M998 GLH-L ‘Ground Launched Hellfire – Light’

United States of America (1987-1991)
Missile Tank Destroyer – 5 Built

The AGM-114 ‘Hellfire’ missile was developed by the US Army specifically to counter modern Soviet main battle tanks in a potential clash of superpowers during a Cold War-turned-hot scenario. Thankfully for all concerned, such a conflict did not erupt, the Cold War ending with the collapse of the Soviet Union.

The missile itself is a third-generation anti-tank missile capable of both air-launch (originally from the Advanced Attack Helicopter program by Hughes Aircraft Company) but also from the ground, in a line of development dating back to the late 1960s with the LASAM (LAser Semi Active Missile) and MISTIC (MIssile System Target Illuminator Controlled) programs. By 1969, MYSTIC, the over the horizon laser missile program, had transitioned into a new program known as the ‘Heliborne Laser Fire and Forget Missile’, shortly thereafter renamed ‘Heliborne Launched Fire and Forget Missile’, later shortened to just ‘Hellfire’.

By 1973, the Hellfire was already being offered for procurement by Rockwell International based in Columbus, Ohio and to be manufactured by Martin Marietta Corporation. Somewhat misleadingly, it was still being considered or labelled by some as a ‘fire and forget’ type of weapon.

Procurement and limited manufacturing followed, with the first test firings of the finished product, known as the YAGM-114A, at Redstone Arsenal in September 1978. With some modifications to the infra-red seeker of the missile and Army trials completed in 1981, full scale production began in early 1982. The first units were fielded by the US Army in Europe at the end of 1984. It is worthy of note that, as far back as 1980, the US Army was considering how to leverage the Hellfire onto a ground-launched platform.

Targeting

Despite occasionally being mislabelled as a fire and forget missile, the Hellfire can, in fact, be used quite differently. Fire and Forget implies that, once the weapon is locked onto a target, it could be fired and then the launch vehicle could retreat to a safe distance or move on to the next target. This was not strictly correct, as the missile also had the ability to have its trajectory changed during flight by up to 20 degrees from the original and up to a 1,000 m each way.

Targeting for the missile was by means of a laser which was projected from a designator, either in the air or on the ground, regardless of from where the missile was launched. An air-launched Hellfire could, for example, be targeted onto an enemy vehicle by a ground designation laser or by other designating aircraft. The missile was not limited to ground targets either, it could also be used to target aircraft, with some emphasis on its ability to counter enemy attack helicopters. Thus, the missile gained a substantial survivability bonus for a launch vehicle, as it did not have to remain in situ and could even be fired from over the horizon, such as over a hill at targets beyond.

The TOW (Tube-launched Optically-tracked, Wire commanded linked) was already available in the US arsenal, but Hellfire offered some things that TOW did not. For example, it had an increased standoff capacity along with an increased range, an increased versatility of use, as the TOW was not suitable for anti-aircraft use, as well as improved physical performance such as armor penetration, explosive blast, and a shorter flight time due to travelling more quickly.

With a continuous laser seeker on the missile following the designation applied, the missile could easily target moving vehicles whilst being harder to intercept or counter (by engaging the launcher).

Improvements in ballistics through the 1980s improved the Hellfire design and the weapon has a maximum effective range quoted as being up to 8 km, with longer ranges being achieved with a reduction in accuracy due mainly to attenuation of the laser beam. Data from the US Department of Defense (D.O.D.), however, provides a maximum direct fire range of 7 km, with indirect fire out to 8 km and a minimum engagement range of 500 m.

The Hellfire missile was first used in anger during the invasion of Panama in December 1989, with 7 missiles being fired, all of which hit their targets.

Ground Launched Hellfire – Light (GLH-L)

By 1991, the success of the Hellfire was readily apparent, as was the potential it offered to the user. With improved anti-armor capabilities, the Army sought to install Hellfire missiles onto ground vehicles for use, ostensibly by the 9th Infantry Division to complete a concept first considered for the unit back in February 1987. This was a light infantry division and had a specific need for improved anti-armor firepower. In order to achieve this need, the HMMWV was selected to be the mount for these missiles. With a maximum effective range of 7 km, the Hellfire in the ground role extended the anti-armor capacity of the division, especially when it had the ability to be guided onto target remotely by a forward-deployed laser designator known as the Combat Observing Lasing Team (COLT) using a device like the G/VLLD or MULE laser designators. Some US$2 million (US$4.7 million in 2020 values) were allocated by the US Congress within the defence budget for development of this project, with the somewhat ambitious plan to have 36 systems deployed by the 9th Infantry Division within 22 months at an additional cost of $22 million for development and $10.6 million for procurement for a total concept to deliver cost of US$34.6 million (US$82.7 million in 2020 values).

Development took place on an ‘off-the-shelf’ basis, meaning it used existing hardware and software rather than redesigning a system from scratch. In this case, the system selected as the donor was the hardware from the Swedish shore defence missile program. Funding for the project also came from Sweden, with five vehicles made for trials. Sweden had already been involved in Hellfire since at least 1984, expressing an interest in the system to fill the role of a coastal defence missile. They had already done significant work and were likely trying to sell back some of the technology they had developed for the system, followed by an agreement for deliveries between the two countries in April 1987.

This was a light system for a light mobile force and was operated as the ‘Ground Launched Hellfire – Light’ (GLH-L) program, as a sub-part of a wider GLH program for both light and heavy vehicles.

The mounts for the GLH-L took the form of the standard cargo-bodied HMMWV vehicle M998. Development was due for completion by 1991 and 5 such vehicles were modified.

M998 HMMWV

The M998 High Mobility Multipurpose Wheeled Vehicle (HMMWV) was the US Army’s replacement vehicle for the M151 Jeep, entering service in the early 1980s. The vehicle was to fulfill a variety of general and light utility roles but also as a platform to carry unit level equipment. One of those roles was to carry a TOW missile launcher on top and, with that mounting, the vehicle was either the M966, M1036, M1045, or M1046, depending on whether the vehicle had supplemental armor and/or a winch or not.

At over 2.3 tonnes, 4.5 metres long and over 2.1 metres wide, the M998 is roughly the length of a family saloon car but substantially wider and nearly twice the weight. Powered by a 6.2 litre diesel engine, the M998, in its Cargo Configuration, as converted to mount the GLH-L, was capable of up to 100 km/h on a good road.

Testing

The vehicles built were sent for testing by TRADOC (US Army Training, Doctrine, and Command) and, with firing trials set to take place at the field laboratory of the Test and Experimentation Command (TEXCOM) at Fort Hunter-Liggett in California in June 1991. However, no orders were even expected for the system. Nonetheless, the firing trials were successful and firing blind over the crest of a hill at a static tank target 3.5 km away saw a missile hit.

This was followed by exercise trials with TOW missile operators from 2nd Battalion, 27th Regiment, 7th Infantry Division crewing the GLH-L vehicles, opposed by crews from the TEXCOM Experimentation Centre (T.E.C.) manning M1A1 Abrams tanks during simulated engagements. The TOW operators received an additional 3 weeks of Hellfire training prior to the exercise from Rockwell Missile Systems International (RMSI). The goal of the exercises was to see if a standard infantry battalion could adequately operate and control the GLH-L under operational conditions, such as deploying them appropriately to engage enemy armor it might encounter.

The only modification from real to simulated operation was the substitution of the laser designator from the standard Ground Laser Designator (G.L.D.) to a lower power and eye-safe system to prevent injury to anyone who got lased. When live-missiles were used, however, the standard GLD was used, although the lock-on for the missiles was set at launch due to the range limitations at play.

Forty day and night trials were conducted with the two forces, with continual electronic monitoring for later review. Using the GLD for these live fire shoots, an advance team was able to lase the target and radio in for a missile launch, leading to 6 missiles being fired and hitting the target.

Mounted on the roof using a ‘GLH Adaptor Kit’, the vehicle carried 6 missiles in the back, with 2 mounted on the roof, for a total load of 8 missiles.

The Army was considering the idea of this system to equip elements of the 82nd Airborne Division but, once more, with no formal requirement and no production orders, the idea was only that – just an idea.

Ground Launched Hellfire – Heavy (GLH-H)

For heavier vehicles, ones with some built in ballistic protection from enemy fire and more suitable for conventional units, two vehicles were the obvious choice of launch platform for the Hellfire, the Bradley, and the ever-present M113. Operating as Fire Support Team Vehicles (FIST-V), the vehicles would be able to lase an enemy target and attack it directly if they wished, or once more use the remote targeting. This was the Ground Launched Hellfire – Heavy (GLH – H), part of the 16-month long GLH project. That work saw a turret put together and installed as a test on an M901 Improved TOW Vehicle (ITV) variant of the M113. The system was substantially larger than the 2-missile system on the M998, holding 8 missiles in two 4-missile pods on either side of the turret.

That system was also tested and found to be functional, but was not carried forward and received no orders for production.

Conclusion

The GLH-L, part of the GLH program, had been supported by the Army and by the Hellfire Project Office (HPO), which had accumulated the work of MICOM Weapons Systems Management Directorate (WSDM) in February 1990. HPO had then followed up on the Hellfire, as it was used in service and was being improved and refined. At the same time, Martin Marietta received a contract for development of the missile, known as the Hellfire Optimised Missile System (HOMS) in March 1990 and both had supported the work on GLH-L. However, in April 1991, HPO was redesignated as the Air-to-Ground Missile Systems (AGMS) Project Management Office, leaving no doubt that official interest seemed to have ended in ground-launched applications in favor of aircraft-launched systems. Indeed, this was just a few months after work on developing the Hellfire missile for the Longbow Apache helicopter had started.

By 1992, HOMS too was gone and its work was simply repurposed as ‘Hellfire II’, which was to finally take the form in the AGM-114K version of the missile. The GLH-H side of things, therefore, was also left out in the cold. There seemed little appetite for a ground launched version of a weapon which was already successful on aircraft and the development work specifically was to focus on airborne use as well.

In recent years however, renewed interest has been shown in a ground launched Hellfire version to replace TOW and upgrade the US military’s ability to strike enemy targets from even further away. In 2010, Boeing, for example, tested the ability of the Avenger turret air defence system to launch Hellfire missiles. This would allow the Hellfire once more to be mounted on light vehicles, like the HMMWV, but also on the LAV and other systems.

However, such systems seeing service seems unlikely, as the Hellfire missile and variants was, as of 2016, destined for replacement by a new missile known as the Joint Air to Ground Missile (J.A.G.M.) as a common missile across all platforms naval, air, and ground.

Overview of Hellfire Missile Variants
Designation	Model	Year	Features
Hellfire	AGM-114 A, B, & C	1982 – <1992	8 kg shaped charge warhead, Non programmable, Semi-active laser homing, Not effective against ERA, 45 kg / 1.63 m long	–
	AGM-114 B			Reduced smoke motor, Safe Arming Device (SAD) for ship use, Improved seeker
	AGM-114 C			Same as AGM-114 B but without SAD
	AGM-114 D			Digital autopilot, Not developed
	AGM-114 E
‘Interim Hellfire’	AGM-114 F, FA	1991+	8 kg shaped charged tandem warhead, Semi-active laser homing, Effective against ERA, 45 kg / 1.63 m long	–
	AGM-114 G			SAD equipped, Not developed
	AGM-114 H			Digital autopilot, Not developed
Hellfire II	AGM-114 J	~ 1990 – 1992	9 kg shaped charge tandem warhead, Semi-active laser homing, Digital autopilot, Electronic safety devices, 49 kg / 1.80 m long	Army model, Not developed
	AGM-114 K	1993+		Hardened vs countermeasures
	AGM-114 K2			Added insensitive munitions
	AGM-114 K2A (AGM-114 K BF)			Added blast-fragmentation sleeve
Hellfire Longbow	AGM-114 L	1995 – 2005	9 kg shaped charge tandem warhead, Millimeter wave radar (MMW) seeker, 49 kg / 1.80 m long
Hellfire Longbow II	AGM-114 M	1998 – 2010	Semi-active laser homing, For use vs buildings and soft-skinned targets, Modified SAD, 49 kg / 1.80 m long	Blast fragmentation warhead (BFWH)
Hellfire II (MAC)	AGM-114 N	2003 +		Metal-Augmented charge (MAC)*
Hellfire II (UAV)	AGM-114 P	2003 – 2012	Semi-active laser homing Shaped charge or blast fragmentation warheads depending on model. Designed for high altitude UAV use. 49 kg / 1.80 m long
Hellfire II	AGM-114 R	2010 +	Integrated blast fragmentation sleeve (IBFS), Multi-platform use, 49 kg / 1.80 m long
	AGM-114R9X	2010+?**	Inert warhead using mass and cutting blades for low-collateral damage removal of human targets
Note	Adapted from US Army Weapons Handbook guide to Hellfire via fas.org * Sometimes referred to as a ‘thermobaric charge’. ** Classified development

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