Posted on 01/11/2024 10:52:20 PM PST by Red Badger
Aurora Flight Sciences’ experimental active flow control aircraft is designed around a system that supplies pressurized air to effectors embedded in all flying surfaces, replacing traditional mechanical aerodynamic surfaces such as flaps and rudders. Photo: Aurora Flight Sciences
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The US Defense Advanced Research Projects Agency (DARPA) and Boeing’s Aurora Flight Sciences are working in tandem to produce an aircraft that utilizes pressurized air rather than physical surfaces for control, a revolutionary design with the potential to reshape the future of aviation and military stealth technology.
This month, Breaking Defense reported that the pioneering prototype, known as X-65, weighs 7,000 pounds and is designed to reach a maximum speed of Mach 0.7. The report says the new-fangled plane could take flight as soon as the summer of 2025.
The Control of Revolutionary Aircraft with Novel Effectors, or CRANE, program aims to break the mold of a feature fundamental to aviation’s century-plus existence by using active flow control (AFC) actuators to shape an aircraft’s flight.
The X-65 will be built with traditional control surfaces and the new actuators, with tests progressively “locking down” traditional flight control surfaces and gradually expanding the role of AFC devices, according to the Breaking Defense report.
The report says that the X-65 will be a valuable test asset for DARPA and other agencies long after CRANE concludes. It adds that the X-65 is designed as a “modular platform”, allowing it to be easily swapped out and serve as a test asset for DARPA and other agencies.
In January 2023, Asia Times reported that the X-65 is intended to serve as a testbed for new aircraft technologies with an eye on revolutionizing current stealth technologies. The CRANE program aligns with the evolution of stealth aircraft, as combat aircraft must improve performance and become more affordable and stealthier to maintain their strategic edge and value.
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.
Concept art of the possible design for the US Air Force’s future Next Generation Air Dominance stealth fighter. Image: Boeing
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.
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.
I watched Alabama buzzards (Turkey and Black Vultures) using just a few feathers to turn around and go up and down in the air. Amazing creatures!
I know I won’t live to see it, but one day these pics will be as quaint looking to people as pics of the Wright Flyer are to us.........................
If I remember correctly in the late 60s ‘North Cape’ by Joe Poyer had a spy plane that had many futuristic features (including an ejection pod like the F-111 ended up with) and flight surfaces that conformed as needed in flight. It was also controlled by thought (think Firefox movie) and the pilot was jacked up on amphetamines when needed and brought down to normal or put to sleep by barbiturates as the computer deemed necessary per the flight profile.
I don't recall having seen DARPA involved in anything like this since the Sikorsky S-72 "X-Wing" project, which was an experiment to see if they could make rotor blades on a (hybrid) helicopter with no moving control surfaces, then vary the lift produced by the rotors by selectively and cyclically injecting compressed air into the airflow around the rotors.
The thing about the X-Wing's rotor is that once they were in high-speed forward flight, they were to be 'locked' in a cruciate "X-shape" and function like a conventional wing. so it potentially could have been much faster than any helicopter.
The narrator in this video talks way too fast (and indistinctly) and is an aviation idiot but the images in the video are priceless:
https://www.youtube.com/watch?v=9IDu97ij3mo
It had stub wings for extra lift, and it did demonstrate the ability to fly with nothing but the sub wings. And the rotor head was always intended to include explosive bolts so if things went pear-shaped they always could jettison the rotor head and fly like an airplane to look for a runway.
This is a cross-section of one of the rotors, showing how they proposed to duct high-pressure air out of the leading edges of the rotors to change their lift characteristics, exactly the same as what this new project is proposing:
The hot air was to be delivered through a series of channels in the rotor mast with delivery to the individual rotor blades controlled by computers. In the short time they were working on it, they couldn't get the system to make a pronounced-enough difference in the amount of lift generated. Critically, they could never get it to create enough lift to make hovering possible, which is kinda sorta a deal-breaker in a helicopter.
So this is really a new application of a very old technology. I'd heard at one time "they" were experimenting with "wing-warping" for stealth a/c, a throwback to the method used by the Wright brothers before the advent of ailerons, because wing-warping could eliminate a seam in the skin of the plane. Ducted jets might not have seams but it seems to me (no pun intended) you've still got to have flaws in the skin for the ducted air to emerge from. But, hey, them DARPA dudes is smarter than I could ever hope to be.
Boeing stock went On Sale this week
That helicopter must be a mechanical nightmare!....................
Apparently, neither of you two geniuses is aware of the Skunk Works. Look it up.
Boeing and DARPA working on a plane together. What could go wrong?
It will be over priced, will want 2 paid holidays per month and the doors will fall off.................
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