# Was metastable solid metallic hydrogen really debunked as viable future fuel?

In this thread about Kerbal Space Program 2 authors says they are building gameplay based on technologies that are potentially viable in the near, or ar future. Main topic there is metallic hydrogen.

It ignited a heated discussion on that technology and some people claim it was already debunked and proven impossible. People there cite various sources that says yes or no for this possibility.

So, what do we know now? For real? Is it already proven impossible? Harder than we thought? Is anyone still working on fuel applications?

What I'm looking for is short impartial overview of the current (beginning of 2020) state of knowledge.

About 3 years ago we had a list of questions on that topic, but supposedly more recent research brings some sad news.

Also, new answers to first two would not help us now because we know it was considered and it's not going to change, and oxidizer one assumes it exists and works, and that assumption is what I want to verify.

• @uhoh linked questions are nice, but 3 years old. Research that supposedly debunked it is, as far as I understood, less than one year old. But I am not sure if I understood. – Mołot Feb 27 '20 at 11:17
• @uhoh question updated with links to old questions and explanation why I believe new one makes more sense than, for example, a bounty. – Mołot Feb 27 '20 at 11:26
• chemistryworld.com/news/…. This article covers a recent probably successful attempt to form metallic hydrogen. Paper: nature.com/articles/s41586-019-1927-3 – Barry Jenekuns Feb 28 '20 at 1:21
• Additional info about the feasibility of solid hydrogen: I remember when working on JWST in the mid-2000 time frame that solid hydrogen was considered for several years, as a coolant. Here is an article about the approach: sae.org/publications/technical-papers/content/2005-01-3041 – DanPro Mar 5 '20 at 14:13
• @DanPro: There is no question about the feasibility of solid hydrogen, which has been used as a coolant on several space telescopes (such as WIRE, which launched in 1999...and promptly evaporated all its coolant by ejecting its dust cover while the telescope was pointed at Earth). The question is about metallic hydrogen. – Christopher James Huff Apr 22 '20 at 20:10

This paper, claims that metallic hydrogen at low temperatures might be relatively long-lived at pressures above about $$50 GPa$$ (with a large margin of error) which is about 500 thousand atmosphere and decay rapidly below that pressure. This does make it seem that tankage for a metallic hydrogen fueled rocket would have to be quite robust, and the consequences of a tank rupture would be quite severe. This is just one paper though -- I don't have an overview.