A rocket fuel should have high energy density (per kilogram) because the weight of the propellant is an important consideration. A favorite fuel is liquid hydrogen plus liquid oxygen. What is the energy density (J/kg) of a stoichiometric mixture of H₂(l) and O₂(l) (assuming they combine to form water in the gaseous state)? The strong nuclear force, in principle, allows the same stoichiometric mixture of two hydrogen atoms and one oxygen atom to fuse to form an isotope of neon, 18 Ne, giving off 4.52 MeV in the process. If this reaction were the source of power for the rocket, what would be the energy density of the fuel?