SpaceX operates a fleet of ocean-going autonomous spaceport droneships (ASDS) for Falcon 9 missions that are not capable of landing back at the launch site (RTLS). Falcon 9 missions may require a droneship landing instead of RTLS due to the weight of the payload or the overall mission profile. SpaceX currently operates three droneships in operation – an original experiment droneship was retired in 2015.