Methalox

Rocket propellant combining liquid methane fuel with liquid oxygen, favoured for new reusable engines.

• Methane burns with little soot, unlike kerosene, whose residue coats engine passages and complicates reuse.
• It is somewhat more efficient than kerosene and far denser than liquid hydrogen, allowing smaller tanks.
• Methane and oxygen stay liquid at similar temperatures, simplifying tank design, and both could in principle be made on Mars from CO2 and water.
• Starship, Blue Origin's New Glenn and several Chinese rockets use it; like any super-cold propellant, it boils off on long missions.