- Duchesne, Tim
- Ship design and development
- RAN Ships
- None noted.
- December 2003 edition of the Naval Historical Review (all rights reserved)
A snorting charge is only taken up to a point just below that at which the battery would start ‘gassing’, i.e. giving off hydrogen. This is because hydrogen is innately dangerous, and also because the continuance of the charge beyond that point would not give an adequate return in battery capacity to justify continuing one’s exposure to detection by snorting.
If the intention was to propel on one engine and charge with the other, it was important to remember to get under way on the propelling engine before putting on the standing charge!
Some considerations which always had to be borne in mind when snorting – and which remain valid today – include an awareness that the snort head valve was a significant visual and radar target in reasonably calm conditions. A continuous periscope watch with the big, binocular search periscope had to be maintained for aircraft and shipping (self-noise due to the engine(s) running rendered the sonar almost useless), and the Electronic Support Measures (ESM) mast had to be constantly raised and an ESM watch for enemy radar transmissions continuously kept. In flat calm conditions, airborne ASW radar could detect a snorting submarine at ranges of at least forty miles. The ‘ger-fuffle,’ or water disturbance, from the ‘drowned’ exhaust was also a major visual target by day. In consequence, unless absolutely essential, one never snorted by day unless the sea-state was fairly high, with lots of ‘white horses’ and the head valve constantly washing over – this has the effect of reducing the reflective properties of this large steel object, which would also be coated with ‘RAM’ (Radar Absorbent Material).
The preferred snorting policy would be to snort by night. This would deprive the enemy of a visual target and force them to use radar. Whilst the head valve, search periscope and ESM array together constituted a significant radar target, thanks to the ‘inverse square law’ of physics, a submarine’s ESM should detect radar transmissions at about twice the range at which the transmitting ship or aircraft could obtain a returning echo and hence a possible detection. All things being equal, this enables a submarine to stop snorting and return to a quiet and covert state before being in danger of detection. The same principle applies to sonar transmissions and their interception by submarines.
It was quite acceptable for the head valve to be washing over, and in consequence opening and shutting at frequent intervals, but if the boat inadvertently ‘dipped’ for any length of time, say, a couple of feet below the ordered snorting depth, the engine(s) would immediately start ‘pulling a vacuum’ and the air pressure in the boat would start descending rapidly below atmospheric pressure. Depending on sea state, speed, the trim, and the planesmen’s skills, this could be a fairly frequent occurrence.
It would not be of great importance if of brief duration. Large barometers in the Control Room and Engine Room would have been synchronised at the commencement of snorting, and four inches of vacuum was the limit permitted. If reached, due to a prolonged ‘depth excursion’, the Officer of the Watch (OOW) would order, ‘Stop snorting, stop snorting!’, and if he failed to do so for any reason, the ERA of the Watch would do so automatically if that point was reached. Little discomfort would be caused by an increase in vacuum, but when the boat regained snorting depth and the head valve opened once more, the rapid and significant increase in pressure required vigorous individual action to clear ears to avoid painful consequences. If one was off watch and asleep, the sweetest dreams would be agonisingly interrupted. To start snorting again after such unintended stops, it would be necessary to ‘blow’ the snort exhaust once more and restart the engine having re-opened the ‘induction hull valve’.
Good trimming, as I hope has been made clear, is particularly important. Depth-keeping is difficult, and often impossible when steering into or down the swell, and a course across the swell would be selected. This would usually also ensure that toxic exhaust fumes were not sucked down the induction and into the boat’s atmosphere – an over-riding consideration.
When going deep from snorting, either as a deliberate manoeuvre or in an emergency on sighting, or detecting sonar or radar transmissions from, hostile ships or aircraft, the induction hull valve and flap valve, together with the group exhaust valve would be shut, and the engine(s) stopped. Additionally, the snort mast locking pin would be taken out and the mast lowered. This permitted the mast to flood, so the Trimming Officer would pump out (to sea) an equivalent amount of water from the ‘snort drain’ tanks. Meanwhile, in the Engine Room and the After Ends, the engine clutch would be taken out and the tail clutch put in (on the shaft on the side of the ‘standing charge’) so that the Captain would have the use of that motor for propulsion purposes as soon as possible. The Engine Room and After Ends in particular would be scenes of frantic, but well-drilled activity whilst all this was going on.