What does the Historical Record Say about the Chances of Surviving an Escape from a Disabled Submarine?

Despite US Navy and international Disabled Submarine (DISSUB) rescue capabilities, escape remains an important means of DISSUB crew survival as the crew may be forced to conduct an escape before rescue assets arrive on site due to adverse conditions onboard or operational or engineering constraints that may render rescue impossible. The main aims of the current study were to conduct an analysis of historical DISSUB records to describe the likely biomedical evolution of crew survivability following the disabling of a submarine in shallow waters, in order to develop a casualty estimate and define the main risks to escapee survival.From unclassified historical and scientific publications, we collated and categorized international DISSUB events in which escape was effected or attempted by any part of the crew, dating from the earliest documented DISSUB escape in 1851 until September 2019. Both non-combat and combat sinkings were included. We also reviewed at-sea submarine escape trial experience and medical incidents from US Navy pressurized submarine escape training records to estimate air embolism and extra-alveolar air casualties and fatalities during escape training. Our analysis identified the casualty risk for DISSUB survivors for the following three phases: (1) survival in the submarine before escape, (2) survival during the escape ascent, and (3) survival on the surface.Using historical data from a total of 437 attempted DISSUB escapes that included 37 accidental and combat submarine sinkings, the following observations were made: The largest number of casualties occurred during the onboard survival phase due to atmospheric toxicity. 72% of the submariners who attempted an escape survived the escape. Escapes have been successful from a DISSUB as deep as 240 feet sea water (fsw) and experimentally during at sea submarine escape trials from depths down to 600 fsw. All historical escapes were effected within the current 72-hour time to first rescue timeframe, with the majority occurring within 4 hours of DISSUB onset. The majority of escapees who survived were recovered from the water within 60 min. Early rescue surface response mobilization and detailed crew knowledge of escape equipment, procedures, and the physiological phenomena encountered under increased and changing pressures are essential to enhance escapee survivability. US Navy submarine escape training records indicated very low risk (<0.5%) of pulmonary over inflation syndrome or arterial gas embolism and no fatalities during the past 11 years of pressurized escape training.