History of unmanned combat aerial vehicles

During the 1960s the US Navy installed thousands of QH-50 DASH torpedo-launching helicopter drones on many of their destroyers. They were meant as a stopgap measure to counter the threat of an ever-growing fleet of Soviet attack submarines. The entire fleet was retired when larger destroyers were introduced, permitting the use of manned helicopters to launch the same kind of torpedo, and the use of more powerful rocket-assisted torpedo systems.

If UAVs could be used for reconnaissance by the army and the air force, it was obvious that they could also be used for active combat missions, at least in principle. In practice, shooting at a specific ground target is much trickier than flying over an area and taking pictures, and it wasn't until the 1970s that the US Air Force seriously experimented with the concept. The objective was to study an attack system to perform the dangerous "suppression of enemy air defenses (SEAD)" mission, or in other words to destroy enemy anti-aircraft gun and SAM sites. The project was known as HAVE LEMON.

Ryan Firebee

HAVE LEMON involved a number of Ryan Firebees equipped with a weapons pylon under each wing, a forward-looking TV camera, and a datalink mounted in a pod on top of the vertical tailplane. These UAVs were given the designation "BGM-34A" and used beginning in late 1971 to perform remote-control strikes on simulated air-defense sites with Maverick missiles and HOBOS TV-guided glide bombs.

The results were good enough to permit follow-on development, resulting in the "BGM-34B", which featured an extended nose to accommodate an infrared imaging system (some sources say low-light-level TV) and laser designator for targeting and control of laser-guided bombs. Tests performed in 1973 and 1974 with the BGM-34B were also successful, and led Teledyne Ryan to develop a "BGM-34C" as a conversion of existing Lightning Bug airframes. The BGM-34C could be used for reconnaissance or strike missions by swapping out nose modules and other elements.

The concept proved to be a little too far ahead of its time. Nobody in the Air Force hierarchy stepped forward to take ownership of the issue, and the HAVE LEMON exercise faded away. The test squadron was disbanded in 1979 and its roughly 60 UAVs were put into storage. However, in the summer of 2003 a UAV "airshow" of sorts was conducted, in which a Firebee was displayed carrying two Hellfire anti-armor missiles, as well as a pod for dispensing remote battlefield sensors; apparently Northrop Grumman was running the idea up a flagpole to see if anyone would salute.

UAV advocates claim the Air Force abandoned UAVs for strike missions because of inclination of "hotshot flyboys" to keep the mission for themselves, but in fact the concept has always suffered from "command and control" problems, such as the vulnerability of communications links to jamming and spoofing, and the need to hit specific targets and not accidentally kill civilians or friendly troops.

As attention focused on the combat capabilities of attack drones, the USN and USAF were looking for drones that could turn 6Gs and quickly roll into tight turns. While at the same time, US designers were wondering if dog-fights between robot planes were just around the corner.[1] The US Navy's Fighter Weapons School established in 1969 at Miramar Naval Air Station in California, better known as Top Gun, was tasked with supplying the USN with trained jet pilots for aerial combat missions over the skies of North Vietnam.[2]

From 25 January through 28 April 1971 a batch of Maneuverability Augmentation System for Tactical Air Combat Simulation (MASTACS) systems were modified onto existing US Navy BQM-34A drones (UAVs). These UAVs were test flown to evaluate their maneuvering characteristics, which were deemed good.[1] On 10 May 1971, the MASTACS exercise was ready to commence off the coast of California, against two USN F4 Phantoms flown by Vietnam combat experienced pilots, who had been students at the Top Gun school. The F4s were equipped with both the infrared homing Sidewinder and radar-guided Sparrow air-to-air missiles.[2] As the two F4s approached Santa Catalina Island, a MASTAC-equipped Firebee was ground-launched. The F4s were vectored towards the interception and the air-to-air battle was on. No restrictions were placed on the F4 pilots, the air battle was to be a "no holds barred contest",[2] with the very real possibility of a Phantom being rammed by a UAV as it maneuvered during the dogfight. The first action was a head-on maneuver, as the Phantom lined up for the kill, the UAV (drone) pulled a high-G turn and flew over the F4's canopy. The Firebee was banking into 100-degree maneuvers, and making 180-degree reversal turns within 12 seconds.[2] The Phantoms were no longer attacking the UAV, they were now the targets![2]

The UAVs had been able to pull and hold 6 Gs within three seconds of receiving the command, and still maintain altitude. The Phantoms were unable to maintain track on the UAV, but fired their air-to-air missiles anyway, receiving no hits.[3]

Over the next two decades, more reliable communications links were developed, automated systems came into much wider use, and the military learned to be much more comfortable with such new technologies. In the late 1990s, the concept of using UAVs for performing actual combat, was revived in the form of various designs generally designated as "uninhabited combat air vehicles".

One of the initial concepts was to develop a UCAV on a fast track for "air occupation". The idea was to use unpiloted aircraft to fly continuous patrols over hostile territory, with some of the aircraft fitted with sophisticated sensors to identify enemy activities and target them, and other aircraft following up with attacks. The idea was obviously inspired by USAF air patrols over Iraq and the Balkans. Lockheed Martin suggested rebuilding old F-16A fighters as UAVs, fitting them with a wide wing to provide additional fuel, and also permit carriage of six or more air-to-surface weapons to provide the air-occupation strike element. The modified F-16As would have had endurance of 8 hours over a target area, and three sets of them could maintain 24-hour coverage.

The United States Navy also began studies for UCAVs at about the same time. The Navy saw that UCAVs had a number of potential benefits. They promised to be cheaper than manned aircraft, with a lower purchase cost and much lower operating costs, since operators could be given much of their training through simulations. UCAVs would also be smaller and stealthier than manned aircraft, and could perform High-G maneuvers impossible with piloted aircraft, allowing them to dodge missiles and enemy fighters.

Indeed, since the Navy found themselves increasingly committed to the use of expensive cruise missiles to perform punitive strikes and other limited military operations, UCAVs offered a potentially cheaper alternative, a "reusable cruise missile". One UCAV could carry a number of smart GPS-guided munitions and hit multiple targets on a single sortie, and then return home to be used again. Even with a high combat attrition rate, the cost would be less than that of a barrage of cruise missiles.

Lockheed Martin performed studies that envisioned a number of different naval UCAV configurations, including "short takeoff and landing (STOVL)" aircraft that could be operated off of aircraft carriers, or "vertical attitude takeoff and landing (VTOL)" or "pogo" aircraft that could be operated off destroyers and other surface combat ships, or even submarines.

Piloted pogo aircraft were flight-tested in the 1950s and proved a technological dead end at the time, since they couldn't carry a useful payload and were extremely difficult to land even under benign conditions. The payload limitations can be addressed with lighter materials and RATO-boosted takeoff, and modern digital flight control systems can address the landing issue. The Navy has envisioned using pogo UCAVs to arm a guided-missile destroyer "unmanned air wing" with 20 pogo UCAVs for strike, and five pogo UAVs for reconnaissance.

The submarine launch concept was even more speculative, since recovery was a problem. The Lockheed Martin UCAV concepts were in the 4.5 tonne (10,000 pound) weight class and carried a warload of 450 kilograms (1,000 pounds). Weapons were carried internally to improve stealth and consisted of 45 kilogram (100 pound) and 115 kilogram (250 pound) small smart bombs, now under development.

Range would be about 1,100 kilometers (680 mi), with capability for probe-and-drogue aerial refueling. Top speed would be in the high subsonic range, and ceiling would be about 12.2 kilometers (40,000 ft). The UCAVs would be equipped with fairly simple radar or electro-optical sensors to give the operators imagery of the target. Long-range sensing would be provided by other platforms in air or space.

One Lockheed Martin UCAV concept was an arrowhead-shaped vehicle with no vertical surfaces and the air intake on top. A shaft-driven lift fan would exhaust through the nosewheel door for vertical landings, while the nose sensor array would pivot forward to expose the intakes for the lift fan. The UCAV would have a retractable refueling probe, communications antennas mounted on the aircraft's spine, and lights for navigation and refueling operations. Moveable wingtips and control surfaces along the sawtooth rear edge of the UCAV would eliminate the need for vertical stabilizers.

Another Lockheed-Martin UCAV concept envisioned a diamond-shaped tailless flying wing, with an engine buried down the centerline, and conformal weapons bays flanking the engine. For greater stealth, the UCAV would flip onto its featureless back and fly upside-down.

Such UCAVs could be available in several versions: one with an afterburning engine for maximum performance; one with a non-afterburning engine, but with a thrust-vectoring exhaust for better maneuverability; and one with a conventional non-afterburning engine for low cost.

UCAVs missions would be conducted by an operator in a ground vehicle, warship, or control aircraft over a high speed digital data link. The operator would not really be flying the UCAV directly, however, since the robot would be able to handle the details of flight operations by itself, leaving the operator in a supervisory role. The UCAV would be able to complete its mission autonomously if communications were cut.