Experimental Studies of Metallic Hydrogen at Very High Pressures.

Atomic hydrogen, because of its small mass and large recombination energy, is theoretically the most promising of all chemical propellants. Currently the best existing chemical propellant is the molecular hydrogen-oxygen fuel. Even in the liquid form, because of its low density, these fuels require large storage tanks, which add to the weight of a vehicle. Thus metallic hydrogen has two important advantages it has a large specific impulse and its density will be more than an order of magnitude larger than that of ambient liquid hydrogen. Together these factors provide enormous advantages in rocket propulsion and are the reason for investigating the feasibility of producing metallic hydrogen in the laboratory. It is now known that to produce the atomic metallic phase by the brute force method of compression of molecular hydrogen, pressures in the range of 2-5 megabars are required. Achieving pressures in the 1- to 2-megabar range, under careful laboratory conditions using diamond anvils, is now fairly routine. With some care, higher pressures have been achieved. jg p7