Transcription
So, next, our next speaker, Stephanie Thomas from Princeton Satellite Systems. Got too close to my mouth. Can you hear me? Is it working all right?
Next. And back. Hi, Ann. Hi to everyone on the livestream. I invited a lot of friends to hopefully come and watch me talk about my fusion rocket because that's what we're here to talk today about. And specifically, going to Pluto with an orbiter.
First, I'd like to acknowledge the team. This is a collaboration between my company, Princeton Satellite Systems, and the Princeton Plasma Physics Lab. Dr. Cohen is the inventor of the reactor I'm going to talk about today. Eugene Evans, one of his grad students, is here with me to help answer questions about the reactor at our poster session. And we've been working together on this concept for, there we go, our two companies, the lab and ourselves, for almost 20 years. And finally come to fruition with this NAI grant, which we're so excited about.
So, our concept is a fusion engine that has propulsion and power in one integrated device. Now, there's actually a lot of fusion engine concepts out there that you may have heard about. And many of those have a fusion reactor coupled with a secondary thruster. So, the fusion is just providing power, or in some cases, the fusion is only producing the propulsion. Our reactor does both. And works.
This is a cross-section view of the reactor. And we have propellant coming in at one end. Fusion happens in a magnetic torus in the center with a rotating magnetic field heating method. And the gas, it gets ionized, flows around the reactor, and then gets accelerated through a magnetic nozzle at the end. So, the actual reactor is the rocket engine. It's one device. We call this process of adding extra gas to produce thrust, thrust augmentation. And for scale, the entire machine is only going to be 1 to 2 meters in diameter. So, this is a very small reactor, and that's why it would fit on a spacecraft.
So, Mike also mentioned New Horizons. When we were writing our proposal, you know, it had just gone by Pluto. It was in the news. People were really excited about it. But it flew by Pluto at 14 kilometers per second. It said, "Hi, Pluto. Bye, Pluto." These two dots. And this is to scale. It says, "One," my pointer, "are only 30 minutes apart." That distance there. And it took, will take 16 months to get all the data back because it has one kilobit per second. So, we were thinking about this and we said, "What if, using our fusion rocket, we could go into orbit around Pluto instead? What if we could put a lander on the surface? What if we could beam power to our lander to the effect of 30 kilowatts and return high-definition video back?" Because we're going to have so much power, we can do optical comms, and not just at 2 watts, but a thousand watts. And get there in only 4 years. You know, we think NASA would be excited about this. And they were.
So, here's our Pluto Explorer spacecraft, as coined by a YouTuber. I love that. Pluto Explorer. So, these would be our rocket engines, our fusion rocket engines at the end. These things that look like solar panels would actually be the radiators. We have a lot of excess heat from converting our fusion to our power in our thrust. So, looks like solar wings with their radiators. And we would have our lander at the end, which would have a solar array for receiving optical power. Actually, Mike had optical power going to his lander as well.
So, here's our mission by the numbers. We would deliver a thousand kilograms of orbiter and lander. Arrive in only four to five years. Provide two megawatts of power to our payload when we get there. Beaming some of that down to the lander. And our launched mass is less than 8,000 kilograms, which could fit onto an existing launch vehicle. You don't have to build it in orbit. You can just launch it and fly directly to Pluto. And the amount of helium-3, which I'll talk about a little bit more, for this mission could be purchased now from the available supply. There's a market for helium-3. The amount we need, you could simply purchase. So, it's a great example of a space mission using our fusion rocket. Did I miss any of these numbers?
So, this is our point mission design for our NAI proposal. We had 20 Newtons of thrust, 10,000 second ISP for all you rocket scientists out there. And we have a specific power we assumed, and total trip time, four years. Our acceleration time in that four years, the amount of time we're actually thrusting would be about 230 days for this example.
So, now let's compare New Horizons to our proposed mission. We get there in half the time because we have 70 kilometers per second of Delta V. New Horizons swung by Jupiter. We're flying straight there. We're going into orbit. We're putting down a lander. Instead of 200 watts, which is a couple light bulbs, which is why it took, going to take 16 months to get the data back, we have two million watts. Easily high-definition TV data rates back. We have non-radioactive fuel. Nuclear isn't an RTG. It can be controversial to launch them because they have plutonium. Our fuels are really safe. And as I said, we're delivering a lot of mass, but we still fit on a single launch vehicle. You cannot do this with any other technology. Not with fission electric, not with solar. And that's why we chose it as our context mission for our NAI. It's a great example of what you can do with a fusion rocket.
But hey, if you had a fusion rocket, or just a small modular fusion reactor, there are a lot of other things you could do with that. For civil purposes, distributed and remote power. There are a lot of military applications. You can put it on a submarine. You can put it on an aircraft carrier. For space, yes, any deep-space mission you want to go to Neptune, you want to go to icy moons, Mars, yes. And this picture here of the Earth being destroyed by a giant asteroid, it's sort of a joke. Did I just turn this off? Still on. This is sort of a joke, but it's actually not a joke because there are a lot of huge and scientists who say that we should be funding fusion propulsion solely to save the Earth from an asteroid. And with our rocket, with a small asteroid, you could simply deflect it with the thrust we have. For a larger asteroid, you could deliver your nuclear. So, yes, we could potentially save the Earth from an asteroid. Power generation and military lasers in Earth orbit. So, there are a lot of things besides Pluto you can do.
So, wait, you say, "This sounds awesome, but we all know fusion is always 20 years away." So, what's different? And why are you different? So, the reason this is our Princeton Field-Reversed Configuration reactor that our rocket engine is based on, three main reasons why it's different: it's really small, it's quite simple in comparison to other fusion concepts, and it's really, really clean, which I will explain more.
So, this is ITER. This is the reactor that's being built in France. That's the experimental tokamak. ITER is 60 meters tall. There's a person for scale right down there. I will probably be about 30 years, you know, from concept to plasma. And it's going to produce half a gigawatt. Okay. This is enormous, and it's costing untold billions of dollars at this point. We don't even have a firm dollar figure. Here's our reactor in comparison. So, it's about two meters in diameter maximum, right? About the size of our person. It's only one to 10 megawatts. No, it cannot be made bigger. If you need more power, you simply need more of them. Two meters in diameter. And because it's, you know, one-thousandth of the volume of the tokamak and so simple, development could be done in only five to 10 years. It's simple as these devices go. We have a linear array of coils, a linear solenoid. We have a couple small miracles. And that's it. That's all we need with our heating system.
So, the one cool thing is that the reactor could be assembled in segments. One coil per segment could be pulled apart for research purposes or for maintenance purposes and simply slid back together again. And it's really clean. So, our fuel of choice is deuterium-helium-3. Our nominal reaction is a neutronic. So, here it is here. So, produces a helium atom and a proton. For those at home, this is showing our protons and our neutrons. So, in our reactor design, a full 98-plus percent of our power is going to be in this one reaction, which doesn't produce any neutrons. And Amy, I put this one up for you. So, these are the side reactions. So, approximately 1.6 percent of our power would be in deuterium-deuterium reactions, which does produce a triton. But our reactor is specifically designed to cool and exhaust the tritons before they fuse. The timescale of the tritons exhausting from the reactor is approximately 0.01 seconds, where it takes about 20 seconds for them to fuse. So, they're gone. That's why this one's crossed out. This is going to be a very small percentage of the power coming out of our reactor. So, very clean, very low neutron production.
In conclusion about the reactor: it's simple, small, and clean. It fits on a spacecraft. It fits on a launch vehicle. Very few coils are required. We don't need to breed tritium. That's a complication of tokamaks. There's no lithium, so no dangerous materials. It's extremely small. I like to use minivan or small truck as a good comparison. Very clean, very few damaging particles. So, we'll probably need some shielding, but certainly not very much. Cheaper and faster to develop than other fusion concepts. For all of these reasons, and it's based on real heating experiments taking place right now. We have an actual experiment. And I have a couple movies for you, which he will run for you now.
So, this is a Princeton University-owned laboratory. It's very much education-based. So, these are grad students and our summer interns working on a run of the machine. You can see the scale of the machine. You can see it's flashing plasma right there. It's a pink flash, pink purple flash. And they're all waving hi. And we've spent the summer upgrading the heating system from 20 kilowatts to 200 kilowatts. And we're going to be doing ion heating experiments over the course of the next year in this machine. And then the next movie shows, this is iPhone videos. And I've, iPhones, a slow-motion video. There was the flash. And we've achieved 300-millisecond pulses in this machine, which is orders of magnitude greater than have been achieved in any other FRC.
All right, so our study, what are we doing now? I'm a spacecraft engineer, and my company, we're the spacecraft engineering people. So, we're focusing on the balance of plant and how can we take this reactor and actually make it work in space. So, we're taking our engine development to a subsystem level. We need to look at every component that we need and figure out how much will it really weigh? Can we really get the specific power we say we can, so that it fits in our mission?
So, this is giving you an idea of all of the different components. Laser pointer. We need a heat engine. We need our radiators. We need a startup system. And we have a patent on an auxiliary power unit that would start up in space. We need our shielding. We need our coolant. We need to be getting all of this heat out of the engine. We need to cool our coils, our superconducting coils. And as I said, we're going through each of these subsystems. Here's a bit of a laundry list of all the things we're looking at in our phase one study. So, our superconducting coils themselves, you know, how big they need to be, their support structure, our heat recycling modeling, the bumps, the long, and the synchrotron, the power generation and distribution, our RF heating subsystem, thrust vectoring. There's going to be an offset between the center of mass of the spacecraft and the engine. We have a hundred-day burn. So, we need to be able to control our momentum buildup. For your spacecraft engineers out there, we have some ideas for how to do that. So, all of these different things. Shielding is down there. And our cryo cooling.
Here's an example of an energy balance for a 10-megawatt engine, which would be something you would use to go to Mars potentially. And again, showing the distribution of power between our, these are our radiated radiation losses from the plasma, bremstrahlung and synchrotron, our neutron heat, which is a very small portion, as I said, of our total power. So, there's going to be a bunch going to thrust power. And then modeling what's left to go to the spacecraft. And this is a driven system. So, about 10%, I think about 10% of our power is being recycled for our radiofrequency heating at all times.
Next. So, this is something near and dear to my own heart as a spacecraft engineer. We're doing trajectory analysis. We did initial back-of-the-envelope style calculations to show we could get to Pluto with fuel mass we say we could. And I had a question last time, "How do you actually get into orbit around Pluto?" So, we have relatively low thrust, 20 to 40 Newtons. So, this is an optimization we did, a time-optimal for about 40 Newtons of thrust in this case, with the mass we would have left coming in to Pluto, and showing us going into orbit. Those are the thrust directions, those arrows, getting into orbit. And Pluto in about the last 28 hours of the mission. So, this is the type of work we're doing. We're looking at our spiral out from Earth, our trajectories, and refining our models of the engine as they feed into this to show we can really do it in the envelope we say we can.
Okay, this sounds amazingly awesome. I want one now. I want to put one on my mission. What do we need? Well, we have the second generation of the machine running now. And we need to build version 3. Version 3 needs superconducting coils. The machine now was able to recycle coils that were hanging. It's using water-cooled magnets that are 50 years old that were hanging around in the lab. And it has superconducting flux conservers. The next machine needs 100% superconducting coils. So, we're talking probably $50 million. And we want to do the engineering of the space subsystems that can be done in parallel with these fusion science experiments. We don't need to wait for them to demonstrate fusion and then build all the engine on top of it. Given that we know, you know, has this potential to produce thrust and power together. So, we want to do them in parallel so that in our five to 10 years, we are ready to go with our space prototype. Once fusion near break-even has been demonstrated, then commercial development can take place. And we anticipate, anticipate tremendous interest. Once you've demonstrated this, people are going to want to build it. People are going to go, "I want to be mining helium-3 from the moon." You know, all those exciting things. So, our best-case timeline is 10 years to a space reactor that could be baselined on a mission.
So, I think I did pretty well on my time. These are our contact information. And thank you all my friends and family who hopefully listened in and learned more about our fusion rocket. So, thank you. And I should also mention that Eugene and I will be at our poster later this afternoon. And he will be able to answer any detailed questions about the heating method. And I am more than happy to answer all your space engineering questions. This one works.
Okay. John Kramer, external counsel. You didn't mention it, but I looked into your proposal after the last, after the June meeting. And there's something amazing that you're doing, which is called a Field-Reversed Configuration, which I never heard of before. And it seems like magic. Namely, you put the plasma in there with a magnetic field going one way, and then you flip the field around, and the, and the, and the magnetic flux from the first field stays there, and it's surrounded by the magnetic flux from the second one. Wait. And that, that really works? Is that true? And people have done this? So, when we're certainly, we have a setup now, right? As the linear field, then it has our wheel. It doesn't go away when you flip the old flux. Doesn't go away when you flip the flux around because the plasma holds it in place. Is that, is that the idea?
This will be a question for Eugene to answer for you in detail. So, but Sam has a story about this. So, FRCs were thought of, you know, say the 50s, the 60s, like many other confinement concepts. And, you know, they had the antennas in a certain way. And he was working on ITER 20 years ago. And he thought, "There must be a better way." He started thinking about this machine. And he changed the configuration of the antennas. He says, "My whole career is this one wire to be a figure eight instead of an open loop." And that figure eight is that's driving all of our experiments, yes, to date. And the electron heating results have been spectacular. The duration of our pulses are spectacular. Our stability is spectacular. All of these things drive from this change, this innovation. So, that is what's so novel, as you said, this odd parity heating method, different from what's been done. I figured out what odd parity means. It means that the field that went into the thing points this way, and the field on the other points the other way, and they flip around. Flip around. That's right. I don't think I added. Oh, here we go. Mm-hmm. But the superconducting coils are supposed to hold it in, right? The rotating magnetic field, this is what's one of them. Sam Colin has pioneered, yeah. Is adds more flux to it? It actually pumps up, continues adding heat on it. I understand the field vector for the rotating field is perpendicular to the axis. And you're talking about B lines are parallel to the axis. Oh, how can it pump it up? So, just like when you have a soapy, imagine how I described it, a polyphase motor or an inductive motor. The you always have a perpendicular component to the magnetic field, but you have a net rotating magnetic field, rotating current. I'm sorry. And that net rotating current creates an axial field. Okay. Okay. I see.
You know, the other question is, you talked about the new configuration using superconducting magnets at the ends to produce the initial field. Are those warm superconductors or are they liquid helium superconductors?
So, that's a great question. The machine we have now uses high-temperature superconductors. And it's the only operating plasma device in the U.S. using high-temperature superconductors at this point in time. And when Sam actually called them up, he needed so little, they gave him a free sample of this high-temperature superconducting tape. And so, for the ground machine, it would also be high-temperature superconductors. So, right. We don't need the liquid helium. These are cooled with nitrogen right now. Now, for our space mission, we're going to need space cryocoolers anyway. And it may actually save us a lot of mass to go with the regular superconductors instead of the high-temperature superconductors. So, that may be a difference between a terrestrial engine and a space engine right there. Is the material used in the coils purely driven by mass? May actually be cheaper to cool regular superconductors than to use the high-temperature superconductors. But for the ground, yes, high-temperature. Okay. Thank you. And that's what's being used in the flux conservers now.
Alvin. Stephanie, we have two livestream questions. The first is from Raji Rajdeep Luthra. He's asking, "How clean is it and what happens to the waste?"
How clean is it? So, the radioactive component and the waste. So, the fusion ash products all exit out the back of the reactor. They all get cooled in the scrape-off layer. So, the gas flowing around the fusion ball, fusion ellipsoid, cools those products and they go out the back. So, in space, they're just gone. On the ground, you need to actually need to process that exhaust and, you know, take out any tritium that is there. You want to reuse the helium-3 that's coming out, ideally. So, on the ground, you would need to do extra processing. Eventually, you would have radioactive materials. You know, there is some radioactivity. But in comparison to a tokamak, where you might need to replace the stainless steel shell every two years, in our reactor, you know, 30-year lifetime for radioactivity on the parts. So, that's definitely something we've looked at. And the answer is, very clean. So, a person could stand next to the machine with some ceramic shielding while it's operating within one meter of the machine, whereas, you know, for a tokamak machine, the people are going to be multiple football fields away and could never ever be any closer. So, you would be able to spend a certain amount of your regular work day like directly against the machine without a problem. So, very clean.
Okay, thank you. The second question, also from livestream, is Preetesh Krishna. She's asking, "What is the maximum temperature that you can safely operate at?" Temperature inside the plasma, I assume.
So, our ions are going to be 100 kilo electron volts for our operating fusion temperature. I do have some, where oh, yes. This shows the reaction rates. So, this shows the temperature for different fusion reactions. And I think there's my laser pointer. So, we're going to be right around here, our operating temperature, which favors the deuterium-helium-3 over the deuterium-deuterium reactions.
Hi, Mark Schaefer with SpaceWorks. Kind of a simple question, and it relates to the previous one. Does your system have to be producing thrust while the engine is on, or while the reactor is on?
Right. So, turning the thrust on and off, definitely. We want a big coast period during our mission. So, an active area of research is what is the minimum amount of deuterium that we need to flow across the reactor for cooling and exhausting purposes, so that we're producing the smallest amount of thrust. And then how do we deflect the thrust when we don't need it? As I said, on the ground, you would be processing that exhaust and getting additional power out of it. And we're using some of your products. And in space, we need to deflect it, have a different configuration of our nozzles so that it can be a diffuse instead of a directed beam. So, sort of an open question. But you will definitely always be flowing some amount of gas around it at all times. Thanks.
Thanks. So, as a fusion guy, I'm not going to harass you about the propulsion part. Could match. I'm not going to harass you about the fusion part. Um, come harass us at 1:30. What? Yeah, exactly. But what I'd like to talk about is what, from my point of view, the real innovation here is, is the way that you're not using fusion alphas, you're not using the MeV particles that come out of this as thrust. You're actually using this extra fuel, this outside layer. Can you talk more about that? Don't, don't gloss over that. That's, I think, the really the key here is that augmentation, the thrust augmentation, taking a different fuel. So, instead of having a million seconds ISP and no thrust, you have 10,000 seconds ISP and Newtons of thrust. So, can you talk about that? What is that fuel? Why are you picking it? Can you use other things?
Right. So, at this point, you know, we're looking at deuterium or hydrogen for the additional fuel. And exactly, so it comes out of our gas box that comes around here. And then there's this interaction in the scrape-off layer. And this is where the size of our reactor is really critical. The fact that this plasma radius can only ever be 20 to 25 centimeters relates to the plasma and the fusion exhaust particles interacting with the electrons in the scrape-off layer. So, electrons get heated here in our propellant flow. And then the transmission of that energy to the ions happens at our magnetic nozzle. So, this is really, as you said, a completely key feature because it's how we get rid of our tritium and all of our products, and how we transfer our energy into this scrape-off layer. And then the magnetic nozzle is how it gets transferred into our acceleration.
So, how much, in terms of, you have a fusion fuel, your helium-3. How much of your fuel you're carrying around on your spacecraft is this thrust augmentation fuel? And how much is you actually get almost all of it? And this, all of it?
Yeah, the amount that you need for the core fusion is, well, for those who helium-3, certainly is hundreds of grams for the entire mission. It's less than a kilogram of helium-3. So, in terms of the actual fusion reaction. So, yeah, the lion's share of it. I don't have an exact number. 90-something percent is all for. Do you think you can use and set your resources? You think you can go to Pluto, pick something up, and come back with it? Come back with it? Sure. Hey, why not? And we might be able to recycle it. We could look into recycling it. So, as I said, all that time that we don't need thrust, we're going to need to be flowing some amount of deuterium around it. Do you capture that? You know, can you carry enough and just send it out, or do you need to reuse it? And yeah, the gas giants have helium-3. When I was at the Advanced Space Propulsion Workshop, people were planning missions to gather helium-3, assuming fusion reactors were going to exist in orbit, and they would need to be refueling them within city resources.
Okay. I'd say sure. Thank you, everyone.