Metalic hydrogen and convetional airplane flight ISP?

[Arugela]

https://patents.google.com/patent/US20160377029A1/en

If you were to use this sort of engine or any other sort of engine in normal flight ranges for an aircraft today(turbojet/turbofan) what ISP could metalic hydrogen theoretically get in normal flight?

Could you get to say, 10,800 ISP or higher?

And I'm a little confused on something. Is liquid metalic hydrogen different than metalic hydrogen? Does liquid metalic hydrogen already exist from a man made or mass produced standpoint? Or are they the same thing? Which one is the holy grail of physics I keep reading about?

Edited March 17, 2022 by Arugela

[StrandedonEarth]

Metallic hydrogen only exists at insanely high pressures, making storage extremely difficult. The holy grail would be “metastable metallic hydrogen” where it stay stable at reasonable pressures, but that form has not been proven to exist yet…

[Terwin]

8 hours ago, Arugela said:

https://patents.google.com/patent/US20160377029A1/en

If you were to use this sort of engine or any other sort of engine in normal flight ranges for an aircraft today(turbojet/turbofan) what ISP could metalic hydrogen theoretically get in normal flight?

Could you get to say, 10,800 ISP or higher?

And I'm a little confused on something. Is liquid metalic hydrogen different than metalic hydrogen? Does liquid metalic hydrogen already exist from a man made or mass produced standpoint? Or are they the same thing? Which one is the holy grail of physics I keep reading about?

To the best of my understanding, metallic hydrogen is a form of solid hydrogen with  a specific internal structure: http://ch301.cm.utexas.edu/imfs/#solids/metallic-solids.html

There have been some experiments using super-chilled diamond anvils that have credible claims to having made solid hydrogen, and I think one of them even tried passing a current through it before it evaporated.

So it is *possible* that metallic hydrogen has been created in a lab in microscopic quantities.

 

The ISP benefit of metastable hydrogen is the fact that there is a huge energy released when metallic hydrogen decomposes into H2, and if there is nowhere else for that energy to go, you get *very* hot H2 atoms.  Very hot translates to very fast for rocket exhaust, which in turn translates into very high ISP when you have very hot pure H2 exhaust.

The down-side of this is that your thrust is low because your exhaust is very light.  Metastable hydrogen would be great for inter-planetary transit, but might not even get an airplane off the ground.   

 

If you want a very high isp airplane, use a battery powered prop-plane.

There is a miniscule amount of mass loss from the battery as the power drains from it, but you get lots of thrust by pushing against the air around your vehicle.  I'm not even sure how to do the math, but I would not be surprised by an ISP over a million. (I think you use e=mc^2 for battery mass loss in this case)

 

ISP matters most to rockets because once you are in orbit, (unless manned) you only care about mass-efficiency, and ISP is a measure of mass-efficiency.  For airplanes, cost-efficiency is a much more important metric, and a fuel that would cost more than an equivalent weight of multi-carrot diamonds is not in any way cost-effective.

 

 

 

[Hannu2]

18 hours ago, Terwin said:

To the best of my understanding, metallic hydrogen is a form of solid hydrogen with  a specific internal structure: http://ch301.cm.utexas.edu/imfs/#solids/metallic-solids.html

There have been some experiments using super-chilled diamond anvils that have credible claims to having made solid hydrogen, and I think one of them even tried passing a current through it before it evaporated.

So it is *possible* that metallic hydrogen has been created in a lab in microscopic quantities.

I think solid non metallic hydrogen have been made and there are some reports of metallic state but they are criticized and need further investigation. And there are no observations or credible theoretical predictions about metastable high density states, metallic or not. It is very scifi-ish hypothesis.

 

18 hours ago, Terwin said:

The down-side of this is that your thrust is low because your exhaust is very light.  Metastable hydrogen would be great for inter-planetary transit, but might not even get an airplane off the ground.   

Metallic hydrogen would be burned in aircraft engine. It would give huge fuel value (MJ/kg) because metallic lattice have much less binding energy per atom than normal H2 molecule. Certainly such fuel would give benefits in planes and terrestrial vehicles if it was possible to store, handle and burn safely. ISP is just not good way to characterize practical plane efficiency.