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Japan's stealth fighter promises more than military defense

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  © Kyodo

TOKYO   The X-2 fighter demonstrator, Japan's first domestically built stealth fighter jet, will soon take to the skies for its maiden flight, marking a major milestone in a project that dates back seven years.

     The X-2 is a testbed aircraft for a host of advanced technologies and design concepts Japan is investigating as part of its quest to develop an indigenous fighter plane that is both highly maneuverable and nearly invisible to radar.

     Building up its store of proprietary technologies will give Japan more choices when it comes to defense procurements and could potentially open up global opportunities for the country's defense contractors.

     Pushing the boundaries of fighter jet technology could also yield significant benefits in other industries down the road, including commercial aviation and power generation.

SEVEN YEARS AND COUNTING   The X-2 has gone by several names, including the codename "Shinshin," which is a reference to Mount Fuji, and the Advanced Technology Demonstrator-X. But whatever the name, the X-2 is an experimental aircraft for testing advanced stealth fighter aircraft technologies, and the prototype has been seven years and 40 billion yen ($35.4 million) in the making.

     If you count the work on elemental technologies, then the research and development goes back 15 years. And if the research and prototyping of engines is included, the Japanese program to develop its own stealth fighter becomes a major project that stretches back 20 years.

     The Defense Ministry's procurement agency chose Mitsubishi Heavy Industries to spearhead the design and manufacture of the experimental aircraft, but a total of some 220 companies are participating in the development plan. Fuji Heavy Industries is in charge of the fuselage and tail assembly, Kawasaki Heavy Industries is accountable for the cockpit, Nabtesco is developing the control instrumentation, and IHI is responsible for the engine.

     Japan is only the fourth country to develop a stealth fighter, following the U.S., Russia and China.

     The prototype was unveiled to the press on Jan. 28 at the Nagoya Aerospace Systems Works of Mitsubishi Heavy Industries. After its first test flight, the jet will be handed over to the Defense Ministry's Acquisition, Technology and Logistics Agency.

     The agency will test the plane for 18 months to evaluate its technologies and performance characteristics, and by fiscal 2018 decide whether to continue with development as a mainly domestic effort or in the form of an international collaboration to develop a successor to the F-2, Japan's fighter plane that will be retired in around fiscal 2028.
TECHNOLOGICAL TESTBED   The X-2 stealth fighter prototype incorporates world-class domestic technologies, including some meant to help make the plane all but invisible to radar, and others designed to give the plane impressively acrobatic maneuverability.

     To absorb radar waves, the body of the plane is covered in a material developed by Ube Industries that is a composite of ceramic and silicon carbide. The cockpit windshield is coated with a special tin alloy.

     For a stealth plane to hide from radar, it must be designed in ways that minimize the cross-section of the reflected radar waves.

     "Radar waves reflect more easily from surfaces that are uneven, but the fuselage panels have virtually no seam joints," explained Hideaki Miwa of the Defense Ministry's procurement agency. "What's more, the plane is shaped in ways that make the radar waves bounce off in different directions."

     Details about the specifications for the U.S. military's F-22 and F-35 stealth fighters developed by Lockheed Martin and other defense contractors are not public record, so comparisons with the X-2 cannot be made. However, the X-2 reportedly has an extremely small radar cross section. How small? "It looks no bigger than a giant beetle viewed from tens of kilometers away," Miwa said.

     Air intake ducts are one of the hardest parts of a jet to hide from radar, since they are positioned face-forward on the plane. The X-2 incorporates a novel design to solve this problem. "By bending the ducts, the reflective surface area is smaller and probably less than that of the U.S. stealth fighters," said a senior official at the Acquisition, Technology and Logistics Agency.

     Fighters are designed primarily for air-to-air combat, and another set of technologies built into the X-2 are designed to make the plane so maneuverable that it can perform acrobatic stunts that would cause other aircraft to stall.

     Fitted to the left and right engine exhausts are sets of three thrust deflector paddles, shaped like the webbed feet of ducks. Moving these six paddles vertically and horizontally to deflect the jet exhaust and alter the direction of thrust enables the X-2 to climb, dive and turn rapidly and at will.

     In dogfights, this is a plus, and it is combined with a system that concurrently analyzes data about plane motion and engine thrust to derive the optimal position to take at any time. A plane flying directly into a headwind has limited control over the rudder, but the X-2 can instantly assess the situation and adjust the thrust deflector paddles so the fighter can turn without stalling.

     IHI's experimental turbofan jet engine, the XF5-1, further supports the maneuverability of the X-2.

     Jet engines generate thrust by jet propulsion produced by pressurized gas, and more thrust is generated by burning the engine fuel at a higher temperature. For the XF5-1, the temperature at the intake to the turbine, situated just behind the combustion chamber, exceeds 1,500 C, which is much hotter than in a civilian jet engine. The XF5-1 is also the first jet engine built in Japan to incorporate an afterburner.

     This hotter engine environment requires better heat-resistant materials, and the XF5-1 is built using a ceramic matrix composite developed jointly by Ube and IHI, together with some domestically manufactured lightweight heat-resistant alloys, including a titanium aluminide alloy.

     "These are advanced technologies that can compete on the world stage," said Tadashi Natsumura, head of defense systems development at IHI.

     The participants in the X-2 development effort are justifiably proud of their accomplishments.

     "Making a stealthy plane and an integrated engine control system are not things that just any company can do," said Mitsuru Hamada, chief engineer in Mitsubishi Heavy's Integrated Defense and Space Systems division.
     But the flight ahead will not necessarily be a smooth one for the X-2.

     As an executive from Lockheed Martin pointed out, although the X-2 is fitted out with a variety of advanced technologies, Japan has no experience operating stealth fighters in actual combat. Japan is still no match for the U.S. when it comes to things like integrating avionics into planes designed for stealth and operating communication systems.

MORE THAN DEFENSE   As with the development of the F-2, the intention is for the stealth and other advanced technology to also have a wide range of potential civilian applications.

     "Developing fighter jets involves a wide range of industries, such as materials and equipment. I hope the X-2 development will lead to technology transfer to other sectors, such as passenger airplanes," Hamada said.

     The technology behind the X-2's small yet high-powered engine, for example, could be applied to power-generating gas turbines.

     Jet engines and gas turbines are similar in structure. Both systems are designed to produce extremely high-pressured gas, and their thermal efficiency increases when the combustion temperature increases.

     The ceramic matrix composite developed by IHI and Ube for the X-2 engine is over 60% lighter, 20% more heat-resistant and 100% stronger than nickel alloy, and the companies foresee it being applied to power-generating gas turbines.

     Observers are similarly optimistic about the commercial potential of the X-2 project.

     "These leading-edge technologies developed for the stealth demonstrator will help bolster Japan's overall industrial competitiveness," said Satoshi Tsuzukibashi, director of the industrial technology bureau of the Japan Business Federation, or Keidanren, who oversees the organization's committee on the defense industry.

PAST ACHIEVEMENTS   Those involved with the X-2 have good reason to be optimistic about its knock-on benefits. Japan's mainstay F-2 fighter jet, which entered service in 2000, has spawned a number of commercial applications.     

     The jet's main wings, which Mitsubishi Heavy developed, are made of carbon fiber reinforced plastic, or CFRP, marking the first time the material was used for the main wings of an aircraft anywhere in the world.  

     The revolutionary technology soon attracted the attention of U.S. aircraft maker Boeing, which implemented it in the production of its 787 Dreamliner, increasing the aircraft's fuel efficiency by more than 20% compared with conventional models. This was the first instance of Boeing commissioning the development of aircraft wings to another company.

     Other manufacturers, such as Europe-based Airbus, have followed suit, and the weight and strength of CFRP mean it is replacing aluminum alloy as the material used for an increasing number of aircraft parts. 

     Moreover, the F-2 was the first aircraft in the world to use Mitsubishi Electric's active phased array radar technology. The system is composed of hundreds of small radiating elements that act as radars, and it can change the irradiation angle of radar waves by simply controlling electric currents. This has eliminated the need for the rotating movement of the antenna, making it possible to detect foreign objects in a much wider area.

     The technology is now used in automotive radars as well as the data transmission and reception of electronic toll collection systems on expressways. A further application is in ground stations of the 5th-generation radio communication standard for mobile devices.

     Spurred on by past achievements, Mitsubishi Electric is working to develop radar technology for stealth fighters incorporating semiconductor devices using gallium nitride, instead of gallium arsenide. This could boost output by 50-100% and expand the scope of detection. Industry experts expect that further applications could include the safety mechanisms for self-driving cars.

POSSIBLE PARTNERSHIP   Based on the X-2 demonstration flight results, the Japanese government will likely decide by fiscal 2018 whether to develop its next-generation fighter jet domestically or through international joint development.

     It would, however, be extremely ambitious, if not impossible, for any one country to shoulder the cost of developing a fighter jet all on its own. Lockheed Martin's F-35, for example, was jointly developed by the U.S. and eight other countries at a reported cost of more than $100 billion.

     Joint development of the next-generation fighter jet has already been discussed at the U.S.-Japan Systems and Technology Forum. "The two countries have started negotiations over how to develop the necessary technology and combat systems by involving private companies, such as Mitsubishi Heavy and Lockheed Martin," said an official.     

      International joint development is something of a double-edged sword. On the one hand it means the manufacturers involved have a limited scope of responsibilities, but on the other, they gain wider access to overseas markets.

     But in the face of the increasing competition in the global defense manufacturing markets, going it alone may simply not be an option.     

     In South Korea, three conglomerates -- Samsung, Hyundai and Daewoo -- integrated their respective aerospace units and created Korea Aerospace Industries in 1999. The company is now pushing to export its supersonic military aircraft.

     "Japanese manufacturers will need to spin off their defense units and consolidate them into one major defense manufacturing company. Otherwise, they won't be able to compete globally," said an executive at Lockheed Martin.

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