 Who of you did not attend the previous talk? Okay, I'm gonna cover the basics again then My name is Paul. I study physics. I'm in my master's years semesters something like that and this is a topic. I'm essentially just interested in so I thought I'd tell you all a bit about how we can go to the stars with nuclear reactors or just nuclear propulsion. First of all You need to talk a bit about rockets what they essentially do and what we want from them Rockets are a thing that make you go faster They don't bring you from one place to another like a car They make you faster because in space you don't define a point by where you are But how fast you are an orbit around the earth has a certain speed if you want to go to Mars You need to match your speeds to speed to the speed of Mars and so on So from a rocket engine you generally want to three things First of all, of course, you want thrust you want a lot of force You want power because you want to gain energy very quickly and then you want efficiency and Thrust and power you can just slap on more rocket motors But efficiency is something you're pretty bound to by the type of motor you choose chemical rockets and This power is measured in specific impulse or ISP It's a term of seconds. We don't really need to know what it means We just need to have a feel of magnitude here chemical rockets can't break above 500 500 seconds ISP That's just chemically not possible. I have a certain amount of energy per molecule. I can use ISP is Essentially how fast Stuff leaves the rocket the faster I can throw things out the more ISP I have That's why ion engines are so efficient. I can throw them out a lot faster So I can get to ISP of around 10,000. That's possible They are actually so efficient that we're trying to dial down their efficiency to get a little bit more thrust a little bit More force because otherwise it would be pretty boring and they would take even more time than they need now If we use nuclear reactors as energy source we can bring that up Essentially The more temperature we can reach the higher the temperature in our rocket is The faster things come out So first of all we need to decide for an energy source Of our nuclear reaction and let's try fusion first fusion is From a nuclear standpoint very simple you take two things you make them go very close together and they will do a reaction You get energy that's simple You look up in the sky and you see millions of fusion reactors all the time. They're called stars The challenges to make something fuse is essentially to have something at extremely high temperatures at a very high pressure and to keep it that way if You have such high temperatures you have a plasma if you have a plasma at such high temperatures touch a wall The heat flow through that single point is so big that essentially all your energy in the plasma is lost through that one point Your wall has is gone. It's vaporized or something and your plasma breaks down your fusion has stopped That's what you're trying to mitigate and just to give you a bit of a feel Where we are here here. We have a measure of reactivity units are unimportant here are different types of fusion And here is the temperature range where we are billion Kelvin That's so hot that the thing radiates in the hard x-ray spectrum You get some UV radiation from the Sun and if you make that a lot hotter you get to x-rays That's where a normal fusion reactor works today That's why it's very simple to observe your fusion reactor You just need to look at it from any point and there is enough x-ray coming through your fusion reactor to observe the plasma What you also see here in the different point different fusion reactions the deuterium treats in reaction That's hydrogen with one neutron plus hydrogen with two neutrons that happens at very moderate temperature of just 10 billion Kelvin's and Then you have different reactions One is called deuterium helium three deuterium hydrogen plus one neutron helium three two proto Yeah, two protons plus one neutron That will be important later on the deuterium deuterium reaction happens at much higher temperatures and actually our Sun doesn't do any of these It goes through a completely different cycle called the carbon cycle and that happens even further off the scale So that's quite good. Yes, I'm here Rocket now is essentially a pressure vessel, which is good. We want a lot of pressure. We want high temperatures. Perfect Let's poke a hole in the plasma to make a nozzle for our rocket That seems to work Of course, it doesn't work. I can't just take our everyday fusion reactor, which by the way, of course, we totally have I Need to be a little bit more clever One way to be clever is to use a special type of plasma confinement. Okay, a plasma is Essentially a very very good conductor. In fact, you can describe some metal properties if you describe the metal as plasma Now you take some plasma in a cylinder usually you establish a magnetic field Marginous magnetic field in one direction and then you very very very rapidly flip the magnetic field What happens is the magnetic field can't penetrate all the all the way down to the core of the plasma So you have your previously established magnetic field in one direction and you're now switched magnetic field in the other direction So the magnetic field at the core is reversed from the magnetic field at the outside. That's why it's called the reversed field configuration what you get through this configuration is This current your plasma is a conductor you take the electrons in the plasma you have a Donut where the electrons flow where your current flows and As long as this current flows the thing is stable Of course a plasma is not an absolutely perfect conductor and this will shrink slow down and at some point your current is gone at the whole configuration Isn't stable anymore There is a problem with this thing and that is that we do not have a complete mathematical model of how this works at the very center where the magnetic field is zero all our Calculations just break down and Right now if you just do this once you just have magnetic field flip it look how long it takes to Be gone again. You can have it stable for about one millisecond The nice thing is you now have a donut and you can do stuff with this donut you can throw it somewhere You can accelerate it other things but first of all we need this a little bit more stable and The way to do this is to just apply a magnetic field Around this donut in different time steps. It works like a motor like a simple stepper motor You just first of a magnetic field like this, then you do it like this and so forth And you just turn the current around in your donut Problem if you do it like that if you do it like a motor you're Injecting another magnetic field and that breaks away part of your confinement and all the plasma escapes there that doesn't work but quite recently a Guys at Princeton University were clever again and what they did. I hope you can see that here. Yeah They used two coils and what these two coils do is they take one magnetic field injected and immediately subtracted So all they do now is they push this donut inside in one point and they are now pushing this donut along All the time and they are keeping this current stable and they're currently at a belief 30 milliseconds Stability and they say you know what? That's enough to get money from NASA NASA gave them money to develop This bad boy What they said would you know what? It's stable enough. We can do this We will have our fusion plasma and then around this plasma We will drive another plasma which will be heated by this fusion and then again. We drive the heat up We have faster particles. We can go let them out faster and now we have a very efficient rocket At least in theory this works Because the other thing Princeton University did was they develop as far as I know the first Computer model the first simulation of how this confinement actually works It didn't do a full computer simulation, but they figured out where exactly the zero magnetic field line is Part of the reason why they got so much money from NASA Then they you see here. They want to use deuterium and helium 3 the reason for that is if you have a fusion reaction and You want a lot of energy from it. You have a lot of fusion reactions if you take tritium and deuterium You get a neutron and the neutron has a lot of problems First of all it takes away most of your energy about one-fifth of the energy of one fusion is taken away by the neutron and The neutron will hit your wall and destroy your wall in certain places if you take helium 3 you get a fusion and a Proton the proton still takes away about one-fifth of your energy But it is now charged and the charged particle will stay in your plasma, so it will heat your plasma It won't hit your wall. That's great That's where you can build this a lot a lot Lighter because you don't need heavy neutron shields, which you would need and yes We do have other fusion propulsion proposals as well. They did not get funded by NASA most of them So yeah, the the main thing they did was they essentially took Current iron thrusters and said look the the biggest problem of these irons for thrusters today is they need a very hot Source of just heat to heat up the xenon They use and ionize it to make a plasma and then they accelerate it and We can use our fusion as this energy source We can ionize this plasma or ionize it further because they need a pre ionizer Then afterwards at the very end You have this nozzle coil which which which actually does the acceleration They claim to be able to start one to ten megawatt reactor in yes, we heard it ten years They propose to go to Pluto with that and they said you know what when it's when it's there We can shut the nozzle down and then we have a ten megawatt reactor which will only weigh ten tons Which is an amazingly great weight to power Ratio So if they are able to do that, I don't really care about going to space at ten megawatts reactor for ten tons We could dig a hole here have bit power this university and probably the rest of the city would be great in other ways as well they proposed it as As a rocket because if you use a rocket you don't need to be perfectly efficient If you're not you're still getting some energy you did not electrically invest into the plasma out in the back end That's already good So there is another proposal and NASA is actively developing this one The problem of fusion is how do you heat this up? How do you heat this up and keep it stable long enough to for fusion to happen and an idea here is to Simply increase the magnetic field very very very rapidly thereby increasing the pressure and temperature Question is how do you do that efficiently this proposal says you know what we take some lithium rings and If you have a conductive ring and you apply a magnetic field you're propelling that ring You can propel it in words. So they're saying again. We are starting with this Plasma donut this field reverse configuration donut We're throwing it out the backside and now we take three rings and we apply a very strong magnetic field and those three rings are now closing in and They're closing in so fast. They're keeping their current that we just induced and by doing that the magnetic field is stronger And stronger at the inside and at the very moment it hits the nozzle it will all fuse and then we can accelerate it backwards nice idea The one they calculated would weigh 15 megatons not tons megatons To produce 36 megawatts of power. Yes, it's usable. But as we've seen the Princeton guys are much more. Let's say ambitious another problem is this thing is not a Constant stream of particles to your backside It's pulsed. They actually you need time to refill these loops these metal loops And they say you know what we can do it with just 14 seconds in between and Between the actual rocket and our engine. We have just shock absorbers that will work Yes, it will work no question about that It's just that you're now you now need to absorb the shock from a third from a 15 megaton heavy engine to your rocket So maybe there are other ways We can propel our rockets Vision is another option again. We can take nuclear energy and maybe Export some some momentum from it. First of all, how does a nuclear reaction work? You take a neutron you hit something you can split some fissile material That will split if you're lucky and you get more neutrons These neutrons you can now throw again at something you can split some fissile material You get a chain reaction with every step You get yes in this graphic three more with each step or the three fold of your previous step You get an exponential curve that whole thing blows up and we can build nuclear bombs We can write nuclear bombs We did some active research on that it is actually a Very good idea Because nuclear bombs are something we understand quite well in the 50s and 60s we did a lot of research on how nuclear bombs would Destroy or not destroy certain metal plates And what looks very complicated here is just a mechanism to inject the neutron bomb through your pusher plate as it's called That's super simple. That's just mechanics You just need a bunch of nuclear bombs. You throw them out your backside. You make them explode. You ride the shockwave simple They calculated a lot of models or actual rocket toy models what they could do They calculated you can go up to 3% of the speed of light with their biggest version and somebody actually calculated if we Start with that thing We would just get one radiation death per year more great if you build today a Motor for a car that was would result in just one more road death per year You maybe get the Nobel Peace Prize That's great. And with this thing we can go to the stars For other methods we first need to talk a little bit about where these neutrons actually come from I Said you have the you split one core and then you get neutrons. That's not the full story You do the splitting you get some neutrons In a nuclear reactor, you don't want all your neutrons to come from the fission itself You get these two parts which are extremely unstable and when they decay They release some neutrons as well if you can use just the neutrons from the fission itself and Have a exponential rate you're what's called prompt critical the prompt neutrons which are there immediately Make you go critical if you're only critical if you only have enough mass that you still need these Decay product produced neutrons. You're what's called delayed critical That's what what you need in a nuclear reactor to just be physically able to control these this thing If you just have a 10 to the minus 15th second to react to a change in your nuclear reactor You've already blown up before your mechanics can start If you've got one hundredth of a second, that's doable. That's not doable if you miss the point But it's mechanically possible if you don't have this delay you have a nuclear bomb Enter the nuclear dust drive This is my favorite thing especially because it's pretty much matches what they use in the expanse You take again in magnetic field You don't need the plasma this time. You just have charged Particles of some fissile material Uranium whatever Particles are very small and that has two advantages first of all They radiate away a lot of heat you're in a vacuum So you can't conduct heat away into radiated the higher surfaces the more you can radiate away So they are very easy to cool The other advantage is if you're having a fission And there are these two products coming out. They're extremely fast and Through a thin piece of paper They might get through the thinner the paper the easier they can get through if you've extremely small particles They can just escape the particle immediately these particles are charged these fission fragments if you use a magnetic bottle You can catch these charged particles and direct them in one direction outwards This is actually an advanced version of this rocket engine. I'll get to the C part a bit later You need a very heavy moderator around this Confinement I'll later explain what exactly the moderator does But that's the biggest problem this moderate is very heavy and that drives down your ISP still you could get an ISP of about 1 million seconds and I didn't mention it because it's hard to calculate with nuclear bombs You get around a hundred thousand to ten thousand ISP the seconds ISP you get ten thousand seconds from an ion drive So that's good. That's extremely good They calculated again that if you want to keep this spheres as solid uranium And we're talking about pure uranium here. You can drive this reactor at about 26 gigawatts if you're going even above that and Allow your particles to melt Then you can go up to 62 gigawatts and then you would have a foggy plasma and they say Nobody really knows how all this handles, but it's possible. We could go to even 62 gigawatts with just dust Which is great and then you get Power source for free the C part here You have several Conductive rings. They're at in there at different potentials. They slow down particles When a particle slows down, it just hits a wall They're charged particles you reduce their energy. They hit the wall you get current now you get as electric power Voltage times current. So you just have an electric generator generator at the back here for free. That's great I love this one. I really do If we want to talk about actual reactors We need to talk about this moderator thing You have this vision you get your neutrons. That's fine and If you just have one vision probably nothing will happen because You get neutrons at a certain energy and those from the fission come out here at the very right end of the spectrum again on the Y-axis we have some measure of reactivity. We don't really care about that All we need to know is that we need to slow down neutrons So they actually react again and do some fission Newt moderators come in many forms One where we can use for example graphite, which we will see soon why we would do that But we can also use water which is used in reactors on the ground down here hopefully So project Pluto Once they said okay, we can't use nuclear bombs for tests anymore. We can't use nuclear bombs in space What a bummer They came up with this idea It's a very simple design For a thing that would transport nuclear bombs from America to Russia below their Detection level they would they would actually call this the super low altitude missile The idea was They're gonna drive at supersonic speeds They would have a funnel in the front that would do the compression and then you would have a nuclear reactor to heat the thing up They built that shit These are two types they were actually three but these are the two types they tested the one on left the red one that ran for about Three seconds they had something that would preheat and pressurize the air. They would they would feed and And That one on the right side ran for five minutes. They actually had a full hangar They would fill with pressurized air preheated and that pump it through this reactor There was a bit of a problem with the reactor a classical reactor is extremely heavy because you have a lot of shielding You have neutron shielding you have radiation shielding so they just Didn't do that That's a nice point about workplace safety here They just left the radiation shielding away That's why they couldn't fit a pilot in there that program actually made huge contributions to automated flying They had a fly-by-wire system and if that crashes they would just contour match the terrain and then it would know where to fly and drop bombs and They operated this reactor at just 150 degrees below the auto ignition temperature of their base plate Which was so they operated it to 2300 degrees Celsius Again ambitious if something happens That's not just gone as in nuclear blast gone. That's gone and it burns up and you get nuclear radiating particles everywhere What a fun time to be alive another idea was project rover project rover was Much more sane in some ways. They didn't use air So you couldn't have anything auto igniting they used hydrogen The idea was to take a simple reactor a reactor type We know pump liquid hydrogen through it So you heat the liquid hydrogen up to very high temperatures high temperatures means very fast exit speed fast exit speed means I have a very efficient rocket So what you see here is one of the fuel elements That's a 1.5 meter long fuel element with 19 holes in it It was made out of graphite and then injected with uranium dioxide spheres They would just stick to it and then coat it in zirconium then you just have a reactor your standard nuclear reactor and Here you see roughly The Relation in size of the reactor itself to the nozzle that the actual nozzle the nozzle is just about as big as your today Rocket nozzles you to have a bit of a feel of size here They tested that Here they did a lot of these reactors The source I found actually claims this one is their last one, but I believe that it would have to be a lot bigger I believe that's just a third version The one you see tested on the left is the so-called kiwi because it's a flightless bird they pump liquid hydrogen through this thing So the fuel elements are about 22 Kelvin hot at the one end and they're about at least 2000 Kelvin hot at the other end There were some problems fuel elements broke all the time they actually At the end of this project. They said we were flight ready now We are only losing 17 kilo of fuel of reactor every two hours They're just blowing out radioactive material there At some point somebody asked what's the worst that could happen some stupid physicist answered. Well, it could go prompt critical some stupid person said Let's try that And they sent a reactor prompt critical the tiny specks you see up there That's liquid reactor They just left that for three weeks because well, it's highly radioactive and Then they sent in an army troop and said, you know what you clean this up as a decontamination exercise Everybody was very glad they at least did it and That project in the end was shut down because they went to the moon and nobody wanted to go to Mars everybody was lazy So they did something different here. We're going to project Timberwind These elements had the problem if you heat them too high at the one end and Let them too cool at the other end. They break or you just flush them away with your hydrogen Another idea was we don't even use long elements. We use tiny pebbles. We use tiny two millimeter wide spheres Fill them up with uranium so the uranium in there can do nice things. It can go liquid So this whole thing can be a lot hotter than our previous elements or a previous fuel elements And Then we can heat up our hydrogen again So this both are the best pictures I found this of course was a secret mission because the military did it I'll get to why What you see here? I just wanted to show you how this all would have looked in the end You just let in liquid hydrogen at the top it would come out the bottom and Here you have a more functional diagram. You may have noticed there are no control rods in this reactor You don't use control rods. What you do is you have at the outside a Very well cooled control cylinder That has a neutron catching material on the one side and the moderator on the other side So if you turn the cylinder you either get the moderator which slows down your neutrons or your neutron catching material which Takes away your neutrons. There is a nice line that they actually they made it fail safe Fail safe in this case means even if one of them are if the one of the control rods is stuck you can still get it super critical so your Engine won't fail any questions to these drawings because they're I know they are quite complex Wonderful so The great thing about this thing is it actually manage an ISP of a thousand Oh, I should have mentioned the project rover before managed an ISP of about 800 They actually at once built a reactor that the last reactor they built drove at 4 gigawatts Which at the time was the strongest reactor ever built So the reason it's on this list is what they wanted to use it for they wanted to use this engine to intercept missiles If you intercept a missile with Something that has a nuclear reactor the whole thing goes boom and You're distributing your nuclear reactor everywhere Have fun with that, but Something good came out of that They invented a new neutron shielding or car called bath and the salts are probably what they took at the time So for the next reactor we need to talk a little bit about how a moderator actually works you have your fast neutron and You can interact with other nuclear cores Without a nuclei if you have a very heavy nuclei Your hydrogen comes along hits it and is essentially reflected no energy is lost On the other hand if you take a very light nuclei Your neutron comes along hits it and you play billiard Neutron stays other thing goes faster a lot faster actually This means that your moderator Essentially takes away the kinetic energy of the neutron You heat the moderator by the neutron getting slower Hydrogen again is an ideal moderator because it's essentially the set or the nuclear of a hydrogen It's essentially the same weight as Your neutron you can use other materials that are light as well, but hydrogen works best This is a very recent Concept I believe it's from The idea here is to create an immense flow of fast neutrons These fast neutrons Heat your hydrogen then you get your extremely hot hydrogen without having heated the fuel great First problem you need to drive this thing prompt critical very very very quickly Then you need to drive it subcritical again very very very quickly And I told you that you have these fissile products, which will give you delayed neutrons You need to get them away. So you cool this thing with liquid lithium liquid lithium Takes away your fissile from your your fission fragments I've talked about very fast They're saying you want to do this at around 10 kilohertz 10 kilohertz reactor up reactor down I told you about The project rover having problems with their fuel elements being essentially eroded away by the strong heat Differences on the fuel element paper did not Go into detail how they want to avoid that they said from Thermodynamic spectrum from how fast heat is conducted through our uranium fuel through our lithium through our hydrogen this works The upside This thing is just you see it here 40 centimeters by 40 centimeters by one meter tall This is just about the cubic meter in size and You can get I forgot to write it down a lot of power from this you in theory can get an ISP in the ranges again of the 1000s or more As you can see here these red lines These are your fuel uranium carbide You have on the one side hydrogen on the other side you have lithium Immediately side-by-side we were talking about eroding a way reactor and that that's a problem if you erode away this reactor You've big problems Another problem is that although this thing can put out a lot of power 95% of your power is not going to your hydrogen because 95% of the power is actually Going into the fission fragments which are carried away by this by the lithium That's also why you need to cool the lithium again, but again if we can build this I want to dig it in my cellar and I have a very very strong reactor which can power a city nice Since we are always having problems with our reactor melting or eroding away, let's just vaporize it The idea here is that we take our uranium we slowly feed it through the back the uranium immediately boils off In a gas bubble we keep this gas bubble off the walls by just pumping through hydrogen at a very very high rate with a lot of pressure and We have some bypassing hydrogen in order not to lose the whole uranium at the same time the Reactor concept wants to keep the uranium inside this reactor as long as possible while heating up the hydrogen as quickly as possible This is from a simulation. They did no we didn't build that thankfully But they simulated this and I'm gonna talk about how realistic it is in a bit first of all the concept itself This is just a much nicer picture Which you can see here is that the gas is supposed to be about 55 Kelvin hot I've seen different numbers in the 60 thousands and so on the problem you have Hydrogen has a bond energy That is pretty much going away at around 52 Kelvin when you do that you have Hard ultraviolet light source They're actually concepts called the nuclear light bulb, but I'm not gonna talk about them This ultraviolet light source immediately splits your hydrogen and I didn't find any research on what exactly happens What I think happens is you have your two hydrogen atoms which immediately Rush away the hydrogen surface of your liquid hydrogen Essentially just blow out your nuclear reactor through the back and you're left without any power at all The fuel we keep inside because we're just pumping through all the time has about two minutes to react Different people say different things, but we are at about at the maximum ten percent Usage of our nuclear fuel Which is more than the five percent we used in the previous example, but still the problem We have here is that we would need to be able to pump our hydrogen at around a thousand bar This may be possible with liquid hydrogen with gaseous hydrogen We're pretty much technically leveled out at around 700 bar Maybe there's been some development, but that was the last time I checked with a material physicist. So We are pumping out our nuclear reactor to the back anyway. So Why not have that as a concept? This is the nuclear saltwater rocket Nuclear saltwater rocket works in very simple way. You have your uranium salt You dissolve it in water Then you take a volume, which is super critical at that volume First of all that creates a problem if you want to store this liquid this nuclear saltwater You need to store it in very very thin tubes, which are laced with boron So they catch the tubes themselves catch away the neutrons The upside is this thing just starts from itself You always have something that will decay and release a neutron So if you just take super critical amount of this water, it will just go boom nice problem We can't really find a material in which we can build a tube that would withstand a nuclear blast solution well, we said these neutrons are Popping into existence at an exponential rate. So if we just rush our water through this tube we can create a tiny bit of neutrons create more and more and more and more and Have the wave that will actually start our prompt critical reaction just outside the tube and That can withstand a nuclear blast. I brought a model here of a nuclear saltwater rocket This tiny little tube Can give you 13 mega newtons of thrust all you have to do is pump through water You can build that in your backyard That's why I love it Just for comparison our most efficient rocket engines the space shuttle main engine Loses a tiny bit to this concept which is essentially riding a nuclear blast constantly We don't need any moderates. We don't need any mechanics the tiny problem We cannot shut it down without going boom because if we shut it down the neutrons will just rush through and our tube goes boom We cannot start it without going boom because if we rush through water We don't know when the first reaction will happen So you rush through a lot of water and then at some point. There's a lot of water that can go boom at the same time Apart from that we need a pressure rise of water to around 11,000 bar But if these tiny problems are solved and I strongly believe they are solvable I hope so because it would be awesome Then we could accelerate away from our solar system at a rate of around 3g for 10 years to go wherever we want and With this I am closing. I hope you all started to believe in riding a nuclear bomb Thank you. I'm available for questions here. My sources is will of course all be Uploaded and you can look up where I found all these funny pictures Thanks to so we over here who actually drew the pulse nuclear rocket No questions. I mean it's questionable in and of itself One of your first engines also produced electricity. I think it was the third one or this one something like this How would or how would you get rid of this electricity if you don't need it in your space shuttle? You could just turn off the okay the way you do it is You have charged particles coming out At a very high speed You're taking essentially two condenser plates And you're applying a voltage and this slows the particle down and then it will hit the wall If you just turn off this voltage, it will just radiate off into Wherever you can take some magnets to drive them away from your rocket Has this one been tried actually this one was not tried. It's a quite new concept. I believe it was 2005 Yes Where things around this was published? But what was proposed was to build a reactor like that Because a big advantage is that since this thing is prompt critical you're throwing away all your delayed neutrons You're having a quite high neutron flux and so you could just throw in some unburned or wasted fuel and Reburn it inside this reactor. I Would not recommend it Sorry, this is the only Drive that I didn't understand at all. Could you explain it again how it works? Yes, very simply You have your dust particle Somewhere inside this particle a nuclear reaction happens With a lot of energy you have your two fission fragments which will leave it in both directions Your particles so small that there is the chance like 99.999% that those particles will leave your fuel grain Then they're inside a magnetic field the magnetic field Drives them to one of the two ends At these ends they can just leave your reactor and Since 95% of your energy is within these first in the kinetic energy of these fission fragments You can utilize your fuel to a very high percentage How is it or at the direction happens with the magnetic field? This is essentially Again, you're having something like where is it? You're having something like magnetic confinement for a plasma These charged particles just it just works the same way if you just have two very strong magnets with a weaker magnetic field at the center That's just I would need to go into plasma physics Why but then you can hold your particles in here and they will only leave through one of the two endpoints If your magnetic field is strong enough Which one do you think is the most reasonable? Question is what you want If you're asking me which one could fly in 50 years nuclear bombs definitely without a question If you're asking me, which one would I like to see flying? Nuclear saltwater reactor definitely there is actually a line in the paper where he states Because there are some you you can't ignite nuclear bombs in the stratosphere He writes clearly this is not a nuclear bomb And I think the simple fact that you have to state that outright tells you something about the system Prominent web page. I can't recall its name actually stated simply writing the Environmental impact factor for a test would pose an interesting challenge Because you're you're just blasting off radiative material in all directions And if you're asking me, which one do I think? Will most probably fly I actually believe in the Princeton University guys They found something in very recent past that wasn't known before they are working very hard on it They got the NASA ground. So at least they think it could work It's ambitious, but that seems plausible and the dust drive I just love because if you read the expands the just the lingo they use it pretty much fits this drive. Ah Sorry this drive Yes, that's all. Thank you Thank you for your attention