Britain created its own version of the U.S. Hellfire air-to-ground laser guided missile, called Brimstone. This version entered service in 2005 and proved very popular because, unlike Hellfire, Brimstone could be used on fast-moving jet aircraft. This not only made Brimstone more widely available but gave a Hellfire-type missile longer range (up to 20 kilometers) because it was moving faster when launched. Moreover, Brimstone was a little longer than Hellfire and had a larger solid-fuel rocket motor. A third distinction was that the Brimstone manufacturer, MDBA, was much more aggressive in developing new features. Therefore Brimstone evolved at an exceptional rate to fill a larger number of roles. The latest of these new jobs is as artillery and anti-aircraft weapons. These two new features were achieved gradually and by 2019 it was realized these new capabilities existed and are now being offered as such.
For example, in 2008 Brimstone got a guidance system upgrade that used an onboard radar to keep track of the target. This is not a novel concept and has been used on other missiles. MDBA decided to do this with Brimstone. This approach quickly became a pattern. The 55 kg (110 pound) Brimstone was originally developed as an upgraded version of the 1980s era Hellfire. Brimstone ended up as a Hellfire in general shape only. Weighing the same as the Hellfire, Brimstone was modified to do a lot of things Hellfire users have been asking for. The most popular request was for a Hellfire that could be fired by fast movers (fighter-bombers), not just from helicopters and UAVs. Aircraft can carry more of these lightweight missiles. These are perfect for small targets, including vehicles that need to be hit without causing injuries to nearby civilians or friendly troops. This is what made Brimstone so popular during the 2011 operations in Libya and subsequently in many other combat zones.
A major factor in the success of Brimstone is its superior guidance system. In 2008 Britain added a dual-mode (radar and laser) seeker to Brimstone. Originally, Brimstone was to be just an American Hellfire with a British seeker (a miniature, millimeter wave radar) and configured to be launched from jets. Brimstone did that but never got a chance to show how effective it was until Afghanistan and Libya. The performance of Brimstone was particularly impressive in Libya because the missile was used so frequently. That got the Americans and French interested in using it as a highly effective anti-vehicle weapon for their jets.
MDBA did not stop Brimstone development but put more effort into it, especially new guidance system features and, because of that, increased range (against unseen targets). Brimstone 2 entered service in 2016 with a new rocket motor that gave the missile a max range of 40 kilometers when launched at a higher altitude from a fast-moving jet. Brimstone 2 could hit targets up to 20 kilometers away even from a low, slow aircraft. Brimstone 2 also had an improved millimeter wave radar that could more precisely identify specific targets or camouflaged ones. This radar detection and identification capability was first installed back in 2008. But the Brimstone 2 version was more precise and accurate in identifying and tracking specific targets. This made Brimstone 2 capable of operating like indirect (operator cannot see the target) fire artillery that is based on the ground, or a ship. That quickly evolved into Brimstone 3 with even more guidance system tweaks.
During Brimstone 2 development the missile was also tested operating from ships, as well as ashore, against small boat swarms. This was aimed at tactics Iran and North Korea were prepared to use at sea as well as the mass use of armored vehicles on land. Brimstone succeeded at hitting multiple fast-moving targets at sea and sinking or disabling them. This work evolved into two different Brimstone variants; Brimstone 3 and Sea Spear. The Sea Spear version has INS (inertial guidance system) for midcourse guidance updates. Sea Spear also has a larger (16 kg versus the usual six kg) warhead to ensure destruction of more types of “small boats”. Some small boats used in swarms are a bit larger and sturdier than others.
Lastly, the Sea Spear guidance was modified to enable multiple Sea Spears to destroy a swarm of small boats, airborne targets (including missiles) or land targets (tanks) without a lot of targets being hit by two missiles. Sea Spear has completed testing and will be entering service in a year or so. Brimstone 3 is undergoing tests for its longer range motor and improved guidance system. Meanwhile, an upgraded Brimstone 2 is available for surface-to-surface use. Similar to the Sea Spear, but without the larger warhead, Brimstone 2 (and 3) have longer surface-to-surface range (20 kilometers) and the ability to fire a dozen or more Brimstones at a distant group of tanks and destroy nearly all of them with single missile hits. Used this way Brimstone is a very effective anti-tank weapon because it attacks from the top, where tank armor is thinnest. Moreover, APS (active protection systems) are least effective against top attack missiles, especially fast-moving ones like Brimstone.
A Polish firm (PZG) has already licensed Brimstone production for the surface-to-surface role as long-range guided missile systems. The Poles are ready to offer a version of the old Cold War era BMP infantry fighting vehicle (which the Poles have plenty of) with the turret replaced by a box launcher carrying twelve Brimstones. All of these missiles can be launched quickly to destroy ten or more tanks up to twenty kilometers away. This BMP also has an RWS (remote weapons system) mount with a heavy machine-gun. Apparently a resupply vehicle can quickly replace the empty launcher box with a loaded one. A second “tank destroyer” vehicle is a larger armored vehicle of a new design carrying up to 24 Brimstones in four box launchers. These “Brimstone Mobile Artillery” vehicles would avoid the front line and take fire requests like an artillery unit. Artillery forward observers would use their laser range finders (often built into binoculars) that can save the GPS location of something the observer has located and transmit that GPS target location, along with the distance between the target and friendly troops, so that the needed number of missiles can be fired. The observer notes the results and calls the mission completed or in need of another salvo of missiles. Brimstone can also home in on reflected laser light. The laser designator is provided by someone on the ground or in the air. This can be used to hit slow-moving or stationary helicopters.
In addition to all these new Brimstone variants, there is a new, larger, Spear 3 missile that weighs 100 kg (twice that of Brimstone) and uses a turbojet engine to achieve a range of over 100 kilometers. Using the same guidance system as Brimstone 2 and 3 plus the larger warhead than Sea Spear, the Spear 3 can destroy mid-size warships and land installations.
The original Hellfire has been around since 1984 and the current version, Hellfire II, weighs 48 kg (106 pounds), carries a 9 kg (20 pound) warhead, and has a range of 8,000 meters. The Hellfire is fast, traveling at about 450 meters a second, meaning that it can hit a target at maximum range in less than 20 seconds. Hellfire is popular for use in urban areas because, with its small warhead (with only about a kilogram/2.2 pounds of explosives) it reduces casualties among nearby civilians (“collateral damage”). The missile is accurate enough to be sent through a window because of its laser guidance. OK, you have to be really good, and lucky, to do this but it does happen. Hellfire is the most frequently used missile during the war on terror and especially in battles with ISIL (Islamic State in Iraq and the Levant), which frequently uses civilians as human shields. In addition to UAVs, Hellfire is most commonly used by the AH-64 helicopter gunship. An AH-64 can carry up to sixteen Hellfires at once. Hellfire launchers are also available for AH-1W, AH–1Z attack helicopters, MH-60R, and MH-60S naval helicopters, OH-58D/Fs, and Harvest HAWK equipped KC-130J gunships. The heaviest user since 2008 has been UAVs, like the MQ-1 Predator, MQ-1C Gray Eagle, and MQ-9 Reaper. Britain still uses Hellfire on AH-64s and MQ-9s but has tested Brimstone both those aircraft and a 2017 order for 1,100 Hellfires may be the last one for Britain. This is especially true since Brimstones cost about the same as Hellfires but have a lot more capabilities.