AHX-1X drone.

  In August last year, the Sukhoi Design Bureau of the United Aircraft Corporation (UAC) said that the Russian Ministry of Defense has approved it to start the production of the S-71 stealth air-launched drone, which will further expand the combat capabilities of the Su-57 fighter after the drone is put into use.

  In March this year, a company under the RTX Group in the United States conducted a test, which was to launch a "coyote" light short-range drone system using a helicopter. This move means that the drone system basically has the function of an air-launched drone.

  These actions by related companies in Russia and the United States are just a microcosm of the development of air-launched drones in countries around the world. In recent years, South Korea, Israel, India and other countries have also joined the ranks of developing air-launched drones. From a global perspective, the acceleration button has been pressed for the research and development of air-launched drones.

  So, what is an air-launched drone? Why are such drones known as "three heads and six arms grown by fighter jets"? In this issue, let us explore its development origin, current situation and prospects.

  From a single-function target aircraft to a multi-powered "clip" of fighter aircraft

  Broadly speaking, air-launched drones refer to drones that are mounted by transport planes, helicopters, fighters, large drones, and other human or unmanned aerial platforms and can be launched in the air.

  In recent years, some countries have also explored the launch of drones with high-altitude balloons, and such air-launched drones are not within the scope of this article.

  In a narrow sense, air-launched drones refer to the "cluster" of fighter jets developed to adapt to the fierce and complex battlefield environment in the future. This kind of air-launched drone has become a hot topic in current research and development.

  Air-launched drones appeared earlier in a broad sense. The "Fire Bee" series of unmanned target aircraft developed in the United States in the 1950s can be classified as this category. This type of target aircraft can be launched with rockets on the ground, or can be launched in the air by a C-130 transport aircraft. However, from today's perspective, this type of air-launched drone has relatively single functions and is basically used as a "wistling stone" and does not directly participate in combat.

  Later, with the advent of the era of information warfare, the danger of performing tasks by some equipment, including people flying platforms, further increased. How to make the flight platform effective in the face of increasingly fierce confrontation and increasing countermeasures has become a concern for all countries.

  The application of a large number of drones in the military field has accelerated this process. On the one hand, the widespread use of drones has brought new threats to manned flight platforms, forcing the latter to accelerate the pace of "evolution"; on the other hand, the development of drones has also provided new ways and new options to reduce the threats to manned flight platforms.

  Driven by modern communications, navigation and positioning, automation technology and new engines, drones can fly higher and farther, and the time to stay in space has also increased accordingly. The development of intelligent air combat technology, especially the fact that the US "Alpha" ultra-visual air combat intelligent program defeated the US Air Force's experienced retired pilot under simulator conditions in 2016, has given people some insight into the potential of air-launched drones in the future battlefield.

  At the same time, the integrated integration capabilities of some countries have been further improved, making drones able to carry sensors with smaller sizes but stronger functions. To this end, the body shape of the drone can be further reduced and can be carried or plugged in the aircraft. The conditions for drones to act as "clusters" of fighter jets have been further matured.

  Against this background, air-launched drones have begun to develop in a real sense and have received attention from more and more countries.

  Effectively expand the scope of manned and large-scale unmanned mother aircraft missions

  For many countries, there is a basic idea for developing air-launched drones, which is to replace manned aircraft and large-scale drone relays to go deep into the battlefield and expand the scope of missions.

  Judging from the current development situation, air-launched drones can indeed perform more tasks and play a role in many aspects.

  Expand the scope of perception. Various threats are increasing in modern battlefields. People's reconnaissance aircraft and large unmanned mother planes usually do not enter the opponent's defense zone to conduct close-up reconnaissance, and the types and quantities of sensors they are equipped with are relatively limited. Therefore, there are certain shortcomings in the accuracy, quantity of targets, the types and capabilities of obtaining intelligence. As a "extended arm", air-launched drones can conduct large-scale, long-term, all-round and high-precision reconnaissance on the battlefield in multiple batches by carrying radar, visible light, infrared sensing equipment, etc., thus forming an effective supplement. In January this year, the US Army issued an information consultation letter, seeking to develop air-launched drones for the special aircraft "Hades", which was modified from Bombardier Global 6500 business jet. The Hades special aircraft is an intelligence reconnaissance aircraft. One of the purposes is to further enhance perception capabilities through the coordination between manned and drones.

  Perform communication relay. Air communication relay is one of the effective means for countries to enhance their communication coverage capabilities. The air communication relay function can be realized by installing a radio signal repeater to the drone. Air-launched UAVs are used for air communication relays with the advantages of flexible deployment and fast networking. When encountering emergencies, they can be quickly launched for communication blindness. In armed conflicts in some hot spots in recent years, some countries have used helicopters and vertical take-off and landing drones as suicide drones and communication relays, which reflects the functions of air-launched drones in this regard.

  Improve the effectiveness of the strike. Although modern advanced fighter jets have certain stealth penetration capabilities, the increasingly perfect air defense system has given air-launched drones a new place to use. Some air-launched drones can be equipped with warheads or rockets to carry out direct strikes. For example, the AHX-1X drone developed by Greece SAS Technology can be carried by unmanned fighters and attack helicopters, and the AHX-1X drone can carry and launch rockets. Some seek to cooperate with manned fighters as "loyal wingmans". For example, the "loyal wingman" project implemented by a US company and the Australian Air Force, the drones developed can use artificial intelligence technology to achieve autonomous flight and coordinate with manned aircraft. Some air-launched drones can form "swarm" attack targets. Russia has tried using helicopter air-launched drone cluster technology and released the "Lightning" swarm drone model in 2021.

  Implement electronic interference. Some air-launched drones can be equipped with electronic interference equipment to suppress opponents’ accusation signals; some can act as electronic bait to confuse the enemy’s integrated air defense system, thereby opening up safe channels for manned aircraft and large unmanned mother aircraft.

  With these mission capabilities that allow fighter jets to develop "three heads and six arms", air-launched drones are accelerating to the battlefield.

  Currently showing a multi-dimensional development trend

  At present, the multi-dimensional development characteristics of air-launched drones are more obvious. Specifically, there are the following aspects.

  The size is relatively small and has high requirements for range. Air-launched drones are deployed and launched by air platforms, which determines that their size cannot be too large. Especially some drones planned for "swarm" operations will have more restrictions on their appearance. However, the positioning born to improve the survivability of manned aircraft and unmanned mother aircraft on the battlefield determines that air-launched drones must be launched by carriers outside the opponent's defense zone in most cases. This is basically the case with the air-launched drones developed by various countries. For example, the "long-range" air-launched drone developed by the United States can continue to fly more than 2,000 kilometers after being launched by manned aircraft, and then launch the missiles it is equipped with.

  We attach importance to both the ability to fight alone and the level of coordination. Whether an air-launched drone can meet higher combat requirements is related to the performance of an air-launched drone. When developing air-launched drones, countries will strive to improve the combat effectiveness of a single drone, such as using stealth design to enhance penetration capabilities, and adopting modular designs to enable them to carry different mission payloads. For example, the Russian S-71 stealth air-launched drone uses a trapezoidal cross-sectional body, which can effectively reduce the radar reflection cross-sectional area. On the other hand, we actively leverage new technologies, especially artificial intelligence, to enhance the coordination capabilities of air-launched drones and other combat platforms. In this regard, the United States started earlier. The country's Altius-600 drone has conducted online "interactive" flight tests, demonstrating certain "cluster" potential.

  Air launch is the main focus, taking into account launches on other platforms. In 2020, the US Army launched the "Air Launch Effect" project to develop two air-launched drones of different heavyweight levels. Later, the project was renamed "Slide Effect". The biggest difference between the front and rear is that the latter emphasizes that such drones can be deployed and launched not only from air platforms, but also from other platforms such as ground platforms. The United States' adjustment of the project name and related practices reflect to a certain extent another characteristic of the development of air-launched drones worldwide, that is, the launch platforms tend to be diversified. For example, the "Coyote" light short-range drone system belongs to the "launch effector" category and can be deployed and launched from air, ground or sea platforms.

  The situations are different in each country and the development progress is different. The current development progress of air-launched drones in various countries is different. Some have been put into use, and some are still under testing; some can only be launched but not recycled, and some have started testing of the recycling process; some can only be mounted at the wings, and some have achieved concealed projection using internal weapons bomb bays. In 2023, the United States tested the A2LE air-launched drone, whose fuselage design allows it to be launched from the internal weapon bomb bay. Another thing worth noting is that the drone adopts a 3D printed body to achieve low cost.

  There are still many technical difficulties before investing heavily in the battlefield

  The accelerated development of air-launched drones is helping drones transform from supporting roles in the battlefield to protagonists. However, if it wants to apply it on the battlefield on a large scale, it still needs to overcome a variety of technical difficulties and have the following capabilities.

  First, optimize and improve the aerodynamic layout. The aerodynamic layout of an aircraft refers to the placement of each wing surface of the aircraft such as the main wing and tail wing. Its types include conventional layout, duck-type layout, tailless layout, three-wing surface layout, variable swept wing layout, etc. One of the conditions for air-launched drones to complete long-distance long-term communication or fire support tasks is to increase the time left to stay. For air-launched drones with relatively small sizes, in addition to using better engines, a more direct way is to optimize and improve the aerodynamic layout, such as choosing high lift-resistance airfoils, large-face wings, or adopting nested wings, small-section drag-reducing fuselages, large-curve thin wing designs, etc., to achieve long-distance high-flying. Some drones such as the AHX-1X can even be used as gliders after adopting new aerodynamic layouts.

  The second is to improve flight control capabilities in complex environments. At present, some countries are seeking to launch drones from higher aerial platforms, while others are trying to achieve low-altitude and ultra-low-altitude drops of air-launched drones. The variety and rapid changes in the application environment require air-launched drones to further improve their environmental adaptability. For example, when launching air-launched drones from high altitude, the influence of the cold environment needs to be considered; when deploying air-launched drones from helicopters, they will be affected by many factors such as the under-rotor scrubbing airflow. After launch, how to quickly unfold the wings and establish a stable navigation sensing signal connection, and how to independently enter a stable cruise flight state are all technical problems that must be solved.

  The third is to explore and strengthen cluster collaboration capabilities. The application of air-launched drones is to expand the perception and strike range of the master, and autonomous information interaction with the master is essential. Only by constantly exploring and strengthening its synergy with the mother machine can its full role be fully utilized. At the same time, in a high confrontation environment, only by continuously improving the autonomous flight capabilities can it ensure that it survives on the battlefield for a long time; by continuously improving the level of autonomous networks, it can play to its strengths and avoid its weaknesses, and effectively make up for the insufficient load capacity of a single overhead drone. How to fully utilize artificial intelligence and make breakthroughs in this regard is also a topic that R&Ds in various countries must face.

  In addition, although many air-launched drones are positioned as one-time consumption equipment, people still hope to fully or partially recover air-launched drones for the sake of cost reduction. Especially the safe recycling and redeployment of air-launched drones in the air have become the focus of research and development in some countries.

  Only by solving these problems can air-launched drones enter the battlefield in large quantities and play a role. (Zhang Hui, Zhou Maofeng, Zhang Xinyue)

[Editor in charge: Wang Jinzhi]