Overview
Liquid rocket engines burn some combination of fuel and oxidizer to achieve combustion, create pressure in the chamber, and then thrust. Selecting which fuel and oxidizer to use for your engine/program is critical and oftentimes a non-trivial task. Note that this page focuses only on bi-propellant systems, not mono-prop, hybrid, tribrid, or any other shenanigans.
The propellant combination is likely the most important decision to make when sizing an engine. It defines nearly all aspects of your propulsion system and will drive significant aspects of your system architecture.
Some “common” fuel choices for both industry and/or amateur use include Liquid Hydrogen (LH2), Liquid Methane (LCH4), Hydrazine (N2H4), various alcohols, various kerosene-based fuels such as RP1 or jet fuel, Propane (C3H8), and Butane (C4H10).