WASHINGTON: The Defense Advanced Research Project Agency’s “Gremlins” drones are proving to be as difficult to wrangle as the 1980s film creatures that serve as their namesake.
During an October 29 test, DARPA successfully recaptured one X-61 Gremlin Air Vehicle, dragging it back into the C-130 cargo bay from whence it was launched, the agency announced today.
The recovery was a huge win for the program, proving that it is technically feasible to retrieve a small drone and put it back into a mothership while in mid flight — something DARPA had failed to achieve in previous flight tests.
The bad news? Another X-61 drone was destroyed during the first of four flight tests carried out in October, said Tim Keeter, Gremlins program manager for Dynetics, the Leidos subsidiary that developed the X-61.
In an interview with Breaking Defense, Keeter characterized the issue as a “power system problem that caused us to have to terminate flight.” Because the issue was unexpected, there wasn’t enough time for the air vehicle to release its parachutes, as the Gremlins drones normally do to perform a ground landing.
“At no time was that incident of safety issue or concern. We were able to quickly diagnose the situation, come up with a corrective action, implement that fix and get permission to return to flight,” he said, noting that the fix was validated in a later flight.
Gremlins is aimed at developing low-cost swarming drones that can be outfitted with different payloads, launched by a mothership, recovered during flight and then reused — a capability that the military services do not have today. Dynetics received a $32 million contract from DARPA for the effort in 2018.
Despite the issues during tests last month, DARPA and Dynetics officials were enthusiastic about the progress of the program.
“We have accomplished the first major objective of this program — to show that air recovery is feasible. That points to being reliable and something that we can do at a reasonable operational pace,” Keeter said.
Lt. Col. Paul Calhoun, program manager for Gremlins in DARPA’s Tactical Technology Office, called the event “the culmination of years of hard work.”
How to recover a Gremlins drone
Recovering a Gremlins drone is a two-step process. First, the X-61 connects with a docking station that stabilizes the vehicle against harsh weather and the turbulence generated by the C-130. Then, a mechanized arm grabs the Gremlin drone and places it back in the C-130.
DARPA and Dynetics first attempted to recover the X-61 aerially in tests held last fall. Altogether, nine attempts were made, but each failed.
After the first few attempts carried out in 2020, the team realized that a successful recovery would likely be out of reach, Keeter said. Instead, the team pivoted to trying to dock the vehicle as many times as possible during the flight to collect data that could be used to ascertain the problem and develop a fix.
“We didn’t make any sweeping design changes,” Keeter said. Rather, Dynetics made software changes to its autopilot system, speeding up the vehicle’s performance and responsiveness and improving its ability to deal with latency.
In the end, the changes worked, and the aerial recovery on Oct. 29 “was smooth. It was as we predicted,” Keeter said.
Still, it will take more development work for the feat to become easily repeatable, as the company learned during the final experiment on Oct. 31.
For that flight, the team used an X-61 that had been aerially recaptured in the previous demonstration and refurbished. Although the aircraft was successfully launched and flown, the DARPA-Dynetics team was not able to recover it in the air, and it safely landed on the ground instead, Keeter said.
It’s unclear when Dynetics will have another chance to perform aerial recoveries of the X-61, or when it will be able to attempt retrieving multiple Gremlin drones at a time.
“Airborne recovery is complex,” Calhoun stated, according to DARPA. “We will take some time to enjoy the success of this deployment, then get back to work further analyzing the data and determining next steps for the Gremlins technology.”