Job Safety

February 15, 2005

O Rings and Friendly Fire

Does sleep deprivation cause accidents? Of course not. But it is often a contributing cause. Too often.

Could testing help reduce these kinds of accidents? In some cases – yes, it certainly could.

A culture of awareness and responsible testing could have helped in the Challenger accident. On the battle field, I am not so sure. But certainly, if a comander had information that his forward troops were reaching their limits he might adjust deployment or even delay an event to insure his troops were at their optimal performance level.

I am going to quote directly from Chapter 6 of a US Army War College publication dealing with the issue of sleep deprivation:


Nancy J. Wesensten, Thomas J. Balkin, and Gregory Belenky

Challenger Disaster
The U.S. Space Shuttle Challenger exploded on January 28, 1986, 73 seconds into its tenth flight, killing all seven crew members, including a civilian schoolteacher, Christa McAuliffe. From an engineering standpoint, the disaster was caused by the failure of an “O” ring in one of the solid rocket boosters to properly seat on ignition. The “O” ring lost flexibility because of the cold temperatures on the day of the launch. The failure to accurately evaluate the reliability of the “O” rings under prevailing weather conditions has been attributed to insufficient sleep on the part of NASA managers involved in the launch decision. Of the 3 high-level NASA managers involved, two had had less than three hours of sleep for 3 consecutive nights prior to the launch. 2

Gulf War Friendly Fire Incident
This case history from the Gulf War illustrates sleep deprivation and time-of-day or circadian effects on organizational performance during military operations. During a night of total sleep deprivation, at approximately 0100 hours on February 26, 1991, a Second Armored Cavalry Regiment Bradley platoon screen line observed hot spots approaching on their thermal sights. They were uncertain as to whether these were friend or foe, and continued to observe. It was not until the lead vehicle actually entered their screen line that the Bradley crews concluded that the hot spots were a column of Iraqi armored personnel carriers. A brief firefight ensued, during which all the Iraqi vehicles were destroyed. However, during the firefight, the two Bradleys at the screen line right flank turned left and faced down their own line, but thought they were still facing the enemy. Perceiving that two Bradleys on the left flank were enemy vehicles, they proceeded to enfilade their own line with fire, destroying the two Bradleys on the left flank.

One of the authors of this chapter led the mental health team attached to the Second Armored Cavalry Regiment and thus was able to reconstruct the friendly fire incident shortly after the event with all crew members present.3 By their own self-report, the Bradley crews had obtained only 3-4 hours of sleep per night over the previous 5 days, and the firefight ensued during the early morning hours. Thus the crews were sleep-deprived and operating at a time of day when complex mental operations are at their worst. Despite this, the crew was still able to put the cross-hairs on the target and fire rounds accurately down-range––as evidenced by the destruction of the Bradleys on the left flank. Their disorientation from the front was the cause of this unfortunate friendly fire incident, because the crew was operating under the axiom that “if it’s in front of us, it dies.”


The case histories above illustrate that even as computer systems, weaponry, and organizations in general become more sophisticated, the individual and his or her performance remain critical to the success of organizational operations, both military and civilian. In its most basic form, effectiveness in any operational environment depends upon the person making the correct decision within a limited time