By Shan Ge
Yesterday, images began circulating online of a J-36 flying over a cultural heritage exhibition hall in a certain southwestern region, escorted by J-20S fighter jets. The triangular aircraft drew gasps from the onlookers, as its design deviates significantly from conventional aircraft typically seen on Earth.
There were earlier speculations that it might be the rumored JH-26, but in the image above, the “360XX” serial number can be clearly seen on the side of the aircraft’s nose. This likely indicates that the aircraft is a testbed or even a prototype for the project codenamed “Project 360.” As we know, the engineering code for the stealth carrier-based aircraft is “3500X,” which we commonly refer to as the J-35. Therefore, for now, we can tentatively call this new aircraft by Chengdu Aircraft Industry the J-36.
From the images, the aircraft appears to feature a double-swept delta wing waverider configuration with no vertical tail, lateral caret inlets, and a design suggesting superior stealth capabilities compared to the J-20. It has an air intake on its back and three engine nozzles—two larger ones and one smaller one. The aircraft seems shorter than the accompanying J-20S but noticeably wider, equipped with dual landing wheels. Its maximum takeoff weight is estimated to be around 50 tons. Rumors on foreign platforms suggest it uses three WS-10C engines, rather than the WS-15 + ramjet TBCC (Turbine-Based Combined Cycle) engine, which will be elaborated upon later.
The aircraft’s weapon bay is massive. Its length is 60% longer than that of the J-20, its width is 40% greater, though the depth remains unclear. The opening area of the bay is approximately 20 square meters. In comparison, the bomb bay of the H-6 measures 6.7 meters long, 1.6 meters wide, and 1.3 meters deep. The author has always emphasized that stealth fighters should be designed around internal weapon bays, but the sheer size of this bay is surprising. It can accommodate a large payload, enhancing strike capability, although its size increases frontal area, thus creating greater drag and structural weight, which can impact flight performance.
In supersonic flight, the aircraft’s frontal area is a key factor influencing drag. One common approach is to lengthen the fuselage to optimize weapon bay design, reducing the maximum cross-sectional area of the fuselage. For example, a tandem weapon bay layout could compress the fuselage cross-section, thereby lowering frontal area and drag. However, overly long weapon bays can compromise longitudinal structural strength, limiting high-G maneuverability. The F-22, for instance, was shortened compared to its prototype, allowing it to sustain 6G maneuvers at 1.7 Mach. For the J-36, however, the design emphasizes increased width rather than length to enhance structural strength and maintain maneuverability.
Additionally, a fighter jet must withstand significant aerodynamic pressure and shock loads during supersonic flight. The large weapon bay opening imposes stringent requirements on structural strength, necessitating the use of large titanium alloy components forged by 40,000 to 80,000-ton presses. Fortunately, such forging facilities are located relatively close to the southwestern testing site.
To mitigate drag and improve the lift-to-drag ratio during supersonic flight, designers have moved the weapon bay forward and the main wings backward to prevent overlap between the widest parts of the bay and the wings.
Although the wide-body structure increases weight and drag, the J-36’s single-engine thrust is sufficient for level flight at subsonic speeds. However, in supersonic states, two engines may not provide enough thrust for a wide-body configuration, necessitating a third engine to maintain supercruise capability. This approach is feasible, given that supercruising typically occurs at altitudes above 15-20 kilometers, where air density is low. However, at such altitudes, oxygen content decreases, and turbofan engines operate at only 60% of their rated thrust at sea level, while fuel consumption increases significantly.
The internal fuel capacity of the J-36 is estimated to be 13-15 tons. At a supercruise speed of Mach 2.2, the aircraft could cover 2,700 kilometers in an hour, consuming at least 10 tons of fuel. Including takeoff and landing, the maximum range is approximately 4,300 kilometers. If cruising with a single engine and engaging in half-hour bursts of supercruise with all three engines, the range could extend to 6,000 kilometers. However, this would create abrupt speed transitions, which is less ideal for a fighter jet that requires sufficient reserve thrust for maneuverability. Nonetheless, such a setup does not seem to align with the concept of a sixth-generation aircraft.
Another potential configuration involves the TBCC engine (Turbine-Based Combined Cycle), which combines two WS-15 (or WS-10C) engines with a ramjet. After the WS-15 accelerates to Mach 2, the ramjet activates while the WS-15 shuts down and its air intake closes. With a thrust-to-weight ratio of 20, the ramjet offers a system-wide thrust-to-weight ratio of 15, making the system very lightweight. It could achieve cruising speeds above Mach 3 and altitudes of 30 kilometers. While ramjets consume twice as much fuel as turbofans, the increased speed translates to greater range. A one-hour supercruise could cover 3,600 kilometers, and including subsonic range, the total reach could extend to 5,500 kilometers. With high altitude, high speed, and stealth, this configuration would pose a significant challenge to any nation’s air defense systems, with strong capabilities for air-to-air, ground, and naval strikes. However, the heat barrier issue must also be addressed. Titanium alloys are more likely to be used than stainless steel, as large-scale titanium processing is now fully mastered.
The J-36’s structure aligns with research into double-swept waverider configurations. Initially designed to leverage “vortex effects” from double-swept leading edges to enhance low-speed aerodynamics, this configuration offers a lift-to-drag ratio of 4-5 at Mach 3 and 12-15 at subsonic speeds. Originally intended for hypersonic aircraft, this design demonstrates the country’s deep foundation in fundamental research.
Conclusion:
There is no universally agreed-upon concept of a sixth-generation fighter. While the U.S. has primarily presented concepts and research, the double-swept delta-wing J-36 already boasts features such as advanced stealth, a wide speed range, supercruise, high maneuverability, and large payload capacity. It possesses robust air combat capabilities and can effectively strike ground targets. Additionally, reports suggest that northern manufacturers are concurrently testing a bomber-focused variant, the “Bomber Fighter XX.”
