The Brimstone missile family is comprised of fixed-wing-, rotary-, and surface launched missiles developed and deployed by the United Kingdom. The baseline missile, the United Kingdom’s version of the AGM-114 Hellfire, has served as the basis for the Brimstone Dual Mode System, Brimstone 2, Brimstone Sea Spear, and the Future Attack Helicopter Weapon (FAHW).

Brimstone Development

The origin of the Brimstone can be traced to the United Kingdom’s cancellation of the Royal Air Force’s (RAF) steerable cluster bomb (VJ291) program in 1978, a program which sought to improve the UK’s BL755 cluster bomb rather than purchase the U.S.-made AGM-65 Maverick.¹

To replace VJ291, the RAF announced in 1982 the Staff Requirement (Air) 1238 (SRA 1238) for an autonomous, all-weather missile that can operate at standoff ranges. After considering several proposals, the UK Ministry of Defense selected the Macroni/Rockewell-produced Brimstone for development in 1988.

The development program was cancelled in 1990. The 1991 Gulf War, however, highlighted the utility of standoff-range precision-guided munitions like the U.S. Tomahawk and Hellfire missiles.²

As a result, Britain restarted work on Brimstone in 1992.³

Inspired by the design and name of the baseline AGM-114 Hellfire, the Brimstone performed initial airborne carriage trials in 1998, and began live-fire testing in 1999. Although scheduled to enter service in 2001, the missile did not join the RAF’s arsenal until March 31, 2005.⁴ The program was delayed several times for upgraded guidance and control software for the missile, as well as system upgrades for the Tornado GR4, the aircraft to which Brimstone was scheduled to be fitted.⁵

In 2007, the RAF issued an Urgent Operational Requirement (UOR) requesting the Brimstone to be upgraded with a Semi-Active Laser (SAL) seeker and improved software.⁶ These enhancements led to the Dual Mode Brimstone variant, as the missile could switch from laser-guided to autonomous targeting. The reported cost of developing the baseline and dual mode models was £380 million ($506 million).⁷

In 2013, MBDA conducted initial flight tests of the Brimstone 2, with double the range of the baseline model. Brimstone 2 entered service with the RAF on July 13, 2016.

The Brimstone family is set to be expanded further to include the Brimstone Sea Spear and Future Attack Helicopter Weapon (FAHW). Although Sea Spear and FAHW remain in development, both missiles have had successful test flights.

Specifications

Brimstone

The legacy Brimstone entered service in 2005, and has since been used by the RAF in Afghanistan, Iraq, and Libya. The missile measures 1.8 m in length and 0.18 m in diameter. Typically loaded on a triple-launching pylon, the missile weighs approximately 50 kg, including its 6.3 kg armor penetrating warhead.⁸

Because of the missile’s relatively light weight, 12 or more may be carried by a single aircraft.⁹

The baseline Brimstone can be launched in two distinct targeting modes: indirect and direct. An indirect targeting fire-and-forget mode is used when targets are beyond the aircraft’s line of sight. The missile is pre-programmed to search a specific area to identify, track, and strike vehicles within a designated “kill box.”¹⁰ These autonomous capabilities are made possible by the missile’s millimetric Wave (mmW) terminal seeker. The seeker captures images at 94 Ghz (near optical wavelengths), producing high resolution images for the system’s target recognition algorithms to evaluate.¹¹

In direct mode, the pilot uses an on-board targeting system to designate the missile’s target prior to weapon release.¹²

Unlike the Hellfire, Brimstone can be launched at supersonic speeds. When launched sub-sonically, the missile accelerates past the sound barrier three seconds after motor ignition.¹³ In addition to the Tornado GR4 and Typhoon F2 aircraft, the baseline model was approved to be fitted to the RAF Harrier G7 in 2007.¹⁴

Dual Mode Brimstone

The Dual Mode Brimstone (DMB) is the same length and diameter as the baseline variant, but it incorporates a semi-active laser (SAL) seeker. Entering service in 2008, DMB introduces a third dual-targeting mode. This mode allows the missile to switch between its SAL and mmW seeker when tracking fast moving targets that cannot be easily painted by a laser designator in a cluttered battlespace. 300 legacy variants were converted to DMB as part of the 2007 UOR, and a total of 500 have been delivered to RAF.¹⁵

DMB was successfully test-fired from an MQ-9 Reaper (Predator B) at the US Naval Air Weapons Station, China Lake, CA, between December 2013 and January 2014. During these tests, the missile demonstrated its ability to strike fast-moving and maneuvering targets, scoring nine direct hits, including a hit against a target moving at 113 kph (70 mph).¹⁶

Brimstone 2

The Brimstone 2 incorporates more advanced laser and dual-mode technology to better track low reflectivity targets, like camouflaged vehicles, in cluttered environments. Its improved Vulcan rocket motor reportedly doubles the baseline model’s range, extending the missile’s reach to over 40 km.¹⁷

In addition to firing the missile farther, the insensitive motor is resistant to explosions, bullet penetration, or other environmental stressors.¹⁸ This safety feature ensures the missile’s small armor penetrating warhead does not explode prior to weapon release.

After overcoming early development issues with the missile’s motor (propellant cracking and debonding between the propellant and case), the missile was tested at a U.S. site in early October 2013. Brimstone 2 successfully demonstrated its multi-seeker capabilities in the test, acquiring a target moving 70 mph via laser guidance before switching to its autonomous mmW for terminal tracking.¹⁹

The missile entered serial production on July 16, 2014, and was selected as the basis for the United Kingdom’s Selected Precision Effects at Range (SPEAR) Capability 2 missile.²⁰ The Brimstone 2 completed its operational evaluation trials on the Tornado G4 in February 2016. During the trials, 11 missiles were fired at “structures, a very small fast moving vehicle, and [targets at the] edge of the weapon system’s performance envelope.”²¹

The only miss during the trials involved a very short range shot in which the missile did not have enough time to effectively acquire its target.

The missile entered service on the RAF’s Tornado G4 on July 13, 2016, with plans to integrate it with the RAF’s Typhoon fighter.²² A Typhoon successfully test-fired the Brimstone 2 for the first time on July 14, 2017.²³

The missile is expected to enter service with the Royal Air Force in 2018.

Brimstone Sea Spear

The Brimstone Sea Spear is an air- and surface-launched antiship missile designed to strike fast-moving, swarming inshore attack ships. Although erroneously considered to be a basic adaption of the Brimstone 2, several features distinguish the Sea Spear from its predecessors. First, the missile is equipped with an inertial navigation system for midcourse guidance, in addition to a SAL and mmW seeker for terminal guidance.²⁴ Second, the Sea Spear carries a 16 kg payload, 10 kg larger than any other variant, to ensure it can sufficiently damage fast inshore attack craft (FIAC).²⁵ Third, the Sea Spear is designed to hit swarming targets, like small unmanned aerial vehicles or missile salvos, not merely fast-moving ones. The Sea Spear model anticipates future battlespaces that will not only present cluttered environments, but also more technologically advanced adversaries.

When fired from a surface vessel, the missile uses a triple-rail launcher similar to the three-round pylon used for air-launched variants.

The missile was developed simultaneously with the DMB variant, performing its initial live-fire tests on June 25, 2012, from Aberporth Range located off the coast of Scotland.²⁶

On April 6, 2013, the missile was tested again from Aberporth, successfully striking a static Fast Inshore Attack Craft (FIAC) target. On May 29, 2013, MBDA tested three Sea Spears from a surface-launcher and hit three FIAC targets, including one mobile target.²⁷ The missile remains in development, with completion expected in 2020.

Future Attack Helicopter Weapon (FAHW)

In September 2015, MBDA announced the development of a helicopter-launched DMB, dubbed the Future Atack Helicopter Weapon (FAHW).²⁸ On July 14, 2016, MBDA and Boeing successfully test fired a Brimstone from an AH-64E Apache attack helicopter.²⁹

The information gathered from this test will be used to optimize the missile’s performance as it remains in development.

Exports

Saudi Arabia is the only other known operator of the Brimstone. The U.K. delivered 350 long-range Storm Shadow cruise missiles and an unknown number of Brimstone missiles to Saudi Arabia between 2011 and 2013.³⁰ In December 2016, the BBC reported more foreign sales of Brimstone and Paveway guided munitions from the UK to Saudi. This report and others have drawn criticism from human rights advocates, who argue the Saudi air force is using British-made missiles to kill Yemeni civilians in the ongoing war.³¹

The British MoD has not publicly disclosed the number of Brimstone missiles it has sold to Saudi Arabia.³²

Operational History

The Brimstone and DMB have been employed in numerous combat operations since they were declared operational in 2005 and 2008, respectively.

The missile took to the skies in its first operational sortie on December 18, 2008, as part of the United Kingdom’s military operations in Iraq, known as Operation Telic, although none were fired during the mission.³³ The RAF fired a Brimstone in combat for the first time in Afghanistan in June 2009.³⁴

The RAF employed Brimstone extensively in Operational Ellamy during the 2011 intervention in Libya. During that campaign, the missile recorded a hit rate of over 98 percent, a performance that drew praise from Britain’s military leaders. In 2012, Air Chief Marshal Sir Stephen Dalton told members of Parliament that the Brimstone “went exactly as per the textbook and did exactly what we expected.”³⁵ Britain used the Brimstone so frequently in Libya that at one point during the operation, the RAF’s DMB inventory was depleted to single digits.³⁶

Britain has also employed the Brimstone against ISIS elements in Iraq and Syria. Between November and December 2015, the RAF fired 12 of the missiles at ISIS targets in Iraq, and an additional nine in Syria.³⁷