Silence is Golden: Stealth Drone Strategies and Developments

The landscape of stealth drone technology is rapidly evolving, with several countries and companies pioneering disruptive technologies and innovative deployment strategies.

A string of nations - including the 'usual suspects' - are heavily investing in stealth drone technology, driven by the need for advanced surveillance, reconnaissance, and combat capabilities.

Who is ahead of the game?

The United States is at the forefront, with significant investments in developing and deploying stealth drones. The U.S. Department of Defense operates a vast fleet of drones, including advanced models from Northrop Grumman such as the B-21 Raider and X-47B, which have demonstrated capabilities such as autonomous aerial refueling and carrier-based operations.

The US has signaled a potential strategic pivot from legacy intelligence, surveillance and reconnaissance (ISR) systems to more advanced platforms leveraging new technologies like space-based assets and stealth drones. The moves reflect a US strategic shift toward more survivable and modern ISR systems in the face of increasing threats from adversaries’ air defenses, particularly from China and Russia. The War Zone says the new ISR approach likely emphasises distributed concepts and advanced computing to collect and prioritise critical data for near-real-time exploitation. It notes that if the RQ-180 continues to receive government funding, it could serve multiple roles including electronic attack and data-sharing, and represents a move away from legacy platforms deemed too vulnerable for modern warfare. Recent US drone losses in Yemen may have exposed the limitations of legacy drones like the MQ-9, whose design and basic technologies date back to the 1990s. Those losses have likely prompted the US to reconsider its strategies for developing and using drones. In June 2024, Asia Times noted the US had lost several MQ-9 Reaper drone losses to Yemen’s Houthi rebels, whose basic air defense systems managed to shoot down the costly drones. Stealthier and more survivable drones such as the RQ-180 could enable the US to enhance the ISR capabilities of its allies.

Shield AI's V-BAT is a next-generation UAS that combines advanced AI with a unique ducted-fan design. This design enhances thrust and stability, making it highly effective in various environments, including maritime and high-threat areas. The V-BAT's ducted-fan technology increases thrust by over 80% at equivalent engine power, allowing for efficient takeoff and landing in confined spaces. Additionally, the V-BAT Teams can operate autonomously in swarms, using Shield AI's Hivemind software to execute missions without GPS or communication guidance. This makes it ideal for maritime domain awareness, monitoring and securing maritime borders, and for the suppression of enemy air defenses by using swarms to overwhelm and neutralise threats.

Northrop Grumman's X-47B is an experimental unmanned combat air vehicle (UCAV) that has demonstrated autonomous aerial refueling and carrier-based operations. The X-47B is capable of taking off, landing, and refueling autonomously, and features low observable design elements to evade detection. It extends the reach of naval air power through carrier-based operations and can conduct precision strikes without human intervention.

Northrop is also lead Prime on the (DARPA) flying-wing drone project featuring hybrid electric propulsion that converts fuel to electricity. The XRQ-73’s maiden flight is expected by the end of this year, and is a trail blazer in the four-year-old Series Hybrid Electric Propulsion AiRcraft Demonstration (SHEPARD) program.

Boeing's MQ-25 Stingray is an unmanned aerial refueling aircraft designed to extend the range of manned aircraft by providing in-flight refueling. The MQ-25 increases the operational range of carrier-based aircraft and features stealth elements to minimise its radar cross-section. It enhances the endurance and reach of manned aircraft, supporting stealth missions with minimal risk of detection.

In Europe, the United Kingdom is investing heavily in the Tempest stealth drone project, set to debut in 2035. France and Germany are collaborating on a significant stealth drone programme, reflecting a broader European interest in developing advanced unmanned systems, incorporating BAE Systems, Rolls Royce, Leonardo and MBDA. Tempest could be the last fighter jet that will need a human pilot to fly it. Air Commodore Martin Lowe, the programme director of the Future Combat Air System, spoke on the Forces News Sitrep podcast in May 2024. While he does not yet believe "we're quite ready to have a fully uncrewed system," that is the plan for the future.

Other countries, including Israel, South Korea, and Japan, are also making substantial investments in stealth drone technology. Israel, known for its advanced drone technology, continues to innovate and export drones globally. South Korea plans to deploy a fleet of stealth drones by 2030, while Japan's Ministry of Defense has allocated significant funds for stealth drone research

Russia has been developing decoy drones designed to mimic the radar and infrared signatures of larger aircraft. These drones are used to deceive enemy air defenses, drawing fire away from more valuable assets. Decoy drones replicate the radar and thermal signatures of manned aircraft and are relatively inexpensive, allowing for mass deployment. They are particularly useful in deception operations, drawing enemy fire and depleting their missile stocks, and in electronic warfare, disrupting enemy radar and communication systems. Russia is also investing in stealth drones, with developments such as the Okhotnik, which has completed multiple test flights. These drones are designed to complement manned aircraft and enhance Russia's strategic and tactical capabilities

China's CH-7 is the latest stealth drone designed for high-altitude, long-endurance missions. It features a flying wing design similar to the US B-2 Spirit, which helps reduce its radar cross-section. The CH-7 is capable of operating at altitudes where it is less likely to be detected, making it suitable for strategic reconnaissance, gathering intelligence over long distances, and precision strikes, conducting targeted attacks with minimal risk of detection. China's focus on stealth technology is part of its broader strategy to enhance its military capabilities and assert its presence in the Indo-Pacific region. The development of naval capabilities including drone carriers has to be an integral part of China’s multi-domain strategy.

These examples highlight the diverse strategies and technologies being developed to enhance the capabilities of stealth drones. From autonomous swarming and advanced propulsion systems to decoy tactics and high-altitude reconnaissance, the field of stealth drone technology is poised for significant advancements. Importantly, stealth innovation spans the spectrum of weight and endurance classes. These innovations not only improve the effectiveness of military operations but also pave the way for new applications in surveillance, electronic warfare, and beyond.

Not just 'big birds'

At the other end of the specturm stealth doesn't have to be defined by size. It is, in essence, a state of mind; how the drone is deployed as much as the phyical attributes.

Edge Autonomy's VXE30 Stalker is a quiet small uncrewed aircraft system (SUAS) and provides long-endurance, long-range mission support in a wide variety of environments. Network-based avionics support multiple payloads simultaneously, rapid payload integration, and allow for configuration flexibility. The vehicle performs fully autonomous Vertical Take Off and Landing (VTOL) with no operator input required. Using either a solid oxide fuel cell (SOFC) or a rechargeable battery, the VXE30 Stalker provides the endurance needed to complete complex aerial operations.?

The Black Hornet Nano is a military micro unmanned aerial vehicle (UAV) developed by Prox Dynamics AS of Norway (acquired by Teledyne Flir), and in use by the armed forces worldwide. The drone measures around 16 × 2.5?cm (6 × 1?in) and provides troops on the ground with local situational awareness. It is small enough to fit in one hand and weighs 18?g (0.7?oz) with its battery.

The Nebraska Intelligent MoBile Unmanned Systems, or NIMBUS, Lab is developing a drone system capable of delivering underground sensors to remote or hostile locations. It’s a partnership with the University of Nebraska’s National Strategic Research Institute. Project leader Carrick Detweiler’s team aims to help the U.S. military monitor enemy weapon caches and perimeters by sending drones to plant sensors. The sensors will wirelessly communicate movement, increasing surveillance capabilities and reducing risks to soldiers.“There’s a lot of pieces in this project,” said Detweiler, associate professor of computer science and engineering. “We’ve really had to focus on robustness and reliability at every stage of the system.” One major challenge was developing a drone and payload system light enough for long-distance travel yet capable of drilling, which requires downward force. Clever engineering and optimized materials overcame a drone prone to spinning instead of drilling. Another challenge: The drone must be launched midair, such as from a larger drone or airplane. Researchers designed a system that can deploy and shed a parachute, spread its rotors and complete the mission. “We’ve had to make it generic enough so that it can hitch a ride on any vehicle,” Detweiler said. “Basically, if they throw it out the door, it has to be able to recover and get to the right place.” Stealth is also key. His team is working on a camouflaged exterior and less noticeable flight path, among other approaches. Finally, failure is not an option. If the drilling drone gets stuck, it’s irretrievable and exposed. The team developed algorithms to abort or try a new spot within seconds if success is unlikely.

Top Five Elements Fundamental to the Development of Stealth Drone UA Systems

The development of stealth drone Unmanned Aerial Systems (UAS) involves several critical elements that ensure these drones can operate undetected and efficiently. The growing polarization of geopolitics is leading to indigenous manufacturing and sourcing of materials, components, engines, and systems by both the US and China. In the case of the US, it is anticipated that NATO will follow the US lead, banning non-Western components. Recent regulations reflect this shift towards self-reliance and security in supply chains.

1.?????? Shape shifting aerodynamics

One of the fundamental elements is low observable airframe design. Stealth drones must have airframes designed to minimise radar, infrared, visual, and acoustic signatures.

This involves using materials and shapes that absorb or deflect radar waves, reduce heat emissions, and minimise noise. Leading players in this field include Lockheed Martin, known for its advanced stealth technology in military aircraft, and Northrop Grumman, developer of the B-2 Spirit and other stealth UAVs. These designs are crucial for military surveillance, allowing drones to gather intelligence without being detected by enemy radar, and for covert operations where undetected entry and exit are essential. The development of new composite materials that can further reduce radar cross-section (RCS) and thermal signatures will revolutionise stealth capabilities.

2.????? Silent power

Another critical element is propulsion technology. Efficient and quiet propulsion systems are essential for stealth drones to avoid detection.

This includes engines that produce minimal heat and noise. Leading players in this area include ePropelled, which specialises in electric propulsion systems and is pioneering hybrid integration and high speed electric propulsion systems for the new generation of drones. Integrated power technologies that support hybrid propulsion systems – cooperatively combining electric motors and internal combustion engines — are rapidly expanding uncrewed vehicles’ capabilities, not only for aerial drones and military applications, but across diverse land and marine vehicle uses.“The dual benefits of reducing logistical burdens and increasing mission tempo make electric drones and hybrid propulsion a game-changer in modern warfare,” says Ewen Stockbridge, a NATO trainer and CEO of specialist consultancy 360iSR. “Electric propulsion offers significant advantages, including reduced acoustic signatures and lower heat emissions, enhancing stealth and survivability. This shift not only improves efficiency, but also operational flexibility, allowing for rapid recharging and redeployment.” Other players count innovators such as RCV Engines, known for rotary engines that are compact and efficient, Hirth Engines, which provides lightweight, high-performance engines, and Skypower International, which develops advanced UAV engines with low acoustic signatures. Beyond it featuring a hybrid-electric propulsion system, details about how the Defense Advanced Research Projects Agency (DARPA) XRQ-73 is powered are limited. Hybrid-electric propulsion systems combine fuel-powered engines and electric motors offering improved fuel economy and other benefits. The addition of batteries further allows for operation in a quieter all-electric mode.

These propulsion systems are vital for long-endurance surveillance, allowing drones to stay airborne for extended periods, and for high-altitude operations where engines must perform efficiently in thin air. Combining electric and traditional fuel engines to enhance efficiency and reduce noise could be a game-changer in stealth drone operations, with the hybrid technology now becoming a must-have for many UAV manufactures in the military and civilian sectors.

3.???? Making sense

Advanced sensor and avionics integration is also fundamental. Stealth drones require sophisticated sensors and avionics to navigate and perform missions without being detected.

This includes radar-absorbing sensors and low-emission communication systems. Radar absorbing materials (RAMs) are used in radar sensors to reduce the side waves that can cause false alarms, ghost images, or trigger other actions. RAMs can also help improve the flexibility of sensor positioning and function. Leading players in this field include Raytheon Technologies, which provides advanced avionics and sensor systems, and BAE Systems, known for its electronic warfare and sensor technology, including adaptive camouflage systems which utilises recent advances in liquid crystal displays systems. Equipping various aircraft types with adaptive camouflage offers numerous advantages, particularly for stealthy surveillance aircraft designed to operate for extended periods over enemy territory. For these missions, visual stealth is especially valuable. Aircraft like the highly secretive RQ-170 Sentinel already minimise their infrared signature and evade radar detection through low observable design features, strict emissions control, electronic warfare, and dynamic mission planning. Adding the ability to avoid visual identification would significantly enhance their survivability.

These systems are essential for electronic warfare, where stealth drones equipped with advanced sensors can jam enemy communications and radar, and for reconnaissance missions, gathering real-time data without alerting adversaries.

4.????? AI autonomy

Autonomous navigation and AI are crucial for stealth drones to operate independently and make real-time decisions without human intervention.

Showcased as a concept at the recent Eurosatory event in Paris, Italy’s Nurjanatech NT Stealth Cargo Drone Swarm System combines a large stealth cargo drone with the capability to release and control swarms of smaller, AI-guided drones. Time wil tell if this translates into a flying solution. The stealth capabilities of the cargo drone ensure low visibility and reduced detection, making it ideal for covert operations. The primary component of the system is the Stealth Cargo Drone, a large-scale UAV designed to reduce its radar cross-section, infrared signature, and acoustic footprint. The smaller drones in the swarm are equipped with advanced AI algorithms that enable them to operate independently or in coordinated groups. The integration of quantum sensors could significantly enhance the detection capabilities of stealth drones while remaining undetectable themselves.

In addition to $14 billion new-wave tech Prime Anduril and General Atomics, which both have contracts to develop CCAs (Collaborative Combat Aircraft) the US Air Force has also contracted five unidentified firms to work on autonomy software. Anduril declined say whether it was involved in that part of the CCA program at a recent demonstration in West Texas.

Anduril officials say they have been working on their Lattice autonomy software for years. The software takes in sensor data, establishes a common operating picture, and presents users with decisions at key moments. The air dominance version, called Lattice for Mission Autonomy, controls decision-making, coordination, and action for multiple aircraft simultaneously.?

In the small drone segments, leading players in this area include DJI, a pioneer in consumer and commercial drone technology with advanced AI capabilities, and Skydio, known for its autonomous navigation technology.

?Autonomous systems are vital for surveillance, allowing drones to patrol areas and identify threats without human control, and for search and rescue operations, where drones can navigate complex environments to find and assist in rescue efforts. The development of AI that allows multiple drones to operate as a cohesive unit, sharing data and making collective decisions, could transform military and civilian applications. The increasing east-west political divide calls into question the position of Chinese market leaders such as DJI - dominant in global volume sales - and what roles they may play in future development of technology applications and where they will be assembled and, most importantly, deployed.

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5.???? Data integrity

Finally, communication and data link security are essential for stealth drones to transmit data without being intercepted or jammed. Leading players in this field include L3Harris Technologies, which specialises in secure communication systems, and Thales Group, which provides advanced communication and data link solutions.

Secure communication systems are crucial for ensuring that sensitive information gathered by drones is securely transmitted to command centres and for maintaining communication integrity in contested environments. Utilising blockchain technology to create tamper-proof communication channels could enhance the security and reliability of data transmission for stealth drones.

Stealth drones employ a variety of technologies to ensure secure communication and data link security. One such technology is Millimeter Wave (mmWave) 5G, which offers high bandwidth and low latency, using non-commercial spectrum frequency bands that are difficult to detect, making it a secure and resilient connectivity option. Advanced data encryption is also used, particularly by military and government drones, to maximize security. Anti-jamming and anti-spoofing capabilities are crucial in protecting against interference and deception. The principle of privacy by design ensures that data protection and privacy are integral from the beginning of the design and development process. Additionally, radio wave techniques can prevent eavesdropping and fraud; for instance, a source UAV can create noise while sending information to a destination UAV, making it harder for a malicious UAV to intercept the communication. Given that data link systems are often the most vulnerable part of a drone's communication system, these technologies are essential in safeguarding against detection and countermeasures.

These elements highlight the potential for disruptive technologies to drive innovation in stealth drone UAS development, paving the way for more advanced, efficient, and undetectable aerial systems.

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