China is already among the top echelon in the drone sector. Not only does it have a vast technical reserve, diverse models, and a complete industry chain, but it also continues to explore new heights in drone technology such as enhanced stealth capabilities, higher flying speeds, more robust collaborative combat capabilities, and advanced AI levels.
Recently, the Institute of Engineering Thermophysics of the Chinese Academy of Sciences revealed that they had completed the development of a domestically-produced light supersonic turbojet engine, which can be utilized as the power unit for high-altitude, high-speed drones. This engine is domestically innovated and is the world’s first light supersonic turbojet. According to reports, this engine adopts a multi-stage combustion concept, which enhances thrust while reducing fuel consumption, effectively boosting drone speeds and cruising times, laying a solid foundation for enhancing domestic drone capabilities.
Looking at the experiences from battlefields like Ukraine, existing low-speed drones find it challenging to operate in high-intensity adversarial environments. Take the Turkish TB-2 reconnaissance and strike drone as an example. It excelled in the Nagorno-Karabakh conflict but was heavily defeated in Ukraine. Hence, future wars require more advanced drones, with high-altitude and high-speed attributes being critical to enhancing their battlefield survivability.
To equip drones with sufficient high-altitude and high-speed capabilities, advanced engines are indispensable, and the domestically-produced light supersonic engine is developed precisely for this purpose. Current aviation engines, such as turbojets, consume a lot of fuel. Turbofan engines, despite their improved fuel efficiency, lag in high-altitude and high-speed performance. Rocket engines, while not considering speed or altitude, face issues with reusability and lifespan. Ramjets need boosters to achieve significant initial speeds before startup. None of these are ideal for next-generation drone propulsion.
Given this, the Institute of Engineering Thermophysics innovatively designed and successfully developed a light supersonic turbojet using the multi-stage combustion concept, addressing the high fuel consumption issue of regular turbojets. With this engine, domestic drones can achieve flight speeds of over twice the speed of sound.
Multi-stage combustion is a novel concept for the new century’s turbine engines. Its principle is to add another combustion chamber inside the aero-engine, thereby enhancing the total energy of the hot gases. The domestically-produced light supersonic turbojet has an added combustion chamber within its duct, which pre-heats the airflow before entering the main combustion chamber for further heating. If additional thrust is required, an afterburner can be used for a third round of heating, maximizing engine thrust.
Thanks to multi-stage combustion, the engine can increase the nozzle’s exit total pressure without changing the turbine’s total power, leading to more significant thrust, enhancing performance. Another invaluable advantage is the increase in engine reliability; even if one combustion chamber faces issues, the engine can still operate, allowing the aircraft to continue flying, ensuring better safety.
Research both domestically and internationally indicates that multi-stage combustion, compared to conventional turbojets or turbofans, provides more substantial thrust, lower fuel consumption, and a broader speed range, reaching up to Mach 3 or even Mach 4. When drones or cruise missiles are equipped with such engines, they can fly faster, remain airborne longer, travel farther distances, and possess superior combat capabilities.
Of course, multi-stage combustion has its downsides. The aerodynamics and internal structures are more complex than typical aero-engines, demanding higher standards for materials and engineering, posing more significant technical challenges, and incurring higher costs. However, given the evident performance advantages over conventional engines, these drawbacks are justifiable.
The successful development of the domestic light supersonic turbojet has cleared obstacles for the growth of high-altitude, high-speed drones in China. With this engine, the performance of the new generation of such drones will be noticeably improved. Taking the domestically-produced Wing Loong-10 high-altitude, subsonic drone as a reference, which has an altitude ceiling of 15,000 meters and a speed of 650 km/h, the new generation will be able to reach altitudes over 20,000 meters and speeds of around Mach 3.
The twin-engine Wing Loong-10 drone, already considered relatively fast, would take about two hours to reach the First Island Chain. In contrast, high-altitude, high-speed drones would only need about 20 minutes. When combined with stealth capabilities, the new generation of drones’ battlefield performance is effectively enhanced, making them more suited for operations beyond the First Island Chain.
Looking at advanced engine development plans like the US RTA, future aircraft will need a broader flight envelope, demanding a combination of engines to meet requirements. Among these combination engines, advanced turbojets are essential, and the speed range of future turbojets must be increased to at least Mach 2.5 to satisfy the demands of future aircraft combination engines.
The successful development of the light supersonic turbojet has provided valuable technological reserves for our future combination engine research, serving as invaluable technical training. As China continues to achieve breakthroughs in aero-engine technology, the advent of the next generation of high-altitude, high-speed drones is not far away, and more advanced domestic combination engines are fast approaching.
Source: Wang Yanan
