Evolution of Collaborative Combat Aircraft - a brief review

The Department of the Air Force (DAF) is defining the Next Generation Air Dominance (NGAD) Family of Systems (FoS), which will incorporate uncrewed aircraft operating alongside the DAF’s fifth or sixth generation crewed fighter. Multiple uncrewed aircraft will take commands from a fighter pilot in the crewed platform, operating semi-autonomously in a Collaborative Combat Aircraft (CCA) approach. The uncrewed aircraft will be a combat aircraft employing a distributed, mission-tailorable mix of sensors, weapons and other mission equipment. They will be significantly less expensive than the crewed platform so that they might potentially be used as attritable assets. To realize the CCA concept with acceptable pilot workload, the uncrewed aircraft will need to be semi-autonomous, taking high level direction from the pilot and then autonomously implementing this direction. Recent advances in artificial intelligence (AI) and machine learning are believed to enable this approach. Research programs at the Air Force Research Laboratory, the Defense Advanced Research Projects Agency, and elsewhere have demonstrated some of the needed capabilities. There are also commercial systems, notably self-driving cars, demonstrating some of these technologies. The DAF will benefit from a study that examines potential CCA concepts of operations (CONOPs) and concepts of employment (CONEMPs) for NGAD, determines technology requirements associated with these CONEMPs and evaluates enabling technologies to understand what capabilities could be credibly achieved in the near-term future and in the longer term. 21

The United States has a number of unmanned aircraft systems (UAS) operating across the military services. These aircraft have demonstrated their ability to perform many types of missions and may perform more complex missions in the future. Congress will likely debate and decide whether and how to allocate funds for military UAS in its yearly appropriations and authorization activity, as well as evaluate them more broadly in its oversight role.

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The U.S. military typically refers to remotely piloted vehicles (RPVs) as unmanned aircraft vehicles (UAVs). UAVs are either a single air vehicle (with associated surveillance sensors) or a UAV system, which typically consists of an air vehicle paired with a ground control station (where the pilot actually sits) and support equipment.3 With the FY2023 President’s budget, the Air Force has begun to use the term “uncrewed” to describe remotely piloted or unmanned aircraft systems.4 The Air Force made this distinction defining all aircraft flying without an aircrew onboard after it started developing optionally crewed aircraft, like the B-21 Raider. An emerging class of UAS is loitering munitions—also called “kamikaze drones”—which serve as a single-use aircraft flying for extended periods of time (from dozens of minutes to potentially hours) that can observe and engage targets. This report uses the terms crewed and uncrewed to distinguish between different types of aircraft, and the term UAS for the broader system.

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The Collaborative Combat Aircraft (CCA) program being pursued by the US Air Force (USAF) is a multi-faceted program to design, test, develop and implement new autonomous and manned and unmanned aircraft teaming concepts. It is intended to rapidly deploy large numbers of autonomous unmanned aircraft, officially designated as CCAs, to team with the fifth or sixth-generation manned fighter aircraft, as part of the USAF’s wider Next-Generation Air Dominance (NGAD) program that envisions a system-of-systems approach with the next-generation fighter aircraft, weapons, sensors, networking, and battle management systems to maintain air superiority in the coming decades. Deploying collaborative, mission-focused CCAs at a large scale is seen as a cost-effective and pragmatic solution to possess a formidable airpower capacity in response to proliferating hostile stealth fighters. 15

The US Air Force is the lead component for the development of CCAs. This program is seeking to create the capacity to deploy a significant number of semi-autonomous unmanned aircraft, CCAs, to team with, or collaborate, with fifth and sixth generation manned combat aircraft as part of the Next-Generation Air Dominance (NGAD) program. 12 The initial plan is to acquire 1,000 CCAs. The service arrived at the number by assuming that two of the uncrewed jets will accompany each of an initial tranche of 200 NGAD fighters and 300 F-35 fighters. This is an approach that integrates multiple systems, or a system-of-systems, to create a more flexible and comprehensive response aimed at maintaining air superiority against near-peer adversaries. 13

Over the past decades, military forces have used UAS to perform various tasks, including:

??????? Intelligence, surveillance, and reconnaissance;

??????? Close air support;

??????? cargo and resupply; and

??????? communications relay.

Analysts and DOD argue that UAS could replace crewed aircraft for a number of missions, including:

??????? aerial refueling;

??????? air-to-air combat;

??????? strategic bombing;

??????? battle management and command and control (BMC2);

??????? suppression and destruction of enemy air defenses; and

??????? electronic warfare (EW).

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Origins of Unmanned Aerial Systems

Throughout its century-long history, combat aviation has always been manned. However, it is less well known that the development of unmanned aerial vehicles (UAV) commenced almost in parallel, with early prototypes dating back to World War 1. In World War 2, planes laden with explosives were guided by remote control for high-precision bombing. 2 The Cold War period saw limited development of UAVs, which were used for secondary roles in support of manned aerial combat vehicles. These uses mainly comprised actions against aerial targets although they were used occasionally also for high-risk intelligence, surveillance, target acquisition and reconnaissance (ISTAR). The development of UAVs for military purposes has been stepped up in the last two decades, spurred largely by their use in the fight against terrorism and insurgency in conflicts that followed the September 11 attacks. Armed drones offer advantages such as persistence over the theater of operations, a shorter sensor-to-shooter chain, and lower political costs compared to manned aircraft. 3

Radio control (1900 to 1920)

Unmanned aerial vehicles (UAVs) are aircraft with no on-board crew or passengers. They can be automated ‘drones’ or remotely piloted vehicles (RPVs). In 1898 The First Radio-Controlled Craft, developed by Nikola Tesla, was a radio-controlled boat used as a demonstration for a crowd in Madison Square Garden. The craft could respond to directional signals sent to it by Tesla and could also flash its lights. Some of the audience members thought Tesla was a magician or had the power of telekinesis. Others believed a trained monkey was inside the small boat. It was a compelling demonstration of what would evolve into radio-controlled aircraft. The first pilotless vehicles were developed in Britain and the USA during the First World War. Britain’s Aerial Target, a small radio-controlled aircraft, was first tested in March 1917 while the American aerial torpedo known as the Kettering Bug first flew in October 1918. Although both showed promise in flight tests, neither were used operationally during the war.

Expansion during the Interwar period (1920 - 1938)

During the Interwar Period, the development of unmanned aircraft was impacted by several advancements in the aviation world. These advancements included the rapid growth of the aviation industry, specifically in the air transport sector. This growth hampered testing and operating unmanned systems and continues to do so today. Advancements in radio furthered development and fielding of radio-controlled aircraft. And, finally, the successful demonstrations of aircraft against capital ships off the Virginia Capes in June 1921 stressed the need for development of radio-controlled target drones for use in fleet training exercises. In 1935 the British produced a number of radio-controlled aircraft to be used as targets for training purposes. It's thought the term 'drone' started to be used at this time, inspired by the name of one of these models, the DH.82B Queen Bee. Radio-controlled drones were also manufactured in the United States and used for target practice and training. 4

World War 2 acceleration (1939-1945)

Upon entry into the war, naval forces in Europe submitted an urgent operational need for a weapon that could be flown into the reinforced U-boat pens along the coast of France. In the South Pacific, the Navy searched for a weapon that could be used to suppress the Japanese defenses of Rabaul. Meanwhile, the Army’s Eighth Air Force attempted to develop a similar weapon that could be used to strike heavily defended strategic targets in mainland Europe, specifically facilities supporting the testing and use of Germany’s so-called “Vengeance Weapons”—the V-1 flying bomb, V-2 rocket, and V-3 cannon. However, as in WWI, these efforts were uncoordinated and mired in intra- and interservice politics, resulting in limited operational success. 5

Post WW2 Advances, Korea through Vietnam (1946 - 1990)

Reconnaissance UAVs were first deployed on a large scale in the Vietnam War. Drones also began to be used in a range of new roles, such as acting as decoys in combat, launching missiles against fixed targets and dropping leaflets for psychological operations. In 1952 the Guided Missile Unit 90 (GMU-90) with six F6F-5K Hellcat drones carried a 1000-pound bomb under the fuselage and a television and radio repeater pod mounted on the wing, took off under radio control from the USS Boxer and, under the radio control of Douglas AD-4N Skyraiders from Composite Squadron 35 (VC-35), were guided against selected targets. In all, six such missions were conducted between 28 August and 2 September 1952 against power plants, rail tunnels, and bridges in North Korea, but with an operational success rate of less than 50 percent, the program was dropped. The Hellcats continued to be used by the Navy as targets at China Lake, California, into the 1960s. 6

Ryan Aeronautical Company developed and built 32 jet-propelled, subsonic UAVs known as Ryan “Firebees.” The Firebee design lives to this day and has dominated UAV history. The Firebee UAV (originally designated Q-2A/B) dates to 1951 and was used initially as a target drone. The political fallout of Francis Gary Powers being shot down over the USSR in his U-2 in 1960 led many in the DoD to start thinking about unmanned reconnaissance of the USSR. Ryan Aeronautical modified some of its standard Firebee training targets into reconnaissance UAVs (recon-UAVs) and designated them the 147A “Firefly.” The Firefly, renamed the “Lightning Bug,” was modified considerably to change it from a target drone to a recon-UAV. In the early 1960s, Ryan Aeronautical Company designed and developed more than 20 versions of its famous Lightning Bug unmanned subsonic target drone. One model, the AQM-34N, had wet wings, meaning that it carried fuel in its wings, giving it a range of approximately 2500 miles. The Vietnam War was America’s first “war” that saw extensive use of UAVs. A total of 3435 operational reconnaissance UAV missions were flown between 1964 and 1975.1 Approximately one-third of these missions were various versions of the Lightning Bug, which was the workhorse of Vietnam-era UAVs. Between 1967 and 1971, 138 missions were launched from DC-130 aircraft and flown via remote control in hostile territory. Many were recovered via the MARS (midair retrieval system), which was a specially equipped H-53 helicopter that caught the drone while in its parachute descent. 7

Following the Vietnam War other countries outside of Britain and the United States began to explore unmanned aerial technology. New models became more sophisticated, with improved endurance and the ability to maintain greater height. In recent years models have been developed that use technology such as solar power to tackle the problem of fueling longer flights.

UAV development basically ceased for about a decade following Vietnam. In the late 1970s, the U.S. Army began a major UAV acquisition effort known as Aquila. It was originally estimated to cost $123 million for a 4-year development cycle, followed by $440 million for the production of 780 vehicles. Its original mission was to be a small propeller-driven, man-portable UAV that provided ground commanders with real-time battlefield intelligence. As development continued, requirements grew and the UAVs small size could no longer handle the avionics and payload items the Army wanted, such as autopilot, sensors to locate the enemy in all conditions, laser designators for artillery projectiles, and abilities to survive against Soviet anti-aircraft artillery. The Army abandoned the program in 1987 because of cost, schedule, and technical difficulties (and after $1 billion in expenditures).

The Gulf Wars, the Drone explosion, Network-centric Warfare and Sensor Fusion (1990 - 2010)

Notable milestones:

·??????? 1986 saw the RQ2 Pioneer Drone, developed by the U.S. and Israel jointly, become one of the most successful UAV platforms to date. The system was an upgraded IAI Scout drone and featured significant payload improvements. During the Gulf War, some Iraqi forces even surrendered to a Pioneer UAV.

·??????? 1991 UAVs Fly 24/7 During the Gulf War the first time in a major conflict, at least one drone was airborne from the conflict’s start until its conclusion.

·??????? 1996 The Predator Drone is developed by Abraham Karem. This platform brought weaponized drones to the battlefield. Probably more than any other UAV, the Predator created the public image of drones striking targets around the world.

·??????? 2006 UAVs Permitted in US Civilian Airspace for the first time. Following the devastation caused by Hurricane Katrina, the FAA allowed UAVs to fly in civilian airspace for search & rescue and disaster relief operations. Predator drones with thermal cameras were able to detect the heat signatures of humans from up to 10,000 feet away. Around this time, the consumer drone industry began to really take shape.

·??????? 2008 Network-centric warfare (NCW) is defined as an information-superiority enabled concept of operations that generates increased combat power.

The NCW objective is to achieve:

·??????? shared awareness,

·??????? synchronized forces,

·??????? increased speed of command,

·??????? faster tempo of operations,

·??????? greater lethality, greater survivability, and

·??????? a degree of self-synchronization by networking sensors, decision makers, and shooters.

NCW translates information superiority into combat power by effectively linking dispersed entities in the battlespace. Having a better, near-real time picture of what is happening in the battlespace reduces the level of uncertainty—the gap between what a commander needs to know and does know—in a meaningful way.

Furthermore, NCW has the potential to contribute to the merging of the tactical, operational, and strategic levels of war.

2009 Cooperative Engagement Capability achieves full operational capability (FOC) with the US Navy Within the context of NCW, UAVs (now termed Unmanned Aircraft Systems (UAS)) provide a tactical and strategic ISR capability into the theater by providing real-time, full-motion video (FMV), imagery, and sensor information to the commanders, significantly increasing their overall situational awareness. Traditionally used as an ISR asset, UAS now provide additional battlefield functions such as strike capabilities, air interdiction, and aerial communications relay. There is almost no limit to UAS’ capabilities, a fact recognized by both the Combatant Commands and the separate military service departments.10

CCA theory and Swarming theory (2010 - 2024)

Swarming theory CCAs will bring the capability to apply Swarming or Swarm Theory to future combat scenarios in highly contested environments. Swarming occurs when several units conduct a convergent attack on a target from multiple axes. Case studies of swarming, ranging from Scythian horse archers in the fourth century BC to Iraqi and Syrian paramilitaries in Baghdad in 2003, can be used to understand:

·??????? swarm tactics and formations,

·??????? the importance of pulsing, and

·??????? the general characteristics of past swarms.

Some considerations under swarm theory:

·??????? command and control,

·??????? communications,

·??????? home field advantage,

·??????? surprise,

·??????? fratricide,

·??????? training.

There are five primary variables most important to successful swarming:

1.????? superior situational awareness,

2.????? elusiveness,

3.????? standoff capability,

4.????? encirclement,

5.????? simultaneity.

The future of CCA Fusing multiple sensor/shooter platforms, CCAs and Command and Control (C2) requires a significant amount of data and analysis which requires advanced applications such as machine learning (ML) and Artificial Intelligence (AI) to maintain an agile combat employment advantage. ((14)) In addition, DOD is developing several experimental concepts—such as aircraft system-of-systems, swarming, and lethal autonomous weapons—that explore new ways of employing future generations of UAS.

What is being done to increase trust in collaborative combat aircraft?

There is a widespread expectation that Artificial Intelligence (AI) and machine learning technologies will revolutionize warfare. For example, the National Security Commission on Artificial Intelligence has stated that “Our armed forces’ competitive military-technical advantage could be lost within the next decade if they do not accelerate the adoption of AI across their missions.” AI technology development and transition are key. However, there is intense concern, societal and in the Department of Defense, about ethical issues associated with replacing human judgement with AI. In commercial industry, this concern has been reflected by the development of RAI principles and tool sets. While AI is broadly applicable across the Department of the Air Force (DAF), the use of AI during combat engagements, including in particular the use of semiautonomous combat air vehicles, is an area of particular concern. The DAF must ensure its systems and personnel comply with laws and with American values.

Creating trust in Collaborative Combat Aircraft (CCA), the next generation in autonomous unmanned air vehicles (UAV), is essential to maximize performance for both CCAs, and the manned aircraft they will collaborate with, to accomplish complex, high-risk missions. The US Air Force is the lead service and Program Executive Office (PEO) for NGAD and the supporting CCA programs. To achieve the full potential of human-CCA teams and build trust in the reliability and viability of CCAs, the Air Force needs to consider the following five imperatives for CCA development:

1.????? Optimize the composition of human-CCA teams based on each teammate’s strengths.

2.????? Include operators in CCA development and provide them with the tools they will need to understand how CCA should perform in the battlespace.

3.????? Ensure warfighters can trust and depend on CCA Autonomy.

4.????? Ensure warfighters can maintain assured control over CCA in highly dynamic operations.

5.????? Ensure teaming workloads are manageable for humans. 2

A program that is specifically focused on the trust aspect of CCA development is the ACE program. The Air Combat Evolution (ACE) Full-Scale Aircraft TA-4 project seeks to increase trust in combat autonomy using human-machine collaboration in aircraft dogfighting. The ACE project relies heavily on artificial intelligence (AI) and machine autonomy in complex air combat maneuvering that involves manned aircraft and combat unmanned aerial vehicles (UAVs). 3 This also serves as an entry point into complex human-machine collaboration.

·??????? ACE will apply existing artificial intelligence technologies to the dogfight problem in experiments of increasing realism.

·??????? In parallel, ACE will implement methods to measure, calibrate, increase, and predict human trust in combat autonomy performance.

·??????? Finally, the program will scale the tactical application of autonomous dogfighting to more complex, heterogeneous, multi-aircraft, operational-level simulated scenarios informed by live data, laying the groundwork for future live, campaign-level Mosaic Warfare experimentation.

A precursor to ACE, the AlphaDogfight Trials (ADT) program was created as a risk-reduction effort for the larger program. This competition-based activity sought to answer three core questions:

1.????? Is it possible to teach an AI algorithm to perform within-visual-range air combat?

2.????? Can we engage a diverse set of companies, including those that are not traditional defense contractors, to capture innovative AI concepts?

3.????? Can a novel program structure accelerate the development of new AI technologies and applications? 16

The technology development on the ACE program addresses four primary challenges:

1.????? Increase air combat autonomy performance in local behaviors (individual aircraft and team tactical)

2.????? Build and calibrate trust in air combat local behaviors

3.????? Scale performance and trust to global behaviors (heterogeneous multi-aircraft)

4.????? Build infrastructure for full-scale air combat experimentation ?

ACE aims to enable a pilot to handle a broad, global air command mission while his aircraft and unmanned aircraft team members attack enemy aircraft and ground targets. ACE will have the human pilot handle complicated jobs like developing an overall engagement strategy, selecting targets, and choosing weapons, and enable the combat UAVs to handle aircraft maneuver and engagement tactics. ((6)) This comprehensive approach to CCA development and building trust into the process up front is critical to the future of air dominance and security for the US and its allies.17

Combat lessons learned indicate an urgent need for reconnaissance, early warning and security. Compelling logic infers that unmanned systems operating collaboratively could provide significant operational flexibility and soldier survivability in meeting this need. This collaborative capability, when combined with the ability for near real-time engagement of identified high value targets, offer prospects for immediate payoff to operational forces. Collaborative behavior is defined as unmanned systems working together to accomplish predefined mission(s) with minimal human operator intervention. The main characteristic of collaboration includes the ability for unmanned systems to work as a team, command one another, pass information directly to each other, and make changes to their missions based on that information while being monitored by a human operator. Few systems have operational requirements documents that specify collaboration, but all signs point to the need for this capability in the near future. There has been a significant increase in development of unmanned systems, each one utilizing a different control system. These unmanned systems will be integrated with manned units and eventually provide lethal engagement capabilities. There must be a technology focus that unloads the burden of low-level control away from the warfighter so that the focus can be on ensuring that the data received from and the capabilities provided by unmanned systems are effectively utilized in the accomplishment of the mission.14

A publication by Fan, Li and Li states there is a limitation currently because the intelligent systems of UAVs cannot replace human thinking and judgment, UAVs cannot easily perform complex combat missions independently.16 Therefore, a mode of collaborative combat of manned/unmanned aerial vehicle (MAV/UAV) has emerged. The collaborative combat systems of MAV/UAV make full use of the advantages of UAVs, such as their low cost, zero life risk, strong maneuverability, and powerful survival ability,17 which compensate for their disadvantages, such as their low intelligence and weak ability in handing emergencies. Collaborative combat systems reduce the cost of using manned aircrafts to execute dangerous tasks and changes in air combat patterns. The collaborative combat capability of MAV/UAV in systemic confrontation has been significantly improved in the information age.

The latest iteration of this development is the Skyborg vanguard program which is placing AI based control systems on UAS’s in a controlled test environment and seeing how the system responds to variables and inputs while maintaining a prescribed mission profile. The goal is to field the first tranche of CCAs by the end of fiscal 2028. In fiscal 2024-2028, the service intends to invest about $5.8 billion in R&D for collaborative combat aircraft, plus another $400 million or so for an experimental operations unit and an autonomy test bed that will support the initiative. Concept exploration, integration studies, technology risk reduction and prototyping are slated to begin in the first quarter of fiscal 2024 and run through the end of fiscal 2028 — the last year covered in the newly released budget justification documents. The Air Force is requesting $392 million for the main CCA budget activity line in fiscal 2024. Annual funding would ramp up to more than $3 billion in fiscal 2028. Meanwhile, a new Experimental Operations Unit program will focus on doctrine, organization, training, materiel, leadership, personnel, facilities, and policy concepts related to the CCA drones.15

A significant factor in any autonomous engagement is accurately identifying the tactical intention of the target can facilitate the prediction of the opponent’s behavior and improve the efficiency of collaborative decision. We have observed that traditional methods could achieve high recognition rate on conventional tactical intent. Nevertheless, their performance would deteriorate seriously when recognizing cooperative tactical intention in a multi-aircraft air combat environment. The main reason resides on key features that are difficult to extract for traditional methods.13

When studying collaborative combat systems, the primary objective is to establish and describe the collaborative combat architecture. A reasonable model can greatly influence the results of scientific research. However, simply building a model and using the results to guide actual operations can be ineffective, and the results must be evaluated. For any weapon system, such evaluations are part of modern military operations. Research on the modeling and evaluation of MAV/UAV collaborative combat systems is the cornerstone of research on complete collaborative combat systems. Such research provides a quantitative decision basis for military development and the procurement of new aircraft types. Moreover, the findings form a reliable basis for the research of combat guiding concepts and tactics.

According to Jie-ru?Fan et. al., in a collaborative combat system, each combat or detection unit can be regarded as a node of the network. Complex network theory is used to create an abstract model of MAV/UAV collaborative combat. Through analysis and evaluation, the architecture of the collaborative combat approach can be derived. The prominent feature of scale-free complex networks is that they are incredibly resilient to unexpected errors. That is, the unexpected faults of some random nodes will negligibly affect the normal operation of the network. However, when important nodes are destroyed, the network will become very fragile.?11

The Air Force hopes to install the Skyborg autonomy core system in a wide array of unmanned aerial vehicles. The idea is for the ACS to steer armed drones with minimal human control to avoid task saturation of the human operators.

The Air Force’s Skyborg team flew two General Atomics MQ-20 Avenger stealth drones on the “multi-hour” Oct. 26 flight over California. One of the Avengers was the standard model of the subsonic, jet-powered stealth drone with a 66-foot wingspan. The other was an extended-range model with a longer fuselage and a 76-foot wing.

Five vendors are currently in the running for an early stage of the program — Boeing, General Atomics, Lockheed?Martin, Northrop Grumman and Anduril.

References:

1. Keane, J. F., Carr, S. S., A Brief History of Early Unmanned Aircraft (2013), ??https://secwww.jhuapl.edu/techdigest/Content/techdigest/pdf/V32-N03/32-03-Keane.pdf

2. Penney, H. R., Five Imperatives for Developing Collaborative Combat Aircraft for Teaming Operations, (2022), https://mitchellaerospacepower.org/wp-content/uploads/2022/10/Five-Imperatives-for-Developing-Collaborative-Combat-Aircraft-FINAL.pdf.

3. DeMay, C. R., White, E. L., Dunham, W. D., Pino, J. A., AlphaDogfight Trials: Bringing Autonomy to Air Combat, (2022), ?https://secwww.jhuapl.edu/techdigest/content/techdigest/pdf/V36-N02/36-02-DeMay.pdf.

16. DeMay, AlphaDogfight

17. DeMay, AlphaDogfight

4. Sayler, K. M., DeVine, M. E. (2022) Unmanned Aircraft Systems: Roles, Missions, and Future Concepts. R47188 CRS, https://crsreports.congress.gov/product/pdf/R/R47188. ?

5. DAF Scientific Advisory Board, FY 2022 Study, Collaborative Combat Aircraft for Next Generation Air Dominance, https://www.scientificadvisoryboard.af.mil/Portals/73/DAF%20SAB%20FY22%20Study%20ToRs_SecAF%20Final.pdf.

6. Blom, D. J., Unmanned Aerial Systems: A Historical Perspective (2010), https://www.armyupress.army.mil/Portals/7/combat-studies-institute/csi-books/OP37.pdf?

7. Clark, R. M., Uninhabited Combat Aerial Vehicles, (2000), ?https://apps.dtic.mil/sti/pdfs/ADA382577.pdf?

8. Liersch, C. M., Cummings, R., & Schütte, A. (2022). NATO STO/AVT-251: A Joint Exercise in Collaborative Combat Aircraft Design.?NATO STO Review.

9. Sweetman, B. (2024). THE NEED FOR COLLABORATIVE COMBAT AIRCRAFT FOR DISRUPTIVE AIR WARFARE.

10. Fan, J., Li, D., & Li, R. (2018). Evaluation of MAV/UAV collaborative combat capability based on network structure.?International Journal of Aerospace Engineering,?2018, 1-12.

11. Fan, J. R., Li, D. G., Li, R. P., & Wang, Y. (2020). Analysis on MAV/UAV cooperative combat based on complex network.?Defence Technology,?16(1), 150-157.

12. Sun, L., Zhang, J., Chang, J., Fu, Z., & Zou, J. (2021). The evaluation of effectiveness for the collaborative combat of an unmanned aerial vehicle based on grey minimum entropy.?Journal of Aerospace Technology and Management,?13, e3021.

13. Guanglei, M., Runnan, Z., Biao, W., Mingzhe, Z., Yu, W., & Xiao, L. (2021). Target tactical intention recognition in multiaircraft cooperative air combat.?International Journal of Aerospace Engineering,?2021, 1-18.

14. Mullens, K., Troyer, B., Wade, R., Skibba, B., & Dunn, M. (2006, May). Collaborative engagement experiment. In?Unmanned Systems Technology VIII?(Vol. 6230, pp. 292-302). SPIE.

15. Harper, J. (2023), Air Force plans to spend more than $6B on CCA drone programs over the next 5 years, Defense Scoop, https://defensescoop.com/2023/03/20/air-force-plans-to-spend-more-than-6b-on-cca-drone-programs-over-the-next-5-years/

18. H. Liu, X. Wei, Z. Fu, and Z. Zhou, “Cooperative task assignment of manned/unmanned aerial vehicle formation in air combat,” Electronics Optics & Control, vol. 20, no. 6, pp. 16– 19, 2013.

19. X. L. Ma, Y. Y. Lei, Y. Q. Sun, and D. X. Liu, “Key technologies for cooperation of MAV/UAVs in air to ground attaching,” Electronics Optics & Control, vol. 18, no. 3, pp. 56–60, 2011.