- Duchesne, Tim
- Ship design and development
- RAN Ships
- None noted.
- December 2003 edition of the Naval Historical Review (all rights reserved)
If, as frequently happened, the boat went deep with a significant vacuum, it would be important to return to periscope depth as soon as possible to raise and drain down the snort mast once more to return the boat’s atmosphere to atmospheric pressure (or ‘equalise the pressure’). This was because the rarified air in the submarine would be dangerously lacking in oxygen, which in turn would cause a level of light-headedness and possibly dangerous behaviour over time. If it was impossible, for operational reasons, to return to periscope depth fairly quickly, oxygen candles would be burnt in the ‘oxygen generators’ sited at each end of the boat. Alternatively, if plenty of ‘HP’ (High Pressure) air was available (at 4,000 lbs/sq in.) in the HP Air bottle groups, the vacuum could be partially relieved, at least up to a more acceptable level of pressure, by releasing HP air into ‘Q’ tank with the inboard vent open. This however was a noisy procedure and could not be employed with an enemy in reasonably close proximity, or with the likelihood of there being air-dropped sonobuoys in the vicinity.
A major improvement in the snort systems of the ‘T’ Conversions, some streamlined ‘A’s and the new ‘P’ and ‘O’ Classes was the introduction of separate and periscopic snort induction and exhaust masts. This meant that the induction system could be drained down and the engines(s) made ready before the induction mast was raised and the head valve exposed to possible detection. Their ‘diesel-electric’ configuration furthermore meant that both ‘sides’ could be engaged in charging the battery, whilst simultaneously, both motors and propellers were available for propulsion. As an added safety bonus, the noise reduction measures inherent in the design of ‘P’s and ‘O’s were so successful that the boats’ sonars were still effective whilst snorting. For an officer raised in ‘S’, ‘T’ and ‘A’ Classes, they were like a dream come true. Sadly for me, even this dream was spoilt by nearly three months as an ‘observer’ in one of the US Navy’s SSNs. Like all nuclear boats she was fitted with a snort system for use in emergency, but not once in over ten weeks dived did I hear the happy cry, usually (in pre-CO days) just as you’d managed to snatch some sleep, ‘Stand by to snort!’ I must confess that I didn’t miss it one bit.