Vulcan's upper stage will be the Centaur V, an upgraded variant of the Common Centaur/Centaur III that is currently used on the Atlas V. A lengthened version of the Centaur V will be used on the Vulcan Centaur Heavy. ULA planned to eventually upgrade the Centaur V with Integrated Vehicle Fluids technology to become the Advanced Cryogenic Evolved Stage (ACES). Those plans were dropped in 2020 with efforts focusing on improving the capabilities of the existing Centaur V upper stage. ULA has plans for tanker called XEUS, developed in partnership with Masten Space Systems, that will be able to land on the moon to be stocked with fuel and then fly to a gravitationally stable "liberation point" in the Earth-Moon system known as L1. XEUS planned to utilize the now abandoned ACES upper stage but will now utilise a modified Centaur V upper stage.