American launch provider ULA (United Launch Alliance), announced on 27 September, that after a three-year competition it has decided on the Blue Origin BE-4 engine, over the Aerojet Rocketdyne AR-1, to power their in-development Vulcan rocket’s first-stage – the first launch of the Vulcan rocket is planned for 2020. With this decision Blue Origin will join other American manufacturers contributing to the new rocket: Aerojet Rocketdyne supplying the RL10 engine for the Centaur stage; Northrop Grumman providing the optional solid rocket boosters (SRBs); and RUAG who is producing the payload fairings.

The BE-4 engine burns Liquid Oxygen as an oxidiser and Liquid Methane as the propellant. The BE-4 will later be used by Blue Origin to power the first-stage of their own planned heavy-lift New Glenn rocket. When installed on the Vulcan it will be in a pair, but seven of the engines will be used for the New Glenn first-stage.