Steve Trimble Aircraft propulsion concepts, radio-frequency sensors, mesh networks and autonomous control systems are driving a reimagining of roles.
Steve Trimble
The sky over the 1.4-million-mi.2 expanse of the South China Sea will be crossed with dozens of a new kind of hybrid-electric combat aircraft. With the ability to sip gas and refuel while in flight, these so-called Defenders will form a persistent air-to-air surveillance net for as long as a month at a time.
Aided by a package of newly invented technologies, including mesh networking radios, multifunction radio-frequency sensors and autonomous control systems, this swarm of Defender unmanned aircraft systems (UAS) will provide a dome of protection over a quadrant of the Western Pacific.
Any hostile aircraft that enters the swarm’s broad field of view will be detected and tracked, with the Defenders feeding the targeting data to friendly stealth fighters. The swarm itself is protected by the sheer complexity it presents to an enemy, which must shoot down enough of the swarm’s members to thwart their mission: to protect friendly air refuelers and vulnerable surveillance aircraft from attack by enemy fighters and missiles.
That is General Atomics Aeronautical Systems Inc.’s (GA-ASI) vision for a futuristic concept called the Defender UAS. The company released an image of the concept last year but withheld a public explanation.
With a series of flight experiments by the U.S. Air Force and defense contractors set to demonstrate the Skyborg control system this summer, a discussion over what purpose—and how soon—such aircraft can serve in combat missions has already begun. The Autonomous Attritable Aircraft Experimentation (AAAX) series by the Air Force Research Laboratory (AFRL) launched in April with the Skyborg control system flown onboard a Kratos UTAP-22. AAAX continued on June 24 when AFRL flew the Skyborg software on a GA-ASI MQ-20 Avenger-Extended Range.
In exclusive interviews with Aviation Week, GA-ASI executives shared the first details of the company’s bold vision for the future of the medium-altitude, long-endurance (MALE) UAS that will follow the MQ-9 into service.
GA-ASI’s Defender concept has emerged as the Air Force searches for its Next-Generation Multirole UAS, which is also called the MQ-Next. The initial role for this more survivable and affordable MQ-9 successor is envisioned as high-value airborne asset (HVAA) protection, according to an Air Force request for information published in March.
Manned fighters are normally used to defend the HVAA fleet, which includes aircraft such as Boeing RC-135 Rivet Joints and KC-46 Poseidons. But a new class of long-endurance UAS equipped to operate alongside manned aircraft and track airborne threats at distant ranges could perform the mission in the future. That would free up the manned fighters to conduct offensive strikes, rather than serving as aerial bodyguards for vulnerable support aircraft.
GA-ASI began developing the Defender concept to perform such a role over five years ago, says Michael Atwood, GA-ASI’s senior director for advanced programs. They were prompted by Will Roper, who was director of the Defense Department’s Strategic Capabilities Office at the time, to reimagine the role of a MALE UAS for future HVAA protection missions.
A GA-ASI MQ-20 Avenger-Extended Range flew with the Skyborg autonomy control system at the Air Force’s Orange Flag exercise in June. Credit: U.S. Air Force
A GA-ASI MQ-20 Avenger-Extended Range flew with the Skyborg autonomy control system at the Air Force’s Orange Flag exercise in June. Credit: U.S. Air Force In conceiving an airborne surveillance system, the company drew upon the decades of experience it had from the MQ-1 and MQ-9 fleets in the ground surveillance mission, Atwood says.
“What you see from General Atomics is inspired from our MQ-9 experience in the Middle East,” Atwood says. “We’re responsive to pattern of life of Taliban movements because we’re always there.
“What I’m talking about is deterrence through detection,” Atwood adds. “This persistent, all-seeing grid is enabled through unmanned airplanes. [The enemy] is scared to launch their bombers because we know the minute it leaves the coastline where it is. That responsiveness comes from that detection [capability] cueing some other effective mission systems. And then that inherently makes the F-35 and F-22 more valuable now, because they’re not forced to do nontraditional [intelligence, surveillance and reconnaissance.] They [can be] the responsive wolf they’ve been designed to be.”
Supporting the company’s flashy new airframe concepts is an internal research and development pipeline that is close to yielding significant new technologies, Atwood says.
A new kind of airborne radio-frequency sensor lies at the heart of GA-ASI’s operating concept for the Defender.
Airborne fire control radars that deliver highly accurate target tracks are typically X-Band, microwave radars, such as the Lockheed Martin F-22’s APG-77 active, electronically scanned array (AESA). The centimeter-scale wavelengths of such microwave radars produce highly accurate tracks, but their range is limited. By contrast, the meter-scale wavelengths of long-wave, ultra-high-frequency or very-high-frequency radars produce significantly greater range and field of view using less power, but these types of radars are limited by tracking accuracy.
GA-ASI is in the final stages of developing a new long-wave, multifunction radar. The novel sensor technology is designed to provide similar levels of aircraft tracking accuracy as a microwave fire control radar but at distances usually associated with early warning radar.
“GA-ASI has been working on that technology for a long time, and we’re having some breakthroughs in it,” Atwood says. “I think that will ultimately be the way in which we generate very-high-quality situational awareness for an air-to-air warfighter.”
A Defender is refueled by a KC-46, which is in turn protected by armed UAS, in this artist’s concept. Credit: General Atomics
A Defender is refueled by a KC-46, which is in turn protected by armed UAS, in this artist’s concept. Credit: General Atomics In broad terms, GA-ASI executives describe a networked swarm of long-wave, radar-equipped Defenders forming a multistatic radar system that benefits by using the fused data from multiple airborne sensor tracks to overcome the accuracy limitations of any one sensor.
“It gives you the ability to correlate tracks and become way more accurate on air-to-air targeting capability and it’s super-wide area,” says David Alexander, president of GA-ASI.
The operating concept on which GA-ASI’s Defender is based also relies on new advances in self-control technology for UAS. With that topic in mind, the U.S. Defense Department is currently demonstrating two different autonomous control systems.
The AFRL’s Skyborg program is the most well-known. DARPA has developed a separate autonomy engine for aircraft under the Collaborative Operations in Denied Environments (CODE) program. The agency has since transitioned the Raytheon-developed CODE algorithms to Naval Air Systems Command, which is continuing to develop the capability under a program called Research and Autonomy Innovation Development Environment and Repository (Raider).
Although developed by different services, Skyborg and Raider share a common goal. In a communications-denied environment, the algorithms give the UAS the ability to respond to real-world threats—steering around a pop-up air defense battery, for example—without seeking permission from a human controller.
GA-ASI is not responsible for developing the government-owned autonomy engines but must prepare its aircraft to receive them. The autonomy algorithms must be allowed access to the onboard systems needed to sense the environment and respond, but they are prevented from commanding the aircraft to perform an unnecessarily unsafe maneuver. For GA-ASI, the challenge is to create an interface to the Operational Flight Program (OFP) software in the UAS’ flight computer that is flexible enough for Skyborg or Raider to use yet restrictive enough to maintain safety.
“We’ve been working on what we call Open OFP,” Alexander says. “It’s a validator that says, ‘Yeah, I got a bad command. I’m not going to do that.’ On both sides of the interface, we’re working to create this open mission capability.”
These component technologies—long-wave sensors, mesh networking radios and the Open OFP software—should be available in the relatively near future, GA-ASI executives say. The ultra-long-endurance aircraft concept optimized for the distances of the Western Pacific by using a hybrid-electric propulsion system will take longer to mature, Alexander says.
“It depends on the funding level and the interest,” he says. “But it could go as quickly as four years. It could be as long as seven.”
In the meantime, GA-ASI plans to transition the component technologies in the short term to the MQ-9 to enable it to perform the base defense mission over land in Western Europe. In this scenario, the MQ-9s would use the sensors and networking radios to create an airborne surveillance system for detecting Russian cruise missiles, such as the medium-range 9M729.
“Think of MQ-9s that can actually attack cruise missiles with this tracking capability,” Alexander says. “That’s really what we think is low-hanging fruit for the Air Force right now.”
