Autonomous combat drones
New technologies are also being unveiled for radar detection. Typical radar evasion design for planes includes sharp edges to scatter signal, and control of electromagnetic emission release, by lowering the power through its transmission devices.
However, so-called ‘active stealth’ is becoming more common in missions deep into enemy airspace. A pod, called the T- SOAR (Figure 5), can be attached to the outside of a drone (currently only the MQ-9 Reaper). This pod detects incoming radar signals, replicates them, and then sends them back, before the aircraft’s signature can be detected (Dubois, 2024). This is a relatively cost-effective way of becoming invisible to radar detection, potentially
Figure 5: MQ-9 Reaper with SOAR pod beneath the rear
making dangerous surveillance missions much easier and more successful.
Propulsion The method by which the drone is powered and propelled will dictate how it can perform. On the battlefield, this may be the difference between its evasion or destruction. There are several different methods of drone propulsion, each with its specific strengths and drawbacks. Turbojets are a widely used method in powering UAVs. A turbojet works by combusting fuel with all the air coming through the inlet, then ejecting the high-energy exhaust gases to produce thrust (Hoeveler, 2024). However, due to the high rate of flow of intake air required, these engines typically perform with optimum efficiency at supersonic speeds (SKYbrary, n.d.). While there are some supersonic UAVs emerging (Smith, 2024), this method of propulsion may not be best suited for drones. An alternative would be the use of a turbofan jet engine, which works like a turbojet, except some of the intake air is sped up by a fan, instead of via combustion (Hall, 2021). This has the benefits of reducing noise and improving subsonic performance, making it the top choice for endurance and surveillance drones. In smaller drones, where cost efficiency and mass production are key, there is an entirely different method of propulsion which stands out: electric motors. Brushless Direct Current (BLDC) motors have high efficiency and reliability, with low maintenance (Defense Advancement, 2025), but they do not offer the peak power that jet engines do. This makes electric motors the preferred option for drones with low energy demands, and they have the added advantage of very low noise and heat signatures.
A current advancing technology is the ‘micro turbojet.’ This method of propulsion aims to provide the high performance of a jet engine in a lightweight package (Jims John Wessley, 2019), allowing for a rapid response, high manoeuvrability and climb rate when needed.
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