Science Fair Project Encyclopedia
The MIM-104 Patriot is a US medium-range surface-to-air missile system manufactured by the Raytheon Company. It succeeded the Nike-Hercules Missile for high and medium altitude air defense in the US Army arsenal. Conceived in the 1960s and in development from 1976 for anti-aircraft use, it was adapted in 1988 (following its deployment in 1984), for a more demanding anti-ballistic missile role as PAC (Patriot Advanced Capability). The weapon became well-known after its use in the Gulf War. Like many expensive American weapons systems, the Patriot missile system has seen a variety of controversy concerning its performance in combat.
The Patriot system is built around a combined transporter-launcher carrying 32 missiles (80 in the case of PAC-3 systems). The missiles are carried in batches of four in a M-901 container; transport is provided by a M-860 semi-trailer. Together with the missiles a separate trailer transports the MSQ-104 engagement control station.
The system uses Track-via-Missile guidance and active radar terminal homing. The missile itself is 5.31 meters-long, weighing 900 kg and powered by a solid-propellant rocket motor at speeds up to Mach 5. It is armed with a 91 kg blast-fragmentation warhead with a proximity fuse. Effective range is around 70 km. Patriot systems have been sold to Israel, Germany, the Netherlands and Belgium.
During the Persian Gulf War of January to February 1991, US Army Patriot batteries were deployed in Saudi Arabia and in Israel. The Patriot batteries were highly ineffective at intercepting incoming missiles, but their success was psychological, as was the threat of Scud missiles with only high-explosive warheads. The Israeli and Saudi publics felt less vulnerable to the Iraqi Scud-class missiles launched against them. When the Iraqi missiles did find targets the results were catastrophic, as when a missile hit a barracks in Dharan, Saudi Arabia, on February 25, 1991, after a failed intercept by a Patriot missile, killing 28 soldiers from the US Army's 14th Quartermaster Detachment . In Israel itself, two people were killed and several hundred were injured.
A government investigation revealed that the failed intercept at Dharan had been caused by an error in the clock of the system. The Patriot missile battery at Dharan had been in operation for 100 hours, after which time the clock had drifted by one third of a second, equivalent to a position error of 600m. The radar system detected the Scud, looked at the predicted next position and, because of the time error, looked in the wrong part of the sky and found no missile. With no missile, the initial detection was assumed to be a false alarm and the missile was removed from the system. The Israelis had identified the problem and informed the US Army and the Patriot Project Office (the software manufacturer) on February 11, 1991. The Israelis recommended rebooting the Patriot system's computers as a workaround; however, Army officials did not understand how often they needed to reboot the system. The manufacturer supplied updated software to the Army on February 16. The updated software arrived the day after the Scud struck the Army barracks.
On April 7, 1992 Theodore Postol of the Massachusetts Institute of Technology, and Reuven Pedatzur of Tel Aviv University testified before a House Committee stating that, by their independent analyses, the Patriot system had a success rate of below ten percent, and perhaps even a zero success rate. This was caused by the targeting software of the Patriot, which aimed the missile at the center-of-mass of the target, behind the warhead and also partly because the Scud missiles were so poorly built that they had an extremely erratic flight path and thus were very difficult to intercept. The Scud also often broke apart before impact, making it a more difficult target. A Canadian Broadcasting Corporation documentary quotes the former Israeli Defense Minister as saying the Israeli government was so dissatisfied with the performance of the missile defense, that they were preparing their own military retaliation on Iraq regardless of US objections. That response was cancelled only with the cease fire with Iraq. Recent upgrades of the Patriot have supposedly addressed this problem, but critics have noted that there has been no significant testing. It is worth noting that the Patriot system was originally intended for use primarily against aircraft and cruise missiles - although the original specification called for the ability to intercept short range ballistic missiles, this capability was still being introduced during Operation Desert Storm. As such, that war was in effect the first major test of the new capabilities, and remains the only time that ballistic missiles were intercepted during actual hostilities.
In 2002, Israel currently uses the Patriot as part of a two-tier anti-ballistic missile defense system, with the Arrow missile in the role of high-altitude interceptor and the Patriot for point defense. Patriots are deployed around Israel's nuclear reactor and nuclear weapons assembly point at Dimona.
The PAC-3 missile is smaller than the PAC-2 missile and is more accurate. During the Iraq war of 2003, Patriot batteries succeeded in shooting down several Iraqi missiles, but mistook a returning RAF Tornado GR4 for an Iraqi missile, destroying it and killing both crew. The claim immediately after the incident was the RAF crew had failed to switch on their IFF beacon. However a US journalist embedded with the army unit operating the Patriot battery said the "army Patriots were mistakenly identifying friendly aircraft as enemy tactical ballistic missiles." Because of the reduced size, a launcher trailer can carry sixteen PAC-3 missiles (four per canister in four canisters) rather than the four that the PAC-1 or PAC-2 missile trailers carry (one per canister in four canisters). This means that not only are the missiles more accurate, but more of them can be fired at each target if necessary to increase the chances of successful interception.
According to the on-line U.S. Army Fact File, PATRIOT is an acronym for "Phased Array Tracking Intercept of Target". Other sources provide a slightly different version, "Phased Array Tracking to Intercept of Target". Some sources  claim that "PATRIOT" is not really an acronym at all. In most cases, official Army websites  and other web sites  simply use "PATRIOT" or "Patriot" without any reference to an acronym.
The PAC-3 variant is expected to receive newer, more advanced rocket motors that allow for up to a 50% increase in range bringing its maximum range from about 150 km (93 miles) to nearly 300 km (186 miles).
External links and references
- Official Army PATRIOT web site
- Official Raytheon (missile contractor) PATRIOT web site
- Patriot MIM-104
- GAO Report on Failed Dharan Intercept
- Theodore Postol and George M. Lewis's Report on Patriot Effectiveness During the Gulf War
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