Daniel and Kelly’s Extraordinary Universe - How far can we go with chemical rockets?

Episode Date: August 11, 2026

Daniel and Kelly explain the limitations of chemical rockets and how physics can propel humans to the outer reaches of the solar system.See omnystudio.com/listener for privacy information.

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should find other places to live, should walk on alien planets, should see sunrises from different distant stars. But what's going to make that happen? For a long time, humans have relied on chemistry. Blow stuff up, funnel the output out the back of your ship. Ship goes forward. Cool, that works, but is that steampunk kind of plan going to power our future? Can we use that chemical technology to explore the outer reaches of the solar system and to reach other stars? And if chemistry lets us down, what's going to come to the rescue? We know it's not biology. Today, we'll dig into the issues with chemical rockets and show you how physics is going to save the day.

Welcome to Daniel and Kelly's extraordinary propelly universe. Parasites and space, and it doesn't matter what method you use, I'm not going to space. Hi, I'm Daniel. I'm a particle physicist who loves thinking about aliens, and I've never been on a rocket-powered anything. Yeah, I guess I haven't either. You had to think about it for a minute. What were you considering where you're like,

ooh, was that bicycle that I strapped a huge engine to rocket-powered or not? Well, I will embarrassingly admit that I was thinking, like, all right, how do planes go? how do ships go, how do trains go? And then the answer to all of them was not fire rocket. So, you know, I just had to make sure I was telling the truth. All right, well, let's close the gap in your answer. You said you wouldn't go to space, but would you get any rocket-powered something here on Earth?

No, I doubt. It's hard for me to imagine that I would do that. What about you? Well, let's check in again after you hear about ion thrusters, because maybe a gentle ion thrusted powered bicycle is something you would ride. But that wouldn't be a rocket then, right? Now we're in a whole different zone. I do travel on vehicles.

I'm not anti-get getting around. But by rocket makes me a little nervous, I think. All right. Well, I hope on today's episode we're going to expand your mental conception of what is and what isn't a rocket. It's not all flames and explosions. Well, then how do I know that I haven't been on a rocket? If I clearly don't have a good conception of what a rocket is and what it isn't. All right, it's time to teach me.

Let's jump in. All right. Well, on today's episode, we're going to be talking about how it's possible to explore the rest of the solar system. Our current technology are ugly, nasty, dirty, expensive, heavy chemical rockets. Can they take us to the edges of the solar system and beyond? That's the question we put to our group of listeners who love to. speculate without a chance to Google or do any research.

If that sounds fun to you, we'd love to hear your thoughts on the topic of the day. Write to us to questions at daniel and kelly. In the meantime, think about it for yourself for a moment. How far do you think we can get with chemical rockets that Kelly hates? All right, hold on, hold on, hold on. Before we hear from the extraordinaries, I want to, a stick up for myself and B, stick up for rockets. You used a bunch of really negative words to describe rockets. But I watched a rocket launch to space once, and I thought it was very moving and beautiful.

And I do think it's amazing that we can use rockets to send stuff to space. So I don't want to be – I'd like to change the negative tone a little bit. It's not perfect. They're not perfect. But they're pretty amazing. They are pretty amazing. And I think it's awesome what humans have built. Every time I see a project like that literally get off the ground, I think, wow, look what we can do.

and I'm odd. The same way I feel like when I see the Golden Gate Bridge or any huge engineering project, like something that's so far beyond the scope of an individual person, yet we can do it collectively. It gives me hope for the future. Yeah, I'd say it gives me goosebumps. I get very excited seeing big projects. But so, okay, but chemical rockets have their limitations.

They take something like six to nine months if you're going to Mars. If we want to explore the rest of the universe, it would be nice if we could go faster, for example. It would be nice if we could go further for sure, yeah. Yes. So we asked the extraordinaries how far we can go with just chemical rockets. Here's what Vox had to say. The moon and Mars, and even Mars will be a stretch.

We're going to need some new form of propulsion to get further. We would need a tank the size of Jupiter to get anywhere. Well, you can get pretty far if you have patience. Not too far, I think. Our space probes to date have got most of their speed. from gravitational slingshots, not chemical rockets. You could explore as far as you want, as long as you can keep finding chemicals, I'd imagine.

We could probably go pretty far with chemical rockets if we could make them big enough to carry a lot of chemical fuel. We need nuclear fuel to go anywhere far away like Mars. With our current chemical rocket technology, we're not able to get even close to the speed of light. I can't imagine it would be very far. It's difficult to even examine. explore Mars.

That's kind of a hard question because I actually don't know what a chemical rock is. To the asteroid belt. I think we need to switch to solar sails or perhaps some kind of experimental ion drive. I think we have a pretty space savvy audience. Yeah. Yeah. I think so. They've all read your book.

They've thought about space. They've been listening to you for years, talk about this kind of stuff and they're paying attention. They know what's up. They didn't know until now, though, that you are anti-rocketed. I've clarified I'm not anti-rocket. If you liked rockets, you would have ridden on one, Kelly. Look, put your money where your mouth is, okay?

Have you ridden on a rocket? I've jumped out of a plane. No, but I'm not pro-rocket. How many people have opportunities to ride rockets? That's a good question. That's fair. Yeah. You're saying you haven't said no to a rocket ride.

That's right. That's right. But you would say no. Yeah, I would. I would. I would. But that doesn't mean I'm not happy they exist. Yes, me too.

I'm happy people go and explore space, even though I never want to do so myself. Amen. All right. Tell me about rockets, Daniel. How do they work? All right. So rockets are a way to increase your momentum.

What you need is energy and mass. And basically the way a rocket works is it uses energy to push mass out the back. And when you do so, you send momentum in one direction. And because of conservation of momentum, you go the other way. A basic example of a rocket is sitting in a rowboat, throwing rocks out. the back of the rowboat. You're using energy to throw those rocks. The rocks have mass. And because they carry mass, they carry momentum. And so the rocks go one way and the boat goes the other way. And the more mass, the more momentum, right? So if you threw a rock or a comparably sized chunk of

styrofoam, the rock would get you farther. That's right. Momentum, non-relativistically, is mass times velocity. And that's going to be absolutely crucial in today's conversation. So equivalent momentum by throwing a really massive thing very slowly or by throwing a very low mass thing very, very fast, you get the same momentum. So those two options. So what you've got to do is transfer momentum out the back. Anything that does that basically is a rocket. You need energy and you need mass. And if anybody out there happens to be a space is not real denialist, yes, rockets can work in space.

You don't need air for rockets. All right, the same principle, throwing mass out the back works just fine in an atmosphere or not in an atmosphere. These things are not climbing up the atmosphere and they're not pushing against the air. You're just throwing momentum out the back so the rocket moves forward to balance the momentum and to maintain conservation of momentum. So if you were on like an old-fashioned paddle boat sort of thing and the energy is your legs and you are spinning like a little paddle thing. behind and it's pushing water out the back. Is that a rocket? Why is that not a rocket? I see. You want to like re-engineer the definition of rockets so that you have been on a rocket. So you have you have told me that the definition of rocket is broader than what I thought it was.

And so now I'm trying to figure out what the bounds are. So unfortunately, I don't think a paddle boat qualifies as a rocket because a rocket needs to bring that mass with it. Right. And, And on the paddle boat, you are pushing against the water. You're not like carrying water that you're then pushing out the back of the paddleboat. Right. So a rocket carries with it mass and throws that mass out the back. A paddleboat is not doing that. It's pushing against the water.

So, for example, a paddleboat would not operate in a vacuum, right? Whereas a rocket can. I feel like you're moving the target. You didn't mention ahead of time that the mass has to go with you. But all right, all right. We're clarifying here. That's why we're having a conversation. Okay.

And in the future, every conversation I have, I will give complete, exhaustive definitions of everything to future prove myself against any questions. This is our last episode, folks. No one's going to want to listen after this. All right. Let's move forward. We're carrying the mass with us. That's right. Okay.

So you need energy and you need mass. And you're going to carry the mass with you to throw it out the back. Cool. That's the basic principles of rockets. And the rockets we're familiar with are mostly what we call chemical rockets. And they solve this energy and mass problem by bringing. fuel. Fuel stores energy, its chemical process releases it, and it provides mass that you can expel at the back. So it's like an all-in-one solution to the rocket problem. It's very cool, right? You burn

the fuel, that gives you energy, and it produces stuff that you can throw out the back. So that combustion reaction does everything you need. Okay. And the difference between fuel and propellant, because the engineers, when we first wrote Soonish, and we made the mistake of saying fuel or whatever, we're very upset. And so the difference between fuel and propellant is that propellant something gets thrown out the back? What is the difference? Yeah, so propellant can be totally inert. It's just something you throw out the back. So in the example of the rowboat, you're throwing rocks out the back, right?

That's your propellant. You're using it to propel yourself. But you wouldn't call rocks fuel. They don't store any energy. Fuel is something which stores energy and has propellant. Okay. So it solves the whole rocket problem all in one. Awesome.

So one of the problems with this is that the stuff that you create that you throw out the back is not necessarily great for the environment. Have we found a propellant that is less bad for the environment? Well, the basic process here is a chemical reaction combustion, right, where you're turning, for example, like methane plus oxygen into COV. and water and energy. So the core reaction is bad only in that it produces CO2, right, which is not good for the environment. Okay. But it can be fairly clean otherwise.

But some of the fuels do produce other nasty stuff. There's a whole range of various chemical processes used here and ranges of kinds of fuel that humans have used to make their glorious launches into space. Ranging from like solid fuel. So the space shuttle boosters had aluminum powder and ammonium perchlor. in them, which you can use as fuel, which is very cool. The SLS core has liquid hydrogen and liquid oxygen, so very basic, very simple stuff. Nice.

But again, this is fuel because it can combust, so it releases energy, and it produces propellant that you throw out the back. SpaceX Falcon rockets use something called RP1 or Carolox, which is basically kerosene plus liquid oxygen. So all the components you need for combustion. And then there's methyl locks, which is basically methane and liquid oxygen. Methane is just CH4. So that's pretty clean.

Yeah. Okay. Great. So the good news about chemical rockets is they produce high velocity and they use a lot of volume very, very quickly. So you can burn through a huge amount of fuel very quickly and produce a huge thrust. So you can get like exhaust velocity of like three kilometers per second. Remember we were talking about throwing propellant out the back.

And what you need is high velocity at high mass to get high momentum. And so this is pretty high velocity, three kilometers per second. But most importantly, it is a large volume here. So, for example, each one of the Falcon 9's Merlin rocket engines burn 250 kilograms of fuel per second. Wow. Wow. Exactly. And so this provides a huge momentum change, right?

Because it's an enormous amount of mass moving with high velocity. And so each engine has a gigawatt of power. And the Falcon 9 has nine of these things. Wow. So the basic principle for chemical rockets is a short, hard burn with a huge amount of thrust, right? You're burning a lot of fuel. You're getting a lot of velocity. It's not just one push.

There's an extended burn as you're watching this thing lift off. But chemical rockets don't tend to burn for very, very long times, for a reason we'll talk about in a minute. It's mostly like a big, hard push at the beginning. Well, all of that sounds amazing. So what's the problem, Daniel? The problem is that consuming a lot of mass means having a lot of mass, right? So you're burning all of this fuel. You've got to have a lot of fuel. And the burning is not very efficient because I'm going to poop on chemistry. It's a chemical reaction, right? Oh, that wasn't the bad part. Sorry. Well, the bad part is that, you know, you're changing the configurations of these atoms. So you're releasing some energy. But the energy was stored in chemical bonds. and chemical bonds can store energy, but it's like a tiny fraction of all of the energy stored in that fuel. If you, for example, combine that fuel with an antimatter equivalent of that fuel, you could convert all of that matter into energy. It would be an enormous amount of energy produced,

but instead you're just like moving the atoms around and clicking them into slightly lower energy configurations. So for a lot of mass, you're getting a fairly small amount of energy out. So there's a small amount of energy carried for every pound of fuel. or every kilogram of fuel that you're bringing along. So is your argument that the problem is that it's chemistry, not physics, because you want things to be happening on an antimatter physics level? Well, physics can access the power of the atom, right? They can annihilate these things and convert all of that store energy if you could do that.

I'm not saying that, you know, I know how to design an antimatter engine or anything, but that's one of the problems with chemical rockets is that you're releasing a small amount of energy per mass. So you need a lot of mass, right? Now, if you need a lot of mass, you're going to need a bigger push to get you up to some velocity. And to get that bigger push, what do you need? More mass. That mass means you now need a bigger push. And so very quickly, to get anywhere far, to get a big thrust, you need fuel, and then you need fuel to carry that fuel, and you need fuel to push that fuel, and you need fuel to carry that fuel. And so eventually, you're mostly fuel. I think it's like a mortgage, but how about you explain it, Daniel?

Well, in a mortgage, what you're doing is you're borrowing money to buy your house and then you're paying it back. But the interest is compounded, right? And so for the first long time, you're just basically paying off the interest before you're ever paying off the principal. So you're not actually making progress on your loan. And by the time you pay off your house, you've ended up paying like three or five times as much as you borrowed, right? You borrow a million dollars to buy a house. You end up paying the bank $5 million over all that time. And so in the same way, when we launch a rocket, most of the mass of that rocket is the fuel. We're mostly launching fuel, right? Yeah. We have like a little capsule on top where we get to put something we want, but mostly we're launching fuel because we need to burn that fuel when we're halfway up. I think the payloads that get sent up on rocket, it's like 10% or less when you look at a rocket is stuff that you're actually sending to space.

And the rest of that skyscraper-shaped thing is just fuel that's going to get you there. Yeah. So most of a Mars-bound rocket's mass is propellant. So it takes like, for example, a thousand tons of methylox fuel to get to Mars from Earth orbit. Wow. So if you're already in Earth orbit, right? And we're going to talk about how to get there in a minute. Then it takes still a thousand tons.

And you're going to burn that fuel in space. It's going to give you a big push. And then you're mostly going to coast the rest of the way to Mars. That's the way a chemical rocket works. But then if you want to get a thousand tons of methylox fuel into Earth orbit, you've got to spend 25,000 tons. is to get that fuel up there. Wow. Right?

So that's a factor of 25 just to get the fuel you need into orbit so you can burn it to get to Mars. Holy Kemp. And a thousand tons of methylox is what it costs at the cheapest transfer moment, right? Remember, Earth and Mars don't go around the sun at the same speed. So sometimes they're on the opposite side of the sun, really hard to get to Mars. Sometimes they're on the same side of the sun. And once every 26 months, they're at their closest approach and it's the best time to go to Mars.

So this is the opposite. the cheapest it could ever cost to go to Mars using methylox fuel. And even then, it's not, you've gone through all of that, you've paid all of that, you've burned all of that into the atmosphere, and it still takes you six to nine months to get there. Yeah. Well, we're not going to solve that problem with ion thrusters today, though we are going to make it more flexible to get to Mars. Okay. But, you know, that's how we can get to Mars. And that kind of works, but say you wanted to go further, right? You wanted to go to Jupiter. Now you need 2,000 tons of methyl. Locks fuel. And then you've got to get all that into orbit. So it becomes very expensive, very quickly.

And the prospect of like going to Alpha Centauri using chemical rockets, you know, you end up needing fuel tanks like the size of the moon. Holy cow. All right. But don't despair because we're going to take a break. And when we get back, Daniel is going to tell us about other solutions that are going to get us to Alpha Centauri. That are still not paddle boats. That are still not paddle boats, which aren't rockets because you're not taking the water with you. Eating well shouldn't be complicated, but somehow it turns into recipes, prep, cleanup, and half your Sunday gone.

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At participating Canadian restaurants, excluding Quebec. Hey, Portlandia fans. Carrie Brownstein and Fred Armisen here. You know us, or rather you know them. Tony and Candice, Nina and Lance, Spike, and yes, The Chicken. We've played a lot of iconic characters over the years, but today we're showing up as ourselves to tell you about Podlandia, AEO rewatch, our brand new podcast. Each week we'll revisit an episode of Portlandia from the very beginning,

breaking down the sketches, exploring the backstories of our most iconic characters, revisiting the Portland locations you know and love, and opening up about our creative process. How did any of this get made? What do you think that was a good idea? We're ready to talk about it. And we'll also be joined by the people who helped bring it all to life. Guestrars, collaborators and friends, including director Jonathan Chrysall, the mayor himself, Kyle McLaughlin,

legendary musician Amy Mann, and many more. Kyle is going for it here. You fully improvised, not just words, but a song, a melody. I thought he was going to write. I thought you were all going to write a song. I remember you thinking that. Listen to Podlandia. Ayo, Rewatch on the IHeart Radio app.

Apple Podcasts or wherever you get your podcasts. Hey, this is Hayes Davenport. And Sean Clements. We host the podcast, Hollywood Handbook. Every episode we're trying to help our guests improve their careers by mainly focusing on how they can help us improve our careers. The show is famously super accessible so you can easily jump into any of our 650 episodes and understand what's going on.

We recommend some of our recent episodes with Ben Stiller. The definition of what is a movie has kind of changed anywhere too, right? What do you think it is now? It's images and words being. spoken, captured by some sort of technology. Danny McBride. He loves Mouthins. Oh, that's fantastic.

And you make it on, you make your own. That's great. I call him Tarot Reed. It's a good name. They're all named after cast members of American Pie. Yeah. Oh, gotcha. I call, I don't, I never looked up if she was in this, but I call him Leachie Sobieski.

Yeah. I don't think she was an American Pie, but I still like that. Haven't looked it up. She was prominent around the same time. Yeah. Then Mary Steam, Virgin. Why are you guys talking to me? I'm worried. Why are you talking so down to me that you think I don't understand your little play

game? I just really, I get it. I'm trying to set you up for success here. Listen to Hollywood Handbook on the Iheart radio app, Apple Podcasts, or wherever you get your podcasts. Hey Kelly, let's design a rocket-powered version of a paddle boat. What would that look like? That would, I would bring the water with me and then I would throw it out the back. Yeah. So if you had like a fire. hose on the back of your boat and you had a huge tank of water and you had some way to have energy so you could pump that water out the back of your boat, then yes, that would be a rocket powered boat. It wouldn't be paddle anymore unless Kelly is a source of energy. There we go.

We have a huge tank of water. We have Kelly on top on a little exercise cycle and she's pumping, pumping, pumping, pumping, pumping, pumping, pumping, there you go. And it's pushing water out the back out of the tank. That's a rocket powered paddle boat that we could legitimately build and then you could say, yes, I've been on a rocket. Okay, but this is like the least exciting rocket history has ever created. Like, boo. Boo to this rocket. Well, that's the principle, though, behind the other technology we're going to talk about today, instead of chemical rockets, where you have the fuel that gives you the energy, though very inefficiently, and the propellant, which requires huge massive tanks to go anywhere. We're going to talk about ion thrusters,

which separate this question of propellant, the mass you're throwing out the back, and the energy source. In the same way that, like, Kelly, pumping the water out the back of the boat, separates the energy source from the water. You're not getting the energy from the water. The water's totally inert, right? Sure. So ion thrusters is the approach we're going to talk about today, and it solves the energy and mass problems separately. First, we're going to talk about the mass, and then we'll talk about the energy. And they're called ion thrusters because they use ions. an ion is just an atom that's not neutral.

So if you take, for example, xenon, it's got a bunch of electrons in it, which balance out the protons in the nucleus. And then if you strip some of those electrons away, then you have an ion. So now it has a positive charge. And that's useful because you can then accelerate it in electromagnetic fields. So if you have a bunch of xenon and you strip away some of the electrons, now they have a charge in them, if you can build an electromagnetic field, it will accelerate those,

ions. Shoot those ions out the back of your ship and it's the ionic equivalent of Kelly's water rocket, right? Just shoot them at the back. They carry momentum with them because you have high velocity now and that's a rocket. Okay, that sounds cooler. If you're bringing ionized gas, does this help you cut down on weight because gas weighs less than propellant or not really because once you compress the gas, it gets heavy? What's the deal here? No, it really does help you cut down on weight because you can be more efficient about the energy. One of the things about chemical rockets is that they're trying to solve both problems at the same time, energy and mass, and the energy extracted via combustion is very inefficient.

And so here, if we can, let's ignore the energy question for now, and imagine we have some energy source to fund our electromagnetic fields. Now, if we have some energy source, we can very efficiently use that to accelerate our ions to very, very high speeds. And so we can get much more push per unit of propellant, right? Because the mass can go to higher velocities. So it sounded impressive earlier when we said like three kilometers per second for the propellant from a chemical rocket. That's cool.

But ion thrusters can get much higher velocities. And so for every pound of propellant that we bring along, we can now get much more push. And this is what rocket folks talk about as specific impulse. If you start reading about rockets, get into all these weird. terms, but it's just a bunch of fancy terms to cloud some basic physics, which is you want as much momentum change per mass. So remember, momentum is mass times velocity. If you're bringing rocks or water or xenon or whatever to throw at the back, you want as much velocity in every kilogram you throw out the back because momentum is mass times velocity. And so for a fixed mass, you want the

most velocity to get the most momentum. And so if you can get these things to higher speeds, which ion thrusters can do better than chemical rockets can do, then you can get more momentum per unit mass that you're bringing. My gut would not have guessed that pushing an ion would get things out the back faster than exploding propellants. Cool. Well, physics is more powerful than chemistry, Kelly. And we're using electromagnetic fields here, right?

And so if you have enough energy and this whole thing hinges on having enough energy, which we haven't talked about at all yet, But if you have an energy source, right, then you can accelerate these ions to very high speeds. Here on Earth, we accelerate protons, which are just hydrogen ions, to nearly the speed of light, right? Enormous amounts of momentum in the collisions at the Large Hadron Collider, for example. So this all sounds great so far. We're talking about a lot of momentum created for every ion, right? The issue is that it's hard to scale up.

So we have a small amount of mass in general, which means a small momentum change. So while for each ion, we can get each one to high velocity, which means that per pound of xenon we're bringing, we're getting a lot more momentum change than per pound of methylox or hydrolocks or whatever fuel chemical rocket is burning, it's a real challenge to get a lot of kilograms out the back to get a huge thrust. Okay. And so instead of like a big hot burn that gives you a lot of thrust all at once, an ion rocket tends to have a slow, gentle, long thrust. So, for example, it might take like two days for an iron rocket to get you up to even, like, highway speeds. Whereas a chemical rocket's going to be like, come boom, we're going pretty fast.

But then it's all spent. Okay, but so does that mean ion thrusters can't get you out of Earth's gravity well? That's exactly right. Iron thrusters, as currently designed, can't get you off of Earth because they're very, very gentle thrust, but they can burn for a very, very long time. and they're very efficient, and they can travel with a small amount of mass. The amount of mass you need to get to Mars, for example, is like thousands of kilograms of xenon, which compares to like a thousand tons of chemical fuel.

So it's a huge difference. Your whole ship is much lighter. And then that's not as hard to get into orbit, right? Even if it's a factor of 25 to get something into orbit from Earth, you need to use chemical fuel to do that. Now it's a factor of 25 times 1,000 kilograms. instead of a thousand tons. So it takes much less chemical fuel

to get an ion rocket into space with the fuel it needs to get to Mars than chemical fuel to get a chemical rocket into space. Okay, but we'd still have to use a chemical rocket to get the ion rocket to space and then you use the ion rocket to get to where you're going. Yeah, exactly. Unless you can build these things in space

with Jeff Bezos's future space-based economy from asteroids or whatever, right? So this isn't the complete solution. It's not like, you know, we're building warp drives or teleportation portals to get to Alpha Centauri, you know, in your living room or something. But this will allow us to get further out into the solar system and even pass the solar system once we can get out of Earth's orbit. So you mentioned it takes two days to reach highway speed. Do you eventually reach high enough speeds that a trip to Mars wouldn't take like five billion years? Yes, absolutely.

And NASA is building exactly this kind of rocket. We're hoping to use it to go to Mars in 2028. It's called SR Freedom. And I'll tell you all about that trajectory. Once we're done talking about the energy source of these things, which is really important. All right. Where do we get the energy? So there's a long history, actually, of ion thrusters, which I think is interesting.

And it traces sort of the different sources of energy. People start talking about these things back in like 1911. And there's a few different approaches for how to build it and then how to power it. The approaches for how to build it are things like a gridded ion thruster. Basically, you just have like an anode and a cathode. You know, you have one thing with a positive charge, one thing with a negative charge. You put your charged particles in it. They get attracted to the opposite side.

They go fast. They zoom out the side. So it's a grid because there are holes in it for the particles to go through. So imagine like two chaining fences. One is positive, one is negative. You drop a positive particle into there, it accelerates towards a negative one, and then shoots through the gaps and out the back. That's the basic principle.

Okay. But so to make the anode and the cathode, do you just like stick magnets on there or do you need like a battery to make that happen? You need energy. Yeah. You need electricity. Magnets can't do that for you. Okay.

Also, that design isn't great because it corrods. You're shooting particles at the chain link fence, which tends to eventually destroy the chain link fence or it gets jammed up or something. So these days, they have even fancier ones, is something called a Hall Effect Thruster, which doesn't have the actual cathode. It has a virtual cathode. You have a magnetic field there, which, traps electrons so they move in circles and they ionize the gas which they collide into so they're sort of like

an electric mixing spoon that breaks up the gas into ions and then you don't actually have a cathode there the electrons there act as the cathode and so there's nothing to get like corroded or broken down so that's the technology but in every case the limit is the energy source if you want to crank up ion thrusters to give you a real amount of thrust then you need a lot of energy and so the first example of an ion thruster I want to talk about is called the CERT one. This is back in 1964. This was a test by NASA. And it was basically like, hey, does this work at all? And it was up in space for 30 minutes. And it worked. And it was powered by chemical batteries. So these were like zinc, silver oxide batteries. And it wasn't a whole lot of energy. It was like 1.7 kilowatts of energy. But, you know, it didn't go for very long. So they didn't even like try solar panels. though a later version of a cert two did have solar panels. But this was like, hey, all the equations match, does it actually work in practice?

And it did. So that's cool. Very cool. Well, I've never heard of it, which is a bummer. Oh, yeah. It's pretty cute. It's just like a little ball. And then people said, all right, well, let's try to go for longer periods.

And let's avoid using batteries. And let's use solar power. And this is really exciting because now you're not carrying the energy with you at all. Then it's not a rocket. No, it's a rocket if you're carrying the propellant. So you still have to carry the mass you're throwing at the back, but it's not a requirement that you bring the energy with you, right? All right. So if you can just beam the energy to the rocket and you can use that, then that's awesome. So they tried this. The first one is called N-star, which has 2.3 kilowatts of solar power.

So these solar arrays generate the electrical power, which then you use to build electric fields to shoot ionized xenon out the back at really high speeds. Wow. And this thing ran for 16,000 hours and used only 80 kilograms of xenon propellant to get pretty good delta V. It was like 4.3 kilometers per second. So it was a good demonstration of these things running for a long time, which is what we need to like, you know, get to Alpha Centauri or get even to the edges of the solar system. The next step up is the Dart mission. And I don't know if people will remember this.

This is the one that went and visited an asteroid. And I think it dropped like a washing machine-sized block of metal on the asteroid. Just like see like what happens. Yeah. Well, you know, it wasn't it also to see, I mean, it was to see what happens. But it was to see what happens in the hopes that if there's ever an asteroid coming towards us, we would have some information about how hard you'd have to like hit it to try to deflect it from the Earth or something, right? It was more than just see what happens.

Oh, no, you're right. I'm actually thinking of the Hayabusa mission. that dropped a huge metallic payload as an impactor onto the asteroid Rugu. But Dart is different. You're right. Dart was there to like, let practice deflecting an asteroid. So it does something else. So Dart's main propulsion was a chemical rocket,

but it also had an ion thruster for testing, which is very cool. Well, and didn't Hayabusa bring back a sample from the asteroid? Didn't it, like, it made an explosion to collect something? I feel like you're being uncharacteristically negative, and I'm being uncharacteristically positive this time. No, no, that's totally positive. I love the idea of dropping a washing machine-sized piece of metal on an asteroid just to see what happens.

Like, that's fantastic. I'm super curious. Like, I love when that mission went up. Total supporter. My tax dollars should definitely be spent on missions like that. Okay, yes, might as well. Okay, so we have gotten to the asteroids with ion thrusters. Yeah, exactly.

And so this one also used sunlight. Electricity from solar panels was used to accelerate zine on atom, The ion engine was not the primary propulsion system for the impact. It was mainly a flight demonstration of this next technology for future deep space missions. And ion thrusters are all over the place. Like China's space station has ion thrusters, which it uses to adjust and maintain orbit. Starlink uses ion thrusters that have Krypton or Argon in them. They're good for like very gentle little pushes to like maintain where you are.

Not like a quick like, ooh, I'm going to hit something. I really got to get out of here. You know, also stuff out in space tries to avoid using thrusters whenever possible because it uses a propellant. You know, for example, like Hubble or the space telescopes, they try to do all of their adjustments using reaction wheels. Like you want to turn the thing. You have internal reaction wheels that store angular momentum. So you can turn without any thrusters. We can talk about that on another episode.

Because every time you're using a thruster, it's a rocket. You have propellant. You're using it up. And so eventually it will run out. But the real question is like, what is the best way to get energy? We've talked about chemical batteries. That was always just going to be a test. Solar power is cool, right?

Because it's up, it's free. It's out there. You don't even need to bring the energy with you. That's very cool. A problem is with solar power is that it drops off really hard with distance. The intensity of sunlight goes like one over the distance squared. So if you're twice as far from the sun, you get one fourth of the energy. And space is big.

And so by the time you're like out by Jupiter, there's almost no usable solar power, especially to power a rocket. So we need something else. We need a low mass source of energy. Physics is what we need. And when we get back, we're going to hear about how physics is going to get us out to Jupiter. Yeah. Eating well shouldn't be complicated. But somehow it turns into recipes, prep, cleanup, and half your Sunday gone. Factors solves all that. These are fresh, ready-to-eat meals designed by dietitians, delivered to your door, and ready in just minutes. No prep, no cleanup, no excuses. And it's not just about convenience. You're getting real food, balanced

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High in caffeine, details at McDonald's.com at participating Canadian restaurants excluding Quebec. Hey, Portlandia fans. Carrie Brownstein and Fred Armisen here. You know us, or rather you know them. Tony and Candace, Nina and Lance, Spike, and yes, the chicken. We've played a lot of iconic characters over the years, but today we're showing up as ourselves to tell you about Podlandia, AEO rewatch, our brand new podcast. Each week, we'll revisit an episode of Portlandia from the very beginning,

breaking down the sketches, exploring the backstories of our most iconic characters, revisiting the Portland locations you know and love, and opening up about our creative process. How did any of this get made? Why do we think that was a good idea? We're ready to talk about it. And we'll also be joined by the people who helped bring it all to life, guest stars, collaborators and friends, including director Jonathan Chryssel,

the mayor himself, Kyle McLaughlin, legendary musician Amy Mann, and many more. Kyle is going for it here. You fully improvised, not just words, but a song, a melody. I thought he was going to write. I thought you're all going to write a song for you. I remember you thinking that. Listen to Podlandia. Ayo, rewatch on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

On Solita, we share the messy stories. of traveling alone as a woman. Your duolingo is not going to come back to you when a man is inside of you. Oh, no. I'm Julie Pinero, and I travel by myself because it's a rare space where I can say yes without asking anyone else first. I'm on a mission to reclaim the word solita, trading the pity for possibility. Every time I tried to be alone, I kept meeting people, and they were like,

You smiled at us. Not a lot of people smile around here. I can wait four hours for the next bus or this random dude is offering me a ride on his motorcycle. It's when you're alone that you're most receptive to the world as it is and not the lies you're sold about it. So whether you're a solo travel veteran or you're too nervous to book your first trip, I hope you listen to Solita on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, Daniel. How is physics going to get your first trip? get us to Jupiter. Yeah, physics is absolutely the solution here.

And so, of course, the better way to make energy is not by burning coal or burning methane or even by solar power, because that's not available out in the outer reaches of the solar system. It's nuclear power, right? We already know that the amount of energy stored in like a kilogram of uranium is huge compared to what you could get from a kilogram of methane, right? Brandon Monroe has this amazing, comic where he shows like the energy density of like uranium versus coal versus wood or whatever.

And it's just off the charts. You know, it's like even on a log scale, it's just insane. And so if you want a bunch of energy and you don't want to carry a bunch of mass around, this is the way to go. Have a fission reactor. So bring a small amount of uranium. Use that to power your nuclear reactor. Your nuclear reactor produces electricity.

You feed that into your ion thruster. And now you have propellant. which is very effective because you're pushing it up to very high velocities. And you have fuel uranium, which is very low mass. You're getting a lot of energy out of it per kilogram. I'm going to look past the fact that you mentioned the competition on this show. No, I'm just kidding. We love XKCD.

It's not a competition. It's good for everybody. And anyway, nobody's in competition with Randall because he wins. He does win. He does. And he's a lovely human being also. Yeah, he really is genuinely a nice guy. Yeah. Okay. All right. So we've decided that nuclear-powered ion thrusters are the way to go. Have we had any nuclear-powered ion thrusters in space? I know we've had little nuclear reactors in space to power satellites.

So it depends on what you mean by we. The United States hasn't. By we, I mean humanity. Well, then the Soviets have done that. The Soviets in 1987 had a nuclear-powered plasma thruster in orbit. So this has definitely. happened, it's worked before. And the U.S., as I'm sure you know, has operated nuclear fission reactors in space. So all the pieces are there. We know ion thrusters work in space when they have an electrical energy source. We've powered nuclear fission reactors in space. And the Soviets even put them together in 87 to use nuclear-powered ion thrusters. Wow. Yeah. And all the pieces are still there because I think our attempt is still in orbit somewhere because it didn't quite go according to plan. Exactly. And so NASA was already building

vision reactors to operate in space as part of the Lunar Gateway Space Station, which was then canceled. But they had a power and propulsion element being built by Linteris space systems. And they were already building those. And so we're going to take those and put them at the end of a very, very long truss to keep the radiation away from like the electronics of the rest of the ship. And that's going to provide power for the new SR1 freedom, which is going to power a mission to Mars in 2028, nuclear-powered ion thrusters to Mars.

Whoa. Okay. All right. I feel like you're still going to need the chemical rocket to leave Earth. Mm-hmm. But now you're carrying with you a nuclear reactor. Yes. What is our plan for making sure that everything stay safe?

Cross our fingers, rely on engineers. There's not a great plan. Like, this is an issue. It's always going to be an issue. Things go boom when you launch them. And so if you're launching radioactive fuel into space, it's always a danger. There's not some way that you can, like, keep it clad in something that's less likely to go boom and then open it up and let the reactions start happening once you're in space and away from Earth. There's no way.

I feel like there's got to be ways to make this less scary. So there are smart folks working on this. And, of course, they're taking whatever precaution they can. One thing you can do is don't turn on the reactor until you get to space, for example. So there's still a risk because you have uranium fuel in there, which is radioactive, but you don't have, like, dangerous nuclear byproducts being produced or already present on the rocket so that if it does go boom, you're spreading some uranium fuel, which is not good, right? But it's not as bad as spreading, like, really toxic, radioactive nuclear byproducts.

Okay. In addition, like, you know, they're putting this thing inside high, durable, heat-resistant containment materials designed to survive extreme launch vehicle explosions. And it's supposed to be subcritical no matter what, even if the launch fails. So they're doing what they can. And I have not dug into the details here. But I trust the engineers are doing their best to solve this problem. And I totally acknowledge that it's very dangerous to be launching nasty, toxic stuff into space because it might not get there.

All right. Thank you for giving me my daily dose of Kelly being able to worry and be a wet blanket. And all right, what do we need to think about next? So the way this thing works is it's a fission reactor, which means you're taking uranium and you're splitting it. And that causes a chain reaction because it produces neutrons. And those neutrons split other uranium atoms. And along the way, it produces heat.

And then how do you turn that heat into electricity? Well, on Earth, we often do something like boil water, right, and use the steam to spin a turbine. And so up in space, we're doing something only a little bit more sophisticated. Instead of water, we're using a helium-neon mixture, which still spins a turbine and creates electricity. So the basic process is the same. And then we can use that electricity to accelerate the ions. The cool thing is the fuel is very, very low mass.

Remember, the propellant is like thousands of kilograms of xenon, which is still really low mass compared to the thousands of tons you need for chemical rockets. But the uranium fuel, to give you the energy to push that out the back, is just like. 10 kilograms. It's like a rounding error. That's how powerful uranium is. It's really amazing. So it's almost as free as sunlight, but you can keep using it when you get past Jupiter. Why haven't we done this already then? This seems pretty obviously better. Is it because of concerns about like where are you going to get the uranium? Yeah. Why haven't we done this already? Well, you know, the Soviets have been doing it since the 80s. But chemical rockets are easier, right? There's no nuclear power issues, and they can get off of Earth. So this is really only useful for exploring in places where you're not fighting

a big gravity well. Okay, got it. And it gives a pretty different signature for your mission. Like for a chemical rocket, you want to get to Mars, you burn for like 10 minutes, and then you travel to Mars for six to nine months, and you're going to like peak velocity almost all the time, like 33 kilometers per second. An ion rocket is going to give you like a year of continuous burn, and it's going to start very, very slow. It's going to eventually get up to the same peak velocity, 30, 35 kilometers per second, but it's not in freefall, right? It's a continuous thrust, and it can be adjusted in flight. And so it's a very different kind of trajectory. And that makes it less sensitive to the timing. So you can't get to Mars when it's on the other side of the sun,

but because you're not just in free fall, you can do all sorts of different kinds of trajectories so you don't have as narrow a window. So it takes a little longer to get there, like a year instead of six to nine months, but you have more flexibility about when you go. I don't think I understand the you're not in freefall thing. Why would a chemical rocket versus an ion thing,

if you had enough chemicals for your chemical rocket, couldn't you have the same flexibility? In principle, if you brought enough fuel along that you were burning it during the flight, then yes, you could do the same thing with the chemical rocket, but then you need even more fuel. Remember, chemical rockets are very, very inefficient. That's why they like to burn it all at the very, very beginning. And it's basically, it's almost like a cannonball launch, right? A cannonball, you give it one push and then it just flies.

Chemical rocket, it's like 10 minutes of pushing, and then it's just a free fall trajectory. And so you're very limited in how you go from one place to the other if you can't burn along the way. So the ion thruster can do that. It takes longer to get up to high speed. So the whole trip is going to be a year. The plus side is you have a little bit more flexibility. So your window is a bit broader. It's still not like we can go to Mars anytime and you can't get to Mars faster.

But there's a little bit more flexibility there. Okay. I mean, that's pretty cool because needing to wait two years for every launch window. Like, you know, you miss that. Now you're waiting two years. Like that's a real pain in the rear end. How do we, how much do we? How much do ion thrusters open this window?

So chemical rockets have like a few weeks of a window when they can effectively get to Mars. And ion thrusters have like a few months. Nice. So it's a meaningful change. Again, it's not like totally solving the problem. It's not like you can go to Mars on a whim, but there is flexibility there. Well, but you could imagine a few weeks of bad weather totally messing up your Mars plans if that bad weather happens during your window.

But like, probably not going to have a couple months of bad weather. So, like, that makes your probability of getting to Mars, I don't know, I think much higher. Yeah, exactly. Look at me being a ray of sunshine. And so, for example, if your launch is, like, delayed by 90 days, the spacecraft just, like, adjust the thrust profile, burns more propellant to catch up to Mars rather than having to scrub the mission entirely. And adding a little bit more propellant is not disastrous because the propellant is fairly low mass here. We're talking about, like, a few more kilograms of xenon, right? And the energy is very, very dense.

So we don't have this rocket equation trap where we fall into where every time we bring a pound more fuel, now we need thousands more pounds of fuel to push that fuel. And we still got to launch this thing up into space. But remember, the fact that it's lower mass means it's cheaper to launch it into orbit in the beginning. And we're going to do this in like 2028. It's just around the corner. SR1 Freedom is going to go to Mars. It's going to drop three helicopters that land themselves on Mars. which is amazing.

Amazing. Given Mars has a very dilute atmosphere and helicopters have a real challenge to navigate there. And then it's going to keep going. It's just going to keep going and explore. I love that when we just like send something out into space. And because it has an ion thruster, it can go for a while. Where is it going next? So the final target isn't specified, but the idea is explore the outer solar system,

including high-powered missions beyond Jupiter. Wow. So they're still figuring it out. But we have flexibility because we're not just limited to narrow launch windows. I also want to give a shout out to the listener who commented on gravitational slingshots, which are another way that NASA has historically used to explore the outer solar system without bringing a lot of propellant. You know, how do you change your direction without any fuel? Gravitational slingshots are super duper cool, but they also take forever.

You need like everything to be in the oriented in exactly the right place. So sometimes you do like two or three swings around things. You could take like 10 years to like gravitationally slingshot your way from one place to another. So ion thrusters are much more direct way to get there. I think Kim Stanley Robinson used gravity slingshots as a really great plot point in Aurora. They were running out of fuel. So everybody had to go into like hibernation and they used gravity slingshots to get you there. It like takes a long time.

Yeah. But if you don't have fuel and you can use that, that if you've got the time, it's a good way to go. Yeah, it's also cool because it's physics again, right? Which inherently makes it awesome. Yeah, better than chemistry. Not as good as biology, but it's a hierarchy. It's okay. And there are other side benefits.

Like if we can get reactors to work in space, maybe that's going to help us figure out how to get reactors to work in crazy environments like on the moon. And people who are talking about building moon bases are talking about powering those things with nuclear reactors. Getting to Mars, it's going to help us open up more launch windows. It's a good way to send cargo to Mars. and it opens up the outer solar system. Remember, solar power is just not useful past Jupiter, which gets like 4% of the Earth's sunlight.

So if we're going to explore the outer reaches of the solar system, it's not going to be with chemical rockets. It's going to be with ion thrusters. So if we wanted to get straight to Jupiter really fast, we'd want ion thrusters powered with nuclear reactors rather than gravity slingshots. Yeah, absolutely. Okay, cool.

And Voyage, what did Voyager use? Voyager is a gravity slingshot situation, right? Yes, exactly. Okay. Well, this is amazing. I can't wait to see how those helicopters fare in the Martian atmosphere like the helicopter that came before. And I can't wait to see if Kelly ever achieved her lifelong dream of sitting on a rocket.

Yeah, well, I hope you're sitting right behind me, Daniel. And I hope it's a safe rocket like our paddleboat rocket and not a chemical rocket. Well, I look forward to sitting on that rocket with you, Kelly. Until then, thank you, everybody, for taking this. journey with us through the history of rocket development and into the future for how humans could explore the solar system. Yay, space exploration. Until next time. Thanks everybody for listening. Please go and do us a favor and rate the show on whatever podcast app you're using. It really helps people find us. Daniel and Kelly's extraordinary universe is edited by the amazing Matt Kesselman.

He really is a wizard. You can also find us online on Blue Sky, Instagram, and X. the and K universe. Come engage with us. You can email us at Questions at Daniel and Kelly.org. We really do want to hear from you. And you can find our website, www.

www.danielandkelly.org, where you'll also find an invitation to join our Discord where everybody comes and talks about the amazing universe. And we also have the most amazing moderators. This is an I-Heart podcast.

Thanks for joining us. Hey, Portlandia fans. Carrie Brownstein and Fred Armis, in here. The Dream of the 90s is alive in podcast form. We're launching Podlandia, AEO rewatch, our brand new podcast where we revisit every episode of Portlandia together, breaking down sketches, going deep on our iconic characters, and pulling back the curtain on how it all got made. And we'll also be joined by the people who helped bring it all to life, guest stars, collaborators and friends, including director Jonathan Chrysall, the mayor himself, Kyle McLaughlin,

legendary musician Amy Mann, and many more. Kyle is going for it here. You fully improvised, not just words, but a song. Well, I thought you were all going to write a song. I remember you thinking that. Listen to Podlandia. A.O. Rewatch on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is Chelsea Handler from Dear Chelsea.

Every week, the news gets worse. The world gets crazier. And Yamanika is here to tell whoever's responsible, you're the problem. Do you know I just found out who Sidney Sweeney was? If he got a bunch of women, then I should have a bunch of men. Do better or do less so I don't have to do so much. I'm Yamanika, and I'm out. Listen to you're the problem with Yamanika on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast.

I'm Nick Totoro. You probably know me from NYPD Blue, the longest yard, or Spike Lee's Black Klansman. And on my new podcast, delivering happiness with Nick Tatoro, I deliver pizza to a new guest. I've shared a slice with everyone from Seth Rollins. What are you doing my belt? To Bill Burr. I don't think I've ever met somebody so exactly out of their mind as I am. And now we even have more great guests coming up, including the great John Tuturo.

It's called Happiness, delivering happiness. And many, many more. Open your free High Heart Radio app. Search Delivering Happiness with Nick Totoro. And listen now. Summer Blockbusters are back. The Odyssey and Spider-Man. Brand new day have taken over cinemas, and Raiders of the Lost podcast,

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