From Halopedia, the Halo wiki
Hydrogen peroxide, chemical formula H202, is a chemical solution used in United Nations Space Command ship-mounted emergency thrusters. When combined with trihydride tetrazene, it produces an explosive force large enough to radically alter the course of UNSC ships. Ship captains use them mainly to avoid Covenant plasma torpedoes, which track enemy ships and inevitably would eventually impact. However, the emergency thrusters buy UNSC ship commanders some extra time to pull off complex maneuvers, such as the Keyes Loop.
It is a very pale blue liquid which appears colorless in a dilute solution, with a slightly higher viscosity than water. It is a weak acid. It has strong oxidizing properties and is therefore a powerful bleaching agent that is mostly used for bleaching paper, but has also found use as a disinfectant, as an oxidizer, as an antiseptic, and in rocketry (particularly in high concentrations as high-test peroxide or HTP) as a monopropellant, and in bipropellant systems. The oxidizing capacity of hydrogen peroxide is so strong that the chemical is considered a highly reactive oxygen species.
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