Why don't we have nuclear powered airplanes?

00:00:00
Speaker 1: Hey, everyone, A quick note to let you know that our preschool science TV show on PBS Kids called Eleanor Wonders Why just launched its second season. It's a show about curiosity and exploration and learning to use science to find your own answers to questions or Hey. And I created the show a few years ago, and the second season has just premiered. We're so excited to share this new batch of stories and adventures. Check it out on PBS Kids. Eleanor Wonders Why. Hey, Kelly, do your kids like to fly?

00:00:38
Speaker 2: Yeah, they do, particularly my oldest. They were a little bit scared at first, but I was explaining to them that likes flying on a plane is probably safer than driving in a car, and I eventually convinced them it's safe and now they just enjoy it.

00:00:51
Speaker 1: Hmmm, you convince them it's safe?

00:00:53
Speaker 2: Huh, Daniel, what does that mean? Flying? Flying is safe? But have you figured out a way to make it unsafe?

00:01:02
Speaker 1: I mean, current airplane technology is mostly pretty safe, but there are some pretty cool ideas out there.

00:01:09
Speaker 2: Okay, wait, safe and boring as you described to current planes. I feel like that's what you're going for. That's what you want with planes.

00:01:18
Speaker 1: I guess so. But I bet your kids want a ride at a new experimental crazy plane that involve nuclear power, don't they?

00:01:26
Speaker 2: I bet they won't because they're not going to hear about it, And I'm about letting you hear my kids.

00:01:46
Speaker 1: Hi. I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I want to bring the fun into Kelly's kids' lives.

00:01:53
Speaker 2: I'm Kelly water Smith. I'm adjoned at Rice University, and I think flying should be boring and safe.

00:02:01
Speaker 1: But what if we have crazy new ideas for how to get big heavy stuff into the air.

00:02:06
Speaker 2: Dream a little, Kelly.

00:02:12
Speaker 1: That's not why I had kids, That's why other people had kids.

00:02:19
Speaker 2: Not sure you understand people in their motivations very well, Daniel.

00:02:23
Speaker 1: That's probably true, And my goal here is not to explain people and their motivations, but the universe. So welcome to the podcast Daniel and Jorge explain the Universe production of iHeartRadio, in which we do just that. We try to explain everything that's out there in the universe to you, the fundamental laws of reality, the nature of space and time, and how we can use our understanding of that, to bend reality to our will, to make it do cool. Stuff might fly tons and tons of metal through the air across the ocean totally safely.

00:02:54
Speaker 2: Yes, safely, cool and safe because cool is safe kids.

00:03:00
Speaker 1: But we're also interested in pushing the boundaries of what can be done. Every time we learn something new about the universe, we wonder, how can we use this to improve our lives? How can we use this to make life more exciting? What new kind of gizmo or what's it can this allow us to create that might change the very nature of what it's like to be a living human in this universe.

00:03:21
Speaker 2: I begrudgingly agree.

00:03:24
Speaker 1: And of course, the last century has given us lots of new insights into the nature of reality at the microscopic level. Zooming in past atoms, we've discovered all sorts of new rules for how the universe works, rules that are counterintuitive, that disagree with our classical intuition for how things operate. This new realm of quantum mechanics has opened up lots of crazy new opportunities and dangers for all sorts of humanity. Atomic weapons, atomic power, atomic devastation, and of course potential for nuclear winter. All sorts of consequences for doing.

00:03:56
Speaker 2: Physics, all kinds of reasons for my kids to not listening podcast. Do we talk about Project Plowshare at all?

00:04:05
Speaker 1: I can't remember what is Project Plowshare? Tell me.

00:04:08
Speaker 2: Project Plowshare was a US project to try to use nuclear weapons for like cool good stuff, like making bays by blowing up land so that you can have a little area where you can bring ships inside close to land at some point. And we had a bunch of projects where we set off nuclear weapons for like funzies and building stuff that we thought might be nice. But of course, you know, being with the US's history, we often did it in ways that were not amenable to the desires of the people who lived in that area, and eventually we stopped doing this, thankfully. But Russia or the Soviet Union had a similar program. And if you look up Lake Chaign, I think that's how you pronounce it Chigan. I don't know. Anyway. They've got a lake and it's perfectly circular, and that's because it was created by a nuclear weapon exploding, and then some poor person had to swim across it like convince everyone, no, it's safe, this is cool.

00:05:02
Speaker 1: Cool, Wow, terraforming with nuclear weapons. That's just terrifying. But there was an era after the discovery of atomic power when people felt like this could change lots of different aspects of our lives. Our nuclear knowledge could wiggle its fingers into all sorts of aspects of everyday life. And of course we know now that we have nuclear power plants, and there are nuclear powered chips and nuclear powered submarines. But today we want to explore another question, which is why nuclear power hasn't made inroads into the skies. And so on today's podcast, we'll be asking the question why don't we have nuclear powered airplanes?

00:05:47
Speaker 2: Well? Should we see what the audience thinks.

00:05:50
Speaker 1: This is a fascinating question, and so as usual, we went out into our list of volunteers to see what people thought about having a nuclear reactor on board an airplane. If you'd like to participate in this segment of the podcast, please don't be shy. Write to me two questions at Daniel and Jorge dot com. We will set you up with random physics questions in your inbox every week. Everybody's welcome. So before you hear these answers, think to yourself, how do you feel about having a nuclear reactor on board your airplane. Here's what people had to say.

00:06:22
Speaker 3: Well, we are too far from having electric powered planes, but if we use water and eating them up with nuclear reactor and use it as a propellant, then it could be. But that would require enormous amount of water to be stored, so it's not very likely.

00:06:38
Speaker 1: But maybe in the future.

00:06:41
Speaker 4: I'd say no, because they're quite heavy, I think, and I think they need to be called down quite a lot. So I know in nuclear submarines they use the sea walls to cool down the reactor, so I don't know what is heavy. And unless it was a very very big airplane with nobody on board and nothing on board other than a nuclear reactor, i'd say no.

00:07:04
Speaker 5: Well, I wouldn't fly on it. I mean, a nuclear reactor is typically just a heat engine, steam engine, or just creating heat like on the Mars Rovers. So to have enough energy to continuously power an airplane would need it to be enormous, and then I don't think you could put it on the airplane, So probably not. But since you're asking, maybe.

00:07:26
Speaker 6: Let's see, the biggest airplanes can carry about four hundred or five hundred tons, so I would say, if you could make one that's light enough, I would say, yes, they put them in submarines, So yes, I.

00:07:39
Speaker 2: Thought these answers were really good. To be honest, heavy wasn't the main concern that I had in mind when you sent the title of this episode to me. My thought was I wouldn't want to ride that close to a nuclear reactor. But then I thought, oh, well they do it on submarines, is probably okay. So then after deciding that that concern wasn't big one, I thought, well, probably I don't want nuclear material flying over my head. When sometimes airplanes don't come down in the safest ways, you wouldn't want them to drop their nuclear material and spread it across earth. But this the most common thing that the audience said was that this is too heavy to work on planes. Were they on the right track.

00:08:21
Speaker 1: That's definitely an issue, and it's actually all entangled because one of the reasons that submarines can be saved is that they have lots of shielding because they don't have to worry about weight, and so these questions of safety and shielding are all connected.

00:08:36
Speaker 2: Excellent, good job, audience. So my first thought here is that planes seem to be doing just fine, But of course it would be really nice if planes were using cleaner energy sources, and nuclear power is a good energy source if you're trying to cut down on greenhouse gases. So let's talk about the pros first. They assume that's one of the pros. So why else might you want nuclear powered aircraft.

00:09:05
Speaker 1: The whole idea for nuclear power aircraft comes out of World War II. Of course, that's when nuclear powers invented, and maybe the primary motivation was to make airplanes that could fly for longer without needing to refuel. And World War Two, a lot of our strategic decisions were based on needing to refuel. You had these bombers and you wanted to drop bombs on enemy territory, and those bombers needed gas, and that limited how far they could fly, and in many missions the bombers came back with just like fumes. It really limited the reach of these bombers, And so people were thinking, could we develop airplanes that ran on nuclear power that could fly for much much longer because nuclear fuel is so much denser. So, for example, submarines can operate for a very very long time without refueling. Same with nuclear powered aircraft carriers. These things can sometimes go decades without refueling, except.

00:09:58
Speaker 2: The humans who ride them would need to refuel by sleeping at night. But I guess, I guess you could have a number of pilots circulate or you know, taking turns that you could keep going. But like those bombers, aren't the figure something like one in four didn't return on each run. Think of the amount of nuclear material that would be falling to Earth with these bombers as they got shot down. But all right, we're probably going to talk about that in the con section. I'm guessing so, but you know me, I always get hung up on the cons. Okay, so let's spok about more pros.

00:10:30
Speaker 1: That's definitely an issue. But if your goal is to have airplanes that could like fly all over the world and drop bombs on any target without needing to refuel, or without needing to worry about like tricky aerial refueling maneuvers which make new and the refueling plane very vulnerable to enemy aircraft, or without needing to like buy territory in foreign countries for refueling bases. Did you know, for example, the United States tried to buy Greenland from Denmark even before Trump offered. They wanted to refueling in Greenland, and they offered one hundred million dollars in gold to Denmark for Greenland, and Denmark said, no, thanks, We'll keep Greenland.

00:11:09
Speaker 2: And we did this so that we could refuel there. That was our main purpose.

00:11:13
Speaker 1: Yeah, Greenland is very strategic location between the US and the Soviet Union. Absolutely. Yeah.

00:11:18
Speaker 2: Did we try Iceland next, maybe for less money?

00:11:24
Speaker 1: And then Island was offended. They're like, what we're not as value is Greenland? Are you guys crazy? Yeah? Hence the Cold War very chilly. But the idea was basically try to get airplanes that could fly longer, right, And the concept there, the physics underneath it is that nuclear fuel is so much more dense. Like if you think about how much energy is stored in uranium versus how much energy is stored in like diesel, it's really just enormous like diesel, and gas has more energy than coal, or more energy than like you know, animal fat or whatever. But just by a few factors, uranium has seventy six million megadewles of energy per kilo of uranium, whereas gas has forty six megadels. So the energy density uranium is a million times that of diesel.

00:12:13
Speaker 2: Oh my gosh, that's incredible. Okay, so this is an amazing power source. Tell us about subs and why it works so well in submarines.

00:12:23
Speaker 1: Yeah, this is something that works very very well for submarines and the newest generation of submarines. They never need to refuel like they think. These subs will last for like fifty years, and the fuel will also last for fifty years. You'd like, just build the sub, you build the fuel in, and you never refuel it because it's so energy dense. It's amazing.

00:12:42
Speaker 2: That's incredible.

00:12:43
Speaker 1: So they have these miniaturized reactors and they're powered by uranium, and you know, there's fission that happens there and the fission releases heat that heats water, which produces steam, which turns a turbine which then directly turns the ship's propeller. Often in land based nuclear power. The turbine then spins a generator which makes electricity. You put it on the grid, but there's no need here to generate electricity. You can just directly have that turbine spin the ship's propeller. And the cool thing is this is much quieter than a diesel engine, and there's no pistons, for example, And so if you're trying to run quiet underwater, that having a nuclear powered submarine that never needs to come up to refuel is quite the advantage from a military point of view.

00:13:25
Speaker 2: That is pretty incredible. Is the US the only country that has these? I'm going to guess that the Soviet Union also came up with this, and so Russia has it too.

00:13:34
Speaker 1: Absolutely, the Soviets have them, and we've had them for decades.

00:13:37
Speaker 2: They're not the Soviets anymore.

00:13:42
Speaker 1: The Soviets had them. The Russians now have them, of course, But this is something which is decades old. It was nineteen sixty when we had the first submerged circumnavigation of the globe, like the first time a submarine went around the globe without surfacing. That's just like a decade and a half after the whole invention of nuclear power.

00:14:01
Speaker 2: Wow, that's incredible.

00:14:03
Speaker 1: Yeah, And a few decades later we had more nuclear reactors in ships than there were on land producing electric power. So, like the military has really been into this idea for a long time because they're like not refueling and they're like the quietness of these reactors, and frankly, probably because they don't also care as much about the potential disasters and the ecological impact.

00:14:26
Speaker 2: And why is that? Is it because the bottom of the ocean is sort of desolate and it doesn't even if a sub crashes, most of the material stays in one spot, so the you know, devastation and the problems are sort of limited. Or why do why would you not care about the ecological Well, I.

00:14:43
Speaker 1: Don't want to speak to the motivations of the military person, but you know you're developing weapons anyway that are causing huge destruction, right Your goal is destruction, So like gentleness about the territory, I mean, I guess it must always be second or a third concern. But you're also right that, like submarine that crashes underwater, water is a pretty good shield from radiation. And so unless that uranium then leaks out and like spreads into ocean currents, the actual radiation from the crash site is pretty limited to that location because water is an excellent shield.

00:15:16
Speaker 2: Okay, that's good, all right, So we use a lot of these underwater. I happen to also know that they're very helpful in space, So where have they been used in space?

00:15:25
Speaker 1: Vivin used underwater, they're also used on the surface. The US Navy eleven carriers are all nuclear powered. Some of these things have two some of them have eight separate reactor units. So, like maritime nuclear power very well established. But you're right, we also use nuclear power in space. Some of the rovers that we have sent to other planets use nuclear power. They don't have nuclear reactors in the same way that these subs do in the sense that they have controlled fission reactions. Instead, they use another kind of nuclear power, where there's uncontrolled decay that essentially leads to heating more like a nuclear battery. These used plutonium and they worked for like ten to fifteen years, providing a gentle source of heat which is then converted into the electricity to run some of these rovers like Curiosity and Perseverance. So we definitely have nuclear powered craft underwater, on the surface and in space.

00:16:18
Speaker 2: Well, we also have little nuclear reactors in some satellites. We don't do it so regularly anymore. The US had snapped ten A, which we sent up and it did okay for a little while. Then it failed and we boosted it to a graveyard orbit. So that didn't go super well for us, and I think maybe it's leaking a little nuclear material woops. And then the Soviets actually sent up something like thirty three nuclear powered satellites and they use these because they wanted to go kind of lower for like surveillance purposes, and they were low enough that they were starting to hit like atmosphere particles, so solar panels would have slowed them down. So the nuclear reactors allowed them to go for a long time without the solar panels which would slow them down, and that went okay most of the time. They didn't always spread nuclear material across Canada, so that's good. There's just that one time.

00:17:13
Speaker 1: You get one freebie, right, I mean, I'm sure Canada is cool with that one time.

00:17:17
Speaker 2: There's a lot of Canada, and like a lot of it's not being used for other stuff. Maybe.

00:17:22
Speaker 1: Wow, you're pretty cavalier about safety when it's not your kids involved, Kelly. You know Canadians have kids also, you understand how that works.

00:17:31
Speaker 2: I am so sorry Canadians. I was joking and I shouldn't have I shouldn't have done it, all right, So we've talked about the various places that we find nuclear reactors. Let's take a break and you know, shield our houses against the radioactive material that might come falling down on us at some point in the future. And we'll talk about engine concepts next, and we're back, all right. So we've talked about the various ways nuclear power has been used in things like submarines and satellites and rovers and of course nuclear power plants. Let's talk about some engine concepts for how you might be able to make this stuff work in an airplane.

00:18:23
Speaker 1: Yeah, it's really fun to think about how you might actually power an airplane using a nuclear reactor, because the basic concept that works underwater is to have it directly spin a propeller. But those propellers can spin fairly slowly and still power the ship. But an airplanes, of course, we have jet engines, and so people have explored lots of different ways to make a nuclear powered aircraft. But the leading idea I think is a nuclear jet engine.

00:18:50
Speaker 2: Ooh sounds epic.

00:18:51
Speaker 1: Yeah, So to review the way a jet engine works in general, is essentially your burning fuel. Jet fuel essentially some fossil fuel to heat the air, and that expands through a turbine into a propelling nozzle to provide thrust. So the goal of the fuel, the reason you need fuel, the reason we have jet fuel in airplanes is to heat a bunch of air which then expands, and that expansion gives you thrust. So the core idea of a nuclear power jet engine is just to replace the source of heat. And so because fission produces heat, right, it produces these energetic particles, people thought, well, let's just use fission to directly heat the air instead of having the diesel fuel do that job.

00:19:33
Speaker 2: And then the air is just whatever air is surrounding the airplane in the sky. Or are you like putting some gas in there that gets heated.

00:19:42
Speaker 5: No.

00:19:43
Speaker 1: That's one of the cool things about a jet airplane is that as it's flying through the air, it's pulling air in, compressing it, and then expanding it with the heat. And that's how the whole jet engine runs. That's why jets don't work so well at low speeds because they require this influx of air into the compressor oka And so.

00:19:58
Speaker 2: Then would fission be able to heat it up even more like better than the other methods, so you could go even faster. Or the point is just that it can heat for longer because it burns slowly.

00:20:08
Speaker 1: Yeah, the idea is just that it can heat for longer that the fuel is much more dense. And that's also an attractive feature of nuclear power jets because you'd like to be able to lower your weight in the air. Right when the seven forty seven takes off or a cross country trip, it's carrying enormous amounts of fuel. Some of that fuel is just in order to provide the thrust to carry the rest of the fuel. It's like the whole rocket equation problem in miniature. And so if you could figure out a way to make your fuel less, then you can lighten the whole weight of the aircraft and then need less fuel. Yeah.

00:20:39
Speaker 2: So okay, So at the beginning of the show, the listeners said that they thought the problem was weight, but it sounds like you were saying that's not the problem. Actually, this could be a less heavy way to fly.

00:20:50
Speaker 1: Weight is definitely an issue, and we're going to talk about like the shielding and the reactor itself being quite heavy. But in terms of the fuel, there is a wind and so we're going to keep track of the weight accounting in terms of the fuel volume and weight. Nuclear power winds. When it comes to the actual equipment involved, you're going to see it's an overall loss, but you know, there's something in the wind category there. And so people have actually people and so people have actually built these things. They have prototypes. You can go to the Idaho National Lab. They have a couple of these set up that you can actually see. They built them in the fifties and they tested them, and there's sort of two different models there. One is a direct air cycle, where the air comes in from the compressor, goes directly into the nuclear core. That air gets heated up by the nuclear power plant and then emitted. That's very powerful, but the problem is the air that comes out also kind of radioactive.

00:21:43
Speaker 2: That's a problem, and so if.

00:21:45
Speaker 1: You're like flying regularly back and forth across your own country and you're spewing radiation and that's you know, bad. So they developed a second model, an indirect air cycle, where you basically have two different loops. You have the air that comes in and then it gets heated by something which has been heated by the nuclear reactor. So for example, the nuclear actor doesn't directly heat the air. It might heat like liquid metal in pipes, or very high pressure water, which is then getting radioactive, but it's not getting sprayed out the back of the jet engine. Instead, it's just heating up the air. So you're sort of shielding the air from the radioactivity by having this indirect loop of liquid metal or high pressure water.

00:22:24
Speaker 2: That sounds more complex but better.

00:22:27
Speaker 1: Yeah, exactly, you're not killing your own people. But now you have to have this extra machinery and you have to hope that your high pressure liquid metal doesn't explode. You have to monitor that, so it becomes more complicated, which is the downside of it, But the basic idea works, like in principle, you can have a nuclear powered jet engine.

00:22:45
Speaker 2: Oh, I don't think I would want that flying over my home. What are what are some of our other options?

00:22:52
Speaker 1: So instead of having a jet engine, you could also have a nuclear powered thermal rocket, so a chemical rocket, the thing that like the set Urn and five used to get off the surface of the Earth. You have some chemical reaction which creates expansion and gives your propellants basically momentum out the back. Right, This is the way a rocket engine works. Well, you could imagine a nuclear powered version of that where the heat comes from the nuclear reaction and that flies off some propellants, and that those propellants are then pumped through the core to heat up something. So it's sort of similar to the jet engine concept. You're using the nuclear reactor to heat something and then that is expanding and flying out the back, but we call this a thermal rocket instead of a jet engine because you also don't have this compression cycle.

00:23:35
Speaker 2: Is this what project Orion was all about.

00:23:37
Speaker 1: Project Oryon was actually blowing up nuclear bombs behind it, So it's sort of similar. It's sort of similar and much more awesome and impossible, but.

00:23:50
Speaker 2: Awesome if you're like not living on the planet where they're trying it out, maybe.

00:23:53
Speaker 1: But yeah, awesome sense Like if you see it, you're like, oh my gosh. Wow.

00:24:01
Speaker 2: So this is a more delicate approach, yeah, exactly.

00:24:05
Speaker 1: The third approach is to think about action generating electrical power and then using that electrical power to run like an electrical engine. So you sort of separate the two components. You have the nuclear planet on board, it's running, it's producing steam that's turning a turbine that's running a generator that's producing electrical power. Then you're feeding the electrical power to like a turboprop engine, So the engine and the power generation are separate.

00:24:29
Speaker 2: So do you have a sense for out of these three methods, which one is like the best. So they differ in complexity, they differ in pollution or you know how bad they are for the environment below, they probably differ in how much power they produce for a given amount of nuclear material. Is there like a favorite amongst people who are excited about these ideas?

00:24:50
Speaker 1: I think the jet engine is definitely the leading idea. People like jets. Jets can go really fast, they work really well on airplanes. People have actually built prototypes of this that it can work. So the jet engine is definitely the leading concept.

00:25:04
Speaker 2: All right, So we've talked about the different ways to make this work. We've talked about the pros. You know why you would want to use nuclear power for an airplane, But we all know that Kelly's the wet blanket around here. So I'm excited for us to move on to the cons. What are the reasons why this idea that sounds bad to me is bad?

00:25:25
Speaker 1: So many reasons. Let's start with the practical ones, and that's the issue of weight, right, So reactors can be big, and they can becumbersome. This has been mostly solved. People have made miniature versions of reactors, like to put on a submarine or to put several of them independent reactors onto a big aircraft carrier, so you can make the reactor fairly miniature. Physicists are really good at figuring that kind of stuff out. What's very hard to miniaturize, though, is the shielding. Like on a boat, a submarine, or an aircraft carrier, you can have lots of layers of steel, not a big deal, right, but on an airplane that really costs you. And so it's possible to miniaturize the reactor itself and reduce the weight there, but the shielding is always going to be an issue. You want to put a lot of heavy atoms between you and the source of radiation, and a lot of heavy atoms are always just going to be heavy.

00:26:17
Speaker 2: So you had said that what was it like, gas was something like fifty mega jeles per kilogram and uranium was almost like eighty thousand. So even with that massive increase in the amount of power that you get that that doesn't do enough to even nearly offset the shielding. Is that is that the message here.

00:26:40
Speaker 1: Yeah, exactly. You either need a lot of shielding or you need to not worry about your crew. And there was actually a time where people talked about only having crew that were like past child bearing age or had a terminal disease. Anyway, people seriously talked about this kind of stuff, like the documents from the Cold War are crazy.

00:27:00
Speaker 2: Gonna die anyway, fly on our plane. You always wanted to be a pilot, right, Crid.

00:27:06
Speaker 1: And basically every step you take to make these things more safe makes them impractical because now they're too heavy. So not just the shielding but also the cooling systems. Right, you want to generate this heat, but you also don't want to overheat the rest of the airplane, and you want to have devices in place to protect yourself against meltdowns and all sorts of other issues, and so all these cooling systems and safety systems and all that shielding just gets heavy.

00:27:30
Speaker 2: And I think perhaps the biggest dagger in this idea to me is that if something goes wrong and you crash, you spread nuclear material across a large area problems, which is a problem.

00:27:43
Speaker 1: Yes, poisoning the earth bad for sure, and it's definitely something people think about also when we go into space with nuclear power, Like every time we launch a rover with a blob of plutonium in it, we worry, like, is this going to be the time it blows up in the atmosphere and then spreads that plutonium on our planet. It's a risk every time they do it, and so they worry about it. But those are pretty rare launches.

00:28:05
Speaker 2: Oh you mean is this going to be the second time?

00:28:07
Speaker 1: Yes, exactly, the next time.

00:28:10
Speaker 2: The next time, yes.

00:28:11
Speaker 1: But if you're talking about regularly flying bombers or even commercial airplanes around the world with nuclear power, then you're constantly taking that risk, and you know, crashes happen and they kill people, and you don't want to then compound the dangers and the consequences by also poisoning the planet.

00:28:28
Speaker 2: Well, especially if these planes are being used as like weapons of war or surveillance things, and you know other countries might specifically be trying to shoot them down. That seems bad. Yeah, although maybe a country won't shoot down your spyplane if they know that they're going to be like contaminating their land with radioactive waste. So, oh, you have forgot that in the pro section, Daniel.

00:28:49
Speaker 1: It's like the poison pill. But you know, realistically and maybe sadly, if you ask me, like, why aren't their nuclear powered airplanes right now? I don't think that's the reason. I think the reason we don't have nuclear powered airplanes or not because they aren't safe or they would kill your crew. I think that people would make those compromises if they thought it was good for our military or our strategic situation. The reason I think is actually just strategic, that nuclear powered bombers are no longer the quiver we thought we needed in our arsenal is that.

00:29:21
Speaker 2: Because satellites are so good, we can just buy from there, or or yeah, why I.

00:29:25
Speaker 1: Think the reason is that you don't need nuclear bombers. You don't really need bombers anymore. I mean, we have ICBMs, we can deliver nuclear weapons from the planes of Montana without putting any humans in the air, And we have nuclear powered submarines which can sneak around the oceans and send nuclear weapons to anywhere on Earth very quietly. So you don't really need nuclear powered bombers to stay aloft for twenty four hours anymore. We can already bomb people with impunity. Oh yay, And I think that's probably the reason we don't have it. All these other concer earns are reasonable, and it makes it impractical and it makes it unsafe. But I think because it's not strategically valuable, it is probably why we don't actually have them.

00:30:09
Speaker 2: I guess we should all be glad that we have ICBMs instead.

00:30:13
Speaker 1: I suppose. But of course, the US spent billions and billions of dollars and more than a decade trying to build nuclear powered airplanes, and they actually flew airplanes with reactors on board.

00:30:26
Speaker 2: Were these jet engine reactors like you were talking about.

00:30:28
Speaker 1: No, we've never actually flown an airplane that was powered by the reactor, but they did fly airplanes that had reactors on them.

00:30:36
Speaker 2: All right, let's take a break and then you can tell us more about that. Okay, So now we're back. So you said that a plane has flown with a nuclear reactor on it. Was that plane just transporting the reactor from one place to another? Or Yeah? Why would you want to carry nuclear material with you on a plane.

00:31:07
Speaker 1: You don't pack nuclear material every time you take a flight, Kelly.

00:31:10
Speaker 2: Not yet. But if it was strategically valuable, maybe I.

00:31:13
Speaker 1: Want, Yes, you might exactly. Now, this was like the first step in the US's exploratory project to build nuclear power aircraft. They thought, well, first let's try to fly an airplane with a reactor on board. Study the shielding issues, the safety issues. Can we actually get this thing working and operating in the environment of an airplane before we actually try to connect the reactor to the engines. So in the fifties they had this project using a modified B thirty six bomber with a working nuclear reactor on board. So you have your standard jet engines flying this airplane, but in the center you have a miniaturized reactor designed specifically for flight.

00:31:51
Speaker 2: Wow, okay, and so this comports with your even if it's hard, we'd do it if it were strategic. Because this was what decade were they trying this in the fifties. I'm going to assume that in the fifties they had enough shielding. Is is that true? Or were they able to do this because they you know, four went shielding for this experiment.

00:32:11
Speaker 1: Well both, Actually they put a lot of shielding. So this is like an eighteen ton reactor producing one megawatt, and they had it in this special version of the aircraft where the humans would live in this little pod, this like special cockpit that was super shielded. If twelve tons of lead and rubber that the humans would get in and the rest of the airplane would just be like totally irradiated. And this little pod had like windows in it that were like twelve inches thick and pockets of water to protect them, but still there was a lot of radiation even though they were shielded. It was well above anything you would consider safe for the pilots.

00:32:48
Speaker 2: Oh yikes. And if you ever need to do any work on the body of the plane, any technician who's working on it is going to be getting your radiated.

00:32:56
Speaker 1: Right, yeah, exactly. The whole thing is going to be a disaster. And you know, for the project, they only recruited pilots above child bearing age because they basically knew that they were killing these people.

00:33:06
Speaker 2: Oh my goodness, you know, us people above child bearing age are still valuable. Just throwing that out there.

00:33:15
Speaker 1: It's kind of amazing how they treated these things, like they knew that there were potential disasters, and they actually tried to plan for them. Like, so, this thing took flight in the fifties. They made forty six flights with this bomber, and every time they did, they also flew it with a special extra bomber that had specially trained paratroopers that if this plane crash, the paratroopers would jump out of the airplane, paratroop down to the crash site and seal it off. They were like nuclear trained paratroopers to help try and contain a disaster.

00:33:44
Speaker 2: Were they all also above child bearing age?

00:33:49
Speaker 1: Yes, and they all wore lead underwear.

00:33:51
Speaker 2: Oh good, good plan, although it's too late, I guess. But so when they were flying over the Southwest, were they I guess specifically trying to fly over portions of the southward but are not populated, like those paratroopers aren't going to be helpful if it lands in Phoenix.

00:34:07
Speaker 1: You know, I hope so. I don't have any details to back that up, but I certainly hope they do. But you know, this thing was airborne over the Southwest forty six times in the fifties, so they definitely took a risk.

00:34:19
Speaker 2: Did it ever crash?

00:34:20
Speaker 1: This one never did crash, but they tried to estimate what would happen if it did crash. They created some situations where they like put a fuel rod into a burning jet engine in Idaho. So they did these experiments and this is pretty bad. Those experiments ended up like releasing quite a bit of caesium one thirty seven into the air above Idaho. Yeah, it's pretty bad. And they called this test operation Wiener Roast because they used because they used a bunch of live cattle at varying distances to help measure the effects of the radiation.

00:34:55
Speaker 2: Wow, I mean they clearly should have been using doxins little Wiener dogs. So I was I was soffing because that was really a missed opportunity.

00:35:06
Speaker 1: But you have just pissed off a lot of dog owners out there, Kelly, I'm sure I have.

00:35:12
Speaker 2: That's right.

00:35:14
Speaker 1: So this is like a real government program.

00:35:16
Speaker 4: You know.

00:35:16
Speaker 1: They invested a lot of money into this program, billions of dollars, decades of research to try to make this thing happen. And they got as far as flying airplanes around with nuclear reactors on board.

00:35:27
Speaker 2: That's that's pretty far, just to confirm, we've never flown anything that was actually powered by the nuclear power source, right, It's just been sort of carried along like the.

00:35:37
Speaker 1: First exactly, we got as far as airplanes with nuclear reactors on board and then on the ground nuclear powered jet engines that never flew, but we never put them together into an airplane that was powered by a nuclear reactor.

00:35:52
Speaker 2: Okay, so there's always a Soviet equivalent to these sorts of things. So did the Soviet Union have a similar project?

00:36:01
Speaker 1: Of course they did. In the fifties, the Soviet Union had a project to fly one of their enormous TU twenties. If you haven't seen a picture of one of these things, this is like a really incredibly huge bomber with this really elegant swept wing design, and they were working on a similar project. Details are a little bit sketchy, and part of the information is a little confusing because in the fifties there was an article in Aviation Week that turns out to have been mostly filled with false information, claiming that the Soviets were already testing a nuclear airplane that was powered by nuclear power. It turned out to be misinformation, but you know, it kept the US program going for a few more years. But the Soviets ended up coming to the same conclusion we did, which is that there's a huge radiation hazard to the crew, and the crash risks were significant, and so they abandoned the projects right around the same time we did.

00:36:53
Speaker 2: Presumably they also had ICBMs and stuff, and so they had the same capabilities without the technology just like did right or were they behind on ICBMs.

00:37:02
Speaker 1: No, that's exactly right, And so in the early sixties both programs were abandoned because people realized that nuclear powered submarines and ICBMs filled the strategic need in a much simpler way than nuclear powered aircraft.

00:37:15
Speaker 2: All right, So does that mean that both Russia and the US, like no country on Earth right now was working on this program because we all have better ways to do this? Is that right?

00:37:25
Speaker 1: Yes? And no no country on Earth that we know of is trying to fly an atomic powered aircraft with people on it. But the Russians claim to be working on and have developed, a nuclear powered cruise missile. A cruise missile is basically like an unmanned aircraft. It can fly, it can loiter, it can turn. It's not just like ballistic You're not just like throwing a bomb. It has like engines and it can steer, et cetera. And the idea of a nuclear powered cruise missile is still kind of attractive because it would have basically unlimited range. This thing could take off, fly around the Earth a couple of times. You could even like hang out for a while, like doing loops, you know, take the long path over the North Pole or something. And so Russia claims to be working on this thing. It's called the SSC x nine, and in October twenty twenty three, Putin claimed that they tested it successfully, though a lot of people are pretty skeptical.

00:38:21
Speaker 2: Yeah, I mean, that guy always tells the truth. So so slam dunk we got. We've got to believe it. Huh. Do you really need a cruise missile that can like circle the world four times? Why not just like know where you're going to shoot it off, and shoot it off from one spot using another fuel source and just get there right away.

00:38:44
Speaker 1: Yeah, a lot of these Russian modern weapons programs seem kind of bombastic and unnecessary. Like he's also talking about his supersonic missiles. It's like, you know, do you really need supersonic missiles? Are there really an advantage to that? I think a lot of this stuff might just be pr I think and wants to advertise to the Russians that their military is cutting edge, that they have advantages over the West, et cetera, et cetera. So analysts that I've read suggest that a lot of this is just for internal propaganda, not actually military strategy.

00:39:15
Speaker 2: I can believe that, all right, So let's bottom line this. Give me the summary the take home points for the nuclear plane story.

00:39:23
Speaker 1: So, a nuclear powered airplane is possible. Physics says you can do it. You put a reactor on board. We have the techniques, We've proven that you can build a nuclear powered jet engine. Problem is the way it becomes very impractical. If you want your crew to survive, then you've got to shield them from the nuclear reactor, and that's going to make your plane very, very heavy. In addition, the crash risks are significant. So it's possible, but dangerous and kind of impractical at this point, and not really necessary anymore because we have other weapons that fill the strategic niche that originally motivated the idea of nuclear power aircraft. So really the only remaining reason to do it is like, ooh, it kind of sounds cool.

00:40:06
Speaker 2: Oh, so if I'd got my kids all excited about flying on one of these nuclear powered airplanes, you're telling me I'd have to let them down by saying, oh, Daniel, got you excited about something that isn't really gonna happen. It's not strategically helpful. Sorry, Kid one and Kid two, they'd be very disappointed.

00:40:23
Speaker 1: Yeah, exactly. And so unless you're like a nuclear nerd who likes to think about nuclear power powering everything and new ways to do stuff, and you want to have like a nuclear toaster on your kitchen, there's not really a good reason that even considered nuclear power airplanes.

00:40:36
Speaker 2: I mean, is this a material science question, like if we can find a much much much better shield that's light, then suddenly this all becomes a better idea or does such a thing not exist?

00:40:46
Speaker 1: From the physics point of view, Really, shielding is just about having enough high z atoms between you and the source. So it's hard to imagine how you're going to do that without a lot of high zy atoms, which are pretty heavy. So unless you come up with a new way to do nuclear power which doesn't produce the same kind of radiation, like, for example, if you had a mini fusion reactor or a fusion reactors don't have the same kind of radioactive output, So a fusion powered airplane that might be possible but first we have to get fusion to work like on the ground before we can get it to work in the air.

00:41:21
Speaker 2: Well, that's a big ask. We've been saying we're pretty close for fifty years.

00:41:24
Speaker 1: But exactly.

00:41:27
Speaker 2: But there are some pretty cool companies doing some cool work, So hopefully we get that eventually.

00:41:31
Speaker 1: Yeah, and maybe eventually they'll develop fusion and then they'll miniaturize it, and maybe we'll have fusion powered airplanes. Because also the fuel for fusion is just hydrogen, and so it's not as dangerous, So a crashed fusion powered airplane wouldn't be any more dangerous than a crash diesel powered airplane.

00:41:47
Speaker 2: Safe is cool. I like it.

00:41:51
Speaker 1: All right. And so while it's fascinating to think about how discoveries in physics can change our world, allowing us to create devastating weapons and also sources of clean energy, they don't always necessarily translate to changes in technology that affects our daily life. Sometimes the old ways are better.

00:42:11
Speaker 4: Yay.

00:42:12
Speaker 1: Thanks very much for joining us today, everybody, and thank you Kelly for taking this trip on a nuclear powered podcast.

00:42:19
Speaker 2: Thank you for having me. It's been a blast as always.

00:42:22
Speaker 1: All right, tune in next time. For more science and curiosity, come find us on social media, where we answer questions and post videos. We're on Twitter, This Org, Instant and now TikTok. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.