Drones turn nasty: the successful firing of laser-homing Lockheed Martin Hellfire anti-armour missiles from CIA-operated General Atomics MQ-1B Predators against ground vehicles in Afghanistan from 2002 (reportedly over 40 rounds) and in Yemen in 2003 opened the eyes of the leading armed services to the possibility of avoiding the use of expensive manned aircraft in some ground attack missions. (Armed UAV).

This turnabout in the nature of aerial warfare should have come as no surprise, since the concept was evaluated by the US Air Force over 30 years ago.

The principal drone in use at the time of the Vietnam War was the turbojet-powered Teledyne Ryan (now part of Northrop Grumman) Model 147 Firebee or AQM-34, which entered service in late 1964. Although primarily a camera platform, the Model 147 was also employed in jamming radars, chaff dumping and elint (including one-way sorties to learn the characteristics of air defence missile fuzes). From late 1971 it was used in US Air Force Have Lemon trials to assess the feasibility of using drones in the Sead (suppression of enemy air defences) mission. The BGM-34A Ucav differed from preceding Firebees in its having two wing-mounted weapon pylons, a forward-looking TV camera and a datalink pod mounted on the tip of the vertical tail. In the initial trials, Raytheon AGM-65 Mavericks and TV-guided North American Rockwell Hobos (Homing Bomb System) missiles were fired at simulated air defence sites. Photographs indicate that the BGM-34A also dropped gravity bombs and fired 70 mm Ffar projectiles. Early successes led to the development of the BGM-34B with an extended nose to house a flir sensor and a laser designator. It was tested between 1973 and 1974 in conjunction with Raytheon Paveway laser-guided bombs. Teledyne subsequently developed a dual-role (surveillance/ attack) version, the BGM-34C, with alternative front fuselage modules. However, the Have Lemon trials unit was decommissioned in 1979 and its Firebees were placed in storage.

It may be noted that the US Army, which was then campaigning for control of close support assets, ran its own tests with Firebees, dropping 227 kg bombs at the White Sands Missile Range, New Mexico in 1971. The US Navy meanwhile flew dogfight trials over the Pacific Missile Range, pitting F-4s against BQM-34As. These drones were equipped with the Ryan Mastacs (Manoeuvrability Augmentation System for Air Combat Simulation), allowing them to make 6 G turns.

The results of the US Air Force ground attack trials were evidently encouraging. Speaking at a largely classified conference on RPVs in Washington DC in April 1972, Air Force Undersecretary John L McLucas stated, "We now believe that we are on the threshold of utilizing them for selected strike missions. However, their use in air superiority may be a longer-term adaptation."

While the US Air Force was experimenting with using drones to deliver weapons, the US Navy was already doing it. In the mid-1960s, Gyrodyne Helicopters delivered approximately 800 QH-50s, with the role of taking a pair of Mk 44 lightweight torpedoes or a Mk 17 nuclear depth charge to a location determined by the parent vessel's sonar. A small batch of the craft was also built for Japan's JMSDF. However, the US Navy abandoned this programme in favour of the ship launched Asroc in 1970, possibly in light of the high accident rate of the QH-50.

Basic Requirements

If a drone is to serve as a low-cost attritable bomb-truck, then it must be smaller than a manned fighter. It follows that the ordnance it transports must be light, which in turn dictates a small warhead, and hence precision (one metre) guidance. Weapons for Ucavs will thus use (for example) laser spot-homing or infrared guidance, rather than a GPS-based system, which is rated as only semi-precise. It is also clear that the candidate weapons must suit launching at helicopter-class altitudes and speeds. (The baseline Predator is credited with an indicated airspeed of 220 km/hr and the Predator-B with 390 km/hr.).

The piston-engined MQ-1B Predator that fired Hellfires has a nominal gross rated at 680 kg, the mid-span pair at 160 kg and the outboard pair at 68 kg. The QH-50D had a maximum take-off weight of 1157 kg with a 417 kg payload (36 per cent of its gross).

To give a better idea of the size of UAVs under consideration as weapon platforms, in late 2002, TRW carried out the first tests of a Northrop Grumman Bat (Brilliant Anti-Tank) missile from a 4.1 kg ejection tube carried by a 727 kg IAI/TRW RQ-5A Hunter. An initial six Hunters are currently being modified to accept these tubes, and with 78 Bats repackaged to suit. Earlier in 2002, Sagem had exhibited at Eurosatory a 350 kg Sperwer-LE with two under-wing pylons and a variety of potential air-to-ground loads. This may well represent the minimum size of aircraft to carry a worthwhile warload.

A rational starting point in considering weapons suitable for drones is the current range of helicopter-launched anti-tank missiles that provide precision (one metre) attack. As discussed above, the obvious example is the laser-guided 48 kg AGM-114 Hellfire, which provides a range of more than seven kilometres, and (given third-party target designation) can be used in a fire-and-forget mode. Although the 50 kg MBDA Brimstone (a Hellfire derivative with active millimetre-wave radar guidance) was developed to provide a standoff capability for aircraft such as the Harrier, it might also be used from drones. A triple launcher complete with missiles weighs 235 kg.

General Atomics is studying the possible use on the MQ-9 of the 210 kg Raytheon AGM-65 Maverick, the 225 kg Boeing GBU-38 Jdam and even the 525 kg Boeing AGM-84 Harpoon.

Lightly armoured vehicles and soft targets could in principle be engaged by a missile costing only ten per cent of the price of a Hellfire. The US Army has recently selected BAE Systems to provide a laser-homing guidance kit for the General Dynamics Hydra 70 rocket. The goals for this Advanced Precision Kill Weapon System (APKWS) include a unit cost of less than $10,000, a 1.2-metre accuracy and a range over six kilometres. The basic Hydra 70 is approximately 1.50 metres long and weighs 12.3 kg. The smallest American 70 mm pod is the seven-tube M260, but Forges de Zeebrugge (FZ) produces both a seven-tube M-157 and a four-tube LAU-112 launcher.

The weapon that is scheduled to replace the Hellfire is the US Army's Comrhon Modular Missile (CMM), a programme that is being competed by Lockheed Martin, Raytheon and a Boeing/Northrop Grumman team. The Raytheon contender is expected to weigh around 32 kg, and to retain laser homing for its air-launched version. One report credits it with a range of 16 km.

Other missiles that might prove suitable include the infrared-guided Rafael Spike, which weighs only 13 kg and has a range of four kilometres, together with its longer range derivative Spike ER (up to just recently known as the N-TD) reportedly weighing 32 kg and extending the range to six kilometres. The Spike's principal rival is the Raytheon/Lockheed Martin Javelin, which likewise employs imaging infrared guidance and a lofted delivery. The Javelin, which is due to be tested from an IAI Hunter this year, weighs 11.8 kg, or 15.9 kg complete with launch tube.

A new generation of smart submunitions provides other options for drone armament. The leaders in this field are the 40 kg Lockheed Martin Locaas (Low Cost Autonomous Attack System), which employs ladar guidance, and the 20 kg Northrop Grumman Bat, which employs passive acoustic and IR seekers. The Viper Strike is a baseline Bat with a semi-active laser seeker, for use when it is necessary to keep a man in the loop. The company is also developing a multi-mode (RF/IR) seeker (MMS) that may later be applied to the Bat.

Air to Air

Turning finally to air-to-air weapons, several lightweight surface-to-air missiles are suitable for UAV application. The KBM Igla (Needle) weighs only 11.5 kg, and is available as a multi-round installation on the Strelets (Archer) launcher. The Raytheon FIM-92 Stinger (already cleared on the MQ-1/MQ-9) is in a somewhat similar weight category, but the MBDA Mistral (which has a larger warhead) is somewhat heavier at 19 kg. General Atomics is currently studying the use of Raytheon's 85 kg AIM-9 and 156 kg AIM-120 on the MQ-9.

Candidate Weapons

System             Manufacturer                 Weight

AGM-84Harpoon      Boeing                      525.0 kg
GBU-38 JDAM        Boeing                      225.0 kg
AGM-65 Maverick    Raytheon                    210.0 kg
CMM                Raytheon contender           32.0 kg
Spike ER           Rafael                       32.0 kg
Locaas             Lockheed Martin              20.0 kg
Bat                Northrop Grumman             20.0 kg
Spike MR           Rafael                       13.0 kg
Guided Hydra       General Dynamics             12.3 kg
Javelin            Raytheon/Lockheed Martin     11.8 kg