급유기 스컹크 웍스가 공개한 무인 공중급유기 개념도

[위종민]

록히드 마틴의 스컹크 웍스가 무인스텔스 공중급유기 개념도를 공개했네요. 개념도상에는 날개 끝부분에 부착된 붐에서 F-35 2기에 동시 급유를 실시하고 있고, 공기흡입구의 위치나 모양은 표현되지 않았습니다. 

연료가 흐르는 붐이나 드로그의 스텔스성이 관건일 텐데 이게 가능한지 여부는 밝혀지지 않았습니다. 붐에 RAM을 떡칠하는 걸로 어느 정도 커버가 가능할지... 

https://www.airandspaceforces.com/skunk-works-uncrewed-ngas-concept/

A Lockheed Martin Skunk Works concept of a stealthy, uncrewed future aerial tanker was shown at the recent Airlift/Tanker Association meeting.

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Skunk Works Uncrewed NGAS Concept Gets New Attention

Nov. 9, 2024 | By John A. Tirpak

An artist’s rendering of a Lockheed Martin Skunk Works concept for a potential stealthy and autonomous Next-Generation Aerial-refueling System (NGAS) aircraft is getting new attention after a repeat display at the recent Airlift/Tanker Association meeting.

The concept breaks with many other notional futuristic tanker designs which have been variations on a crewed flying wing or blended wing body. The Skunk Works artwork shows an uncrewed aircraft with a conventional planform, shaped for some degree of stealth.

The image, displayed at the A/TA’s conference last week in Grapevine, Texas, reveals a highly flattened design with Air Force-style refueling booms deployed from pods on the far outboard of the wings. Two outward-canted stabilizers at the tips of the elevators sit well apart from a central, sawtooth exhaust, but out of the way of the two refueling stations. The exhaust suggests a single engine, but the angle of the depiction does not reveal where the air intakes are, or their shaping.

Another image of the same concept published by The War Zone also conceals the intake shaping. The image shown at A/TA was first published by Aviation Week.

It’s not clear whether the flying booms used to connect to receiver aircraft could be made stealthy, a problem long acknowledged by designers. The ones shown in the image appear similar to those used on the KC-135, although a differently-colored leading edge on the control winglets may suggest a stealth treatment.  

The notional NGAS images show the aircraft refueling two Lockheed F-35s. No central refueling station is depicted, nor is there an indication of a Navy-style probe-and-drogue capability.   

There is no apparent cockpit in the images, indicating the aircraft would be autonomous. That fits with a growing trend, as Boeing’s MQ-25 tanker for the Navy is an autonomous aircraft, and several other companies have demonstrated the ability to conduct air refueling without a human crew onboard. The Air Force has also expressed a desire to reduce the number of aircrew required on tankers.

The general shaping of the design—chines, sawtooth seams, and wing leading edges at the same angle as the elevators—suggest a low-observable design, but perhaps not an extremely low observable concept.

“This graphic depicts a notional concept of an optionally-crewed future air-refueling platform,” a Skunk Works spokesperson said.

“Our team has been maturing the next generation of air mobility through investments in survivability, autonomy, resilient communications and digital transformation that will enable the range and persistence needed for contested air refueling operation.”

The spokesperson noted that the design was publicly displayed at the 2023 A/TA conference but it “didn’t draw the attention it’s receiving this year.” Lockheed has subsequently released other NGAS artist’s concepts, and the spokesperson said none of them exactly represent what the company may submit to the Air Force for an NGAS competition.  

The concept art is drawing attention as the Air Force wraps up its NGAS Analysis of Alternatives. Air Force acquisition executive Andrew Hunter has said on various occasions that the AOA would be concluded in the fall of calendar 2024 and provide a way ahead for NGAS and a potential “bridge tanker.”

Hunter has described the latter as a way to keep some kind of tanker in production until the stealthy NGAS is available, circa 2033-2035. The current contract for Boeing KC-46As concludes around 2028 at 179 aircraft. Air Force officials have said the “bridge tanker” program could involve as many as 75 aircraft.

The concept for the NGAS is that it will accompany crewed fighters and Collaborative Combat Aircraft into contested airspace. It will be much smaller than traditional tankers like the KC-46 and KC-135 in order to have comparable stealth with the aircraft it escorts, and to be able to operate out of smaller airfields. The concept also calls for the NGAS to shuttle between older, larger tankers, flying out of reach of adversary missiles, and combat aircraft well inside the combat zone. The Lockheed concept shows the tanker with an aerial refueling receptacle of its own, centrally located on the aircraft’s spine.

Whether the NGAS will come to fruition is in considerable doubt, however. Air Force Secretary Frank Kendall, speaking at the A/TA meeting, said the service cannot simultaneously afford the NGAS, Next-Generation Air Dominance (NGAD) air superiority fighter and Collaborative Combat Aircraft (CCA) fleet of autonomous wingman drones simultaneously. Absent a large influx of resources, the Air Force will have to “get creative” to come up with a scheme for air dominance that will work with a mix of new and old systems.

Analysts at several think tanks have said that five percent funding increase above inflation for the U.S. military, suggested by some close to incoming President Donald Trump, would not be sufficient to address the wave of conventional and strategic weapons modernization deficits facing the Air Force.

Skunk Works' Latest Stealthy Tanker Concept Revealed

Skunk Works’ Latest Stealthy Tanker Concept Revealed

The USAF is firming up requirements for a stealthy tanker to fit with its Next Generation Air Dominance ecosystem, which could change dramatically due to cost.

Joseph Trevithick

Posted on Nov 6, 2024 7:35 PM EST

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Lockheed Martin Skunk Works

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Lockheed Martin’s Skunk Works advanced projects division has put forward a new notional vision for a stealthy pilot-optional aerial refueling tanker. This comes as the U.S. Air Force is refining requirements for a future Next Generation Air-Refueling System (NGAS) ‘system of systems’ and amid serious concerns about how the service expects to pay for that and other modernization priorities.

Skunk Works provided a rendering of its latest tanker concept refueling a pair of F-35A Joint Strike Fighters, seen at the top of this story and below, to The War Zone. A different view of this same conceptual design was first shown publicly at the Airlift/Tanker Association’s (ATA) recently concluded annual symposium, as reported by Aviation Week.

Lockheed Martin Skunk Works

The rendering shows an aircraft with swept main wings and horizontal stabilizers with canted outboard vertical stabilizers. The tanker also has stealthy (low-observable) features, including a chine line that wraps around the forward fuselage and continues on either side behind the wing roots and saw-tooth panel lines at various points. Low observable shaping on its wingtip pods is also evident. Where the aircraft’s engine intakes might be situated is not entirely clear, but there is a single large shrouded ‘platypus-like’ exhaust with serrated edges at the upper rear of the fuselage.

The tanker is shown with a pair of refueling booms extending from pod-like sponsons toward the end of each main wing. The boom refueling method is the U.S. Air Force’s preferred means of getting gas into other aircraft in flight. It is possible that the booms on Skunk Works’ new design concept could also be configured to provide fuel via the probe-and-drogue method, which the U.S. Navy and Marine Corps prefer. Probe-and-drogue is also used to refuel Air Force CV-22 tiltrotors, as well as helicopters across the U.S. military. This system is often installed internally on the centerline rear of large tankers, such as the Air Force’s KC-46 and now-retired KC-10, as well as the Airbus A330 Multi-Role Tanker Transport (MRTT).

Whether or not the booms might be expected to collapse and/or retract when not in use is unclear. Though such a system could offer aerodynamic and radar signature-reducing benefits, it could also limit the strength of the boom. That, in turn, could present potential operational limitations and safety concerns. The booms on traditional tankers have been known to break under the wrong circumstances as happened just earlier this year in a mishap involving an Air Force KC-46 and an F-15E Strike Eagle combat jet, which you can read more about here. The KC-46, specifically, has been beset by various technical and other issues over the years, including a still unsolved “stiff boom” problem that prevents it from being used operationally to refuel A-10 Warthog ground attack aircraft at all.

A KC-46 refuels an A-10 Warthog ground attack aircraft during a test. USAF

Aviation Week had reported that Skunk Works’ notional design is pilot optional, with no clear provision for a crewed cockpit seen in the renderings available. It is possible that a cockpit could be fitted, as required, in place of a faired-over section on top of the forward fuselage. Another variation of the rendering might also exist showing a cockpit.

A pilot-optional design versus a completely uncrewed version does offer certain benefits. The War Zone previously explored this in detail after the emergence of the stealthy Model 437 Vanguard technology demonstrator jet from Northrop Grumman subsidiary scaled composites earlier this year, writing:

“Unmanned aircraft are still quite restricted as to where and how they can operate. A pilot totally changes this massive bottleneck and means the aircraft can be flown wherever it needs to go, to participate in any developmental flights or training exercises, no matter how complex. It can do this unburdened by typical drone airspace restrictions and the need for chase aircraft that can be required in certain situations. Just ferrying to a different location while manned, so it can access airspace where it can fly as if it were an unmanned aircraft, is a giant advantage.”

“For many tests, having a human onboard can accelerate the speed at which they can be accomplished. At its most basic, initial primary flight testing of the airframe will go far faster with a pilot at the controls. Overall, more risks can be taken when executing autonomous activities with a pilot there to take over and act as a safety backstop if needed.”

Skunk Works has publicly shown a number of other notional advanced crewed tankers in the past, including a boom-equipped one with an almost fighter-esque appearance just earlier this year, the features of which we previously explored in detail. Lockheed Martin has presented variations on a blended-wing-body design concept configured for boom and probe-and-drogue refueling, as well.

A rendering of a stealthy crewed tanker concept that Skunk Works distributed earlier this year. Lockheed Martin Skunk Works

A model of a blend wing body aircraft concept that Lockheed Martin displayed in the late 2010s and said could be adaptable to meet future tanker requirements. Joseph Trevithick A model of a blend wing body aircraft concept that Lockheed martin displayed in the late 2010s and said could be adaptable to meet the requirements of what was then known as KC-Z. Joseph Trevithick

Lockheed Martin art from the late 2010s depicting stealthy blended wing body tankers fueling aircraft using the boom and probe-and-drogue methods. Lockheed Martin

“Our team continues to explore a variety of configurations that deliver mission effectiveness through a connected, affordable, survivable and autonomous next generation tanker capability,” a Skunk Works spokesperson told The War Zone when asked for more details about the newest notional design. “We look forward to providing the U.S. Air Force with the range and endurance needed to fulfill the future of NGAS as it continues to define requirements.”

As already noted, the Air Force currently describes NGAS as a proposed family of systems, which could include a crew or uncrewed stealthy tanker, or a pilot-optional design, or some combination thereof. Boeing has also been pitching a land-based derivative of the MQ-25 Stingray tanker drone that it is developing for the U.S. Navy as a possible option for NGAS.

The complete NGAS ‘system of system’ is also expected to include existing non-stealthy tankers like the KC-46 and the KC-135 with various self-defense and other upgrades. The Air Force has also been actively exploring ‘buddy store’ podded aerial refueling systems that can work with aircraft configured to use the boom, which would also allow other aircraft, including tactical jets, to contribute to this refueling ecosystem.

Uncrewed tankers could be paired with crewed ones in a hub-and-spoke arrangement, with the drones helping ferry fuel to areas closer to the tactical edge while reducing risks to human aircrews. It is worth noting here that Skunk Works’ new rendering shows a notional design that can be refueled in flight itself.

Other tactics, techniques, and procedures could also help reduce the vulnerability of key aerial refueling assets, including linking up with receivers at lower altitudes below an enemy’s radar horizon. This is something the Air Force’s special operations community already has experienced doing, including with a pocket fleet of specialized KC-135RT “receiver-tankers” that can refuel and be refueled in mid-air, which you can read more about here.

A mid-air refueling capable KC-135RT about to link up with a regular KC-135 tanker. USAF

The War Zone has been highlighting the increasingly critical need for stealthy or otherwise more survivable tankers for years now. Expanding and evolving air defense threats, especially in the context of potential high-fight with China have only underscored this reality and are key drivers behind the Air Force’s current NGAS planning.

“Essentially the threat, China again, has reached out with new counter-air systems that could threaten our aircraft, especially tankers, at longer ranges, beyond the ranges which we normally would refuel fighter planes,” Secretary of the Air Force Frank Kendall said in a keynote address at the same ATA symposium where Skunk Works first rolled out its new tanker rendering. “This put our whole tanker acquisition strategy in question. It is still in question, but we are working to resolve the uncertainty as quickly as possible.”

Critical factors in this ongoing debate are range considerations, which are particularly pronounced in the Pacific region, together with the typically short combat radii of America’s current tactical combat jet fleets. This, in turn, puts existing tankers dangerously close to, if not inside anti-access/area denial bubbles near-peer competitors like China have already established and continue to expand.

Stealthy tankers that are not meant to penetrate deep into high-threat airspace, but to persist and operate on the edges of those zones, allowing existing tactical airpower and newer platforms to make it to their targets, could be part of changing that equation. Air Force plans for a new sixth-generation crewed stealth combat jet and Collaborative Combat Aircraft (CCA) drones as part of the Next Generation Air Dominance (NGAD) initiative have been set to have significant impacts in all this, with discussions about their expected ranges (and other capabilities) also tied in with how NGAS evolves. Procurement of a stealth tanker could help trade range and thus the complexity and cost of these new tactical platforms, while also keeping existing ones more relevant. The NGAD combat jet program is currently undergoing a deep review and the outcome of that reassessment will also have direct ramifications for the NGAS and CCA efforts.

In addition, “unfortunately, any new [tanker] design cannot be fielded for several years at best, even if affordable,” Kendall warned while speaking at the ATA gathering, highlighting potential lower cost-near term alternatives, such as upgrading existing tankers.

An artist’s depiction of a blended wing body concept aircraft employed in the tanker role. This art was produced in relation to a program called Speed Agile in the late 2000s-early 2010s. Public Domain An artist’s depiction of a Speed Agile concept aircraft employed in the tanker role. Public Domain

The Air Force’s top civilian also added new and even more dire remarks to a growing chorus of concerns about the affordability of a host of next-generation modernization efforts beyond NGAS that the service has previously described as essential for fighting and winning future high-end conflicts.

“The variable that concerns me most as we go through this analysis and produce a range of alternatives is going to be [the availability of adequate resources.] … to pursue any combination of those new designs,” Kendall said, referring to the NGAD combat jet and CCA drones, as well as NGAS.

You can read more about this brewing budgetary crisis here.

The Air Force is hoping to have firmer understanding of its NGAS requirements before the year is out. At that point, it may be clearer whether or not something like Skunk Works’ newest design concept is what the service is looking for to meet its future aerial refueling needs, if it can afford them.

Contact the author: joe@twz.com

[Minowski(김유철)]

붐도 그렇고 드래그도 그렇고 어차피 말단은 접촉을 많이 하는 부품이니 램을 도포해놔도 오래가지 못할 것 같습니다. 거기다 드래그는 적어도 지금 형상이면 레이더파 난반사가 장난아닐거 같고......상상도의 벌지부분 같은 곳에 붐이나 드래그나 신축수납으로 해서 도킹부를 최대한 감추고 있다가 전개하는 방식으로 가야할 듯 합니다. 그렇게 보관하면 스텔스도료가 1회 급유때까지는 허용되는 피탐수준을 유지할 수 있을 것 같습니다.

[위종민]

공중급유 공역을 최대한 전장에 가까운 곳에 설정을 하는 게 목표일 텐데, 과연 기술적으로 가능한 건지가 참 의문이란 말이죠..

[ssn688]

결과론이지만, 접근거부(에 대응해야만 하는) 시대에 전술기에게 적합한 급유방식은 호스였으려나요...

[위종민]

재질상 아무래도 붐보다는 드로그가 레이더를 덜 반사하긴 하겠네요.