The U.S. Army recently received its 20,000th GMLRS (GPS guided MLRS) rocket. This total includes thousands of cheaper (reduced range, no explosives) practice rockets. All these rockets are packaged and used in containers (pods) holding six rockets each. Most of these rockets are used by the American army but many are for the U.S. Marine Corps and foreign customers. So far about 2,300 GMLRS rockets have been fired in combat, with a success rate of 98 percent. GMLRS rockets cost about $100,000 each.
The 309 kg (680 pound) GMLRS (guided multiple launch rocket system) is a GPS guided 227mm rocket that entered service eight years ago. It was designed to have a range of 70 kilometers and the ability to land within meters of its intended aiming point (GPS coordinates) at any range. This is possible because it uses GPS (plus a backup inertial guidance system) to find the target location it was programmed with.
Four years ago the army tested GMLRS at max range (about 85 kilometers) and found that it worked fine. This enables one MLRS/HIMARS vehicle to provide support over a frontage of 170 kilometers or, in places like Afghanistan where the fighting can be anywhere, an area of over 20,000 square kilometers. This is a huge footprint for a single weapon (an individual MLRS/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 mortars about 7.5 kilometers.
Another edge GMLRS has is the HIMARS rocket launcher. Only costing about $3 million each, these smaller, truck mounted rocket launcher systems have become very popular. HIMARS carries only one, six MLRS rocket, container (instead of two in the original MLRS vehicle). But the 12 ton truck can fit into a C-130 transport (unlike the 22 ton tracked MLRS) and is much cheaper to operate. The first HIMARS entered service in 2005, about a year after GPS guided rockets did.
Most of the GMLRS rockets are fitted with a 89 kg (196 pound) high explosive ("unitary") warhead. About half of that is explosives. That's twice as much explosives as the air force 130 kg (285 pound) 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. Last year a GPS guided 120mm mortar shell entered service. This shell has about 2.2 kg (five pounds) of explosives in it and has become popular for situations when you want pinpoint accuracy in areas with nearby civilians.
GMLRS has been used with great success in Iraq and Afghanistan. The guided rocket is much more effective than the older, unguided version and is replacing it in most cases. No more of the unguided rockets are being purchased by the U.S. 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, even when there's a lot of combat.
Noting the success of GMLRS, Russia and China have developed and put into service their own GPS guided rockets.