6세대 전투기의 조건은? 개발은 이루어질 것인가?...

 

다소 장문의 기사입니다만, 6세대 전투기를 이해하는데 도움이 되는 자료로 판단되어 소개합니다. 또한 미 공군과 해군이

6세대 전투기를 개발 도입한다면 어떠한 성능을 요구하고 있으며, 6세대 전투기로써 유인기를 선택할지 아니면 무인기로

넘어갈지에 대한 고민도 이해할 수 있는 기사입니다.

 

끝으로 현재 미 공군과 해군이 각각 진행하고 있는 6세대 전투기 개념(계획)에 대해서, 역시 통합 연구가 진행되어야 할

것으로 예상하고 있습니다.

 

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Next What?

What makes a sixth-generation fighter is not yet defined, but needs to be a game-changer

Aviation Week & Space Technology, 07/19/2010

Author : Graham Warwick

 

Avoiding the pitfalls of the Lockheed Martin F-22 and F-35 programs is the highest priority for the U.S. Air Force and Navy as they think about the next generation of tactical aircraft to enter service after 2025.

 

Overambitious requirements, immature technology, program complexity, development delays, escalating costs, procurement cuts — all are to be avoided as the services draw up their requirements for what are likely to be stealthy, supersonic, agile and networked — in other words, expensive — systems.

 

“Job one is make it affordable,” says Dixie May, Boeing Phantom Works’ program manager for next-generation air dominance (NGAD) — the generic term given to separate Air Force and Navy efforts to define their requirements for “sixth-generation” fighters.

 

What constitutes sixth generation is not clear, but affordability is the most important characteristic emerging from discussions with customers, May says. Given the development and procurement budget growth on the fifth-generation F-22 and F-35, and the likely tight fiscal environment, “cost is a significant issue,” he says.

 

Capability is being traded against cost as requirements are developed, including explicit consideration of an “80% solution” for NGAD. “They are still talking in terms of 6th gen, not 5.2 gen, but they will not push the envelope on every area,” says May, adding “We’ve been cautioned against using ‘more’ in every category.”

 

Boeing is the most vocal on NGAD as the Navy aircraft would replace its F/A-18E/F on carrier decks and a development start soon after 2015 is the company’s best chance of keeping its fighter capabilities intact. The Air Force mission offers Boeing a chance to re-enter a market lost to Lockheed Martin.

 

In developing their requirements, the Air Force is focusing on air superiority, May says, and while the Navy sees a significant air-to-air capability gap in the 2025 timeframe it is more interested in an aircraft that can perform multiple roles. “But they don’t expect this to be a Swiss Army knife, like the F-35. There is concern about the compromises that had to be made to meet all needs with the F-35,” he says.

 

After affordability, the most important characteristic coming out of studies is increased reach, through a combination of platform and weapons range. “They realize we are building a short-range Air Force and Navy,” says May. “Given the ability of potential adversaries to reach out and deny access, we need to reach further than we can now.” China’s ability to keep U.S. carriers at arm’s length with anti-ship ballistic missiles is a key factor.

 

Unrefueled combat radius is expected to be 1,000-1,250 nm., says Boeing Phantom Works President Darryl Davis. This compares with 500-600 nm. for the F/A-18E/F and F-35, which will make up the bulk of the U.S. fighter fleet by 2025. “We need to try to reduce the dependency on aerial refueling as it is difficult to maintain sanctuaries for tankers,” says May.

 

Speed is also part of the equation, making supercruise a likely requirement. “The aircraft needs to be able to cover a large distance in a short time, to reposition in the battlespace rapidly,” he says. Supercruise — the ability to cruise supersonically without afterburner — is a capability of the F-22 that has proved valuable in combat exercises.

 

Increased firepower is another goal at the top of requirements lists. Post-2025 “the U.S. will very rarely show up with overwhelming force, which means different types of weapons will be required,” says May, citing directed-energy, smaller munitions and hypervelocity weapons.

 

Directed energy, whether high-energy lasers for self-defense or high-power microwave for counter-electronics, will place increased demands on aircraft power and cooling. In anticipation, the Air Force Research Laboratory has launched a “sixth-generation energy- optimized aircraft” program to develop technology providing a five-fold increase in power-generation and thermal-management capacity over the F-35.

 

Given demands for increased range and firepower, aircraft size will depend on engine efficiency, May says. The starting point is a variable-cycle powerplant to be demonstrated under the AFRL-led Adaptive Versatile Engine Technology (Advent) program, which promises a 25% reduction in specific fuel consumption over engines in the F-22 and F-35.

 

Davis expects the range requirement to produce an aircraft with an empty weight in the 40,000-lb. class, making it as big as an F/A-18E/F or F-22. This opens the door to an air vehicle that could be operated in manned and unmanned versions, he says, as the penalty for having a pilot would be only 1-2% of the design weight.

 

“We’ve been asked to look at both manned and unmanned,” says May. “As we look at the platform piece, we try to maintain optionally manned as a go-forward position.”

 

Both services would like to go optionally manned, he says, but for the 2025‑30 timeframe there are still issues with technology maturity and “the cultural and legal readiness to employ a completely autonomous vehicle.”

 

For the Navy mission, Davis says Boeing is looking at a single configuration offering variable levels of agility depending on whether it is operated manned or unmanned. The unmanned NGAD would offer g-onset rates and accelerations well beyond what a human could withstand, the vehicle self-adjusting its flight characteristics depending on whether a pilot is on board or not.

 

Also a priority is the ability to connect to other forces via assured communications and high-speed data links. Whereas the U.S. anti-access force — B‑2s, F‑22s and F-35s — will be able to talk to each other, they will have only limited ability to share information with non-stealthy platforms. Recognizing that any aircraft operating inside denied airspace will also be a sensor, “there is more interest in sharing information,” says May.

 

There is also interest in being able to keep operating when space-based communication and navigation assets are denied by an enemy. “They want to look at what happens if we don’t have space-based assets,” he says. The emphasis on being able to operate without GPS or satcom has increased since China’s anti-satellite test in 2007. “We don’t think anyone in 2025 will be able to completely deny those space-based assets, but we need to reduce our reliance on them,” he says.

 

Operating in denied airspace raises the issue of stealth, which was a cost driver on the F-22 and F-35. “They are not looking for all-out signature reduction at the expense of other things,” says May. “They are definitely looking at a balanced approach, but we must recognize that the signature levels of today are probably not adequate in the 2025 timeframe. There has to be enough signature reduction across all spectra to accomplish the mission, but not at the expense of other capabilities.”

 

Technology maturity — or the lack of it — was another cost driver on the F-22 program, and pressure is growing to get research efforts underway to support the proposed timeframe for a sixth-generation fighter. Based on times from development start to service entry of roughly 15 years for the F-22 and F-35, technology needs to be at the readiness level required to enter development by 2015 at the earliest.

 

Key efforts are already under way, including the Advent engine and AFRL’s parallel Integrated Vehicle and Energy Technology program, which includes the energy-optimized aircraft. Advent is demonstrating the ability to vary fan flow and pressure ratio to minimize fuel consumption, and to introduce a “third stream” of air between the engine’s core and bypass flows to increase the cooling for aircraft systems. Rolls-Royce will run an Advent ground demonstrator engine in 2013.

 

The Office of Naval Research, meanwhile, is planning a Variable-Cycle Advanced Technology demonstration program, which could begin in Fiscal 2012. This may involve tailoring the Air Force-led Advent configuration to the unique requirements of naval aviation, including reducing engine noise during carrier flight-deck operations.

 

Both the Air Force and Navy are still developing their requirements. The Navy completed its capabilities-based assessment, required to produce the initial capabilities document for the NGAD, at the end of 2009, while the Air Force’s is now under way. The Navy is expected to launch an analysis of alternatives, the next step towards a program of record, in the Fiscal 2012 timeframe.

 

Given the notional in-service dates of around 2025 for the Navy and 2030 for the Air Force there is definite technology overlap, but no talk yet of a joint program. “The same dust cover?” asks May. “They are not on the same path yet.”

 

With Robert Wall in London and Andy Nativi in Genoa.

 

 

  F-22A Raptor ⓒ USAF

 

  F-22A Raptor ⓒ FlightGlobal

 

  F-22A Raptor ⓒ Lockheed Martin

 

  F-35C, CF-01 ⓒ Lockheed Martin