Because they are generally much smaller and thus less easily detected than their manned equivalents, drones allow sensors to be taken closer to the target and maintained there for significant periods. Proximity also allows economies through the use of low-cost direct attack munitions, rather than expensive standoff weapons. Drones may well offer advantages over manned aircraft in the use of directed energy (DE) weapons, i.e., high-power lasers and microwave devices. Drones will require less shielding around such weapons, and target proximity will reduce the emitted power demand.

Against such advantages must be reckoned the increased possibility of fratricidal incidents and collateral damage, since the drone is controlled by a remote operator, quite possibly in another country. The ’weaponised‘ drone now stands where the manned aircraft stood just over a century ago, and there will inevitably be teething problems before anything like the same level of dependability is achieved in ordnance delivery.

Test-firings of the 48 kg laser spot-homing Lockheed Martin AGM-114 Hellfire from a 1040 kg General Atomics MQ-1L Predator-A began on 16 February 2001, this trial series producing 12 successes from 16 rounds. The first operational engagement with this combination was carried out by the CIA in Afghanistan in October 2001. It was followed on 3 November 2002 by a CIA mission in Yemen, in which a Predator operating from Djibouti employed a Hellfire to destroy a four-wheel drive vehicle believed to contain six terrorists.

Some commentators glossed over the fact that the Hellfire (developed to destroy a main battle tank in a supersonic attack at long range) represents an uneconomic way to deal with a non-armoured and undefended vehicle. The Hellfire/Predator combination has also been used in Afghanistan to engage even softer targets, such as small groups of personnel. Considerable efforts have subsequently been directed at finding or developing weapons that are not only light (and thus are easily carried by smaller aircraft) but are also substantially less expensive than the Hellfire, while retaining effectiveness against a broad target set, under a useful range of environmental conditions.

History

Although armed drones first hit the headlines in Afghanistan, they existed as far back as the Vietnam War, in the form of the US Navy’s shipborne torpedo-carrying Gyrodyne Dash (Drone Anti-Submarine Helicopter) or QH-50C/D. On a similar timescale, armament trials were carried out with the US Air Force’s AQM-34 Firebee, a target drone converted for reconnaissance duties.

	Test firings of 70 mm rockets have already been carried out from a Northrop Grumman MQ-8 Fire Scout, of which eight are being built for the US Army and four for the US Navy. (Northrop Grumman)

Although Vietnam-era trials demonstrated the technical feasibility of delivering ordnance from drones, this was concluded to represent only a long-term possibility. Out of 746 QH-50s built for the Dash project, 411 were lost in accidents. The programme was finally terminated in 1970. There was evidently a long way to go before drones could be relied upon to fulfil the attack mission.

In the fixed-wing field, the fighter pilot lobby drowned out any calls for money to be diverted to armed drones. It was only later, after the effectiveness of Soviet-developed air defence systems was fully appreciated, that there were demands to explore the potential of uninhabited aircraft for the most dangerous missions.

When the need for a drone-compatible air-to-ground weapon arose in the ‘Global War on Terrorism’ in the aftermath of nine-eleven, the emphasis was on light weight, precise delivery, effectiveness against a wide range of targets (including fortifications and mountain caves) and fire-and-forget capability. The 48-kg laser spot-homing Lockheed Martin AGM-114M/K Hellfire was the obvious choice, although remotely controlled firings from a Predator have been severely limited by its seeker’s eight-degree field of view.

In the case of the new AGM-114P (‘P’ for Predator) version, recently developed by the US Army Redstone Arsenal in Alabama, the weapons engagement zone (WEZ) has been greatly increased by extending this look-angle to 90 degrees. This version also has an improved gyroscope and modified targeting software, making possible engagements at large off-boresight angles. They also allow the maximum release altitude to be increased from 10,000 to 25,000 ft, thus eliminating the need for the Predator to descend prior to firing. The AGM-114P was cleared for service in early 2005.

	The US Army plans to acquire eleven Warrior systems, each with twelve Thielert heavy fuel-powered aircraft. (General Atomics)

The Hellfire is evidently seen as the principal weapon for the US Army’s Extended-Range/Multi-Purpose (ERMP) drone, which is to carry one on each of four pylons. This ERMP requirement is to be fulfilled by the General Atomics Warrior, a 1360-kg Thielert heavy fuel engine version of the Predator-A, with slightly larger 17- metre wings, four weapon pylons with a total capacity of 227 kg and modernised avionics. The Army plans to acquire eleven Warrior systems, each with twelve air vehicles. The Warrior will have an endurance of over 30 hours and a ceiling of 29,000 ft. The first delivery is due in 2007, leading to initial operational capability in FY2009.

	Missiles tested from drones include the Rafael Spike, which employs fibre-optic guidance and can be locked on to the target after launch. The 33 kg Spike-ER has a range of 8000 metres. (Armada/RB)

At the 2005 Paris Air Show, General Atomics exhibited a model of the much heavier (4765 kg), turboprop-powered MQ-9A Predator-B with a pair of four-Hellfire arrays, and two Raytheon AIM-9 Sidewinders for self-defence. The US Air Force has subsequently revealed that YQM-9A prototypes have been deployed for operational use with clearance for two 225 kg GBU-12 Paveway II laser-guided bombs. These are to be followed by four interim-standard Predator-Bs with the General Atomics Lynx radar and clearance for the GBU-12, 225 kg Boeing GBU-38 Jdam, AGM-114 Hellfire and one other air-to-ground missile.

The uneconomic use of Hellfires against relatively trivial targets in Afghanistan has highlighted the need for a less expensive complement. One very light option is the 2.4 kg Spike missile, which was originally developed by the US Naval Air Warfare Center (NAWC) at China Lake, California, and more recently by DRS Technologies. The Spike was conceived as a cheap ($ 4000) surface-to-surface guided weapon, to complement the US Marine Corps’ $ 100,000 (class) Raytheon FGM-148 Javelin anti-armour missile. Intended to deal with non- or lightly armoured vehicles, the Spike employs electro-optical guidance with a contrast-lock facility giving fire-and-forget operation. For nighttime use a laser seeker is proposed. The Spike has a range of about 3.2 km.

The DRS-built Spike is one of several weapons that have been tested from the same company’s 147 kg Sentry HP drone by the US Air Force UAV Battlelab at Eglin AFB, Florida. Other missiles fired from the Sentry are believed to have included the fibre-optically guided Rafael Spike-ER, a completely different and far more potent weapon. Weighing 33 kg in its launch tube, the Israeli missile has a range of eight kilometres and can be locked on to the target after launch. It can also penetrate 1000 mm of rolled homogeneous armour. The Spike-ER, which has also been fired from the 330 kg Sagem Sperwer, is rumoured to have been used operationally from Israeli drones against terrorist targets in the Gaza Strip.

The operational potential for armed drones further benefits from a range of parallel weapon developments for other purposes. For example, the US Army has vast stocks of the helicopter-launched 12.5-kg General Dynamics Hydra 70 unguided rocket projectile, which would be far more cost-effective if given laser spot-homing guidance and control kits. This APKWS (Advanced Precision Kill Weapon System) programme has been thrown open to competition in its second phase (APKWS-II), in which GD is teamed with BAE Systems, Raytheon with Aerojet, Goodrich and EFW.

	At around 12.5 kg, the General Dynamics Hydra 70 will be an obvious candidate for use from drones when given a laser guidance and control kit, as exemplified by this Raytheon APKWS proposal. (Armada/RB)

Another US weapon development applicable to drones is the SDB (Small Diameter Bomb), which is aimed at achieving the penetration capability of a 900-kg BLU-109 bomb, but as an advanced technology munition that would fit inside the small internal bay of a stealth aircraft. The first phase was won by Boeing in 2003 with the 130-kg GPS-guided Increment I or GBU-39, which was designed to destroy fixed targets of known location.

The Increment II version of the SDB is to deal with moving targets in any weather, which requires a multi-mode seeker. In August 2005 this SDB-II programme was thrown open to competition. This led to Boeing teaming with Lockheed Martin, thus benefiting from seeker work on the latter’s JCM (Joint Common Missile), Lam (Loitering Attack Missile) and Smacm (Surveilling Miniature Attack Cruise Missile). Other contractors with the necessary seeker experience are Northrop Grumman and Raytheon. Raytheon is partnered with Lockheed Martin on the US Army NetFires Nlos-LS (Non-Line-Of-Sight Launch System) programme, and is leader on its Pam (Precision Attack Missile) component, which – like the Lam – has a multi-mode seeker. With a wing-kit, the SDB-II is expected to provide a range of around 75 km from a 40,000 ft release.

	Seen on a Northrop Grumman MQ-5 Hunter, the Textron Systems BLU-108 dispenses four Skeet sensor-fuzed warheads, which scan in a spiral pattern and fire an explosively-formed projectile. (Textron Systems)

It may be noted that, since they each weigh less than 50 kg, both the Lam and the Pam (designed to be fired from a US Army 16-tube vertical launch unit) may well be employed from drone aircraft. The Raytheon Pam is primarily an anti-armour weapon powered by an Aerojet variable-thrust rocket motor and has a range of around 40 km. It is equipped with an uncooled imaging-infrared sensor and laser seeker. An improved version (iPam) is credited with a range of 85 km. The Lockheed Martin Lam has a miniature turbojet engine and extendable wings, making possible about 30 minutes on station at 70 km distance. It is equipped with a ladar seeker and has an automatic target recognition facility. The Raytheon Precision Attack Air-to-Surface Missile (PAASM), derived from the Pam, was test-fired from a Bell UH-1 on 13 December 2005.

	Textron Systems’ Selectively-Targeted Skeet employs a Samara Wing and tangential rockets to give the slow spinning descent previously imparted by the BLU-108 dispenser. (Textron Systems)

Another loitering missile in the 50 kg category is the projected Boeing Area Dominator, which would patrol for up to 42 hours at an altitude of 3500 ft and dispense up to eight submunitions. Its advanced technology features include a StarVision Technologies VisNav sensor system, to make possible autonomous in-flight refuelling.