In chemistry, peroxides are a group of compounds with the structure R−O−O−R, where R is any element. The O−O group in a peroxide is called the peroxide group or peroxo group.
In the aerospace context, peroxide refers to hydrogen peroxide, which is a liquid chemical compound composed of hydrogen and oxygen (H2O2). It is used as a powerful oxidizer and a source of oxygen in rocket propulsion systems and as a propellant in some aircraft emergency power systems.
One example of its use is in the propulsion system of the European Space Agency's Ariane 5 rocket, where it is used to power the rocket's Vulcain engine. Another example is the use of hydrogen peroxide in the emergency power system of some military aircraft, such as the British Aerospace Harrier and the Lockheed SR-71 Blackbird, where it is used to power the aircraft's auxiliary power unit (APU) in the event of a main power failure.
Additionally, hydrogen peroxide can be used as a powerful sanitizer and disinfectant, it's been used in cleaning and disinfection procedures in the aerospace industry, specially in the air-filters and air-conditioning systems of the aircrafts.