South Korea's proposed KF-X stealth fighter program has not been short of influential opponents. Now it has another. A defense ministry think tank, the Korea Institute for Defense Analysis, has told a public meeting that the country is not technologically equipped to develop the aircraft, that the project is economically unviable and that the KF-X would not be a successful export product. The institute challenges cost estimates by the Agency for Defense Development, which is leading development of the aircraft.

KF-X development would cost more than 10 trillion won ($9.2 billion), one of the institute's researchers, Lee Juhyeong, has told a seminar on the program. Over the life of the program, the KF-X would cost the country more than twice as much as an imported aircraft, Lee says.

The institute's stance has not previously been publicly stated, although the Naeil newspaper reported last year that it had submitted a confidential report doubting the viability of the project. Now speaking openly, the institute questions whether the U.S. will be willing to help develop the KF-X. Other skeptics wonder how it could be exported in competition with U.S. aircraft, since South Korea would probably have to use major U.S. components, whose export could be blocked by Washington. Another influential think tank, the Korea Development Institute, reported as early as 2007 that the KF-X was not viable.

KF-X program director Lee Daeyearl, of the Agency for Defense Development, told the same seminar that the fighter would cost 6 trillion won in development, 8 trillion in production, and 9 trillion for operations over 30 years, according to an aerospace industry executive who attended.

South Korea needs to develop its own fighters to be capable of upgrading them and to install South Korean weapons systems, Lee Daeyearl says. “It will contribute to the nation's aerospace industry in the future,” Yonhap news agency quotes him as saying. “Without making a first step, we'll have to rely on imported aircraft and that will benefit foreign defense contractors.”

The agency has prepared two series of designs, one for an aircraft with its horizontal stabilizers aft, which it considers to be a U.S. style, and one for a “European” fighter with a canard stabilizer. The aft-tail series has run through the iterations C101, C102 and, now, C103, all with two engines and a single seat. The C102 design was further broken down into three variants: C102E with one engine, C102I with internal weapons and C102T with two seats. Those ideas have been discarded, however; the current aft-tail design is C103. Similarly the C201, C202 (with variants E, I and T) and the current C203 follow the same pattern, except for a canard planform.

The agency proposes that either C103 or C203, whichever was chosen, would then advance through three design standards. Block 1 would be “reduced observable,” which it says would be equivalent to the B-1B, Boeing F/A-18E/F Super Hornet and Eurofighter Typhoon. For its low signature, Block 1 would rely on fuselage and inlet shaping, including edge alignment, and on radar-absorbing material and semi-conformal weapons carriage.

Block 2 would carry weapons internally, a provision for which would be made in the Block 1 design. Antennas would be conformal, and sensors would be “integrated”—for example, in the radar, radome and apertures. There would be minimal gaps and a radar-absorbing coating on the canopy, and the structure of the aircraft, not just its paint, would absorb radio waves. The result would be an aircraft as stealthy as the F-117, the agency proposes.

Block 3 would advance the aircraft to the level of the B-2, F-22 and F-35, but no details are given.

All of this is a step beyond the previous concept, in which the KF-X would have aimed only at something like the Block 1 standard.

The aircraft is expected to be between the Lockheed Martin F-16 and Boeing F-15 in size. Consistent with that, the agency shows the C103 design with two engines of 18,000 lb. thrust each. According to a 2009 external review of the program, the empty mass of the KF-X should be 10.4 metric tons.

Since work began in 2002, the KF-X has been stuck in feasibility studies, concept definition and preliminary design. The finance ministry last year put a stop to it entering full-scale development this year. Instead it allocated just 4.5 billion won for further studies.

The agency's Lee says that if full-scale development begins in October 2014, the first prototype could be rolled out in August 2019 and fly in September 2020. Two years ago, the South Korean air force said it expected the KF-X or an alternative to enter service in 2021. That would obviously be impossible for a type that made its first flight in 2020.