Jinmu ZF-21 Dragon

The Jinmu ZF-21 Dragon is a Zhenian single or twin-seat,, all-weather   developed for the Republic of Zhenia Air Force and the Republic of Zhenia Navy. Although originally intended as an when development began, it has been developed to carry out missions as a multirole fighter, capable of taking out both air superiority and precision ground strike missions, as well as  and  (ISR), although its design was largely streamlined towards air superiority missions. Although primarily built by Jinmu Heavy Industries, other contractors, including Signus Systems, took part in the development process as well.

A result of decades of continuous development that had been mostly in secret, the ZF-21 Dragon was first revealed to the public during its test flight on June 4, 1588 and was introduced to service in 1594. Later developed in tandem with the ZF-33 Black Eagle, later variants and upgrades introduced in the 1600s and 1610s feature a considerable amount of cross-development with technological input gained from developing the ZF-33 Replacing the ZF-7 Vanguard, the ZF-21 Dragon is planned to form the higher end of the RZDF's projected of combat aircraft. The Republic of Zhenia Air Force and Navy combined plans to field a combined total of up to 720 ZF-21 units in total by 1616.

Origins and concept demonstration
Shortly after the November Revolution, the Republic of Zhenia Air Force issued a requirement for a next-generation air superiority fighter aircraft that was to supersede the ZF-7 Vanguards that were being produced and fielded into the service. While many were skeptical regarding the need for a new air superiority fighter with the existence of the ZF-7 Vanguards in service, the service branch, then under the leadership of the then-Chief of the Air Force Kim Wonil, managed to defend minimal budgets needed for preliminary research into conceptual designs and characteristics for a future air superiority fighter. An array of rough, preliminary concepts emerged from the Jungchuwon's design bureaus and defense contractors, each with different characteristics and emphasis on different fields: however, many shared the denominator of taking advantage of new aviation technologies developed at the time, as well as large amounts of lightweight alloys and, advanced control systems and  technology that were merely being tested in deep secrecy. Among many preliminary concepts, those from Jinmu, Paragon and Hanshin were selected in 1576 AC and were given the way forward, being awarded contracts to bring a working by January 1582.

With the introduction of new ZF-7 derivatives in the late 1570s, however, particularly the multirole ZF-7E and ZF-7G "Super Vanguard", the purpose of what would become the ZF-21 came under attack, with additional budget cuts threatening the very existence of the program as a whole. The program, however, received the further go forward with the involvement of the Republic of Zhenia Navy, when they issued requirements to introduce a complementary replacement to the ZF-7 Vanguards within service aboard its aircraft carriers and land bases by 1595 AC. It was the Navy's involvement that ultimately changed the direction of the aircraft's development from a pure air superiority fighter to a multirole fighter with an emphasis on air superiority and survivability in contested airspace, as the Navy gave great emphasis to acquiring platforms capable of long-range naval and surface strike even in contested airspace. In the process, the key avionics that were to be included on the new aircraft were changed, with the addition of, electro-optical targeting systems and other augmentations to improve the aircraft's air-to-surface capacity, while the airframe was partly restructured to accommodate arresting gear and reinforced landing gears for operation aboard aircraft carriers. The concept was revised as the Next-Generation Air Superiority Fighter (NG-ASF) program in 1578 by the Ministry of Defense and the Jungchuwon, although most of the development before the technology demonstrators were made in secret.

The first technology demonstrators from the three respective contractors were revealed in 1582, although in deep secrecy. Each labeled ZX-20, ZX-21 and ZX-22 respectively by order of completion, they were evaluated across various fields within RZAF bases in Heuksu and Shingang Province, including flight performance and sensor fusion.

Production, procurement and upgrades


After its introduction to service, upgrades and improvements made to the ZF-21 drew significant inspiration and technology from the adjacent development of the ZF-33 Black Eagle. The cockpits on later variants of the ZF-21, for instance, are largely similar to the on the ZF-33, featuring a pilot-friendly interface centered around touchscreens rather than screens controlled by buttons. Upgrades to the ZF-21 also significantly leverage newer avionics introduced on the ZF-33, such as the Cheongu Distributed Aperture System, which augments and replaces the existing (IRST) mounted near the nose of the aircraft while also providing 360-degree situational awareness to the pilot. Mission computers, the electro-optical targeting systems, pilot interfaces and software updates are also key features of upgrades made to the ZF-21. Many of such upgrades are visible since the ZF-21C variants.

Armament


In order to preserve its stealthy shape, the ZF-21 is equipped with a total of three internal weapons bays - a large main bay running through the center of the aircraft and two smaller bays on the side of the fuselage, between the landing gear and the air intakes. Split along the center line of the aircraft, the large main bay is capable of accommodating up to six long-range air-to-air missiles at a time, while the smaller side bays are in theory capable of accommodating up to two air-to-air missiles each, although they normally carry only one in practice. Unlike the side bays, the main bay is also capable of carrying a broad range of air-to-surface weapons, being able to carry up to 1,300 kg of ordnance in each hardpoint. Ordnance in both the main bay and side bays are connected to the weapons bay via robotic arms, which are engaged when the weapon is set to be fired. The usage of internal weapon bays allow for non-stealthy ordnance to be carried within the airframe, minimizing radar signatures.

In addition to the internal weapon bays, the ZF-21 is also equipped with three external hardpoints on each its wings, with a capacity of carrying up to 8,000 kg on each side of the wing. The external hardpoints can be used to carry large munitions that do not fit inside the main weapon bay, carry munitions in missions that do not require a stealthy configuration, or external weapon pods to increase its ordnance capacity while maintaining its stealthy configuration. Although only able to be installed at the internal hardpoints on each wing, the external weapons pod is capable of carrying up to four additional long-range air-to-air missiles. The ZF-21 is armed with a 20 mm Gatling gun mounted in the right-hand spot near the wings with 450 rounds for close-range warfare and strafing. The centerline of the aircraft, just behind the main weapon bay, has an additional hardpoint not for munitions but for multi-mission pods, including jammers and reconnaissance pods.

Sensors, electronics and countermeasures
A major element of the ZF-21's system is the Cheongu Distributed Aperture System, a system consisting of multifunction infrared-range camera sensors installed around the airframe. Intended to provide 360-degree coverage around the aircraft in extended ranges, the Cheongu Distributed Aperture System is expected to allow for reconnaissance, threat detection and target acquisition in both air and the surface. The system is more or less the same with that seen on the ZF-33, with the ZF-21 having one more multifunction camera to provide higher coverage due to the larger size of the airframe: this is due to the fact that the ZF-21, unlike the ZF-33, did not initially come with the electro-optical targeting system installed. The Cheongu Distributed Aperture System has become a key element in the ZF-21's sensor fusion network, increasing the pilot's situational awareness and providing an additional source of threat data around the aircraft.

While earlier variants of the ZF-21 required external or manual guidance of precision-guided munitions, most ZF-21s in operation today are equipped with the  (EOTS). Replacing the functions of existing targeting pods, and  (IRST) sensors, the EOTS provides the pilot with high-resolution imagery and targeting information. Due to its interconnections to the Cheongu DAS, the EOTS is often considered a component of the Cheongu DAS, with data from the EOTS often doubling as data needed to adjust the data for higher precision.

Cockpit
The ZF-21 uses a to maximize the pilot's situational awareness. Primarily centered around a 20-by 8-inch (50 by 20 cm) panoramic and the  at the top, the cockpit's information display system allows for flexible display of flight instruments, aircraft status, information on the aircraft's surroundings and incoming threats. The cockpit itself has been designed to reduce complexity and increase flexibility of screen usage at the end of the pilot, which has been factored into the lack of screen side buttons. While some have proposed to remove the head-up display altogether and replace its functions with a, it has been decided that all variants were to retain the head-up display to augment the pilot's own situational awareness.

Stealth
Although its exact remains a closely-guarded secret, there are speculations that the estimated radar cross-section of the ZF-21 without any external armaments is most likely smaller than 0.001m2 - roughly comparable to a metal golf ball. The ZF-21 was designed to minimize its radar cross-section and probability of being detected by enemy sensors. Such measures include planform alignment on the edges, curved vanes behind the to cover the engine turbines from external radar waves, extensive use of radar-absorbent material (RAM) and minimization of clear bumps and design irregularities that can possibly give a radar return. Reduction of radio emissions, infrared and acoustic signature has also been taken into account upon the ZF-21's design, with its saw-toothed three-dimensional designs both to scatter radar and heat signatures, active cooling on leading edges and other heat-concentrated areas to reduce heat buildup and the internalization of almost all antenna systems.

Although it takes extensive use of radar-absorbent material (RAM), the ZF-21 primarily uses more durable radar-absorbent fibermat skin modules that allow for less and easier maintenance than its predecessors, increasing its and availability in emergency situations. While its stealth is primarily focused on achieving very low observability (VLO) against threats, it is said to also have achieved at least low observability (LO) against S-band and L-band threats, among other lower-frequency threats. Although its exact remains a closely-guarded secret, there are speculations that the estimated radar cross-section of the ZF-21 without any external armaments is most likely smaller than 0.001m2 - roughly comparable to a metal golf ball. The aircraft can additionally mount a total of six reflectors to disguise its actual radar cross-section.