The BE-4 engine project started in 2014. It would be the most powerful liquefied natural gas (LNG) fueled rocket engine ever developed. Using an oxygen-rich staged combustion cycle, BE-4 is capable of producing 2,400 kN (550,000 lbf) thrust with deep throttle capability. The ULA (United Launch Alliance) Vulcan rocket plans to use the BE-4 engine and Blue Origin has designed a Falcon Heavy class New Glenn rocket to use BE-4 engines.

ULA said the Vulcan program "is now focused on completing BE-4 qualification testing and flight engine deliveries. [Its] other elements are progressing through final qualification testing to support initial launch capability."

Before it can gain flight certification, ULA must complete two successful flight tests. Then, it will be greenlit to launch sensitive U.S. military and intelligence cargo.