Daniel and Jorge Explain the UniverseWill a plasma-based spaceship engine let humanity zoom between planets?
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Hey Daniel, have you guys made any progress on that new spaceship engine that can cross the vast distances between stars?
Nothing to report yet?
Sorry, Oh man, I feel kind of cheated. Thought I made that a rush order.
Well, no problem, you know, once we finish building it, delivery is going to be a snap.
Yeah, are you going to deliver my spaceship on a spaceship?
Now? It's sort of like when you buy a new car, it comes on a huge truck.
Oh nice, So I can expect a huge, giant space truck pulling up next to my house soon.
Absolutely, the kids are gonna love it.
Is it gonna come with a nice big bowl tied around it?
For an extra twenty million dollars, I'll put a bow on it.
Hi am Jorge Maad, cartoonist and the creator of PhD Comics.
Hi, I'm Daniel. I'm a particle physicist and I've never actually bought a new car.
You've never bought a new car, never.
Bought a new car, always a used car.
Wow, I guess you are cheaper, right, because as soon as you buy a car, they start depreciating.
That's right. But I've never had that amazing experience of seeing your brand new, shiny, zero mile car pull up on the fancy truck.
What's new to you? So it is technically a new car.
That's right. And we like to drive our cars into the ground until they're falling apart around.
Us instead of like a podcast. Is that we're what we're doing here now?
Is this a used podcast?
Technically? It is right because we record this a few weeks in advance, so by the time people will listen to it, it's got.
Some mileage on it, but it's new to them.
That's right. Let's maybe spray some of that new car smell around.
That's right, new podcast smell.
Yeah, wif an end people, But anyways, welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio, which we take.
You around this very very old universe that's been around longer than we have and try to answer some questions about it. What questions do we ask? We ask all the questions. We ask the biggest questions, the hardest questions, the silliest questions, and the deepest questions, and we try to find answers. And when we don't find them, we are happy to admit what science doesn't know. We take all that, we mix it around, we throw in some bananas, and we serve it to you as a podcast smoothie.
That's right, because the universe might be old and it might be used. In fact, it's actually a several billions of years old, but it's still full of amazing and new things to discover for us puny humans.
That's right. Do you think we have to pay full price for this universe? I mean it's like really pretty old by the time we got it, we should have gotten some kind of discount.
Really, did you think we have an option? Do we have like other newer universe we could have bought.
I guess you've got to have another option if your negotiation is going to be credible, right, I you're gonna be able to walk out of the universe dealership and say I'm just going to go down the street and get a universe somewhere else.
We have no leverage.
We have no leverage.
We're stuck with this universe, and we love it. It is the only car and the lot, that's.
Right, And let's not pretend we don't love it. It's a wonderful, amazing, crazy place filled with all sorts of mysteries. I just sometimes wish we could see more of it.
Well, we can see a lot of it, right, We can see up to billions and billions and billions of light years away. But the hard part is getting to those places and seeing them up close.
Yes, exactly that's why. I mean that we could visit more of them, that we could go there, that we could walk on the surface of Pluto, or we could see what the atmosphere of Venus is like. It feels like there are so many amazing mysteries of science and physics that are right in our neighborhood, and yet it's still so strangely hard to get there.
Yeah, not just even our solar system. It'd be cool to travel to other galaxies and see if things are quite the same as they are here in the Milky Way.
That's right. I'd like to be home before dinner, though, so I'm not sure I'm going to join you on that intergalactic voyage, but somebody should go, and somebody should report back.
What if you make the spaceship your home, Daniels, then you'll always be home.
Ooh like a space RV. That sounds great.
The couch and a rocket and rocket fuel. That's all you need.
Really, Well, if my family is going along, then my kids definitely need their own rooms, because there's no way they're getting along if they're sharing a room in the space RV.
Al Right, we can add an addition to the extra couches there you go. But yeah, getting around space is difficult because space is so big. It's gigantic, it's ginormous, it's a pretty spacious it's.
Hard to really wrap your mind around how big space is. We have this image of the Solar System. It's sort of this cozy place where all the planets are zooming around the Sun and kind of near each other. But there are vast distances. You know, even just from the Earth to the Moon is a much bigger distance than most people imagine. Did you know that if you took all the planets in the Solar System you could fit them in the distance between the Earth and the Moon.
Wow, I take it that's a bad idea that you're not actually planning on doing that.
You know what, I'd love to see it. So if you have somehow the power to do that, go ahead from your underground.
Layer, well you just want to see it, then, you know, I can do that in photoshop pretty easily. But the idea I think is that space is big. Right like between here in the Moon, it's several hundred thousand miles even right.
Absolutely, it's really really far, and you know, the outer planets are really really far away, like we are much much closer to the Sun than we are to Jupiter, for example.
Yeah, I think we used to maybe thinking of our Solar System as this cozy, little like collection of planets, but really it's quite sparse. It's quite empty, Like if you took a picture of it, you would only see little tiny dots as the planets.
Yeah, that's why Jupiter seems like almost a star because it's so big, but it's so so far away, and so the Solar System is hard to get around because everything is so far away. And when we launch even robotic probes to the outer Solar System, it can take ten, fifteen, twenty years to reach those places.
Yeah. I think the trip to Mars, just to Mars, it takes several months, right.
Yeah, and that's if you're lucky, right, Earth and Mars are near each other sometimes and far apart other times, and so the sureness trip to Mars is like more than half a year, and so it'd be awesome to be able to get to Mars much faster. It make it easier to explore the Solar System, to send people there if they didn't have to spend like seven months in a tin can together.
Yeah, I think the big question is like, how can we get to these planets faster? Like, how can we you know, make a new kind of spaceship or a new kind of propulsion technology to basically push us there faster, because traveling through space is really hard.
It's all about the speed.
You know.
One hundred years ago, the Earth seemed much bigger because it was a bigger deal to get to the other side of it. To go to China two or three hundred years ago was a days, weeks, months long endeavor. Now you can do it in just you know, eighteen hours or so on an airplane. It's not that big a deal. And that transformation came because we had new technology, new engines that could take us there faster. And so we hope we fantasize about a technology that could take us around the Solar System faster, that could effectively compress the Solar system so it doesn't seem so big.
To shrink the Solar System. In a sort of metaphorical way of speaking.
Right, maybe one day you could buy a ticket to Jupiter and all you have to worry about is like how many movies am I going to watch? Have they made enough Avengers movies? So I could just watch them all between here and Jupiter.
Well, by then maybe they will make five months worth of Avenger movies.
Yeah, and maybe by then the Avengers movies will each be forty hours long.
So right, yeah, they seem to could be getting longer and longer.
That's right. It's the opposite of time dilation. It's movie dilation, which works in the opposite direction.
It's marvel dilation.
Marvel dilation.
It's like the quantum realm.
Yeah, well, what if I watch the Avengers movies while moving at high speed, Maybe they'll shrink it back down to two hours long.
Maybe you'll actually like them.
I like those movies. Come on.
But anyways, there are people out there working on new technologies that might get us to other planets and other stars faster and faster. And in particular, there's kind of a new exciting technology with a pretty cool name.
That's right. People are working on this. People try and develop ideas. People have all sorts of different plans for how to develop new engines for spaceships.
So today on the program, we'll be asking the question how do plasma thrusters work? Now, Daniel, I just like to say the word plasma thrusters. I feel like that's so, you know, science fiction. I feel like, you know, some something out of a movie.
I know, it sounds a lot like plasma blaster, right, it sounds like a weapon you could use against something with like lots of limbs and gooey insides.
Yeah, some sort of glowing technology that you know, kind of like what you see behind the starship Enterprise.
Yes, but that's the exciting thing about science fiction is that it gives people ideas and then we try to make it real. Scientists watch science fiction and go, man, why can't we actually do that. I've got an idea, maybe we could actually do that, And then they go off into their laboratories and they tinker until boom, it's a reality.
And the funny thing is that those science fiction writers probably got these names and these ideas from science itself, Like plasma is a real thing and thrusters are a real thing. They just thought, Hey, why don't we put the two together and sell more books?
Is that the process of science fiction? You're like, take two things, stick them together. If we get a banana thruster or a plasma.
Banana, yeah, it's like taking two words like science and fiction and then sticking them together and see what happens.
Boom, new genre invented. Yeah, I think that's the whole process.
So plasma thruster sounds cool, but what is it? So we were wondering why people out there knew about these two words stuck together and whether or not they can actually be real. So, as usual, Daniel went out there into the Internet to ask people if they knew how a plasma thruster works.
And so my eternal gratitude to those of you who volunteered to answer random physics questions for the podcast and enjoy hearing your voice speculating on the podcast. If you'd like to contribute your voice as well, please write to me to questions at Danielandjorge dot com.
Yeah, so think about it for a second. Do you know how a plasma thruster works? Here's what people had to say. I have absolutely no idea what a plasma thruster is or how it works, but it sounds pretty naughty.
Well, I don't know exactly, but it's way better than a chemical like we have now would luck to us.
I'm guessing the plasma thrusters would work by igniting this ionized gas in one direction that causes a force that pushes whatever rocket or object it's in in the other direction.
I'm one hundred percent sure that the plasma thrust is a dance move that particle physicists do parties.
Well, this is a guess on my part based on the words, but I assume that it excites an atom to the point where the electron is stripped off, and it throws the nucleus through some sort of magnetic or field at rather high velocity out the back, which gives you thrust the same way any normal rocket motor would work, except that instead of using chemical energy, you're using magnetic or electric energy to throw out plasma nuclei.
All right, pretty cool answers. I like the one that says it's a dance move that particle physicists do at parties.
You like that. You really want to imagine a bunch of particle physicists dancing. I mean, is that a mental image you want in your mind? I've seen it, and trust me, if you.
Don't do particle physicists have party coal parties.
There are particularly good parties.
Yes, particularly awkward, as I think, say.
When we discover a nice particle, then yes, we have a party, we celebrate, we drink champagne, we shake our booties just like everybody else.
Wow. Sounds exciting, all right, And so a lot of people don't seem to have a pretty good idea, although they definitely, you know, have some ideas of what plasma is, but maybe not what a plasma thruster is.
Yeah, but they're excited about it. They want this thing to be a reality. That sounds like a promising step in the direction of getting us around the Solar System. And so I think everybody's in favor.
All right, Well, Daniel, let's talk about first why we might need a plasma thruster. You know why this idea of creating something that can push you in the vacuum of space, why is that so hard?
Right?
So, one of the reasons that this is a hard problem is that when you are in space, you need to push against something. Right. If you're in space and you want to get speed, what you have to do is throw something out the back of your rocket ship. Because of conservation momentum, if you're going to go in one direction, something else has to go in the other direction. So this is like the reaction you know, you could like fire a bullet, for example, out the back of your spaceship, and the gun will push you in one direction and the bullet in the other direction. So the basic elements you need of any thruster are some energy and then something to throw out the back, some reaction mass to push the other direction.
Right, Because I guess when you're out in space, if you're out there floating, it's not like you can swim your way to Mars or to the moon. You can't just there's something to like push against, right, So you need to throw something out the back, and for that you need energy. So that's what you're saying. You need energy and then something to throw out the bag using that energy.
Exactly, you have to carry with you stuff that you can throw away so that you can move along. As you say, you can't like grab space and swim through space itself. Right, it's not like air or water that you can pull against.
Right, You can't just like blow out the back like or maybe you can can.
You Yeah, actually that would work. I mean that is a form of a rocket engine, right, you blow air out the back. And you could even use a flashlight, right, if you turn on a flashlight on a spaceship out the back of your spaceship. Then that's a form of a thruster because you're shooting energy in one direction and so the spaceship will go the other direction.
Right, that would be a photon thruster. That's a different episode.
That's a different episode. Yeah, exactly. But you know, it reminds me some listener wrote in and asked about their headlights. Every time you turn on headlights in your car, are those effectively like photon brakes? And they kind of are, because you're like throwing energy forwards, sort of like having tiny little thrusters pointing forwards. So yeah, every time you turn on your headlights, your car slowed down the tiniest little bit.
And it just made me think when you hit the brakes and you turn on the brake lights in the back, and you're also sort of working against yourself there because you're breaking, but you're also kind of propelling yourself using photons.
Yeah, brake lights should be in the front. Oh my god, so much better.
I think that would defeat the purpose of brake lights.
So one of the problems with using a rocket is that you've got to have all this stuff on board. You've got to have the fuel. You've got to have the stuff to throw out the back. And then the further you want to go, the more fuel you need, and the more fuel you need, the more fuel you need to push that fuel. And so pretty quickly this is sort of like a runaway mass problem. You need to have a really really big ship to get anywhere at all, because you need fuel to push all the fuel that you're pushing with all the fuel.
Right, And that's kind of how rockets work right now, right like the ones in current spaceships and spacecraft and rockets. That's how they work. They use a chemical reaction to explode something and then that explosion pushes the stuff out the back.
That's right. The fuel itself is the propellant and the source of energy, right, Like you have something along like diesel fuel or liquid oxygen or something that has energy stored inside of it, and then you release that energy and at the same time creates something at high velocity which can get thrown out the back. So most chemical rockets work in that way. They're both the propellant and the source of energy. And that's how, for example, rockets lift off the Earth, and that's how the space shuttle maneuvers in space. All these are chemical rockets.
Right, And what makes it work, I think is the idea is this kind of this difference or this ratio between the energy and the mass of what you're throwing behind you. If your plan was to like throw out you know, your trash or throwout your couch to propel yourself in space, that wouldn't last very long, right, because you would run out of couches soon. Yeah, and you know maybe RVs and children. You wouldn't get very far. But the idea with the chemical fuel is that it has a lot of energy stored in it, right, So like it you really that energy. It throws a little bit of mass out the back, but with so much energy it actually pushes you forward.
That's right. The key thing is having high exhaust velocity so that those particles you're throwing out, whatever they are, particles of counter particles of smoke, or particles of burnt rocket fuel, whatever, are carrying a lot of momentum. Because any momentum that's going out the back is equivalent to the momentum gained by your rocket ship. Right. This is all about conservation of momentum, and so the higher speed the higher exhaust velocity that goes out the back, the more momentum you're throwing away in your exhaust, and so the more momentum your rocket ship is going to get.
Right, because momentum is like mass times velocity. So if you want to conserve on how much stuff you throw out the back the mass, then you just need a lot of velocity.
Yeah, exactly, that's the way to do it.
So those are chemical kind of rockets, and that's what we used to get off the Earth, but those are kind of tough for going across to other planets or stars, right.
Yeah, If you wanted to travel, for example, to the nearest star system like Alpha Centauri, and get it up to a reable speed, like you know, a few percent into the speed of light, so that the trip, which is just a few light years would only take you know, fifty or one hundred years, you would need an enormous amount of chemical fuel to accelerate you up to that speed. And because you'd need so much fuel, you'd need a lot more fuel to push that fuel, and so you'd end up with like a toothpick sized chip pushing a Jupiter sized gas tank.
That sounds crazy, I think A good analogy I think we've read once was that it's sort of like if you're trying to drive a truck across the country without stopping for fuel, you sort of need to bring all your fuel with you. But then the more fuel you bring, the more fuel you have to use because you're heavier, exactly.
And then pretty quickly you're driving basically like a stadium size gas tank behind you, and that's pretty inefficient and takes a lot of fuel, so it really limits how far you can go.
Right, And that's kind of why rockets are so big. Like if you look at a rocket the ghost of space, most of it is just a giant fuel tank, right.
Yeah, I'm not sure sure people really understand how massive these things are. Like the Saturn five rockets, one of the workhorses of the American space program, is taller than the Statue of Liberty. Like, this thing is enormous, but most of the actual active part of it is this tiny little nose cone on the very top. Basically it's a huge gas tank with a tiny little cab on top.
Because you need to bring a lot of that fuel with you, and so that's really the hard part about space travel is like, bring all the fuel that you'll need later, because there are no gas stations in other planets, right, there are no gas stations out there in space.
It sounds like you're identifying a business opportunity here, you know, rocket fuel for sale on Pluto or halfway between here and Alpha Centauri. You could sell a lot of slim gyms also, you.
Know, yeah, there you go and turkey jerky. But then what do you do with the restroom waist. That's the hard part.
That's just more rocket fuel. Man, you could just mix it all in.
Oh, there you go, biomass, biomass.
Fuel, biofuels exactly.
Solutions solved all at once. All right. So that's the main problem with thrusters and getting around the solar system in space. And so there's this new idea of using plasma based thrusters. So let's get into that and whether or not they're real and whether they can work. But first, let's take a quick break.
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All right, we're talking about plasma based thrusters. Now, this sounds really sci fi, Daniel plasma. Anything I think with the word plasma sounds cool, but it's the opposite. It's not cool.
No, it's not cool. It's very, very hot, and it's actually one of the most common forms of matter in the universe.
Right.
People think of plasma's weird and rare and unusual, but it's really just weird and rare and usual here on Earth, where it's sort of weirdly cold, Like the Sun is basically a huge ball of plasma. And since the Sun is most of the stuff in the Solar system, the Solar system is basically all plasma with a few crumbs like us, we.
Should just call the Sun the plasma ball, the giant plasma ball in the sky.
It basically is, it's such a big hot plasma that we can feel it even ninety three million miles away.
And thank goodness, but maybe step us through what is exactly a plasma? You said, it's a state of matter.
Yeah, you're familiar with several states of matter. Right. There's solids when the atoms are cool and sort of locking into a crystal structure, so they become solid and then liquid. If you heat it up, then those atoms get liberated from those bonds and squish around. Keep heating something and it becomes a gas, as those atoms like to whizz around and aren't even connected to each other. If you keep heating it, then what happens is that the electrons that are whizzing around those atoms get so much energy that they're no longer held on by the nucleus. So you have a positive nucleus and a negative electron, and usually the strength of that electromagnetic bond is enough to keep the electrons bound to the nucleus of the atom. But if you get them hot enough, then they escape and then you have something which just has nuclei and electrons floating around, whizzing around. You have charged particles. So plasma is like a gas that's been heated up so much that it becomes ionized that the electrons are now free.
Right, it's basically like just regular matter, right, that's heated up so much that it breaks the atoms. Like the atoms kind of break apart.
Yeah, they're broken apart, and it's sort of like the original state, you know, before things cool down. Electrons got captured by the nuclei. They were free. Electrons were born free. They were captured, and some of them have been in this state for millions of years. And now if you heat something up, you were returning them back to their original state of freedom.
Oh man, Now you make me sad for the atoms in my body and the electrons in my body. You make it sound like I'm trapping them and I'm keeping them from being free.
No, some atoms are very happy to be married forever, you know, but other ones want to be single, and so you know.
There's good side both to each your own.
Yeah, but a plasma is basically like a singles bar right now.
It can anything be a plasma, Like, can any kind of matter be a plasma if I heat it up enough?
Yeah, anything can be a plasma as long as you heat it up enough. That it starts to lose its electrons and it's made out of ions and its components are now charged instead of neutral. Then that's a plasma. So yeah, you can have a plasma out of hydrogen. That's what most of the universe is. You can also have a plasma out of like iron. You heat of iron enough, you get an iron plasma.
And you know, you said it happens in the sun, and it happens when you heat things up a lot. But there are other ways that you can make plasma that doesn't heat them up that much, right, Like there's I think you can use radio waves or some sort of radiation to create a plasma, like in your desktop.
Yeah, we have plasma all around us. Like fluorescent lights have a plasma in them, right, that's why they glow. You know, you can talk about the definition of temperature. I find it's a little fuzzy. You are making those particles move fast than if you're giving them enough energy to be released from their atoms, so they have that high velocity even if there's not that much actual heat. Right, A plasma doesn't have to be very very hot, even if it's high temperature, because it doesn't store a lot of heat because the gas is very diffuse and dilute. Then you might not like burn yourself from touching a container that has plasma in it, but it still would be officially high temperature because the particles are moving fast.
So fluorescent lights, like the lights we all have in our offices in stores and stuff, that's plasma. That's like a canister of plasma.
Right, that's a canister of plasma. And neon for example, neon lights, those have plasma inside them. So those are atoms that are whizzing around and they have so much energy that they glow and they give off photons. Right, They're just like shedding energy constantly.
I wonder if they had named those plasma lights, if we would feel the same way we feel about fluorescence lights right now, Like it would be this name that's associated with something like unpleasant, boring, unpleasant.
Yeah, yeah, a fluorescent blaster. I'm gonna shoot fluorescent light at you and give you a headache.
Yeah, there you go. That will make for enough for science.
Fiction Medel the headache gun.
All right, So that's plasma. So how does a plasma thruster work? Like, how would you use something like fluorescent light to push yourself through space.
Well, a plasma is glowing, it's giving off energy, it's stuff moving around fast. The problem with the plasma is that generally glows in every direction, and so it's sort of throwing momentum off in every direction. Like the sun isn't an engine, it's not flying in one direction because it's giving off energy in every direction. So if you want to take a plasma and turn it into a thruster, what you need to do is make it only point its glow, only shoot particles out, only send momentum away in one erection. And the way you do that is you just take a plasma and you put it in basically a magnetic bottle. I mean, the plasmas are charged particles, and charge particles bend in magnetic fields, and so it's hard to contain a plasma because there's so much energy. You'll basically eat through anything. It's sort of like acid. But if you could build a bottle around it that bends the particles back into the plasma, but leave a hole in one side, then particles will shoot out through that hole and effectually push the whole plasma the other direction.
I see, it's like you're heating a water kind of like you're making a water a gun, kind of like you heat up the water, it steams up, it becomes a high pressure gas, and then you shoot it on one side, and that's kind of what would push you in space, but you're doing it with a plasma material.
Yeah, take a water balloon for example. If you poke a water balloon on one side, then water is going to squirt out through the hole that you made, and the rest of the balloon is going to go the other direction. And so that's basically what a plasma is. It's hot and high speed, and so it's always shooting particles off. It's basically trying to expand. But if you contain it in every direction but one, but only where the hole is, can particles leave and they will carry momentum. And that's basically an engine.
And so that's kind of the basic mechanism of a plasma thrust. It's like you're heating something up and then you're letting it escape out one end of your spaceship.
That's the basic mechanism. And you remember once we talked on the podcast about using the sun as an engine, or building an engine that could move the whole sun. It was the same basic idea. It's to build something around the sun that reflects its energy back into the sun, except in one direction. And so you can use this idea to move the whole sun, or you can build your own little mini plasma, your mini sun, and reflect most of its energy back into itself, except in one direction. So that's the basic premise.
Right.
It's kind of like a flashlight or even your headlights, right, like you're heating up an element, it's creating photons, but then you're focusing those photons to one side.
Yeah, because flashlights usually have like a mirror on one side, So the photons that are generated that come back towards a handle get reflected to go the other direction, so it produces a more collimated beam. So that's the basic principle. If you can shoot off momentum in one direction, then the rest of the engine goes the other way. And so what you need to do is get some cold stuff, really almost anything, and heat it up until it becomes a plasma and confine it in all but one direction.
I guess the tricky thing here that I'm not seeing is how is this better than a chemical reaction? Because it seems like you're just you have to spend a lot of energy to heat up this plasma as opposed to like rocket fuel, which explodes because it has that energy stored inside of it.
Yeah, that's true. It sometimes can be an advantage to decouple those things. Like here, you're right that the source of energy is something else, and that means that you're sort of free to get that energy from another source, like solar power. If you have huge solar cells, you can collect that energy, turn it into electricity, and then hook that up to a plasma rocket and use it for propulsion. So that's one advantage, sort of like the way you have an electric car. It's nice that you have an electric car because it means that you can accept energy from lots of different kinds of sources, not just dirty coal burning power plant, but also clean solar panels. For example.
Oh, I see, do you want to somehow collect solar energy while you're out there in space and somehow convert that to thrust and instead of bringing the fuel with you.
Yeah, because it's lower mass, right, So if you can gather the energy along the way, then you can have this plasma thruster and you don't need to bring all that fuel with you. But it can also be a disadvantage, right because you need to gather that solar energy and that's complicated, or you need to have some other source of electricity. The nice thing about rocket fuel is that it's sort of like all in one, as you say, So there are pros and cons there.
What are some of the other cons.
Well, one of the cons is that plasma is really really hard to contain. You know, like you have a plasma, it's going to be eating away at the walls that you're trying to use to contain it all the time. One of the big challenges we have with fusion research here on Earth is that we're trying to make a plasma and contain it. We can't just like have our own little sun and it'll destroy the Earth. So we need to build these magnetic bottles. But they are hard. Plasmas are always trying to escape and keeping them stable and keeping them contained is really tricky, and you don't want your spaceship engine breaking down or the plasma leak out and basically destroy your ship. So it's got to be really really robust, especially if you're talking about like a year's or decades long journey and there are no repair stations along the way.
Yeah, you need like a cool container to keep that plasma in check.
Yeah, and the plasma gets hot and it generates a lot of waste heat, and so you need some like large way to radiate off all of that heat from the plasma that you're not using, And so that's a huge waste of energy. It's inefficient, and sometimes it requires like large fins just to cool this thing, which means more mass, which means that you're not going to be moving as quickly. So there really are some disadvantages there. I think the main disadvantage though, is that plasmas don't get particles up to very very high speeds like a rocket engine or ion thrusters or other things that have like active acceleration of these ions can get much higher exhaust velocities. A plasma is basically just saying, hey, you got something that's kind of already hot. The particles are already kind of moving around, so why don't you just use that. You're not really getting very high exhaust velocity.
Yeah, it doesn't seem that efficient because you're you're basically just throwing stuff out the back, right, you're not sort of like releasing any sort of inherent energy on it. You're literally like just pushing stuff out the back, like you're throwing your couches at the back of your spaceshit.
Yeah. Well there is some extra flexibility there, for example, because you can almost use anything. Like you said, you could turn anything into a plasma. And so you can use like astronaut urine or astronaut waste and throw it in the engine and it will turn into fuel. Oh no, yes, you really can, or your couch if you want to think more cleanly. You know, other things sometimes require very special chemicals, like you got to use rocket fuel and a chemical engine, or if you have an ion thruster for example, and need some very sort of like inert gas like xenon. You know, things that like those Starlink satellites have these are little ion engines that create a little plasma, but they have to start from zene on. But if you have a real plasma engine on your spaceship, you can basically toss anything in their banana peels, coffee grounds, astronaut urine, whatever.
Right, you can have a poop plasma.
That's a crappy idea.
Yeah, I know, let's flush that down the toilet. All right, Well, then, so what are some of the pros of using a plasma thruster, Like, why convince me that it's a good thing.
Well, I'm not sure I can give into is a great thing. This is sort of the basic design for a plasma thruster. There are improvements we'll talk about in a minute that make it more appealing, but they do have some advantages over other approaches, like, for example, the exhaust is naturally uncharged, doesn't have electric charge because what you have are both positive and negative particles shooting out the back, and so as they come out the back, they naturally sort of recombine into neutral particles. You don't need to do something extra to make sure they're neutral. Like for ion thrusters. You're only shooting positively charged particles out the back, and you need to add electrons to them as they come out the back to recombine them so they don't get like sucked back into your ship. So there's one positive. Another positive is that they're sort of simple. You know, they're basically just magnetic bottles that you're heating up using some sort of electrical energy. So there's not a whole lot of stuff to break, except of course, for the plasma eating the bottle.
All right, well, it sounds like simplicity and flexibility in the kind of fuel is a good thing. So let's get into how to actually make one of these and whether or not it would be practical to do. First, let's take another quick break.
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All right, we're talking about plasma. Thus theists that may or may not be made out of panu.
In space definitely on the main notfe yes.
Or hopefully not. You don't want to be like the car behind that spaceship that's getting all that you know, high energy waste.
Yeah, then again, do you really want to carry all that waste with you to Alpha Centauri, so that when you show up and you meet the aliens, the first thing you ask them is like, hey, do you have a place I could put all this stuff? Because I have a huge storage tank filled with it.
Right, do you want to recycle it? All? Right? Well, talk to us about whether or not people are actually making this, and maybe what kind of specific technology people are focusing on.
So people are definitely working on this. They are developing these things in the laboratory. And the one that we just talked about, the most basic sort of plasma thruster, there's a version of it called the Vasimir vasimr that people are working on, and it has like a magnetic nozzle at the end of it, so you can sort of tune how much of the plasma comes out and at what velocity. That's cool because it lets you adjust this exhaust velocity so you can like ramp it up when you get into outer space and get more thrust. So that's pretty cool. People are working on that. But then there are some other exciting ideas. There are sort of more cutting edge that people are working on to improve plasma thrusters and sort of next generation devices.
Yeah, and these involve another pretty cool science fiction word, which is fusion. Are we actually considering like making fusion possible for space travel.
Yeah, we are, because what we talked about so far is just plasma right now. Plasma is an important component of fusion in the sun, but you can have plasma without fusion, or plasma in your fluorescent light is not doing nuclear fusion. It's not like a bomb. But the way that we do fusion is through a plasma. You gotta get a gas, you gotta heat it up, then you've got to squeeze it down so that those very high energy particles smash into each other and make heavier elements. And so people are working on taking plasma thrusters to the place where they actually can fuse some fuel to release additional energy as a way to avoid having a pump in external energy like from solar panels or from some sort of electrical sot.
So now we're talking about making fusion in space.
Fusion in space like a.
Fusion engine that you put on a space ship.
Yeah, and it's called a direct fusion drive. And you might be wondering why you would want to do that, because the whole idea of a plasma thruster was that you could take energy from all sorts of different directions. But the idea here is that again like a chemical rocket, you're now bringing the fuel that has the energy inside it. Right, it's more like a chemical rocket, but this fuel is very very dense. You know, fusion is much more efficient than chemical burning because you're turning mass into energy much more effectively. That's why, like, for example, hydrogen bombs are much more powerful than T and T because fusion is much more powerful than just chemical burning, and so you have a much denser source of fuel, and so it's more efficient transformation of that fuel into energy. So you just don't have to bring neatly as much fuel if you can use fusion as the source of energy.
Right, it's like you're bringing all the energy that's trapped inside of the bonds or that's and trapped in the potential bonds of the fuel that you're bringing. So it's almost like you're being extra clever about it.
Yeah, it's all about getting as much energy as possible out of the same mass of fuel, because then you need less fuel mass for that energy. You know, the best case scenario is to bring like antimatter fuel and to smash matter and antimatter together because it's total annihilation of mass into energy. But you know, antimatter is basically impossible to fabricate in large quantities and very difficult to transport. Fusion is sort of like at the edge of plausibility, Like it might be possible to build a fusion reactor in space that transforms the energy stored in the nucleus into energy you can throw out the back of your rocket.
Yeah, that's the thing, because I feel like, you know, we've been working on trying to get fusion working here on Earth for like fifty years, and we still don't have a pretty good or a working or an efficient fusion generator. What makes us thing that we can suddenly do it in space.
Well, I talked to some plasma physicists and they don't They don't think this is possible. They're like, no, I don't think so. I mean, some people make the argument that it's simpler. They think it doesn't have to be such a huge, massive thing, like you could build basically a minivan sized fusion container, rather than like the fusion reactors we're building here on Earth, like eater. This new reactor they're building in France is like sixty meters high, and so they think it could be simpler, it can be smaller, but frankly, there's a lot of skepticism in the plasma physics community about whether this is plausible at all. It's basically relying on an uninvented technology, small scale fusion that would have to work and be reliable for years.
And so what's the basic idea that would we somehow trap plasma and then somehow ignited so that it fuses together and then that energy goes out the back.
Yeah, that's the basic idea. You start the plasma with some other external heat source, maybe RF energy or whatever you've captured from before, and then once you've gotten it hot, you put in your fuel, and then that fuel releases more energy, and then it's sort of like a fire because it really is the energy needed to ignite the next piece of fuel, and so it's self sustaining. So you're putting in energy, but only in terms of this like very very dense fuel that releases a huge amount of energy. So then the particles are now very high speed and they flow around the field lines of your magnetic bottle and they shoot out the back. And so that's pretty cool. It generates very high speed particles, which are very good for a rocket engine, and at the same time you can capture some of that energy and turn it into energy for your spaceship. Right, you also want to like heat coffee and power your life support systems. Well, you have a fusion reactor on board now that not just is generating thrust, but also can generate direct electricity.
I guess maybe one advantage too is that unlike a fusion generator here on Earth, you're not trying to like power a whole city, right, Like, it doesn't have to be maybe energy positive for a space engine, like you actually want to spend some energy to push yourself, so it doesn't maybe have the same requirements as a fusion generator here on Earth.
Yeah, that's true. Some of these designs, though, are even more complicated than the ones that are working on here on Earth. Here on Earth we try to use simpler fuels like deuterium and tritium. These are isotopes of hydrogen with extra neutrons on them. But the ones that people are talking about for space travel use like advanced fuels like helium three. And these are cool because you can find like deposits of it on the Moon, but nobody's made fusion for helium three work. It's even much more complicated than the kind of fusion we're talking about on Earth that we also haven't made work. And so this is definitely in the category of like the could work, would be awesome, might never work.
It's currently at the science fiction novel stage. Yeah, it's currently at the Marvel movie name drop stage.
No, they're like, there are prototypes. They are working on it at Princeton. Princeton has an incredible plasma physics laboratory. They're great at fusion, and so there are people working on it, but you know, it's far away from being approven technology.
Well, there are some pretty new and interesting ideas. I think you spoke to some of the scientists there at the Princeton lab and they have some new concepts for making this.
Yeah, there was a new idea just this year from an Iranian scientist at plasma, doctor Fatima Abrahimi, and she was actually thinking about the way the Sun works because the Sun is a huge ball of plasma and the Sun has these crazy releases of energy, right, like these huge coronal mass ejections, and these happen when the magnetic fields on the sun like reconfigure themselves and snap into a new direction, and what you get are these like bubbles of plasma that are trapped in these little magnetic field ripples and they move really really fast through the plasma. So she thought, well, I wonder if you could use that to build an engine, Like what if you could have a plasma that generated these little magnetic bubbles and then shot them out the back. That would be an effective way to take your plasma. You wouldn't necessarily need it to be fusing and to shoot really high energy plasmoids out the back. So that's what these little magnetic bubbles are called plasmoids.
This is just some like phenomena that happens with all plasmas. And she's saying, let's to those bubbles and use them.
Yeah, let's capture those bubbles and direct them. And if we can make our magnetic fields in such a way that they always shoot in one direction, then we can basically shoot these magnetic bubbles out the back. And because they move at very high speeds, like twenty kilometers per second, then you can get a very high exhaust velocity from your plasma, much higher than the generic plasma thruster we were talking about before, which is just like a hot gas with stuff leaking out. This is like magnetically directed and accelerated inside the plasma.
Yeah. The generic version is always you know, a little suspect cheaper, but yeah, cheaper, Yeah, but you never know, right, So this is sort of like using plasma burps, right, Like this could be called the plasma burp engine.
Yeah, the plasma burp engine. I'm sure she'd love to have it called.
That better than the other name you could give it for, you know, shooting gas.
Yeah. Well, these are high velocity burps, right, This is like ten times faster exhaust speed than a generic plasma engine. And that's exciting because the exhaust speed is key, right, That's the thing that gives you that push of momentum. That's what lets you really get your spaceship going up to high speeds very quickly.
Yeah, these are name brand burps, not the generic kind. All right, Well, let's be hopeful, and so let's say they make this work and we have this exciting technology. Can it takes us around the Solar system faster? Like, could we get to Mars in less than a month?
Yeah? If you had this kind of technology and it was reliable and you trusted it, then you could get to Mars in like thirty nine days. They've done these calculations and this kind of engine again, if it works, can get you to Mars in a pretty short amount of time. That's great because it means you could also get to like Saturn in just a couple of years. You can get the Pluto in like less than five years, whereas currently it takes more than a decade to get out to those outer parts of the Solar System, Mars.
In thirty nine days. That is like a Marvel movie a day, So your dream might come true.
Yeah, and they keep making them so they can just beam them to you.
Can download them there you go.
I hope they have free Wi Fi you can.
You can burp your way through the Marble catalog.
What if you shoot Avengers movies out the back of your ship. That's the potential engine right there. They're pretty massive.
Yeah, definitely takes them all the money that Marble has made to make these engines work.
So and it's not just humans that need to get around the Solar System. There are very real reasons why we want faster ways to move around the Solar System, and one is to intercept asteroids. You know that we're always on the lookout for objects that might hit the Earth, that might come and impact the Earth and cause an extinction event, and we're pretty good at watching these things, but sometimes they appear with very little warning. And the critical thing when you're trying to avoid getting hit by a rock is to spot it as early as possible, because that's when you can give it, like just a little bit of a nudge and push it off course to spare the Earth. But if you see this rock, you got to get to it. You got to get out there to give it a nudge. And so a faster a rocket, like a plasma based interceptor might literally save the Earth someday if it means that we can get it out there and give that asteroid a nudge before it comes and hits the Earth.
Interesting just gives you faster first responders in case of an emergency.
Yeah, so you can get to it sooner, which means you need a smaller push, which means there are a lot more asteroids that you could deflect. Right, a really really tiny push two years in advance is the equivalent of like a massive nuclear thrust five minutes before it hits the Earth. It's much easier to deflect these things if you catch them early.
All right, well, then maybe you should stop watching so many Marvel movies and get to work on this Daniel, Come on, would you never know when that asteroid might come?
I would happily do it if anything I did ever had any practical benefits. But you know that's not true.
Yeah, maybe you're not the person to put on this project. All right, Well, last question, Daniel. If somebody did make a spaceship but that is powered by direct fusion and plasma plasma thrust earth, would you buy it if it was used?
Well, I guess it depends on what happened to the last people who used it, right, If they're still around and they had a good trip, then yeah, I would trust did better than spending all that money on a new fusion drive.
Geez, who said new spaceship spill? All right? Well, I think that the answer is the question what is a plasma thruster and how that might work and how it could work in the future. And again, scientists are hard at work trying to get us out there into space so that we can explore more and see things up closed and learn more about the universe.
That's right. Some of these things are real and working in the laboratory, and some of these things are still pipe dreams that scientists are working on. And there's lots of room for new ideas. So if you have an awesome idea for a new spaceship engine that lets us get around the solar system, hey, get to work.
That's right, and you could create the next name brand spaceship. All right, thanks for joining us, see you next time.
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