When the Navy’s Super Hornet fighter jets take off from an aircraft carrier, they are sometimes accompanied by squadmates loaded down with five extra tanks of fuel. A few hundred miles into the mission, these fighter-jet tankers will top off the tanks of their compatriots, boosting their range, before heading back. This is complex, difficult work, and it strains their air frames. But by 2024, the Navy plans to have that work done instead by a sophisticated, autonomous drone called the MQ-25A Stingray, which will operate from carriers as a tanker and let the fighters do the fighting.
On a runway, the MQ-25A Stingray looks like half a plane. Its sleek, gray body, with narrow wings and condensed fuselage, gives it an appearance that is somewhere between a fictional starfighter and a real-world stunt jet with the cockpit lobbed off. Built by Boeing, the Stingray is a wholly uninhabited airframe, made to autonomously refuel other fighters mid-air. It’s crucial to the US Navy’s vision of war robots for the future, and it will soon be flying routine missions near California’s channel islands.
On March 16th, the Navy released its Unmanned Campaign Framework, outlining the present state of Navy robotics and how it intends to evolve those capabilities for the future. That same week, the Navy released its environmental impact assessment for basing the Stingray at Naval Base Ventura County in California. The future of the Navy is one filled with robots, and the Stingray will be crucial to seeing that vision realized.
The Navy expects the Stingray to enter service as part of normal operations in 2024, though the service has been less forthcoming on earlier milestones. When it does so, it will be the culmination of an 18-year long journey, an ambitious accomplishment nonetheless scaled down from the grand visions put forth for super capable flying robots in the mid-2000s.
The story of the Stingray is the story not just of the MQ-25A, but of the expansive vision for combat drones that preceded it, and of the future of robot fighters that will likely build on its success.
“The Stingray is emblematic of this push to grow the envelope of what uninhabited vehicles can do and their roles on the battlefield,” says Dan Gettinger, an analyst at the Mitchell Institute for Aerospace Studies and an independent consultant. “We’ve had drones proposed for resupplying infantry [and] for carrying cargo—that isn’t new—but taking us to an air-to-air tanker mission is pretty novel in the history of drones.”
In the present, the Stingray has to prove that it can do three difficult tasks well, and do them repeatedly. Every aircraft carrier is a small runway, and launching from that short runway is often aided by a catapult, which hurls the plane into the sky with extra momentum. Landing on a carrier is harder, as the runway isn’t just small—it is also moving on water.
Human pilots train for this in simulators and then repeatedly while underway, mastering day landings and then moving on to night approaches. The Stingray will have to do it all autonomously, with algorithms and sensors supplanting human experience and knowledge.
In the air, the Stingray’s primary mission will be the aforementioned aerial refueling. This involves flying out 500 miles, dangling an ovipositor-like tube into a special refueling spigot on the receiving plane, maintaining steady flight until the fighter’s tank is topped off, and then repeating the process until the tanker has exhausted the 15,000 pounds of fuel it carries for this purpose. (Sometimes, it will also involve flying out to meet fighters as they return from a mission, and topping off the tank so they have enough juice to get home.)
When human pilots are in both airborne vehicles as they are now, they can, if all else fails, at least radio each other to communicate and make sure everything lines up. Flying autonomously, the Stingray will have to rely instead on its programming, and on the limited means of responding to humans in-flight to handle any of this bumpiness.
“The MQ-25 will give us the ability to extend the air wing out probably 300 or 400 miles beyond where we typically go,” Vice Admiral MikeShoemaker told the US Naval Institute magazine Proceedings in September 2017. “We will be able to do that and sustain a nominal number of airplanes at that distance.”
A Super Hornet can fly about 450 miles before needing to return for refueling. While the current strategy of using Hornets to refuel other Hornets is effective, every refueling demands human pilots, and keeps useful fighters from participating in long-range attacks. It also increases the wear and tear on the Super Hornets that fly as carriers, shortening the overall lifetime expectancy of the fleet. Handing that mission off to a drone frees up existing Super Hornets and human pilots for the far-reaching missions.
What the Stringray does is the fundamentally unflashy support work of war. Having them in the fleet makes the fighters better, and it means that the carriers the fighters fly from are able to stay further away from danger, or able to send fighters further afield to harder-to-hit foes. The Stingray facilitates air war, even if its main mode of operations will be as a fuel depot in the sky between the runway and where the bombs hit.
It is a modest start for a program that can trace its roots back to the early 21st century. In 2006 the Navy was exploring what, exactly, it could do with flying robots. A defense budget from October 2000 had called for “one-third of the aircraft in the operational deep strike force aircraft fleet” to be uninhabited by 2010. For the Navy, this meant developing a stealthy, autonomous, carrier-based Unmanned Combat Aerial Vehicle-Navy.
A report from the Congressional Research Service in October 2006 outlined this vision. UCAV-N’s first mission would be surveillance, and its second would be the suppression of enemy air defenses and strike operations. (Suppression can be done with jammers or electronic warfare, messing up sensors; the second part refers to the use of bombs, missiles, and bullets.)
Development on a combat drone for the Navy started with DARPA in 2003, with research then handed off to a joint Air Force and Navy office in 2005, before the program became entirely Naval in 2006. This program paid off in the X-47B, a wedge-shaped autonomous drone that first flew in 2011.
Built as an experimental technology demonstrator, the X-47B was capable of taking off from and landing on an aircraft carrier, though it didn’t always stick the landing. In later flights, it demonstrated the ability to fly with fighters in formation, and as a finale of sorts, it was even successfully refueled in mid-air.
[Related: China is building drone planes for its aircraft carriers]
After the X-47B, it was expected that the Navy would look to develop the drone out into a fully fledged combat aircraft, capable of following human-issued orders to find enemies and drop bombs on them. Instead, the Navy scaled back the scopes of its vision for uninhabited aircraft, moving it away from direct combat.
In part driven by a slight budgetary constraint, the Navy looked to move its drone out of a combat role and into intelligence, surveillance, and reconnaissance instead. This work was what grew the Air Force’s drone program, with Predators starting as unarmed scouts before adding weapons, and leading to the Reaper line of scouts armed from the beginning.
“[The] idea from the start was that the Stingray could perhaps in the future take on the missions that were envisioned for the X-47B, but until last week there wasn’t much word from the Navy on expanding that mission set beyond the tanker role,” Gettinger says.
As Secretary of the Navy Ray Mabus outlined in 2014, “the end state is an autonomous aircraft capable of precision strike in a contested environment, and it is expected to grow and expand its missions so that it is capable of extended range intelligence, surveillance and reconnaissance, electronic warfare, tanking, and maritime domain awareness.”
That may still remain the end state in mind, but the Stingray is going to get there first by figuring out how to be a reliable tanker, and then by adding scouting onto an already successful tanker platform. The Navy set out to make its big carrier drone a tanker in 2016, over the objections of Congress, which wanted to focus that energy instead on an attack aircraft.
That switch to a tanker also meant that Northrop Grumman, which built the X-47B, decided to exit the competition for the contract, which was ultimately won by Boeing.
At a Capitol Hill hearing about the Navy’s new Unmanned Campaign Framework, Vice Admiral James Kilby floated the possibility that the Stingray’s capable airframe could take on tasks and payloads beyond that of mid-air refueling.
“Let’s move to [intelligence surveillance and reconnaissance], maybe electronic attack, strike, and then other things as complexity grows across that mission set,” Kilby said. “But I think the MQ-25 has great promise for us.”
Electronic warfare, broadly, refers to jammers and other weapons that interfere with or incapacitate electronic systems, through means other than explosive destruction. The Stingray could be another way for carriers to put weapons on far-away targets, be they tanks, radar installations, or people marked as enemies.
Getting the Stingray, or some other drone built on its success, to fly those missions will be crucial if the Navy is to reach “upwards of 40 percent of the aircraft in an air wing that are unmanned,” as Kilby promised in that same hearing.
Before all of this happens, the Stingray fleet will need to settle into its new home, the naval base at Point Mugu, just west of Malibu in Ventura County on the Pacific coast.