Boeing, DARPA Revolutionizing The Future Of Stealth Aircraft

Innovations in inlets and exhausts are needed to conform to flying wing designs of future stealth aircraft. Advances in systems integration, miniaturization, actuators, sensors and computing power have made AFC technology feasible for military aircraft. Moving control surfaces, meanwhile, can impact aircraft radar cross sections (RCS), potentially compromising stealth.

AFC is more desirable than passive measures like traditional hinged flight control surfaces, as it can be turned on and off as required. AFC technology enables multiple opportunities for aircraft performance improvements including the elimination of moving control surfaces, drag reduction, the creation of thicker wings, increased fuel capacity, and simplified high-lift systems.

Future stealth aircraft, like the sixth-generation US Next Generation Air Dominance (NGAD), may use AFC to leverage multiple advantages afforded by the technology.

In a January 2022 article for The National Interest , Alex Hollings notes that AFC can supplement or remove traditional moving control surfaces to improve aircraft flight performance and reduce mass and volume compared to conventional control surfaces, enabling greater payloads, speed and lesser maintenance requirements and leading to higher operational readiness rates.

Hollings notes that in cases where stealth is required, pilots can use AFC technology for broad control of the aircraft when flying in contested or heavily defended airspace, then transition to traditional flight control surfaces for life-or-death situations where maneuverability is needed such as in aerial dogfights.

Next-generation stealth drones may also feature AFC technology to improve their survivability in contested or heavily defended airspace.

In July 2022, Breaking Defense reported
that the US Air Force plans to phase out its RQ-4 Global Hawk drones by 2027 to make way for newer drones that are more survivable in contested and defended airspace.

The US Air Force has described the RQ-4 as a“legacy” platform that offers limited capability against near-peer threats. However, the Breaking Defense report notes that divesting the RQ-4 too early might leave a significant intelligence, surveillance and reconnaissance (ISR) capability gap while a replacement is in the works.

The Warzone noted in an April 2021 article
that the stealthy RQ-180 may take over the RQ-4's ISR role and serve as a high-flying information and networking node.

While details are scant on the RQ-180's specifications, The Warzone describes it as a large, twin-engine flying-wing aircraft with slender laminar-flow optimized wings whose design was mandated by highly advanced, broadband, all-aspect stealth requirements.

The Warzone mentions that the RQ-180 is meant to fly at high altitudes above 70,000 feet for prolonged periods without being detected. Later generations, or even the successor of the RQ-180, may feature AFC to further enhance its already formidable stealth characteristics.

Moreover, AFC may feature in the next generation of armed combat drones designed to penetrate heavily contested airspace and engage in high-tempo combat.

In September 2023, Asia Times reported
on General Atomics and DARPA's so-called“LongShot” program, a wingman drone designed to launch air-to-air missiles for beyond-visual-range (BVR) combat.

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While the LongShot drone could use AFC to maintain stealth while moving into contested airspace, it could also switch to using traditional control surfaces for aerial combat maneuvers.

Increasing stealth may have refocused the spotlight on dogfighting skills, which have recently been de-emphasized in favor of BVR engagements. The increasing stealth of both fighters and drones means that opposing sides can end up within visual range (WVR) of each other, inadvertently ending up in a close-quarters fight.

At the same time, AFC technology still faces significant technical challenges, specifically in regard to miniaturization and diverse applications.

Artist's concept of a drone swarm. Credit: C4ISRNET

In an October 2021 article in the peer-reviewed Annual Review of Fluid Mechanics journal , David Greenblatt and David Williams note that energy efficiency is a significant challenge in applying AFC in flapping-wing micro and nano-drones.

Greenblatt and Williams wrote that AFC systems have no dominant design philosophy or approach due to different control objectives, flight regimes and actuation methods. They state that design approaches vary depending on the specific application and objectives.

Greenblatt and Williams also state that the practical application of AFC involves comprehending the aerodynamics of control effectors and their interaction with flight vehicle dynamics using methods like experimental correlations, dimensional analysis, reduced-order modeling or high-fidelity computational fluid dynamics.