Technology / Rockets / Oxidizer: All things need oxygen to burn. When a pile of wood burns in an open fire, it sucks in oxygen from the surrounding air. When rocket fuel burns, it can't suck in oxygen from the surrounding air because the fuel is in a closed environment. For this reason, rocket fuels need oxygen to burn in and they get it from an oxidizer which may be in the form of liquid oxygen for liquid propellants in the big NASA rockets or ammonium perchlorate for solid propellants. Also, many rocket fuels require more oxygen to be present in a smaller space per amount of fuel for it to burn properly or even at all.
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