America's relationship with Japan has improved considerably over the last several decades, but this chummy relationship definitely has its limits, which manifests specifically in America's unwillingness to sell Japan any of our new F-22s. That's why Japan has decided to build a better warbird than the Raptor, all on its own.
Our refusal to share the new plane wasn't the only factor. The primary reason was that, at the start of the century, the Japanese Self Defence Force's stable of Mitsubishi F-2s and and F-15s were quickly becoming obsolete, hence their overtures of buying a few Raptors from the US. Upon that refusal, Japan took it upon itself to domestically develop a 5th Generation stealth fighter jet to augment its ageing flyers. And after nearly a decade of development, the initial prototype for the platform is nearly ready to fly: the ATD-X (Advance Technology Demonstrator-X), nicknamed ShinShin ("Spirit"), a technological testbed and showcase for Japan's most cutting-edge avionics.
The ATD-X, being a single-seat demonstrator, measures 14m long with a 9m wingspan — that's only one-third the size of what the production aircraft would measure. But despite its chibi size, the ATD-X is loaded with among the most advanced flight systems on Earth.
While many of its systems are still under wraps, initial reports suggest that its engines will utilise 3D thrust vectoring to help control the aircraft while lessening its reliance on aerodynamic control surfaces. the engines themselves are thought to be incredibly powerful, especially given their slender stature. As Aviation Week explains,
The power of the IHI demonstrator engine is surprising. It would generate 50% more thrust than the General Electric F414, two of which power the BoeingF/A-18E/F Super Hornet. The Super Hornet's thrust is not notably high for its empty mass, 14.6 tons (32,100 lb.), but in a twin-engine installation the output of the IHI demonstrator would be abundant for a larger, budget-straining aircraft. It does seem that Japan is looking for a twin aircraft: In a single installation, the engine would be adequate for only a modestly sized fighter, hardly suitable as an F-15 replacement.
The ATD-X is also rumoured to employ fly by optics controls, which is like fly-by-wire but using the massive increase in data throughput speeds that fibre optic cables provide. What's more, fibre optics aren't affected by EMP blasts, thereby fortifying the aircraft against such attacks. And in addition to its Multifunction RF Sensor, which handles both electronic countermeasures (signal jamming) and electronic support measures (signal boosting), the entire skin of the plane may be impregnated with antennas to help actively reflect radar beams, making the plane as stealthy as it wants to be. And while the demonstrator isn't armed, there have been rumours that the production fighter might be outfitted with microwave-based weaponry.
The most fascinating system however may well be the proposed Self-Repairing Flight Control Capability. This electronic nervous system will be able to detect faults and damage to the aircraft's flight control surfaces and recalibrate, while in flight, the remaining control surfaces so as to maintain control of the aircraft.
The JASDF expects the STD-X's maiden test flight to take place later this year. If everything goes according to schedule, the 5th gen fighter, dubbed the F-3, will enter production around 2027. [PopSci - Aviation Week - Janes - Wiki - Defence Aviation]