Blue Origin dixit:
“The BE-4 is our fourth-generation liquid rocket engine, made to take us into orbit and beyond.
The BE-4 uses oxygen-rich staged combustion of liquid oxygen and liquefied natural gas to produce 550,000 lbs. of thrust. Liquefied natural gas is commercially available, affordable, and highly efficient for spaceflight. Unlike other rocket fuels, such as kerosene, liquefied natural gas can be used to pressurize a rocket’s propellant tanks. This is called autogenous pressurization and eliminates the need for costly and complex pressurization systems, like helium. Liquefied natural gas also leaves no soot byproducts as kerosene does, simplifying engine reuse.
United Launch Alliance has selected Blue Origin’s BE-4 as the engine that will power the Vulcan rocket’s first stage. The announcement ends the need for the Russian made RD-180 on their next-generation vehicle Vulcan with the American-made BE-4.”
From the ULA press release: “Following completion of a competitive procurement, ULA has selected Blue Origin’s BE-4 engine for Vulcan Centaur’s booster stage. The liquefied natural gas (LNG) fueled booster will be powered by a pair of BE-4 engines, each producing 550,000 pounds of sea level thrust. As previously announced, ULA has selected Aerojet Rocketdyne’s RL10 engine for ...