Metallic Hydrogen - Most Powerful Rocket Fuel Yet?

oh it's Scott Manley here and today I want to talk about metallic hydrogen because you asked for it yeah I get a lot of requests to talk about things and everyone has been asking about this because it's been in the news last week a team of researchers claimed to have produced metallic hydrogen which is kind of like the holy grail of material sciences one of these things that's been theoretically predicted but hasn't yet been produced in a lab but more interestingly enough for I guess my audience is that they claim that it would be the best rocket fuel ever and to understand why this is the case we're going to talk about what we currently have so yeah the most efficient rocket fuel we have right now in terms of chemical fuels is hydrogen and oxygen I mean yes you can do better with fluorine and hydrogen but let's just say hydrogen and oxygen that reaction releases over 10 mega joules per kilogram right that's quite a lot compared to TNT TNT only gets 4.2 mega joules per kilogram so that's all right it's a pretty energetic reaction but let's think about how this works to make a water molecule from hydrogen and oxygen well hydrogen exists as a diatomic molecule as does oxygen so you've got to take this hydrogen molecule and you've got to break the bond and split it into two and that actually takes a lot of energy and then of course you have to break the oxygen bonds and then you reassemble them and the net result is the release of 10 mega joules per kilogram but if you do the math the energy that is holding the hydrogen together is vastly more interesting if you had atomic hydrogen and you somehow just let it combine if you could stop it combining until you needed it it will release a whopping 206 megajoules per kilogram that's like 50 times the energy of TNT I mean that you're crazy right and even better the exhaust or the results of this reaction would be hydrogen gas so it would be the lightest possible exhaust product this makes it really interesting as a rocket fuel because you have a lot of energy and you have a very light exhaust product which means in theory you should get very high specific impulses but as I've mentioned hydrogen doesn't really like being single if you have atomic hydrogen it's gonna react and form regular hydrogen very very quickly because of its position on the periodic table is believed that hydrogen could become metallic under the right circumstances and when I say right circumstances these are pretty extreme circumstances for example we believe that there may be metallic hydrogen in the crushing pressures near the core of Jupiter because Jupiter has a lot of hydrogen it has a lot of mass and produces insanely high pressures near the core and also Jupiter has a very powerful magnetic field and actually there's some evidence that hydrogen more metallic hydrogen may become a superconductor at the right temperatures and pressures so yeah that might explain the very powerful magnetic field so the pressures that would create the metallic hydrogen would break apart those strong double double atom molecules or whatever and leave a regular lattice of hydrogen atoms which could be really useful right but researchers have been trying to make metallic hydrogen for a long time and they've tried various things obviously they tried squishing it and that doesn't work they tried squeezing it using dynamic pressure right they tried firing high velocity gas guns squeezing the material squeezing hydrogen with the a projectile they've tried squeezing it using electric fields using something called the Z Zed machine and they have actually produced metallic deuterium which is nice but these have all been very short-lived experiments however the recent claim comes from a team that is using a diamond anvil now a diamond anvil is a device which is designed for high pressure materials researchers squeezes a sample between a pair of diamonds and diamonds are of course it's very hard so they can generate very very high pressures it's possible to generate pressures inside a diamond anvil which are greater than the pressures at the core of the earth however attempts to produce metallic hydrogen by this method generally lead to fractures in the diamonds and the diamonds shattering right because well it's the theory is that the although the surfaces of the diamonds have been polished as still tiny imperfections and as the pressure increases the hydrogen gets forced into these causes of fracture to develop and the Diamonds shatter so this team strategy was to take synthetic diamonds and polish them using they used an ion process to actually skim off the top layers and then because they worried about hydrogen actually squeezing into the diamond lattice they actually quoted the surfaces with alumina right so they then of course ran their experiment raised the pressure on their tiny sample of solid hydrogen at cryogenic temperatures and they observed that it began to reflect light like a mirror and that was kind of the signals they were looking for that was enough convincingly that they needed they put together a paper a good peer-reviewed and it get published in science but not everyone thinks that this is actually the production of metallic hydrogen people have been working on this for a long time aren't 100% convinced just yet for one thing it's been pointed out that the pressure is required to cleave the hydrogen molecules maybe enough to also cleave the alumina and basically take the aluminium out of its a molecular prison let's see and creatin as a rather more mundane metal in the test cell so it's entirely possible that this is a false alarm and I'm not an expert in high-pressure physics or any of this stuff so I'm going to let the experts decide but let's go all sci-fi and see just how awesome would a metallic hydrogen rocket engine be well the first thing is to be practical as a rocket fuel you would have to store it you can't you can't store your fuel inside a diamond anvil that doesn't have very much room inside it you couldn't make your tanks out of diamonds it's really the high pressures you need however there's definitely some suggestions that on that metallic hydrogen would be metastable that means that after compressing it down to these super high temperatures and far sorry super super high pressures and forming a chunk of metallic hydrogen you could release the pressure and be left with a chunk of metallic hydrogen that's just ready to explode at the right time I say explored it would be yeah it would be pretty powerful if it happened to explored in spontaneously so yeah it could potentially be stable or metastable at room temperatures but given hard enough kick it could explode on the other hand there are certainly people that say that claim that the quantum tunneling would cause it to fail long before it was storable for any useful amount of time but again assuming that you could store it and maybe store as a grain or something what you could do is take these little gray means of metallic hydrogen and then heat them up just enough that it drops out of the metallic state and produces hydrogen atoms right this releases a lot of energy based upon the composition of hydrogen based upon the energy that we expect to be released the reaction would produce an exhaust that measured about 7,000 Kelvin with an exhaust velocity of about 16 kilometers per second now for comparison garden-variety hydrogen oxygen engines they are more about 3,600 degrees Kelvin I was an exhaust velocity of maybe four and a half kilometers per second and hey those wimpy wolf thrusts hall-effect thrusters electric thrusters they get a bit the same specific impulse as in metallic hydrogen engine so that would be pretty amazing you wouldn't then have to worry about things like electricity or nuclear fuels you could just use this as a fuel directly the downside of course is that this furiously powerful reaction is simply too hot to be contained by any material that we know and the only way to reasonably tame it is to introduce a cooling agent such as liquid hydrogen so you could cool the combustion chamber with this and then inject the regular hydrogen in alongside your metallic hydrogen keep the temperature low enough that nothing melts and unfortunately you would pay the penalty by having a lower combustion chamber temperature so bringing the combustion temperature down to about 3600 Kelvin that would be roughly the same as what goes on inside and rs.25 space shuttle engine so we we can probably get away with that that would be about half the temperature but one thing to note is that while it would be the same temperature as a space shuttle engine the mass of the exhaust products would be roughly nine times smaller because of course we be ejecting pure hydrogen rather than water and if you know about exhaust velocities one part is temperature the other part is atomic mass so you would still get something that was two to three times higher or more efficient than a Hydra logs engine so that's good now there is one other big or small advantage the metallic hydrogen has and that is that because it's been squeezed down its density is actually much higher a bit 10 times higher than that of liquid hydrogen liquid hydrogen is a notoriously low density propellant that is one of the reasons why it's not used on every single rocket because you need really big tanks and that requires entirely different engineering problems so on paper it looks amazing but in practice well there's a lot of unknowns we still have to wait for the team to actually show that they created this then we have to find out whether the material remains stable at once the pressure is removed and then if that is the case then have to find out how stable it can be and whether it can be stored and handled in a way that would make amenable for use as a fuel remember if this thing explodes spontaneously at 50 times the energy pound for pound of TNT that would be crazy but if it could soar moan if you could get over all those obstacles and you could design an engine you would then need some sort of fuel production system and the fuel production system what do we do that we take a lot of energy in and then it would produce this metallic hydrogen because of course you need that energy input to break those bonds and squeeze it into the metallic state this would never be a fuel that you would use on earth incidentally this is something that you would squeeze down to try and put as much energy into a rocket as possible so yeah the answer is I guess watch this space and we'll find out in the coming months whether this is some thing for real whether the could team whether the team's claims are reproducible and maybe we'll find out more about the physics of metallic hydrogen until then I'm Scott Manley fly safe [Music] you [Music]

Channel: Scott Manley

Views: 737,857

Keywords: science, rockets, rocket fuel, hydrogen, metallic hydrogen

Id: nMfPNUZzG_Q

Length: 13min 47sec (827 seconds)

Published: Mon Jan 30 2017

Reddit Comments

[u/Clovis69]

It's not even confirmed to be a thing humans can make yet. And even if it has been done we are decades away from industrial production

[u/Flaashbang]

Scott Manley, AKA the Kerbal Space Program gamer guy? Yeah no credentials there