Submarine under-ice oerations

In late 1988 at the height of Canada's controversial plan to acquire nuclear submarines, Captain Richard Sharpe, RN, the Editor of Janes' Fighting Ships, gave a talk about submarine operations to a Financial Post conference. His views on operating any form of submarine under the ice are worth bearing in mind any time such operations are considered. Richard's story is one of the few short descriptions of submarine under-ice operations in print and it is well worth raising those points again; operating a submarine under the ice is definitely not easy, as anyone who has done it will attest.

Richard, with whom I served while I was on loan to the Royal Navy for submarine duty, made two under-ice trips: one as CO of a British SSN and a prior one in March 1962 in HMS Alderney in company with HMS Astute, USS Nautilus and another SSN (which was probably USS Sea Dragon) in the Gulf of St. Laurence. Richard was the Torpedo Officer of Alderney, I was the navigator. At that time, some four years before the formation of the Canadian Submarine Squadron, the equivalent of two and a half submarine crews of RCN officers and men were loaned to the Royal Navy to off-set the people serving in the RN Sixth Submarine Division in Halifax. The RCN personnel did not have to serve in Halifax, and in fact tried to avoid it, but it was traditional to have at least one RCN officer an a handful of Canadian ratings in each of the A-class submarines assigned to SM6. This is why I and a couple of other RCN submariners made under-ice trips in the 1960s.

Some of Richard's reflections may in fact come from Alderney's 'adventure', especially the incident of finding a block of ice covering the conning tower hatch. His comments about the relative comfort of the internal climate of the submarine are exclusive to the SSN. Life in a diesel-electric submarine under the ice was wretched; it was bitterly cold and damp with icicles forming on the inside of the pressure hull. The A-class submarines had been designed for Pacific operations and were woefully short of internal heating; we had small strip heaters in the living spaces but could not always use them because of the need to conserve the battery. We had to charge batteries about twice a day which changed the air inside the submarine, and so we seldom had major atmosphere quality problems; nevertheless, we watched CO2 and oxygen content of the atmosphere carefully. CO2 scrubbers and oxygen generators were pretty basic in those days and did not provide instant response when the submarine had been shut down for a while and air quality was poor.

Operating under the ice was a challenge. By day we could sometimes see the ice keels through the periscope as we made our way very carefully along the underside of the ice. Even though it was new ice, it could still be 4 to 5 feet thick with keels hanging down as much as 25 feet. By night we had to rely on sonar to find the keels and the open areas which gave the same sound return as a sheet of unbroken ice, hence the problem of surfacing because the upward-looking sonar (essentially an echo sounder) could not determine the difference between three feet of smooth ice and open water. Surfacing through 2 or 3 feet of ice is an "interesting" experience especially when battery capacity is low.

The two weeks in the Gulf of St. Lawrence were mainly a work-up for the Americans who later went much further north. We also acted as targets for the SSNs and the RCAF in simulating (trying to simulate to be accurate) Soviet missile-firing submarines operating in the Gulf of St. Lawrence. We were woefully ill-equipped for that whole experience having only an upward-looking echo sounder and partial fairings over the main vents as the concessions to the ice. I had been in the ice twice before on surface patrols off the Labrador coast and on the Grand Banks in winter and so knew a little about the conditions but being underneath the ice was a completely different experience.

Contrary to what some would like to believe, that generation of diesel-electric submarines was not effective operationally while under the ice. With only limited battery endurance, virtually our entire effort was devoted to survival with the management of the battery being the greatest concern. Not being able to come to the surface to snort (or snorkel in US terms) and charge the batteries when we wanted to was a major factor. We had to have open water to raise the snort mast -- it was hinged rather than periscopic as in the later types of submarines. Even with a periscopic mast you still needed open water to raise the mast. With a full battery, we would only occasionally go deep and try to find the SSNs using passive sonar which was all we had other than very short-range equipment. But with the very poor acoustic conditions we seldom found them. People have no idea just how noisy the underside of the ice can be.

It was indeed an adventure, and I think most of us would agree that we were often a little apprehensive, especially when the battery was very low and there was no sign of open water. Alderney had to "punch" through a sheet of ice one day, and it was a frighteningly clear testament to why diesel-electric submarines don't belong under the ice -- we nearly didn't make it. Quick ventures under fringe ice may be OK, but going under sheets of relatively extensive and thick ice is a questionable exercise.

Even though you might be able to solve the power problem with AIP and the latest battery technology, the question of "How does one extricate one's self from a problem?" remains the real concern. As Richard so rightly points out, fire and flood are the submariner's worst fears and both require a quick return to the surface to solve the problem. You cannot fight a fire submerged because the fire destroys the oxygen very quickly and the internal breathing gear has a finite life. Flooding also demands a fast return to the surface to solve the problem; stopping a flood in a dived submarine requires that the outside pressure on the hull be reduced as quickly as possible.

Reading the stories of the early SSN under-ice trips, especially those written by the COs of Nautilus and Sea Dragon, you will find many of the same apprehensions over safety. Those of us who did time in the older submarines have been through enough fire and flood emergencies to know that they are indeed what submariners fear most. Under the ice, where the normal escape route of surfacing isn't guaranteed, fire and flood become a heightened concern.

So, to Richard Sharpe's views, which remain valid today.

For operations under the ice, structural and sensor requirements include a robust fin and casing for penetrating thin ice; short range side scan and upward looking active sonars and closed circuit television to measure ice thickness and observe conditions in the vicinity; navigational systems which work in the polar zone and communications equipment which can receive signals under the ice, and perhaps in due course also be able to transmit.

As you approach the ice edge the sea surface becomes oily and sluggish and waves stop breaking even in a strong wind. Sonar conditions deteriorate in this marginal zone because of the ice movement which generates a great deal of noise covering the whole acoustic frequency spectrum. Once underneath the permanent ice cover charted depths become spasmodic with some areas virtually unsurveyed in detail, although the ocean floor contours are reasonably well documented. The thickness of the permanent canopy can vary from nothing to a maximum of 8 metres with a mean of about 3 metres (obviously greater in winter than in summer). The Arctic Ocean, which is about 3 times the size of the Mediterranean, has about 10% of open water but most of the ice free leads and polynyas are constantly on the move, both as a result of currents and tidal streams and because of turbulence caused by ice movement and weather temperature variations. Ridging can occur down to 50 metres, and in the vicinity of some land masses, icebergs, with keel depths of up to 500 metres (Greenland is the worst), must also be avoided, by now, having passed under the fringe ice, you have reduced speed - this is no place to rush around. As long as the depth of water allows a submarine keel depth of 90 metres you will be well underneath even the deepest ridge. The water is isothermal at about 6 F below freezing but there is a marked salinity layer at around 50 metres. Apart from causing buoyancy problems, this will have an effect on sonar performance producing two zones with a virtual cut off of sound between them. To communicate with the outside world and to update the inertial navigational system it will normally be necessary to come up to the fresher water level and perhaps even to break through the ice.

If you plan to surface it may take well over 12 hours to find a suitable polynya or thin area of ice. Once found, you traverse backwards and forwards measuring ice thickness by sonar and calculating the speed of the local ice drift. Having found a bit you think you can break through, you manoeuvre the submarine to match the drift, normally less than 1 knot in speed, and very slowly inch upwards until the fin casing is just below or resting against the ice canopy. Then you partially blow the water out of the main ballast tanks creating a few tons of positive buoyancy which cracks the ice and drives the fin through and into the open air. At this stage you can put up a periscope with its heated top window to check for aircraft, polar bears or lost Arctic explorers. If for any reason you want to open up the conning tower, for instance to replenish the stored high pressure air you may have used to surface, or hoist a flag for PR photographic purposes, you have to hope that there isn't half a ton of ice sitting on the top hatch because if there is you are going to have to go through the whole surfacing procedure again.

To dive, you proceed with equal caution destroying your positive buoyancy and descending vertically until the whole submarine structure has cleared the canopy.

Internally there are few indications of the hostility of the conditions outside. The atmosphere on board is maintained at 70 F and 50 % humidity which boffins tell us is the optimum' working environment for human beings. There is no shortage of power both for air purification and for the maintenance of a standard of personal hygiene unknown to previous generations of submariners. A bit more condensation and mould than normal can be expected on exposed parts of the pressure hull but this is easily controlled.

In terms of warfare, passive sonar conditions are reasonable away from the fringe ice zone and land masses as long as you and the potential target - which can only be another nuclear submarine - are on the same side of the salinity layer. High powered active sonar is virtually useless because of reverberations from the canopy. This is not an easy environment for torpedoes but I know that at least one has a proven under-ice capability, and missiles of all varieties can be launched from the surface.

What can go wrong? Fire and flood are always the submariner's nightmares. Even the smallest fire can fill an enclosed space with thick smoke within minutes and the noise of uncontrolled running water is a close second in the list of events which may ruin your whole day. One response to both emergencies may be to surface at speed but this is not an option under the ice so even more alertness is necessary than usual. All equipment and spaces are well policed. An inadvertent reactor shutdown would also be unpopular, but could be recovered, and anyhow is statistically highly improbable. Breaking through the ice can also be hazardous if it turns out to be thicker than expected.

This extract from Richard Sharpe's talk was first published in the Navy League of Canada's Maritime Affairs Bulletin No. 4/88.