Patriot Missile Failure 1991 The American Patriot Missile

Patriot Missile Failure 1991: The American Patriot Missile Battery in Dhahran

Dhahran, Saudi Arabia

The Patriot Missile ► Phased Array TRacking Intercept Of Target ► Unproven in 1991 ► Results after Gulf War: controversial

February 25, 1991 8: 40 pm (12: 40 pm EST) ► An Army barracks was struck by a Scud in Dhahran ► 28 American soldiers were killed ► 97 people injured in the strike ► The Alpha Patriot Battery did not track and intercept the Scud

What Happened? ► The system was unable to identify the Scud ► The range gate was inaccurate

The Design Flaw ► Old software ► Time stored in 1/10 of a second, in integer format ► 0. 110 = 0. 000110011… 2 ► 24 bit registers ► Operation outside the range of expected use: 100 hours vs 14 hours

How We Almost Avoided It ► Data recorders: the US did not use them, but Israel did ► February 11, 1991: Israeli forces reported the Patriot errors back to US

Lessons Learned ► When you adapt an older software system to a new use, make sure you also analyze the likely behavior of the users. ► Take the results of testing seriously! If user A could find the error, user B can too. ► You can’t be too accurate when lives are at stake. Military software must be robust. ► Don’t rely on assumptions; if it’s a usage standard, include it in the operating instructions. ► Protect against error, not against error discovery.

References http: //en. wikipedia. org/wiki/Gulf_War ► http: //en. wikipedia. org/wiki/MIM-104_Patriot ► http: //plichta-travels. blogspot. com/2007/03/patriotmissile. html ► http: //www. fas. org/spp/starwars/gao/im 92026. htm ► http: //www. 1 stfighter. com/F 15 s/desertstorm. html ► http: //www. ima. umn. edu/~arnold/455. f 96/disasters. html ► http: //shelley. toich. net/projects/CS 201/patriot. html ►