Advanced Cryogenic Evolved Stage
The Advanced Cryogenic Evolved Stage (ACES), formerly the Advanced Common Evolved Stage, is a proposed liquid oxygen/liquid hydrogen upper stage rocket for use on the Vulcan space launch vehicle.
The design concept is from the American company United Launch Alliance (ULA). ACES is intended to boost satellite payloads to geosynchronous orbit or, in the case of an interplanetary space probe, to escape velocity. Other alternative uses include a proposal to provide in-space propellant depots in LEO or at L2 that could be used as way-stations for other rockets to stop and refuel on the way to beyond-LEO or interplanetary missions, and to provide the high delta-v technical capacity for the cleanup of space debris.
As of 2016[update], ULA announced conceptual plans to transition the Vulcan rocket to the ACES second stage after approximately 2024. Vulcan will initially launch with the Centaur upper stage, beginning with its first flight no earlier than 2019.
Originally proposed as the Advanced Cryogenic Evolved Stage by Boeing in 2006 as a concept for use as a new Delta IV second stage—and subsequently, the Advanced Common Evolved Stage by its corporate successor, United Launch Alliance by 2010— ACES was intended to boost satellite payloads to geosynchronous orbit or, in the case of an interplanetary space probe, to or near to escape velocity. Other alternative uses included a proposal to provide in-space propellant depots in LEO or at L2 that could be used as way-stations for other rockets to stop and refuel on the way to beyond-LEO or interplanetary missions, and to provide the high-energy technical capacity for the cleanup of space debris.
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