The purpose of HIMARS is to engage and defeat artillery, air defence concentrations, trucks, light armour and personnel carriers, as well as support troop and supply concentrations. HIMARS is able to launch its weapons and move away from the area at high speed before enemy forces are able to locate the launch site.

HIMARS retains the same self-loading and autonomous features installed on the MLRS. The Improved Launcher Mechanical System (ILMS) upgrade and electronics of the Improved Fire Control System (IFCS), now being implemented onto MLRS M270 launchers, will be standard equipment on production HIMARS vehicles.

HIMARS is operated by a crew of three - driver, gunner and section chief - but the computer-based fire control system enables a crew of two or even a single soldier to load and unload the system. The fire control system includes video, keyboard control, a gigabyte of programme storage and global positioning system. The fire control computer allows firing missions to be carried out in automatic or manual mode.

In a typical mission, a command and control post would transmit the selected target data via a secure data link to the HIMARS on-board launch computer. The computer then aims the launcher and provides prompt signals to the crew to arm and fire a pre-selected number of rounds. The launcher can aim at a target in just 16 seconds. It is possible for the crew to select preprogrammed multiple mission sequences which have been stored in the computer.

In addition to the standard MLRS round, HIMARS is capable of launching the entire MLRS family of munitions, including the Extended-Range Rocket, the Reduced Range Practice Rocket and all future variants. HIMARS will carry a single six-pack of MLRS rockets, or one Army Tactical Missile System (ATACMS) missile.

The Extended-Range MLRS Rocket (ER-MLRS) improves the basic M26 range of 32 km to more than 45 km and the area of influence by 107%. The extension of the rocket motor has resulted in a reduction in the payload to 518 M85 grenades, but the dispersion of the grenades is improved for better effectiveness with fewer grenades.

HIMARS is capable of firing the long-range ATACMS (Army Tactical Missile System) guided missile. ATACMS Block I and Block IA are the currently fielded systems and ATACMS Block II and Block IIA missiles are in development.

The Block I missile delivers 950 anti-personnel anti-materiel (AP/AM) baseball-sized M74 submunitions to ranges exceeding 165 km. The Block IA missile doubles that range to more than 300 km by reducing the payload to 300 bomblets, and is augmented by a global positioning system (GPS). The Block II missile, scheduled to be operational by 2002, also has an improved missile guidance section with GPS, and delivers 13 BAT (Brilliant Anti-Tank) submissiles to Block I ranges to defeat moving armoured targets. The Block IIA missile, scheduled to be operational by 2003, will deliver six improved BAT submissiles to the same ranges as the Block IA missile.

HIMARS will carry a single six-pack of rockets on the Army's new Family of Medium Tactical Vehicles (FMTV) 6x6 all-wheel drive 5-ton truck supplied by Stewart and Stevenson, Texas. The HIMARS vehicle weighs approximately 24,000 pounds compared to more than 44,000 pounds for the MLRS M270 launcher.

HIMARS is transportable on the C-130 aircraft, allowing the system to be moved into areas previously inaccessible to the larger C-141 and C-5 aircraft required for the M270 launch vehicle.