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Metallic Hydrogen created, will change spaceflight


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48 minutes ago, PayadorPerseguido said:

Why call it metallic hydrogen? Is the 'metallic' related to metallic and ametallic connections between atoms? 

It's called metallic because it's a metal. Solid, crystalline structure and free electrons in between atoms.

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Wouldn't this have basically the same chemical properties as hydrogen? Also it seems like if it is treated carelessly a lot of the energy put into compressing it could be released as heat?  I think fire codes would have to be a lot stricter if it sees use as a building material. Also machining it may create sparks. We know what happens when gaseous h2 catches fire, betting that metallic h2 is even worse.

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We dont know whether metallic hydrogen exists or what its properties are. Its not likely to be a structural metal, and if it is stable enough to be used that way, it cant be used as a rocket fuel. If it is useful, its either going to be as a room temperature superconductor or as a rocket fuel with ISP rivalling nuclear engines and no radiation hazard. 

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40 minutes ago, andrewas said:

We dont know whether metallic hydrogen exists or what its properties are. Its not likely to be a structural metal, and if it is stable enough to be used that way, it cant be used as a rocket fuel. If it is useful, its either going to be as a room temperature superconductor or as a rocket fuel with ISP rivalling nuclear engines and no radiation hazard. 

Exactly.

 

As far as exploding, technically with the right engine design you could use little pellets of C4 as fuel if you wanted. It wouldn't be worth it to do so, but you could. A rocket is really a controlled explosion on the most basic level. Big balls of debris and shrapnel and flame are what happens when the explosion becomes uncontrolled.

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1 hour ago, Carl said:

Exactly.

As far as exploding, technically with the right engine design you could use little pellets of C4 as fuel if you wanted. It wouldn't be worth it to do so, but you could. A rocket is really a controlled explosion on the most basic level. Big balls of debris and shrapnel and flame are what happens when the explosion becomes uncontrolled.

I'm fairly sure that the process you typically want is combustion, not detonation*.  There is research into detonation in rocketry (mostly as air breathers) but I don't think much has come of it (other than spectacularly loud rockets).

*I'm pretty sure the difference is that detonation has a supersonic wavefront and shock wave and combustion does not.  "Explosion" is a bit non and can be either, but typically C4 is used for detonation (although you are supposed to be able to destroy it by burning.  Not something I would want to risk, especially if nearby).

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(although you are supposed to be able to destroy it by burning.  Not something I would want to risk, especially if nearby).

In emergencies troops have supposedly used it for fire fuel, the stuff is incredibly stable. 

 

Also i'm aware of the technical difference, i just simplified the point. Namely that rocket engines are all about controlling how the energy is released. 

 

Incidentally, maybe i'm off base but i though MH was a liquid metal like mercury, (the element, not the planet space heads). 

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12 hours ago, Carl said:

Also i'm aware of the technical difference, i just simplified the point. Namely that rocket engines are all about controlling how the energy is released. 

The point was more that rocket propulsion by detonation was a relatively popular "blue sky" tech in the 90s or so.  I haven't heard a peep in years so I think its dead.  It was supposed to get the Isp up a bit higher than combustion, but Isp on an air breather first stage just isn't an issue.

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20 hours ago, kerbiloid said:

It doesn't have unfinished inner electron levels, so probably no reasons to change its valence under pressure. So. H2O.
But its metal → molecular state pass releases 20 times more energy than its oxidizing, so not very much sense in this.

Umm, hes it does. It has 1 electron, an the s1 orbital is full at 2. The only elements with "unfilled" valence electrons are the noble gasses.

On 1/29/2017 at 6:54 PM, insert_name said:

Wouldn't this have basically the same chemical properties as hydrogen? Also it seems like if it is treated carelessly a lot of the energy put into compressing it could be released as heat?  I think fire codes would have to be a lot stricter if it sees use as a building material. Also machining it may create sparks. We know what happens when gaseous h2 catches fire, betting that metallic h2 is even worse.

#1) this is about more than just the chemical properties, but the physical and structural properties. Like water vs ice

#2) Hydrogen an element, and this is still the element hydrogen - so your statement if read to refer to the element, is a tautology. If its read to refer to molecular hydrogen, H2, then its false. H2 would have different chemical properties than monatomic H, and it would have different chemical properties than metallic H.

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17 minutes ago, KerikBalm said:

Umm, hes it does. It has 1 electron, an the s1 orbital is full at 2. The only elements with "unfilled" valence electrons are the noble gasses.

It's only electron is always in the innermost orbit, so it cannot be "pressed down" from the upper one into a free orbit, changing electron count on the outermost. That's what I mean.
Say, electron of Ni - can.

Edited by kerbiloid
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are there any elements that normally have unfilled inner orbitals? Sure electrons can be put into an "excited" state in a higher orbital, but they typically emit a photon fairly quickly and the electron drops back to the base state (fluorescence). So I don't understand why having no lower orbitals is relevant here, given that for practical purposes (ie bulk material characteristics) the lower orbitals of other elements are full

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15 minutes ago, KerikBalm said:

are there any elements that normally have unfilled inner orbitals?

Not exactly.

https://en.wikipedia.org/wiki/Electron_shell#List_of_elements_with_electrons_per_shell

They are mostly distributed filling inner to outer, but the... penultimate? ... shell can have incomplete electron number, while the outermost already has one or two, due to quantum effects.
For example look at Ni or Pd. They have incomplete penultimate one (16 of 18), but are already filling their outermost.
So, as far as I know, this makes Ni be a metal in normal conditions, but under (can't say how much but very much) high pressure their electrons redistribute filling the shell in the most compact way.
This makes Ni instead of its usual 16+2 be 18+0 and it would become chemically inert.

Edited by kerbiloid
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Any ideas if a metalic hydrogen Orion could be a thing?  Theoretical Isp of H(metal) is somewhere around 157k, while any realistic rocket would be limited to roughly a nuclear thermal rocket's Isp (possibly somewhat higher since the reaction mass need not be heated uniformly, if you could keep the cooling gas near the nozzles, that might be a huge thing).  But in an Orion, all bets are off.  Frequency could be vastly higher (I'm assuming that it is easier to build small samples of H(metal) than large), although this might not be a bonus if you plan on using H-bombs as a propellant in space* (I'm assuming they are cheaper, it would be weird if available power->H(metal) would be cheaper than fusion).

Just out of curiosity: one of those critical "things that KSP doesn't teach you about rocket science" is nozzles.  Is it possible to build a low-density rocket nozzle in vacuum that would need less coolant per-fuel used?  Temperature!=heat, and it should be possible to cool a nozzle next to ridiculously hot temperatures as long as the pressure is low enough to keep the heat transfer low. 

* Note: The big [technical] issue with Orion is that it needs to get to roughly escape velocity (i.e. roughly around the Moon) before you can safely light the [nuclear] engines.  The calculations that said "nearly all fallout will wind up in space" didn't account for the magnetosphere trapping everything in the Van Allan belts (they weren't well known yet).  You can pretty much expect *all* the fallout to come back to Earth (although most of the worst bits of the decay might happen before it comes down).

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50 minutes ago, wumpus said:

* Note: The big [technical] issue with Orion is that it needs to get to roughly escape velocity (i.e. roughly around the Moon) before you can safely light the [nuclear] engines.  The calculations that said "nearly all fallout will wind up in space" didn't account for the magnetosphere trapping everything in the Van Allan belts (they weren't well known yet).  You can pretty much expect *all* the fallout to come back to Earth (although most of the worst bits of the decay might happen before it comes down).


Nit:  The fallout from an Orion drive will be microscopic and submicroscopic particles and free molecules and atoms.  Even if these are trapped in the magnetosphere, I suspect they aren't coming back to the Earth's surface anytime soon.  (And there's not going to be that much of it - weapon debris and a miniscule amount of local gases and particles.)

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I saw Scott's talk over at youtube about metallic hydrogen, but have also heard of ice-canopy habitats for human explorers on Mars that shield from radiation because water is hydrongen-rich material (obviously).

Since protons are good at reducing energy of incoming radiation particles, i thought that shell of metastable metallic hydrogen would make a good shielding both for astronauts in space and on surface. And it probably wouldn't need to be very thick because of good density (it's pure hydrogen after all).

Any thoughts ?

Edited by fatcargo
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18 minutes ago, fatcargo said:

I saw Scott's talk over at youtube about metallic hydrogen, but have also heard of ice-canopy habitats for human explorers on Mars that shield from radiation because water is hydrongen-rich material (obviously).

Since protons are good at reducing energy of incoming radiation particles, i thought that shell of metastable metallic hydrogen would make a good shielding both for astronauts in space and on surface. And it probably wouldn't need to be very thick because of good density (it's pure hydrogen after all).

Any thoughts ?

Almost certainly. However, since high temperature (i.e abouve 200 K) metastable metallic hydrogen would likely be a room temperature superconductor, it would also likely be the most valuable thing on earth and so cost prohibitive to just use as shielding.

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