Bryan Clark, a senior fellow for the Washington think tank Center for Strategic and Budgetary Assessments and former submarine officer, said it is difficult to say how long the missing sub crew might be able to hold out. Diesel-electric submarines like the San Juan, unlike nuclear submarines, need to regularly surface to recharge their electrical systems and do not have the same level of operational endurance as nuclear submarines.
“Normally, it could deploy for up to 30 days. It could remain submerged that entire time, snorkeling every few days to recharge its batteries. It could deploy longer, if it could be resupplied with food at sea and does not use a lot of fuel,” he said.
The submarine would have emergency equipment like oxygen tanks and chlorate candles, which use chemical reactions to generate oxygen, Clark said. The true hazard would be carbon dioxide generated by the crews respiration, he said.
The submarine would have tanks onboard with chemicals that could absorb carbon dioxide, but there would be limits, Clark said.