On Christmas day, a terrorist attempted to explode 80 grams of the explosive PETN on an airliner while it was landing at the Detroit airport; the explosive had been hidden in the terrorist’s underwear – specifically, the crotch of his underpants. SEE ABC NEWS STORY.
Not surprisingly, this incident has generated a considerable amount of political debate during this holiday week, along with new rules for passenger behavior during airline flights. One aspect that has not been discussed is ‘could 80 grams of PETN in a person’s crotch have caused an airliner crash?’
Before answering this question, I should mention that while I am not an explosives expert, I do teach Chemistry and a Weapons of Mass Destruction course that includes a very basic discussion of explosives.
One issue is that 80 grams (about 45 cc, or 1.6 ounces by volume) of PETN isn’t a lot of explosive. As demonstrated by the show Mythbusters, considerably more than 1.6 (volume) ounces of a powerful explosive (such as PETN) is required for a highly damaging explosion (http://www.youtube.com/watch?v=VKZZLw5kTJk); the 3 cc of the high explosives (possibly PETN) in the video blew a grapefruit sized hole in a foam board. The terrorist had 45 cc of PETN, which would blow a larger hole in a foam board.
Another issue is the location of the PETN – specifically that it was inside the crotch area of the terrorist’s clothing. Had the PETN exploded, it would have seriously damaged his legs and crotch area – the only possibly fatality would have been to the terrorist, as his body would have absorbed the blast and, ironically, protected the other passengers.
Could the terrorist have caused the plane to crash? The answer is: highly unlikely, as 80 grams of PETN does not have enough explosive energy to have seriously damaged the plane fuselage or damage the controls.
At worse, the terrorist could have blown a hole in the fuselage, which would have caused the plane to depressurize. It is highly unlikely that this would have lead to any fatalities as the passengers would have the emergency breathing masks. However, for 80 grams of PETN in a person’s crotch to be able to blow a hole in the plane fuselage, the terrorists would have needed to be in a window seat and had his crotch pressed against the fuselage during the explosion. Even had this happened, the explosive shockwave would have taken the ‘path of least resistance’ which is through the terrorist’s body and not the fuselage wall. Once again, the terrorist would have fared much worse than the passengers, crew or plane.
While we often want absolute safety, we need to admit that this is impossible. It is unreasonable and impractical to find every hidden small packet of a substance that may be incorporated into a person’s clothing. The only way to ensure that another underwear bomb incident cannot occur would be to have all airline passengers remove all of their clothing prior to boarding; presumably, everyone would either fly naked or would be issued secure clothing for the flight. This wouldn’t ensure absolute safety either as a terrorist could always have an explosive surgically inserted in his or her body.
One problem with terrorism is that while we can try to guess at every method that might be used to attack us, however, we can never know what the terrorists have conceived but we haven’t. Consequently, they act and we react. As with all risk management issues, we must keep things in perspective; time and time again, we become overly concerned with unlikely risks and ignore those that are more likely to harm us.
JOHN NAIL, Ph.D., is Chair of the Chemistry Department at Oklahoma City University