Autonomous Rotorcraft Project -- Retrospective and Future Outlook

This paper presents an overview of the Autonomous Rotorcraft Project (ARP), a collaborative research initiative launched by the US Army and NASA in 2000 aimed at advancing rotorcraft autonomy. ARP has made substantial progress in areas such as real-time reactive obstacle-avoidance, threat- and terrain-aware navigation, identification of safe landing zones, autonomous flight-control, external sling-load operations, scalable autonomy, and pilot-autonomy interfaces. These advancements have undergone extensive validation through both simulation and flight test. This paper chronicles ARP's research evolution, highlighting milestones achieved and remaining challenges.