The drone's sting.

Some projected combat drones are already being designed to carry two 900 kg class bombs, but most ordnance applied to unmanned air vehicles in the near term will be relatively lightweight guided weapons and smart submunitions. If weaponised drones are to fulfil their potential in carrying out the most dangerous defence suppression missions, we may well see small new anti-radiation missiles designed specifically for multiple internal carriage on stealthy platforms.

Drones have come a long way from early lightweight radio-controlled model aeroplanes, a prime example being the Northrop Grumman RQ-4B Global Hawk, which takes off at almost 15 tonnes. The fundamental aim of a pilot-free aircraft nonetheless remains to achieve savings in weight and cost (in both dollars and lives), while retaining as much as possible of the operational capability of a manned air vehicle. In general, the emphasis in drone armament will thus continue to be on combining light weight and high single-shot kill probability. In the context of internally carried weapons for first-day-of-war stealthy drones, small overall dimensions will also be of crucial importance.

The use of drones as weapons platforms began with the US Navy's torpedo-carrying Gyrodyne Helicopters' QH-50 in the 1960s. US Air Force trials in the early 1970s, aimed at developing an unmanned defence suppression system, used Teledyne Ryan (now Northrop Grumman) Model 147 Firebee surveillance aircraft. Equipped with two wing pylons, a forward-looking TV camera and a datalink pod, the BQM-34A fired 70 mm rockets and TV-guided Raytheon AGM-65 Mavericks. It also dropped gravity bombs, and the North American Hobos and Texas Instruments (now Raytheon) Paveway bombs. Nonetheless, these trials, like contemporary US Army bomb-dropping and US Navy air combat tests (similarly with the BQM-34A) led to no immediate change in operational concepts.

However, as the decades passed, air defence systems became more effective, the more developed nations came to place higher value on human lives, and technological capabilities expanded across the complete aerospace spectrum.

Renewed Interest

In early 2001 drone-based firing tests were carried out with the 48 kg Lockheed Martin AGM-114 Hellfire laser-homing anti-armour weapon launched from the 1042-kg General Atomics Predator-A (subsequently designated MQ-1L). The first such operational firings were performed from a CIA-operated MQ-1L over Afghanistan in October 2001, and the Agency carried out a similar strike over Yemen in November 2002. Armed Predators also took part in the invasion of Iraq in 2003.

The Hellfire appears likely to be used from other drones in the medium-altitude, long endurance class, and has recently been proposed as armament for a 900 kg multi-mission derivative of the US Air Force's BQM-167A Skeeter target vehicle (now replacing the Raytheon MQM-107D/E Streaker), in which Boeing is acting as subcontractor to Composite Engineering. Intended for deep penetration strikes, this derivative could alternatively carry electronic attack payloads. The BQM-167A had its first flight on 8 December 2004.

Armament tested on the Predator-A have included the 10.4 kg Raytheon Fim-92 Atas (Air-To-Air Stinger) for self-defence against fighters. General Atomics has also studied use of the 85.3 kg Raytheon AIM-9X and the same company's 156.5-kg AIM-120. The much heavier (4765 kg) turboprop-powered Predator-B (MQ-9B) can carry an external load of up to 1360 kg (e.g., six 225 kg bombs or 14 Hellfires) on six pylons. Drop tests with the 230-kg Raytheon GBU-12 Paveway II have been successfully completed with an MQ-9B at the US Naval Air Weapons Center at China Lake, California. Ongoing trials there will also clear its use of Hellfire, the 130-kg Boeing GBU-39/B SDB (Small Diameter Bomb) and that company's 225-kg GBU-38 Jdam (Joint Direct Attack Munition).

Submunitions

The majority of drones are much lighter than the Predator series, hence there is a substantial market for correspondingly smaller yet effective air-to-ground ordnance. The obvious solution is the new generation of smart submunitions that have already been developed for use in air-dropped dispensers and surface-to-surface missiles.

Typically designed to be ejected laterally from a submunitions bay by the inflation of a central bag, these devices require modifications to allow carriage on and release from a drone. In the case of the Northrop Grumman Bat, a 20 kg anti-armour submunition, for drone use it will be carried in a tube (Buet = Bat UAV Ejection Tube) that is released from a wing-mounted MA-4 rack. The Bat is then thrust forward from the tube by means of a gas-driven piston. Flight trials began in 2002, with the tube being released from a Bell UH-1N helicopter. Later that year, tests were performed with Bats released from the 725-kg Northrop Grumman RQ-5A Hunter. Initially six US Army Hunters were modified to carry the submunitions and 78 Bats were sealed in these launch tubes.

Northrop Grumman then developed the laser-homing Viper Strike derivative of the Bat, which in baseline form employs acoustic and infrared homing (and GPS and millimetre-wave guidance in its P3I form). In trials in July 2003 a US Army Hunter armed with Viper Strikes scored nine direct hits in nine tests against a variety of ground targets. Some targets were found and marked by the Hunter's own sensors and designator, but others were designated by a soldier on the ground. Future possibilities include use of the Northrop Grumman Eagle Eyes seeker, which fuses infrared and millimetric wave imagery. It may be noteworthy that the company's tri-mode seeker for the Lockheed Martin Joint Common Missile adds a semi-active laser.

Recent reports indicate that the US Army has deployed a unit with two Hunters and 33 Viper Strikes to Iraq, where the submunition's small (1.8 kg) warhead is seen as providing a valuable reduction in collateral damage; this compared to a missile such as the Hellfire. It has also been reported that Northrop Grumman is aiming to reduce the weight of the Viper Strike to 11.3 kg to make it more suitable for the latest version of the Shadow 200, the 168-kg AAI RQ-7B.

The 1430-kg Northrop Grumman RQ-8B Fire Scout helicopter, which is currently funded by the US Navy and Army, is to perform firing trials with both the Viper Strike and four-tube pods with 70 mm General Dynamics APKWS (Advanced Precision Kill Weapon System) rockets. The APKWS weighs 12.3 kg and is now available in laser-homing form. The US Army expects to achieve initial operational capability with the RQ-8B in 2011, and to acquire around 180 air vehicles.

Another relevant submunition is the Textron Systems BLU-108, which weighs 29 kg and dispenses four 5.4 kg Skeet sensor-fuzed warheads. The BLU-108/B is retarded by parachute into a near-vertical attitude, and spun up by a rocket motor prior to releasing the Skeets. The rotation of the Skeet allows its two-colour infrared and laser sensors to scan the ground below, and fire an explosively formed penetrator (EFP) warhead at any tank that it detects. The BLU-108 has been successfully employed from the 147-kg DRS Unmanned Technologies Sentry HP drone in tests at the US Army's Redstone Arsenal in Alabama and Eglin Air Force Base in Florida.

In 2003 Textron Systems unveiled its Selectively-Targeted Skeet concept, in which the warhead is fitted with a fabric Samara Wing, providing autorotation and a 30-degree axis inclination for area search. Other submunitions actively under study for drone applications include the 6.5-kg Bofors Defence/Giat Bonus and the 40-kg Lockheed Martin Locaas (Low-Cost Autonomous Attack System).

A wide range of lightweight anti-armour missiles has significant potential in this context, such as the 11.8-kg Raytheon Javelin and the 13-kg Rafael Spike. In the air-to-air category, obvious contenders include the 11.5-kg KBM Igla and the 18.7-kg MBDA Mistral.