The U.S. Army has successfully tested its SLAMRAAM antiaircraft missiles being fired from a modified HIMARS rocket launcher vehicle. HIMARS is a five ton military (FMTV) truck with a six cell container for MLRS (multiple launch rocket system) rockets on the back. The container can be raised to fire the rockets. The SLAMRAAM missile (180mm in diameter 152 kg/335 pounds) is smaller than the MLRS rocket (227mm and 306 kg/675 pounds), so there's no problem with the six SLAMRAAM missiles fitting into the same space. Until now, the SLAMRAAM were launched from the back of a smaller hummer vehicle (that carried 4-6). The HIMARS launcher could carry at least eight missiles. The FMTV/HIMARS is also more rugged, armored and reliable than the hummer launcher. However, although the U.S. has developed SLAMRAAM, the U.S. Army has not yet agreed to use it, although several foreign countries (Norway, Egypt, UAE) have.
The problem is that, in the U.S. military, ground based air defense systems get no respect. It took two decades to develop the current Patriot system, and most of the money the system received since it entered service in 1984, has gone for developing an anti-missile capability. The "problem" is that American warplanes have controlled the skies for over sixty years, and U.S. ground forces have not felt compelled to spend a lot on anti-aircraft systems. There is a portable missile (Stinger) for the troops, mainly to be used against enemy helicopters. But there's never been much in between stuff what you can carry on your back, like Stinger, and high end systems like Patriot (which has never shot down an enemy aircraft, but has destroyed several friendlies so far.)
In the past, there have been improvised systems, that usually had vehicles equipped with larger heat seeking missile, like the Sidewinder. Such a system, called the Chaparral, was used by the U.S. Army from the late 1960s to the late 1990s. A replacement system, Avenger, now using Stinger missiles, was introduced in 1993. But what the army really wanted was SLAMRAAM, using a larger air-to-air missile (AMRAAM).
SLAMRAAM has been in development for a decade. The army has been criticized for taking so long, especially since the Norwegians put together such a system in the late 1990s. This is what inspired the U.S. Army and Marines to do the same. But it was not a high priority project. The main technical problem with these systems is integrating the missiles' control system into an air defense radar network. The Norwegians simply used the older HAWK missile system (which Patriot replaced). The U.S. Department of Defense was supposed to just adapt the Norwegian system for American use.
Four years ago, The U.S. Marine Corps cancelled their version of SLAMRAAM (called CLAWS, or Complementary Low Altitude Weapons System.) The marines didn't have the money, and didn't see an urgent enough need to go find the money. Air defense was not a big deal when American fighters rule the skies.
The U.S. Army had started work on SLAMRAAM two years after the marines began developing CLAWS. This system initially mounted four U.S. Air Force AMRAAM radar guided air-to-air missile on a hummer. A firing battery consists of one fire-control center, a radar (with a 75 kilometer range) and four to eight hummers carrying missiles. The missiles have an effective range of 25 kilometers, and can knock down cruise missiles, as well as helicopters. It was the need to knock down cruise missiles that has kept the army going.
The AMRAAM is the most modern air-to-air missile in American service, and has its own radar for making its final approach to its target. The Norwegian system (using AMRAAM) has been seen deployed around Washington DC, along with U.S. Army Avengers, for the last six years, as a defense against any terrorist aircraft attempting to attack. The SLAMRAAM concept, as first developed in Norway, has been adopted by several other countries (including Spain and Kuwait).
A box launcher is used by the Norwegian system (called NASAMS). The ground launched AMRAAM can hit targets as high as 4,200 meters (13,000 feet). NASAMS was developed so that it could easily work with different search radars. The AMRAAM SAM costs more (about $600,000 each) compared to the air-to-air version (about $380,000), but is basically the same missile. The four meter (twelve foot) long AMRAAM has a 22.7 kg (fifty pound) warhead, and can take down just about anything that flies, including wide-body commercial transports.
The army is starting to take some heat from Congress over the delays in getting SLAMRAAM into service. But with a war on, SLAMRAAM is a low priority project that is being given just enough money and attention to keep the lights on, not to push the system out the door and into the hands of the troops who don't really need it at the moment.