text: In September 2014, ULA announced that it had entered into a partnership with Blue Origin to develop the BE-4 LOX/methane engine to replace the RD-180 on the new Vulcan rocket. The new stage and engine first flew in 2024.
  In December 2014, legislation to prevent the award of further military launch contracts to vehicles that use Russian-made engines was approved by the US Congress. The bill allows ULA to continue to use the 29 RD-180 engines already on order at the time. In September 2021, ULA announced that Atlas V will be retired after they fulfill their remaining launch contracts, and that all remaining RD-180s for the remaining rockets have been delivered.
  Formerly proposed launch vehicles
  Prior to the April 2015 announcement of the Vulcan launch vehicle, during the first decade since ULA was formed from Lockheed Martin and Boeing, there were a number of proposals and concept studies of future launch vehicles.  None were subsequently funded for full-up development.  Two of those concepts were the Atlas V Heavy and the Atlas Phase 2.
  Atlas V Heavy
  The Atlas V Heavy was a ULA concept proposal that would have used three Common Core Booster (CCB) stages strapped together to provide the capability necessary to lift 25 tonne payload to low Earth orbit.  ULA stated that approximately 95% of the hardware required for the Atlas HLV had already been flown on the Atlas V single-core vehicles.