It’s called the ATD-X Shinshin:

Japan has rolled out its ATD-X Shinshin fighter technology demonstrator, is considering buying more Lockheed MartinF-35s and will decide within four years whether it will develop its next combat aircraft alone or with a foreign partner.

When the ATD-X was launched in 2007, Japan’s vision was to progress from its then-current fighter program, a heavily modified F-16, to independent development. Now, with a policy change allowing defense exports, the technology from the demonstrator may end up in aircraft that emerge from foreign production lines as well as from one in Japan.

The single ATD-X aircraft, about the size of a Saab Gripen, is undergoing ground tests, says the defense ministry’s Technical Research and Development Institute (TRDI), the sponsor of the program. TRDI is due to fly the ATD-X this year, beginning an evaluation program that will run until 2016. The aircraft has been built to demonstrate technologies—including stealth shaping, skin sensors and fly-by-light controls—that the ministry hopes to apply in its next fighter development program (AW&ST Aug. 6, 2007, p. 26).

Official photographs taken on May 8 show the ATD-X on the apron outside a factory building of airframe builder Mitsubishi Heavy Industries (MHI) at the Komaki South plant in Nagoya. The airframe underwent static testing last year. The ATD-X will be powered by two 11,000-lb.-thrust IHI XF5-1 -engines.

U.S. involvement in the program, probably peripheral, appears in TRDI’s budget statement for the fiscal year to March 31, 2014, which lists contracts signed with the U.S. Air Force in support of the program. One item, costing ¥114 million ($1.12 million), is for testing outside Japan. Another, for ¥760 million, is for unspecified training from the U.S. Air Force. Japanese authorities have not mentioned a plan to fly the ATD-X outside Japan. The U.S. clearly has refused to supply stealth technology for the ATD-X, since Japan sent a radar model of the intended design to France in 2005 for evaluation.

Not a surprise on the last bit.

The Pentagon is desperate to sell as many F-35s as possible, to drive down their price, but the basic mathematics of Stealth have been known for over 40 years, when the equations were published in a public Soviet academic journal, so the secret sauce ain’t so secret.

Of interest is that the Japanese also intend to use the Shinshin as a radar target to develop counter-steath techniques.

One function of the ATD-X is to serve as a radar target, supporting development of counter-stealth technology, because, TRDI has said, stealth aircraft are hard to simulate. In 2008, it hoped to use the ATD-X to validate the abilities of the FPS-5 radar, E-767 AWACS and Airboss infra-red turret to detect stealth aircraft. Six years later, it would not be surprising if other sensors have been added to the list.

The aircraft is clearly too small for internal carriage, which could be amelorated with stealthy pylons and pods, bu I don’t expect them to look into this at this stage, since they are doing this on the cheap:

The ATD-X appears to be costing ¥77.1 billion, including airframe and engine development and manufacturing, plus the flight-test program. Engine development cost ¥14.7 billion, basic design of the stealth configuration with thrust-vectoring control ¥13.4 billion and system integration ¥7 billion. TRDI spent ¥2.7 billion researching airframe structure suitable for the skin sensor. Manufacturing and flight testing is budgeted at ¥39.3 billion, but spending of ¥22.5 billion under that heading last year alone suggests that that figure will be exceeded.

Even so, Japan appears to be spending much less than half of the present-day value of what Britain and partners spent on airframe and engine technology demonstrator programs that preceded the Eurofighter Typhoon. Admittedly, those 1980s efforts resulted in full-scale equipment, whereas the ATD-X is probably half as big as the fighter for which it is laying groundwork.

Given that there are about 101 Yen to the dollar, the program looks to run less than $1 billion.

This is a lot more than the Have Blue ran in the 1970s, Wiki says $35 milion, but the ATD-X is far more capable than the Have Blue, and military procurement inflation is insane, in 1978, an F-16 sold for $3 million.

My guess is that tis is more than a hedge against F-35 costs.