Work and rest on nuclear submarines

Hours of work and sleep were recorded in daily activity logs by 46 enlisted men on two fleet ballistic missile submarines during routine patrols. Total working time (watch standing, non-watch work, and study) averaged 12 hours a day. Daily steep time averaged 8.4 hours a day on one ship and 7-6 on the other. Sleep was mildly fragmented in that the men averaged 1 ? sleep episodes, of somewhat less than 6 hours duration, in 24 hours. Thirty of the men were standing watch on a 6-hours-on-12-hours-off rotation which effectively imposed an 18-hour cycle on their activities. The 6-on-12-off watch schedule appeared to result in less sleep fragmentation than the traditional 4-on-8-off schedule employed on other Naval ships. Questions in the logs were used to assess subjective sleep quality and sleepiness. Sleep quality on patrol was not as good as in a post-patrol period, but the difference between on- and off-patrol sleep quality was small.