In the northwest United States the army is refurbishing an airstrip adjacent to a firing range at the Yakima Training Center. This is so that C-17s or C-130s can land and unload troops training promptly open fire with mortars, missiles, artillery and whatever. American has done this in a combat zone a few times but the army and air force agree that sort of thing will become more common in the future.
One novel (and very rare) feature of the Yakima site is that the airstrip is next to an artillery firing range. This enables the army to test its concept for landing aircraft, quickly unloading one or more M142 HIMARS (High Mobility Artillery Rocket System) vehicles which would then fire one or more GMLRS (GPS guided MLRS) rockets at targets on the artillery range. Shorter range HIMARS training rockets would be used because the range cannot handle the combat rounds that go as far as 80 kilometers (or more). The HIMARS vehicles could also get back on the transport and leave for another location. The army and air force call this HIRAIN (HIMARS Rapid Infiltration) forcible entry missions where U.S. forces quickly enter an area by air and immediately get to work because of nearby hostile forces.
The air force already has special engineering teams trained to land at an airstrip and quickly prepare it to handle large transports. This includes establishing an air control center and supply facilities for refueling and emergency maintenance of the transports. Until HIMARS and GMLRS came along there was no easy to provide instant precision artillery support. GPS/INS guided rockets and shells have changed everything and taken some of the load for that work off the air force. In a crises, the air force often does not have enough warplanes to deal with everything. HIRAIN is one fix for that problem.
Yakima became an artillery range in 1942 and later became a combined arms training center enabling infantry and armor units to also use the live fire range. The airstrip was closed down (except for UAV use) in 2003 because the money was not available to keep it in shape to handle heavy transports. The introduction of HIRAIN tactics made Yakima an ideal training center for that once the airfield was refurbished.
The army isn’t the only one developing unique uses for HIMARS and GMLRS. The U.S. Marine Corps has found several other new ways to use their HIMARS. There were two recent examples of this that have greatly improved the usefulness of HIMARS. In 2018 the Marines found that the multitude of sensors on their new F-35B vertical take-off jets could spot ground targets in all weather and at night and pass the target location on to a nearby HIMARS vehicle that would then fire a GMLRS rocket at the target. To maintain maximum stealth capabilities the F-35 carries bombs and missiles internally but the capacity of the internal bomb bays are limited. HIMARS can supply the guided weapons for one or more F-35Bs. Some helicopters are equipped with similar sensors and digital communications systems and can also pass on GPS target data to a HIMARS vehicle. An F-35B could even maintain its stealth by sending the target information via an encrypted burst transmission that is difficult to use for location finding. The air force could use this with their F-35As and the navy with their carrier-based F-35Cs.
The marines have been enthusiastic users of HIMARS and recently added a third HIMARS battalion as well as buying additional HIMARS resupply vehicles (in addition to the hundred they already have). The 28 ton Mk37 resupply vehicles carry two MLRS rocket pods and have the handling equipment to remove an empty pod from a HIMARS vehicle and replace it with one containing rockets. The HIMARS battalions and ammo supply units use the MK37s to move loaded and empty MLRS pods into and out of the combat zone. The C-17s can also fly in MK37 vehicles as well as additional MLRS pods with rockets and fly out the empty pods. Loaded MLRS pods are shipped four to a standard shipping container before resupply or firing (usually HIMARS) vehicles get them.
In 2017 the marines found that with a few modifications to the HIAMRS fire control software the vehicle could accurately fire GMLRS rockets from the flight deck of one of the many amphibious ships marines operate from. As far back as World War II the U.S. has fired unguided rockets from ships in support of amphibious operations. But the use of GMLRS meant HIMARS could provide precision fire support from a ship at sea and the next version of GMLRS will have a range of 135 kilometers, making the ship-based version even more useful because it can support troops even farther inland. The long range version also makes HIMARS more effective at supplying F-35s in stealth mode with more guided missiles. This GMLRS has been successfully tested at ranges up to 110 kilometers. This TC-GMLRS (Tail Controlled Guided Multiple Launch Rocket System) rocket is the same size as the current GMLRS rocket and can be fired from existing pods.
The $6 million HIMARS system is a 6x6 U.S. Army truck with an armored (against small arms fire and shell fragments) crew cab carrying one MLRS (Multiple Launch Rocket System) six rocket pod instead of two in the original larger, tracked, MLRS vehicle. Initially, a major attraction was that the 12-ton HIMARS truck could fit into a C-130 transport (unlike the 22 ton tracked MLRS) and was much cheaper to operate. The HIMARS vehicle can move at up to 85 kilometers an hour on paved roads and travel 480 kilometers on internal fuel. In 2016 it was revealed that HIMARS vehicles in American service had reached a million operational hours with a 99 percent readiness rate. The tech HIMARS used enabled HIMARS to operate (move, receive a target order and launch the GMLRS) using as few as one of the normal three man crew. The first HIMARS entered service in 2005, about a year after GMLRS did. The two new innovations worked well together and were a major reason for the success of the GMLRS and the HIMARS rocket launcher. The U.S. no longer buys the tracked MLRS or unguided MLRS rockets. An MLRS pod with six GMLRS weighs 2.8 tons and has attracted a lot of export orders.
The 309 kg (680 pound) GMLRS missile is a GPS guided 227mm rocket. It was designed to have a range of 70 kilometers and the ability to land within meters of its intended target, at any range. This is possible because it uses GPS (plus a backup INS/inertial guidance system) to find the target location it was programmed with. In 2008 the army tested GMLRS at max range (about 85 kilometers) and found that it worked fine. This enables one HIMARS vehicle to provide support over a frontage of 170 kilometers. Thus one HIMARS vehicle can provide precision fire support over an area of about 20,000 square kilometers. This is a huge footprint for a single weapon (an individual HIMARS vehicle), and fundamentally changes the way you deploy artillery in combat. By way of comparison, Excalibur (GPS guided 155mm shell) has a max range of 37 kilometers, and 120mm GPS guided 120mm mortar shells about 7.5 kilometers.
Like the unguided version, the GMLRS is packaged and used in containers (pods) holding six rockets each. The fire control system was upgraded to handle precision targeting rather than just a general area. Since 2004 over 3,000 GMLRS rockets have been fired in combat. GMLRS rockets cost about $100,000 each and have been very successful. That has meant even less work for tube artillery, which had dominated the battlefield since the 17th century. Export demand for HIMARS has meant the U.S. manufacturer has had to resume production for the growing number of foreign customers.
Early on most of the GMLRS rockets were fitted with an 89 kg (196 pound) M31A1 high explosive ("unitary") warhead. About half of that is actual explosives. That's twice as much explosive as the U.S. Air Force 130 kg (285 pound) SDB (Small Diameter Bomb). A 155mm artillery shell has 6.6 kg of explosives, and the 500 pound (227 kg) bomb has 127 kg of explosives, which produced an excessive blast for many urban combat situations. The GMLRS seemed to be just right most of the time. In 2014 an M30A1 warhead was introduced in 2016 and it used less explosive but added 180,000 tungsten pellets which were effective against personnel and unarmored vehicles over a much larger area. The larger GPS guided ATACMS rocket (one per MLRS pod) has a range of 300 kilometers and a 230 kg (500 pound) warhead.
GMLRS has been used with great success in Iraq, Afghanistan and Syria where most have been fired so far. The guided rocket is much more effective than the older, unguided, version, and has replaced it for most users. The accuracy of GMLRS means that one rocket does the job that previously required a dozen or more of the unguided ones. That's why HIMARS is so popular. While HIMARS only carries six rockets, that's often enough to last for days in places like Afghanistan, even when there's a lot of combat.
From the beginning, there were always non-divisional MLRS battalions, as the MLRS was seen, from the beginning, seen as an ideal weapon for massed artillery fire. The Gulf War allowed the MLRS to show off what a potent weapon it could be. The larger rockets also provided room for more complex payloads (cluster and "smart" munitions) and guidance systems. This was another example of how technology can transform an old weapon. While the Russians have been using rocket launchers since the 1930s, they never got around to enhancing their effectiveness with a lot of technology until recently and then only because they noted others were doing so and succeeding. Now everyone is changing their artillery forces and adapting to the use of many fewer guided projectiles.