density than the Martian atmosphere. Martian atmosphere is very thin, and of course a balloon floats by having contents that are less dense than the atmosphere. So in an atmosphere with lower basically in a thinner atmosphere, I would have assumed it's got to be harder for a balloon to float. But here is where I would have been wrong. Of Course, a vacuum is always less dense than even a very thin atmosphere. So if it can be contained and it displaces more atmosphere than the weight of the craft itself than the weight of the shell and the payload, it will float. The real benefit of Martian atmosphere is in its pressure to density ratio, so the main constituent of Martian air is carbon dioxide. Unlike on Earth, which has mainly nitrogen and oxygen. At a molecular level, carbon dioxide is denser than nitrogen and oxygen, and the cold temperatures on Mars also help make that CEO two even denser. You're probably familiar with the idea that hot gas expands, cold gas contracts, and yet at the same time, a cool advantage of Mars is that there is far less atmospheric pressure pressing on the outer shell of the airship, so you should be able to construct a vacuum envelope that can stand up to the weight of the atmosphere on Mars without buckling, using a design that is still light enough to float. To read a section from the n I a C Paper quote, Mars having the most suitable atmosphere for the vacuum airship is quite remarkable, since the martiantmosphere is a severe detriment to all other flight vehicle designs. So you know you try to do like a fixed wing aircraft on Mars, that that's going to be really hard. Continuing the quote, the Martian atmosphere is comprised almost entirely of carbon dioxide, so vehicles cannot use typical combustion fuels which require an atmospheric oxidizer. Glider, plane and helicopter designs are all hindered by the atmosphere of Mars due to the low Reynolds number and relatively low density. Additionally, the vacuum airship provides benefit over other airship designs and super pressure balloons because of the inherent robustness of the design. Moreover, if damage is sustained, the vacuum airship can land be repaired and then re evacuate to resume operation, whereas another airship would need to be refilled with a lighter than air gas. Therefore, the evacuated airship design thrives in an environment where most other aircraft are added disadvantage, and in this paper, Clark and colleagues claimed to have already modeled the design that should be able to carry a payload of fives in Martian air and UH and that way, they say could be increased with further design improvements. So the argument here is that not only is it a situation where to make uh, to make our vacuum airship dreams possible, we must go to Mars, it's instead, no, that makes this the concept that makes this the design that makes the most sense on Mars if we're going to have anything flying around, right, that's their argument. And I don't know if this has ever made it beyond this this phase one or phase two proposal level. So I'm not aware of any evidence that this is actually like being developed for Mars missions. But at least the initial case they make is really interesting, and I wonder if if anybody's going anywhere else with it, But yeah, I'm certainly intrigued. So Earth, with its thick atmosphere, may well hate vacuum airships. It may just forever crush them. Maybe there's no way we could really design one that would would feasibly work on Earth, but Mars maybe a completely different story that that thinner atmosphere. Maybe just the place to make the stream of reality. Now, of course, this this all brings to mind a previous episode of the show that we did titled airships over Venus, which discusses the the hypothetical use of airships in the opper atmosphere of Venus, at least for unmanned craft, but also in some of the more extreme and in fantastic concepts that have been discussed in some of the literature, the idea that you could potentially have a human being travel to the upper atmosphere of Venus and be inside especially designed airship. I think one of the ideas for for crude aircrafts there is literally that you could have the crew inside the balloon because in the Venusian atmosphere, breathable air floats. Yeah. Now, looking around, I noticed that there there have been some papers that have come out, uh, speculating about the use of vacuum airships in the Venusian atmosphere, the upper atmosphere. So it looks like there there at least are some individuals out there who are thinking about taking the vacuum concept to the upper atmosphere of Venus as well. You just hope it doesn't sink. I talk about heavy, heavy, crushing atmospheres, yes, yeah, the Venusian atmosphere ultimately is is an atmosphere that crushes everything all right. Well, on that note, we're gonna go and close out this episode, but we'd love to hear from everyone out there if you have thoughts on vacuum airships or just airships in general. Uh, some of these uh, these these concepts we've discussed regarding the atmospheres of other worlds. Everything is fair game, right in, let us know what you think. We'd love to hear from you. As always, Core episodes of Stuff to Blow Your Mind, the podcast we found in the Stuff to Blow Your Mind podcast. Feed Core episodes on two season Thursdays, Listener Mail on Monday's short form Artifact or Monster Fact on Wednesdays, and on Fridays, we do Weird How Cinema. That is our time to set aside most serious concerns and just talk about a strange film. Huge thanks as always to our excellent audio producer Seth Nicholas Johnson. If you would like to get in touch with us with feedback on this episode or any other, to suggest topic for the future, or just to say hello, you can email us at contact at stuff to Blow your Mind dot com. Stuff to Blow Your Mind is production of I Heart Radio. For more podcasts for My Heart Radio, visit the iHeart Radio app, Apple podcasts, or wherever you're listening to your favorite shows.