Electrolysis of H20 into hdrogen and oxygen uses up more energy than is netted by the combustion of hydrogen. I believe this process is used on subs to make oxygen- the hydrogen is vented. The space shuttle uses solid rocket boosters( propellant and oxidizer) along with a liquid rocket main engine and shuttle attitude motors. The liquids are liquid oxygen (oxidizer)and a propellant ( liquid hydogen or kerosene) the propellant is mixed with the oxidizer, ignited, forced through a rocket nozzle, and viola! the space shuttle launches! No, I am not a rocket scientist- but I do play one on TV.