These days, a fighter pilot with a kill is a rare specimen. Yet, despite living in a world with few air battles, aviators still need to know what it is like to shoot down another aircraft. For a lucky few, that can mean shooting at disposable jet-powered target drones.
Many of those subscale target aircraft are built by Kratos Defense & Security Solutions. In July, the company gave FlightGlobal a tour of its Sacramento, California manufacturing plant where it makes the BQM-167A, the only subscale aerial target platform operated by the US Air Force (USAF), and the BQM-177A, the sub-sonic aerial target, the US Navy uses, which is designed to mimic sea-skimming cruise missiles.
Kratos's work building target drones is growing. It has also heavily influenced the USAF's work developing tactical jet-powered unmanned air vehicles (UAVs) – novel aircraft designs that some military thinkers believe could be the next big thing in air combat.
While the practice of shooting down target drones for training goes back to the Second World War, today it is somewhat rare for UAVs to be destroyed in training. Only about one in five target drone flights carried out by the USAF, USN and US Army are kill missions. Smaller military budgets mean international customers shoot down even fewer of the aircraft: less than one in 20 fights are kill missions.
"It’s a happy day at the office when one of those pilots gets to shoot one down," says Steve Fendley, president of the unmanned systems division at Kratos Defense. "They start calling themselves an ace."
Kratos delivers roughly 100 UAVs to the USAF, USN and US Army each year. About 20 to 50 examples each year go to international customers such as Australia, France, South Korea, Sweden, the UK and Taiwan.
To make the most of their limited supply of target drones, militaries often find clever ways to simulate kills. Perhaps the most unusual means is the tow target method, in which a target drone drags another, smaller target drone through the air, sometimes using more than 2 miles (3.5km) of cable.
"A tow target effectively looks like a missile body. We will deploy that out to that long distance and then the customers shoot at the tow target," says Fendley. "A lot of times they do it because they want to be able to distinguish between the two."
For example, an air force might want a weapons systems operator to be able to differentiate between a threatening aircraft and a friendly aircraft on a radar screen. Tow targets can be given a radar signature that looks like a particular aircraft, such as an RAC MiG-35, using a radar reflector, a small device that mimics the radar cross section of particular aircraft. Radar reflectors are also used on Raytheon's Miniature Air-Launched Decoy missiles to deceive or confuse enemy radars.
"For international customers 90% of the time they are using tow targets," says Fendley. "For the USA less than a third of the time will they use a tow target."
US Air Force
Another way to prolong the life of a target drone is to program an offset into a missile shot at the vehicle; militaries credit a kill when the missile flies within a certain range of the target UAV.
"The airplane has a scoring system on it and the missile has a scoring system on it," says Fendley. "Because you can measure that distance, you know if you had taken out the offset you would have killed the airplane. But, it didn't cost you anything because you still have the airplane and you didn't waste a warhead."
Alternatives aside, there is nothing like getting a hard kill after dogfighting with a target drone, says Fendley. But at a size that is smaller than a light fighter and with the ability to manoeuvre with turns up to 12g – far beyond what a human pilot could withstand – it's no small feat to down a target drone. "The threat needs to be more capable than the fighter that needs to go after it, so that you know that you are really offering a challenge," says Fendley.
Kratos's target drones are able to withstand high g forces due to their almost entirely carbon composite structures, says Fendley. Target aircraft are built using a proprietary epoxy with carbon that is primarily supplied by Park Electrochemical. The company uses little foam core to strengthen its aircraft, but instead relies on a wing with a monocoque structure, reinforced with zig-zag composite material ribbing. The ribbing adds strength, but also allows for more spare fuel volume.
The UAVs are powered by jet turbines made by Jetcat or Safran's Microturbo. The latter's Microturbo TRI 60, which produces about 1,000lb (4.45kN)-thrust, powers Kratos's BQM-167A and BQM-177A targets. Drones are recovered with a parachute that deploys from the back of the vehicle. The UAVs land on a crushable cone in their nose. The smaller MQM-178 Firejet is launched via a pneumatic-powered launcher rail, while the larger BQM-167A and BQM-177A use rocket-assisted take-off. "They are subjected to up to 30g at launch and about 25g on landing," says Fendley. "So they are extremely survivable."
Each target drone is optimised for certain missions. "The 167 is the Air Force workhorse," says Fendley. "The Air Force application is optimised for air-to-air, to look like and act like a fighter jet." The UAV’s maximum speed is 586kt (1,085km/h) and it has a maximum operating altitude of 50,000ft. For the USN, Kratos's BQM-177A is optimised to mimic a cruise missile – flying as low as 6-9ft above the surface at speeds of up to Mach 0.95.
The smallest, and lowest-cost, target system is the Firejet. Built for the US Army, it is 3.3m (10ft) in length and has a 1.9m wingspan. It is now being built at Kratos's new facility in Oklahoma City and has a maximum speed of 435kt and a maximum operating altitude of 35,000ft. Fendley describes is as high-g, high-speed and high-utility, but "very low cost, on the order of one-third the cost" of a large system like the BQM-167A.
US Air Force
RIDE OF THE VALKYRIE
Many of the design characteristics that give Kratos's target drones high-g, high-speed, long-endurance capabilities have found their way into the USAF's emerging tactical UAV concepts. The idea dates to 2010, when Kratos noticed a capability gap with existing UAVs, as outlined within the Department of Defense (DoD) Unmanned Systems Integrated Roadmap: FY2011-2036 document. Fendley says the company thought its existing line of jet-powered target drones could be modified to fill that gap – and now, after two successful test flights of the XQ-58A Valkyrie, the service is considering buying up to 30 examples, possibly by the end of 2019, for further experimentation.
Following Pentagon confirmation that it was indeed interested in fast-moving, jet-powered drones, Kratos spent some of its own internal research and development money to convert its BQM-167A into the UTAP-22 Mako tactical UAV. From there, the company developed the clean-sheet XQ-58A Valkyrie design using internal funding and money from the Air Force Research Laboratory (AFRL).
Production is now primed to ramp up. To support that effort, Kratos has ordered six Williams International FJ33 turbofan jet engines with options for up to 30 more. Two Valkyries have been delivered and a third is in final assembly. Kratos believes the aircraft could be operationally capable by 2022 or 2023.
Such aircraft could have a wide variety of roles. A so-called "loyal wingman" UAV is designed to fly in co-ordination with a manned fighter aircraft, but the USAF believes tactical jet-powered UAVs could also conduct independent intelligence, surveillance and reconnaissance (ISR) missions – and even work as part of a swarm to overwhelm a target during an air-to-ground attack.
Low-cost tactical UAVs promise to amplify the abilities of an air force. Kratos claims it could build the first 99 XQ-58As at a unit cost of $3 million or less, a price that would fall to $2 million for purchases of 100 units or greater.
The XQ-58A can carry 272kg (600lb) of ordinance in its weapons bay and 272kg on its wings, enough for four small-diameter bombs, says Kratos. It launches without a runway and parachute-lands on its belly using an airbag cushion.
In fact, the USAF's impending Valkyrie purchase could be the leading edge of an incoming wave of thousands of tactical UAV purchases by the Pentagon and allied militaries.
Kratos says it is playing a major role in 11 UAVs under development for the USA including the XQ-58A. Also in the works are the Defense Advanced Research Project Agency (DARPA) Gremlins programme, the DoD Defense Innovation Unit's UTAP-22 Mako, and projects with names such as Apollo, Athena, Program F, Thanatos and Spartan for undisclosed and classified customers.
In one instance, Program F, the company believes it could receive an order in the next couple of years for 1,000 examples to be produced and delivered over a three-year period after demonstration flights are complete.
In reaction, other manufacturers and militaries are ramping up their efforts. In just the last 12 months, Airbus Defence & Space, Boeing Australia, Bombardier Aerospace's Belfast unit, Blue Bear Systems Research, Dassault Aviation, Northrop Grumman UK and RAC MiG have announced tactical UAV development efforts.
The USAF expanded its efforts in 2019 to integrate loyal wingman aircraft into its squadrons. The service is funding the Lockheed Martin F-35's Block 4 upgrade and Technology Refresh 3, which will include a command, control and communications capability for unmanned-manned teaming with drone systems.
The AFRL in March 2019 announced that it was developing artificial intelligence (AI) software to control a prototype tactical UAV. The organisation wants an early operational capability AI prototype fielded by the end of calendar year 2023.
Off-the-wall ideas for tactical, jet-powered UAVs applications are also emerging. For instance, DARPA's Gremlins programme envisions launching groups of small, jet-powered UAVs from bombers, fighters or transport aircraft from beyond the range of an adversary's defences. The Gremlins would carry out an ISR mission before flying back to a loitering Lockheed Martin C-130 transport aircraft, which would grab them out of the air with a sort of skyhook.
Dynetics is the prime contractor on Gremlins, with Kratos subcontracted to build the aircraft fuselage. The composite-constructed Gremlin UAV weighs 363kg and has a pivoting wing. The Dynetics-Kratos team has delivered two aircraft so far, with units three and four in production. DARPA expects demonstration flights before the end of 2019 or early 2020.
Separately, Kratos and AeroVironment, a manufacturer of small, propeller-driven ISR drones, announced in May that they are experimenting with launching loitering munitions from tactical UAVs, starting with a demonstration using the Firejet. Fendley says trials likely to begin by year-end could see AeroVironment's Switchblade weapon launched off the wing of a Firejet – adding 200nm (370km) to the flying munition's 5.4nm range.