Has anybody ever heard of this stuff? http://www.sciencedaily.com/releases/2009/05/090511181356.htm Okay, so that means it has at least been produced, so it exists. But is it stable once the confinement pressure has been removed, or is it just a fleeting substance? For it to be feasible as a fuel, I'd imagine it has to be a stable, persistent material. Could it be useful for powering spacecraft one day? Presumably its compact mass density would allow for a lot of fuel within a small volume. Is there any danger that such a high-density material could somehow chain-react, or spontaneously explode due to entropy pressures?