Gremlins Air Vehicles: The Road to Airborne Recovery

Wednesday January 05, 2022

Dynetics, a wholly owned subsidiary of Leidos, has been hard at work to advance the technology and capability of our nation's airborne unmanned systems. The Gremlins program, developed with funding from the Defense Advanced Research Projects Agency (DARPA), is designed to integrate with most existing strike, reconnaissance and cargo aircraft. The overarching goal of the Gremlins Program, managed by DARPA's Tactical Technology Office, is to demonstrate aerial launch and recovery of multiple low-cost reusable unmanned aerial systems (UASs), effectively enabling the distribution and management of swarms of sensors in denied environments, while allowing humans to keep a safe distance from adversarial threats.

After a series of successful flight tests designed to collect data, the Gremlins Air Vehicles (GAVs) endured a rigorous string of tests on the road to airborne recovery.

The GAVs are the actual unmanned aircraft launched from wing pylons of existing aircraft, such as a C-130. They are low-cost, modular, reusable "trucks" that operate individually or with coordination in larger quantities, and require minimal human supervision to operate. In 2019, the GAV earned the Air Force X-61A designation.  

In October 2021, the Dynetics test team, a subset of Gremlins program engineers and subcontractors, traveled to Dugway Proving Ground near Salt Lake City, Utah, with a successful mission in mind. Their goal: to accomplish a safe recovery of the X-61A utilizing the entire integrated Gremlins Demonstration System, which includes the launch system, recovery system, operator control and the X-61A vehicle.

Spoiler alert: they were successful. The team captured a GAV, checking a box on a critical and historic milestone for airborne unmanned systems.

Since the first GAV flight in 2019, the team has analyzed, observed and progressively improved the way the system functions through a series of ground and flight tests. Additional testing of automated and manual safety behaviors were also extensively tested and studied prior to the most recent flight test and recovery event.

Prior to every flight test, the team first deploys a very rigorous pre-flight checklist across the entire demonstration system. Any anomalous behavior is investigated and mitigated before proceeding. While in the air, the GAV and operator control system are first checked out in "mission mode". When it is time to recover, the operator sends the command for the X-61A to rendezvous with the recovery C-130. The GAV proceeds to autonomously position itself and maintain an assigned station, keeping location behind the C-130. When the engineering team in the control room is satisfied with the performance of the system, the GAV moves closer to the capture device towed below and behind the C-130. Capture is finally commanded, and the entire system autonomously closes the final gap. Once the GAV is securely attached, the engine quickly shuts down. Then, the wing closes, and the operators onboard the C-130 command the recovery system to reel the hardware into the cargo bay, where its safely stowed in the aircraft.

To date, the GAVs have logged 17.3 total hours of flight and demonstrated a new milestone in unmanned flight.

Not only do the GAVs boast transformative technical and innovative capability, they also have names: Greta (the first GAV to fly), Gabby, Gertrude, Grace, Gloria (the historic first GAV to be recovered in the air).

"The idea for the 'G' names came from a random discussion on a long car trip with my family," said Brandon Hiller, chief engineer for the Gremlins program. "I took the liberty of naming Greta, and the other folks on our GAV team named the rest of the fleet. Each GAV received her name when we ran the engine for the first time at the Wildwood test site here in Huntsville."

Unfortunately, Greta, the first flight-tested GAV was lost during the ground recovery sequence due to a failure to extract the main chute. Grace was also lost in 2021 due to a power system fault in flight.

"This is why we built five GAVs," said Tim Keeter, Dynetics Gremlins program manager. "Aggressive programs like this come with risk, and we knew we had to be able to continue system testing if we lost or damaged one or more GAVs. This is a normal part of flight system development and provides important opportunities to mature the system."

The remaining three GAVs may be used to demonstrate airborne recovery of multiple GAVs in the same flight, moving the Gremlins Demonstration System closer to an operationally relevant capability.

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