Patriot Missile Failure
Dhahran, Saudi Arabia
The Patriot Missile
February 25, 1991
What Happened?
The Design Flaw
How We Almost Avoided It
Lessons Learned
References
925.50K

Patriot Missile Failure

1. Patriot Missile Failure

1991: The American Patriot
Missile Battery in Dhahran

2. Dhahran, Saudi Arabia

3. The Patriot Missile

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

4. February 25, 1991

8:40pm (12:40pm 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

5. What Happened?

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

6. The Design Flaw

► Old
software
► Time stored in 1/10 of a second, in
integer format
► 0.110 = 0.00011001100110011…2
► 24 bit registers
► Operation outside the range of
expected use: 100 hours vs 14 hours

7. 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

8. 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.

9. 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/im92026.htm
► http://www.1stfighter.com/F15s/desertstorm.html
► http://www.ima.umn.edu/~arnold/455.f96/disasters
.html
► http://shelley.toich.net/projects/CS201/patriot.html
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