A report of the government accountability office entitled patriot missile defense. We will look at the operation of the pac2 missile first. While deployed with the us army, i witnessed a successful scud hit over dhahranal khobar in 1991. Scud, the range gatean electronic detection device within the radar system calculates an area in the air. Officers examining an r17 missile shot down by a patriot mim104 sam system in the desert during operation desert storm. Round off errors and the patriot missile t wentyeight americans were killed on february 25, 1991 when an iraqi scud hit the army barracks in dhahran, saudi arabia. Us patriot missile systems to be obsolete by the time. In afteraction studies of the patriot systems performance in the 1991 gulf war, both the u. Software problem led to system failure at dhahran, saudi arabia reported on the cause of the failure. On february 25, 1991, during the gulf war, a patriot missile defense system let a scud get through. Round off errors and the patriot missile the numerical. The software error wiki alludes to is that the patriot missile kept track of its internal clock with floating point numbers.
At least one of these software modifications was the introduction of a subroutine for converting clocktime more accurately into floatingpoint. Software bug may cause patriot missile errors network world. A report of the general accounting office, gaoimtec9226, entitled patriot missile defense. The gao report describes the patriot missile systems operation as follows. It turns out that the cause was an inaccurate calculation of the time since boot due to computer arithmetic errors.
This is a mechanism to avoid false alarms and to avoid shooting down other flying targets e. America risks entering into a war with the mistaken belief that it has a shield against the enemys missiles when all it has is a sieve. Army and general accounting office estimated its effectiveness against all missiles fired, not just against missiles engaged. The us military is investigating the possibility that a software problem in the patriot missile defence system may be responsible for targeting two friendly aircraft in the iraq war. The missile itself weighs 2200 pounds and its range is 43 miles. There was a lot riding on the patriot missile systems success. After the patriots radar detects an airborne object that has the characteristics of a. First tests of this air defense system took place in 19691970. Speaking to sputnik, russian military expert andrey golovatyuk, polands drive to purchase the patriot systems can be explained by political rather than defense considerations. In 2003, the patriot missile defense system, employed to defend against missiles during the iraq war, was responsible for the death of three airmen in three separate friendlyfire incidents. Software bug may cause patriot missile errors itworld.
The patriot missile is only launched to intercept after the incoming missile is detected a second time. A calculation shows each of these relative errors to be both very nearly 220, which is approximately 0. When the machine had been booted in the recent past, such as every time in testing, the floating point number spent most of its precision to the right of the decimal point. Disasters due to rounding error university of texas at. The problem was in the differencing of floating point numbers obtained by converting and scaling an integer timing register. The first aircraft carrier battle in history duration. The patriot battery failed to intercept the missile due to a software error. S military made in deploying the patriot missile to israel and saudi arabia and in reporting the effectiveness of the patriot system.
It was intended to replace the previous nike hercules and hawk air defense missile systems. The segments on the patriot missile systems performance in israel during the gulf war included in the wgbh world wide web site internet frontline material are inaccurate, incomplete and misleading. On 25 february 1991, a patriot system failed to track and intercept an incoming iraqi scud. Report gaoimtec9226, information management and technology. Atbm threat soviets improve scud accuracy modification program pac1 modification program started leading to. The computer failure that blinded a patriot missile defense system to an. Contemporary issues in cs a study of the software failure in the patriot missile system. The circular pattern on the front of the vertical component is the systems main phased array, consisting of over 5,000 individual elements, each about 39 millimeters 1. Defective software made it impossible for patriot missiles in saudi arabia to detect and track an iraqi scud missile that killed 28 american troops in.
The errors were proportional to the time on the clock. The problem of the patriot system was that a 24 bit number was used to measure time, and it was incremented by 110. Patriot missile failure is the property of its rightful owner. General accounting office gao imtec9226 entitled patriot missile defense. Software problems led to system failure at dhahran, saudi arabia. The discipline focused on the production of software, as well as the development of tools, methodologies, and theories supporting software production, is most accurately called. It should be pointed out that the patriot missile was originally designed to be a. The patriot missile battery at dhahran had been in operation for. Why the patriot missile might fail americas military.
But, as is the case in any failure of a complex system, many factors may have contributed to the failure of. Patriot missile software failure, 28 soldiers died. Famous number computing errors penjee, learn to code. Developed by raytheon, the mim104 patriot became operational in 1985 and is now the us armys main missile. A computer software glitch shut down the patriots radar system, blinding dhahrans antimissile batteries. When patriot systems were brought into the gulf conflict, the software was modified several times to cope with the high speed of ballistic missiles, for which the system was not originally designed. The cause of the failure was later found to be a programming error in the computer embedded in the patriot s weapons control system. The patriot is armed with a 200 pound highexplosive warhead detonated by a proximity fuse that causes shrapnell to destroy the intended target. This time around the patriot missile was going to live up to all the hype, unlike in the first installment of the gulf war when the missiles nearly struck out against iraqi scuds, the softballs of the ballistic missile world. It gave the patriot missiles the ability to intercept tactical ballistic missiles and. Why did patriot missile system fail during persian gulf.
A patriot missile battery operates slightly differently depending on whether it is firing pac2 or pac3 missiles. Terminal high altitude area defense thaad, formerly theater high altitude area defense, is an american antiballistic missile defense system designed to shoot down short, medium, and intermediaterange ballistic missiles in their terminal phase descent or reentry by intercepting with a hittokill approach. The patriot missile system was mostly successful with intercepting its targets during the first gulf war. Patriot missile defense system failure patriot is the us armys mobile surfacetoair missile defense system, which was designed to defend against aircraft, cruise missiles, and shortrange ballistic missiles. The patriots trajectory calculations revolved around the timing of radar pulses, and they had to be. Eventually, the army attributed the patriot missile failure in dhahran to a software failure in the computer as a result of long use of the radar system u.
The gao report contains some additional information. Raytheon was the main contractor of the system, while the missile was developed by martinmarietta. There is a nice concise writeup of the problem, with a prefatory background on how the patriot system is designed to work, in the official postfailure analysis report by the u. According to macierewicz, the patriot will help poland to effectively counteract russias iskander missile systems. Details flaw in patriot missile the new york times.
The patriot missile system all of the abovewas designed to shoot down airplanes. Due to the missile s speed this was equivalent to a miss distance of 600 meters. Ppt patriot missile failure powerpoint presentation. The fatal flaws in the patriot missile system corpwatch. No, because all missiles are strong that can kill any people, there is no question or the patriot can proved there missiles are strong. Patriot longrange air defense missile system military. The patriot defense system had failed to track and intercept the scud. Patriot missile defense software problem led to system failure at dhahran, saudi arabia, gao report, general accounting office, washington dc, february 4, 1992.
In the pac1 phase the guiding software for the radar and the missiles was changed. The patriot missile battery at dhahran had been in operation for 100 hours, by which time the system s internal clock had drifted by onethird of a second. The radar antenna scans the sky looking for incoming targets. We recently got a chance to see a patriot system at fort bliss.
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