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DARPA GREMLIN developed airborne launch, and retrieval system of swarming UAVs to defeat A2/AD environments

US military is facing increasingly Anti-access /Area denial environment, a set of overlapping military capabilities and operations designed to slow the deployment of U.S. forces to a region, reduce the tempo of those forces once there, and deny the freedom of action necessary to achieve military objectives . “A2/AD capabilities enabled by integrated air defense systems that include advanced fighters, advanced surface-to-air missiles, active and passive cuing systems, and directed energy weapons” make many U.S. fixed facilities vulnerable to attack in ways hard to imagine a decade ago, according to Harry Foster from National Defense University.


UAVs are ideal fit for risky military missions, however most of the current inventory of Unmanned Aerial Systems are not not well-matched in A2/AD environment against more technologically advanced enemies who present higher levels of threats, contested electromagnetic spectrum and relocatable targets, according to DARPA. Drones, which currently are flown individually, “are operated by large crews,” “This is expensive and incompatible with an organic system able to react quickly to a dynamic situation.”


One of the technology DARPA is developing for defeating A2/AD Strategies is UAS swarm capability. The large UAVs have large radar cross section hence more vulnerable, hence DARPA is trying to replace large UAV with swarms of small UAVs which shall be difficult to detect and engage under its Collaborative Operations in Denied Environment program (CODE).


The capability of UAVs can be multiplied when operated in swarms. Swarms can find, fix, and communicate precise target location of ground, sea, and air targets; they can serve as weapons platforms to attack air defense systems from multiple axes; or they can pass missile targeting data to any platform carrying a counter air missile.

DARPA’s “Gremlins” Could Enable Cheaper, More Effective, and Distributed Air Operations

However, one of the limitations of swarms has been the technology to project volleys of low-cost, reusable systems over great distances and retrieve them in mid-air, which has remained out of reach. Small UAS have limited range and responsiveness, compared to larger airborne platforms.


In November 2014, the Defense Advanced Research Projects Agency (DARPA) request released request for information seeking information from industry on how to expand the operational envelopes of smaller UAS by using existing military aircraft to transport multiple small UAS into the theatre of operations and launch them while airborne.


“We want to find ways to make smaller aircraft more effective, and one promising idea is enabling existing large aircraft, with minimal modification, to become ‘aircraft carriers in the sky’,” said Dan Patt, DARPA program manager. “We envision innovative launch and recovery concepts for new UAS designs that would couple with recent advances in small payload design and collaborative technologies.”


The program envisions launching groups of gremlins from large aircraft such as bombers or transport aircraft, as well as from fighters and other small, fixed-wing platforms while those planes are out of range of adversary defenses. When the gremlins complete their mission, a C-130 transport aircraft would retrieve them in the air and carry them home, where ground crews would prepare them for their next use within 24 hours.


The gremlins’ expected lifetime of about 20 uses could provide significant cost advantages over expendable unmanned systems by reducing payload and airframe costs and by having lower mission and maintenance costs than conventional manned platforms. The Pentagon’s Strategic Capabilities Office, an initiative aimed at harnessing near-term emerging technologies for operational use, demonstrated an ability to launch small drones from the flare dispenser of an F-16.


Gremlins program, seeks to develop innovative technologies and systems enabling aircraft to launch volleys of low-cost, reusable unmanned air systems (UASs) and safely and reliably retrieve them in mid-air.  The program plans to demonstrate an ability to launch and recover small drones  carrying 60-pound sensor payloads  from an Air Force C-130 up to ranges of 300 nautical miles aircraft.  The program also aims to prove that such systems, or “gremlins,” could provide significant cost advantages over expendable systems, spreading out payload and airframe costs over multiple uses (expected lifetime 20 uses) instead of just one.


DARPA’s Gremlins program has completed the first flight test of its X-61A vehicle. The test in late November 2019 at the U.S. Army’s Dugway Proving Ground in Utah included one captive-carry mission aboard a C-130A and an airborne launch and free flight lasting just over an hour-and-a-half. A video of the test flight shows a C-130 belonging to International Air Response launching an X-61A Gremlins Air Vehicle off one of its wing pylons. The jet-powered drone flew for an hour and 41 minutes, but the craft was lost due to a malfunction with its parachute recovery system.

Scott Wierzbanowski, programme manager in DARPA’s Tactical Technology Office explains: “The programme provides an affordable solution to conduct air combat operations in the growing Anti-Access/Area-Denial (A2AD) environment. Gremlins are small and affordable unmanned vehicles, which means the user has the ability to deploy them in higher risk scenarios that would not be acceptable to manned aircraft.





“Our goal is to conduct a compelling proof-of-concept flight demonstration that could employ intelligence, surveillance and reconnaissance (ISR) and other modular, non-kinetic payloads in a robust, responsive and affordable manner,” said Dan Patt, DARPA program manager.


“With the ability to air-recover vehicles, we can use higher cost, more capable sensors to increase our overall intelligence, surveillance, and reconnaissance (ISR) capability and do so at a reduced per-mission cost, well below what either expendable systems or manned aircraft can provide.”

DARPA plans to focus primarily on the technical challenges associated with safe, reliable aerial launch and recovery of multiple unmanned air vehicles. As algorithms for increased levels of autonomy advance, aircraft will be able to control drones from the cockpit with a pilot in a command and control role, service experts have explained.


“The Phase 1 program showed the feasibility of airborne UAS launch and recovery systems that would require minimal modification to the host aircraft,” said Scott Wierzbanowski, DARPA program manager. “We’re aiming in Phase 2 to mature two system concepts to enable ‘aircraft carriers in the sky’ using air-recoverable UASs that could carry various payloads—advances that would greatly extend the range, flexibility, and affordability of UAS operations for the U.S. military.” Agency has now awarded Phase 2 contracts to two teams, one led by Dynetics, Inc. (Huntsville, Ala.) and the other by General Atomics Aeronautical Systems, Inc. (San Diego, Calif.) Gremlins Phase 2 research seeks to complete preliminary designs for full-scale technology demonstration systems, as well as develop and perform risk-reduction tests of individual system components.


Gremlin  phase 3

The Defense Advanced Research Projects Agency (DARPA)  awarded the third and final phase to develop a full-scale technology demonstration of the hard dock and recovery system to a Dynetics-led team of industry partners, including Kratos Unmanned Aerial Systems as the leader of fabrication, assembly, integration, and testing of each UAV. Under Phase III, Kratos will support air vehicle flight tests, recovery tests, system demonstration, as well as planning potential future capabilities.


Phase 3 goals include developing one full-scale technology demonstration series featuring the air recovery of multiple, low-cost, reusable unmanned aerial systems (UASs), or “Gremlins” and conducting flight demonstrations involving airborne launch and recovery of multiple gremlins. Safety, reliability, and affordability are the key objectives for the system, which would launch groups of UASs from multiple types of military aircraft while out of range from adversary defenses. Once Gremlins complete their mission, the transport aircraft would retrieve them in the air and carry them home, where ground crews would prepare them for their next use within 24 hours. Extensive modeling and simulation have also been conducted to mitigate risks.


The team met all objectives of the test in November 2019 , including gathering data on operation and performance, air and ground-based command and control systems, and flight termination. A parachute anomaly occurred in a recovery sequence that is specific to the test series and not part of the operational plan. The incident resulted in the loss of the test vehicle, one of five in the program. Four vehicles remain operational and available for the test series, which will continue in 2020.


“The vehicle performed well, giving us confidence we are on the right path and can expect success in our follow-on efforts,” said Scott Wierzbanowski, the program manager for Gremlins in DARPA’s Tactical Technology Office. “We got a closer look at vehicle performance for launch, rate capture, engine start, and transition to free flight. We had simulated the performance on the ground, and have now fully tested them in the air. We also demonstrated a variety of vehicle maneuvers that helped validate our aerodynamic data.”


The next step for the program is a full evaluation of the test data, as well as to understand any issues related to the failure for the main parachute to deploy. The team anticipates the second flight test at Dugway in the spring 2020 timeframe to remain on track.


The C-130 is the demonstration platform for the Gremlins program, but Wierzbanowski says the Services could easily modify the system for another transport aircraft or other major weapons system. Gremlins also can incorporate several types of sensors up to 150 pounds, and easily integrate technologies to address different types of stakeholders and missions.


“We see the potential for using this technology on our own Predator B/MQ-9 Reaper® to offer our customers new mission capabilities,” David R. Alexander, president, Aircraft Systems, GA-ASI, said in a written statement.

Design of launch and Recovery system

The Gremlins program plans to explore numerous technical areas, including:

  • Launch and recovery techniques, equipment and aircraft integration concepts
  • Low-cost, limited-life airframe designs
  • High-fidelity analysis, precision digital flight control, relative navigation and station keeping

The design involves deploying a towed, stabilised capture device below and away from the C-130 transport aircraft. The Gremlin would dock with the device in similar style to an airborne refuelling operation. Once docked and powered off, the air vehicle is raised to the C-130, where it is mechanically secured and stowed. According to DARPA, this technology can be easily adapted to allow under-wing recovery and bay recovery by other cargo aircraft.


Wierzbanowski says: “The Gremlins air vehicle must take into consideration the position and velocity of the host vehicle, the relative position of the recovery system attached to the host vehicle, and environmental factors such as turbulence. It must then translate all of these variables into guidance control inputs to the air vehicle, which will allow it to make contact with the recovery system.


“While challenging, recent modelling and flight test activities have reduced overall technical risk to an acceptable level. Final flight tests and system demonstrations in 2019 will prove the feasibility of the capability. The swarm coordination technical challenge will continue to be worked through Gremlins and other programs.” Additionally, the program will address new operational capabilities and air operations architectures as well as the potential cost advantages.


Leidos subsidiary Dynetics has carried out the third flight test series of the X-61A Gremlins Air Vehicle (GAV) in Jan 2021

Leidos subsidiary Dynetics has carried out the third flight test series of the X-61A Gremlins Air Vehicle (GAV). Conducted at the Dugway Proving Ground in Utah, US, the test series also included the Gremlins airborne recovery system. The latest test series demonstrated the automated and manual safety behaviours of the vehicle.

According to Dynetics, the X-61A air vehicle operated safely in proximity with a manned C-130 recovery aircraft. According to Dynetics, the X-61A air vehicle operated safely in proximity with a manned C-130 recovery aircraft. Dynetics Gremlins team programme manager Tim Keeter stated: “Our innovative safety functions are a critical part of the Gremlins system. “With five total flights to date, almost 11 hours logged in flight and a thorough, disciplined test plan, we are pleased with the safe operation of our system. That’s a significant milestone for Gremlins.”


Gremlins to Use Collaborative Autonomy Technology

The fourth and final phase of the Gremlins unmanned aerial system program will include collaborative autonomy software that allows one person to control multiple unmanned air vehicles. The technology extends the capability of unmanned aircraft systems to conduct long-distance engagements of mobile ground and maritime targets in areas with poor communications or limited navigational signals.


The Defense Advanced Research Projects Agency (DARPA) and the U.S. Air Force agreed in 2019 to add a fourth phase to DARPA’s Gremlins program. The program was expected to complete Phase III by the end of the 2020 calendar year and then move into the additional stage. That fourth phase, which the Air Force is partially funding, will be used to prepare the technology for Air Force operations and to help determine the operating concepts for the systems.The final tests will include collaborative autonomy technology that DARPA developed under the Collaborative Operations in a Denied Environment (CODE) program. That technology has since transitioned to Naval Air Systems Command.


Most unmanned air systems demand continuous control by a dedicated pilot and sensor operator supported by numerous telemetry-linked analysts. This requirement severely limits the scalability and cost-effectiveness of unmanned air operations and compounds the operational challenges in contested electromagnetic environments, according to DARPA’s website. The CODE technology is designed to overcome those limitations with new algorithms and software that would extend mission capabilities and improve the ability to conduct operations in so-called denied or contested airspace where communications and GPS-enabled navigation are difficult. The website describes CODE technology as “a modular software architecture beyond the current state of the art that is resilient to bandwidth limitations and communications disruptions.”


DARPA completed the CODE program in 2019. “We have since transitioned that program to [Naval Air Systems Command], but we knew that it was somewhat brittle. There were certain things we knew you could do that would make the system hang up a little bit or just not do exactly what you wanted because it was still a developmental program,” says Scott Wierzbanowski, who served as DARPA’s CODE program manager and who manages the Gremlins program as well.


Incorporating CODES onto the Gremlins unmanned systems will help answer the “what-ifs,” he explains. For example, officials hope to determine how to reestablish a connection or re-plan a mission when communications are lost. “We’re taking that foundational work that we did in autonomy, and we’re going to build upon it as we work with these Gremlin air vehicles,” Wierzbanowski states.


He lists that collaborative autonomy as the biggest challenge the agency would like to overcome in the final phase of the Gremlins program. “It’s going to be working on the ability for the autonomy to work when pop-up threats are happening. What we demonstrated in CODE was excellent. It was really a significant step forward in how autonomy can work for heterogenous systems.” DARPA demonstrated CODE’s capabilities using a combination of six real and 24 simulated RG-23 TigerShark unmanned systems built by Navmar Applied Sciences Corporation. The systems worked together to conduct suppression of enemy air defenses (SEAD) missions, strike missions and intelligence, surveillance and reconnaissance missions.


Depending on how warfighters choose to use the Gremlins, which are built by Dynetics, a Leidos company, the unmanned systems might also benefit from another former DARPA program, the Persistent Close Air Support program. That effort developed technology designed to fundamentally increase close air support effectiveness by enabling personnel on the ground and combat aircrews to share real-time situational awareness and weapons systems data. The system enables ground agents to quickly and positively identify multiple targets simultaneously.


“What it really comes down to is the concept of operations. We envisioned different ways the Gremlin vehicles could be used. If you wanted to launch these vehicles, and then allow a ground agent to take control to do the intelligence, surveillance and reconnaissance mission, that is one concept of operations that could work, and you could leverage a strategic use of unmanned air vehicles within a very close tactical setting,” Wierzbanowski suggests.


Another possibility, he explains, will be to have someone control the unmanned systems from aboard whichever aircraft might be used to launch the Gremlins. “The goal is to demonstrate that a single operator can control multiple unmanned aerial vehicles in complex mission scenarios. During Phase IV, an operator would be able to launch, control, and recover multiple Gremlin air vehicles from a host aircraft. This would demonstrate to the services that the technologies needed to conduct distributed air operations is mature enough to be considered in future programs of record.”


While the Gremlins can be launched from virtually any type of military aircraft, including transport planes, fighters and bombers, they will need to return to a C-130 simply because that is the aircraft the recovery system was designed to fit. The recovery system is a mechanical arm that extends from the rear of the aircraft and connects to the drones.


It is even possible, but probably not practical, for the military services to attach weapons to the drones. Wierzbanowski explains that the unmanned systems are designed to carry roughly 150 pounds of sensors in the nose. Adding weapon systems would require reengineering the craft to integrate the weapons in the middle to maintain ballast. In the end, it is more feasible to simply launch an existing weapon system, such as Lockheed Martin’s Joint Air-to-Surface Standoff Missile.


“This vehicle is made for sensors and nonkinetic capabilities. My take is that if you really want to put weapons on it, then just go ahead and use a weapon that we already have,” Wierzbanowski declares. “If you really wanted to have a vehicle like this that was going to release something, well, it would be small, but I think it’s going to be an inefficient way.”


In addition to the Air Force, both the Navy and the special operations community have shown interest, Wierzbanowski reports. The Navy officials, he notes, like the idea of having a system they can launch from aircraft already aboard aircraft carriers rather than having to design a whole new plane. And special operations forces are interested in having an intelligence, surveillance and reconnaissance system they can own and operate rather than requesting support from unmanned systems controlled by others, such as a Predator or Reaper. The additional stage of the Gremlins program, Wierzbanowski states, is where it starts to get fun. “This is where we switch hats from the developmental test perspective and start looking through the lens of an operational tester.”


The effort likely will incorporate a variety of sensors on the unmanned systems. “While we are still working out the details the intent is to demonstrate the integration of different intelligence, surveillance and reconnaissance sensors within an autonomous formation of unmanned aerial vehicles,” Wierzbanowski offers. The added phase is expected to last about 27 months. “We wanted to keep it short so that from a DARPA perspective, it’s scoped, and when we’re done, we’re done. Then it becomes the responsibility of the service to move forward with it if they deem it worthy,” Wierzbanowski says.


DARPA demonstrates successful recovery in Nov 2021

Defense Advanced Research Projects Agency (DARPA) in October 2021 for the first time caught an airborne X-61 Gremlins unmanned air vehicle (UAV) using a mechanical arm and towed docking “bullet” deployed from the cargo ramp of a Lockheed Martin C-130.


The successful recovery of the experimental drone came after abortive and failed attempts over the course of three testing events since late 2019. DARPA used two Dynetics X-61 UAVs during its recent flight tests, one of which was destroyed due to electrical system failure, it said on 5 November 2021.


The flight tests at Dugway Proving Ground in Utah validated all autonomous formation flying positions and safety features of the X-61 system, says DARPA. “This recovery was the culmination of years of hard work and demonstrates the feasibility of safe, reliable airborne recovery,” says Lieutenant Colonel Paul Calhoun, programme manager for Gremlins in DARPA’s tactical technology Office. “Such a capability will likely prove to be critical for future distributed air operations.”


Four flights were conducted in October to gather data on aircraft performance, aerodynamic interactions between the recovery bullet and the UAV, and the dynamics of making contact with the UAV during retrieval, says the agency. As part of the final experiment, DARPA retrieved and then refurbished an X-61 and conducted a second flight within “24 working-hours”. The refurbished UAV was recovered on the ground.


Five examples of the experimental X-61 drone were built as part of the Gremlins programme. An X-61 was also destroyed when its parachute failed to deploy during an initial test flight in 2019. “Airborne recovery is complex,” says Calhoun. “We will take some time to enjoy the success of this deployment, then get back to work further analysing the data and determining next steps for the Gremlins technology.”


In a conference call with reporters , Dynetics’ Gremlins program manager Tim Keeter said the program now must prove it can recover multiple drones repeatedly, reliably and quickly enough for real-world operations.

For DARPA, Keeter said, making the American program work at an “operationally relevant rate” would mean being able to recover four drones within a half-hour. He called last month’s successful test — the Gremlins’ fourth such deployment — a milestone for both the program and unmanned aviation, adding that the effort could “dramatically expand” the military’s ability to carry out distributed airborne operations.


If the program works as intended, he added, it could one day allow the military to deploy “swarms” of drones into denied areas. That way, the mothership could stay out of harm’s way while the drones gather intelligence, conduct targeting or perform other functions with their sensors in dangerous airspace. The drones also could be deployed early in a conflict to overwhelm an adversary with numbers, he noted.



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