Updated DARPA Hybrid-Electric XRQ-73 Makes First Flight

The U.S. Defense Advanced Research Projects Agency (DARPA) has made the first flight of its experimental hybrid-electric XRQ-73 aircraft. The agency announced the flight on May 6, reporting that it had happened the previous month.

The uncrewed demonstrator, which was developed with prime contractor Northrop Grumman, is intended to support military uses for hybrid-propulsion applications. The test was conducted as part of DARPA’s Series Hybrid Electric Propulsion AiRcraft Demonstration (SHEPARD) program.

The program leverages technologies from an earlier development project called Great Horned Owl. SHEPARD officially received its official experimental ‘X-plane’ designation of XRQ-73 in June 2024, a month before Northrop Grumman subsidiary Scaled Composites publicly unveiled the completed demonstrator.

At the time, DARPA suggested the aircraft was undergoing ground testing, with a first flight scheduled for the same year. However, it appears the concept has since been modified, with the current airframe sporting two vertical stabilisers near its wingtips. Amendments have also been made to the air intake configuration.

Under its U.S. Department of Defense classification, XRQ-73—which weighs approximately 567 kilograms (1250 pounds)—is a Group 3 sized drone. This is larger than the hybrid-electric Great Horned Owl XRQ-72 vehicle, which received its designation in 2017.

In 2011, the Intelligence Advanced Research Projects Activity (IARPA) confirmed that Great Horned Owl’s subscale XQR-72 was seeking to “develop technologies that significantly extend the operational endurance and payload capacities of ISR [Intelligence, Surveillance and Reconnaissance] UAVs.” DARPA confirmed that the SHEPARD X-Prime program will integrate its predecessor’s hybrid-electric architecture and selected component technologies.

Although the XRQ-73 is not necessarily destined to enter service, its operationally-representative fuel and mission systems will nevertheless help mature a specific propulsion architecture and power class “of potential benefit for the Department of Defense.” Northrop Grumman added that the hybrid-propulsion system would enable “new mission possibilities [while] supporting the evolution of new aircraft designs.”

According to SHEPARD officials, the DARPA X-prime program is intended to “take emerging technologies and burn down system-level integration risks to quickly mature a new missionized aircraft.” It added that validation of these technologies will now help to develop a platform “that can be fielded with the objective of first flight in 20 months.”