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A lot of news come these days about metallic hydrogen and its possibility of releasing 20 times more energy than just oxygen-hydrogen reaction. Like here: https://www.nasa.gov/pdf/637123main_Silvera_Presentation.pdf

But what if we use metallic deuterium or tritium (especially, tritium)? Would they release more energy and, therefore, be more efficient fuel than even metallic hydrogen? (the means of compression are out of topic)

Or maybe metallic deuterium\metallic tritium fission would give more energy (than fission of normal ones)? - OK, made a mistake here: fusion, sure (edit). (This part got answer and is clear now, but question about metallic tritium in comparison to metallic protium still remains open)

Can somebody help with this, please?

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    $\begingroup$ D-T would be fusion, not fission. But, even in the metallic state you will not get fusion since the nuclei are not going to interact. $\endgroup$
    – Jon Custer
    Commented Feb 3, 2017 at 3:32
  • $\begingroup$ Okay. But what about conversion of metallic tritium into normal one? Hydrogen is said to release 216 MJ/kg, but what about tritium? $\endgroup$
    – Ditrius
    Commented Feb 3, 2017 at 3:42
  • $\begingroup$ Interesting question. I'm not sure what the free energy implications of the heavier mass of tritium vs protium is in the transition to the metallic state. But I'm not thrilled at trying to use a phase change cycle involving explosive (and radioactive) materials... $\endgroup$
    – Jon Custer
    Commented Feb 3, 2017 at 3:52
  • $\begingroup$ Personally, I think that the idea of metastable metallic hydrogen is a little unrealistic and has been hyped up a bit. I've studied metallic hydrogen myself and was in fact on the Lawrence Livermore Lab team that produced fluid metallic hydrogen by multiple shock compression. ( journals.aps.org/prl/abstract/10.1103/PhysRevLett.76.1860 ). I don't think that any experimentalist seriously thinks that there is a good chance of recovering metastable metallic hydrogen, although it does make a good story to news reporters. $\endgroup$
    – user93237
    Commented Feb 3, 2017 at 5:51
  • $\begingroup$ Thank you very much. But if we just could compress tritium to the same levels for a moment of time (without taking metastability into account), in theory, how more energy could it release in transition to normal state, how do you think? $\endgroup$
    – Ditrius
    Commented Feb 3, 2017 at 15:01

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In short, no. We're talking about two energy scales orders of magnitude apart, the electronic/chemical (low end) and the nuclear (high end). By compressing hydrogen it's possible to force its electrons in to a metallic state. The energy from rocket fuel is chemical, firstly from solid hydrogen decomposing to molecular hydrogen as the pressure is released, and secondly the hydrogen reacting with oxygen to form water. Nuclear reactions have an impractically activation energy barrier (you need to give them a lot of kinetic energy to overcome the proton repulsion barrier), but would yield much more energy.

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  • $\begingroup$ Ok, thank you very much. But, again, what about tritium? If we could, in theory, somehow compress it to metallic state, how much energy could it release in transition to normal one? Would it be significantly more than that of hydrogen (protium)? Or, maybe, if tritium is too unstable, metallic deuterium? $\endgroup$
    – Ditrius
    Commented Feb 3, 2017 at 15:06
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    $\begingroup$ Deuterium and tritium would be chemically identical to hydrogen, and would release the same amount of chemical energy. The difference would be in the free energy, i.e. the vibrational contribution, arising from the difference in masses. My guess would be that tritium would have the lowest free energy due to lower vibrational frequencies, making it more stable, but it's hard to say what affect (if anything significant) this would have on the relative stability. $\endgroup$
    – Paraquat
    Commented Feb 3, 2017 at 16:04
  • $\begingroup$ I've long been a fan of "muon catalyzed fusion," which unfortunately has some show stoppers in practice (helium carrying away the catalyst muons). I wonder if that might be any different in the much denser lattice of metallic hydrogen... $\endgroup$
    – Jim Pivarski
    Commented Aug 10, 2019 at 4:04

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