Post-War Developments

Schnorkel, Propulsion and Streamlining

HMS/M Scotsman in 1955.

At the end of the war, the British, in common with most navies, had learnt some vital lessons for future submarine operations. Principally, they were the need to remain submerged, and quiet, for longer periods, in any part of the world. Alternative propulsion systems were being considered, in the light of the British government's intention to develop atomic energy for peaceful purposes. Submarine experts were not slow to appreciate the threat that atomic submarines could bring to our seaborne links, and there had to be means of detecting them, whether we could afford our own nuclear submarines or not.

Up until the end of the war, submarines of all nations which were sunk in two world wars were, with the exception of those sunk by accident or mining, lost for one of three reasons: -- they had to surface for long periods to recharge batteries and became vulnerable, their slow underwater speed deprived them of the ability to outpace the hunting surface vessels, or they could not dive deep enough for evasion.

The Dutch had shown a way of remaining dived while charging batteries, with their invention of the Schnorkel. Indeed, their own submarines which escaped the Netherlands and the Dutch East Indies to join the Allied forces had their own Schnorkels, but the technology was ignored by the British, even when the equipment was available in their own harbours. It was known that the Germans were using the schnorkel from 1942 in their Type VII U-boats. The schnorkel was simply an air-induction mast raised out of the water while at periscope depth, in order to run the diesel engines, which would re-charge the battery. Exhaust air was usually pushed out through a pipe which remained underwater, but later was combined with the induction mast in some submarines. There must have been a decision made somewhere in the British Admiralty to ignore the Schnorkel at that time (1940-41), but I've yet to find a record of it.

It wouldn't have taken long to fit into British boats while building or during the course of refits, and it would have given the RN far greater capabilities. The ability to remain in the more dangerous areas overnight for recharging could have kept the Mediterranean boats close to Italian and Axis-occupied ports for much longer periods, without the need to leave the area to surface nightly. The same would have applied to anti-shipping patrols in the Skagerrak and Kattegat, and in the Malacca Straits later. Was the decision made for financial reasons? For the cost of two or three Lancaster bombers, all British boats could have had Schnorkel from 1941 - the development costs were minimal, as Dutch experts were available. Frankly, I see no reason for the decision except a severe ineptitude on behalf of the Admiralty.

Almost as if to purposely annoy British submariners, dummy schnorkel masts were fitted to at least one submarine (Vulpine) towards the end of the war, only in order to train aircrew in identifying a 'schnorkelling' submarine.

On the credit side, however, the A Class - designed from 1943 but too late to see action in WW2 - were at least designed for speed, range and improved habitability, though the Schnorkel was an afterthought.

The A Class, too late for service in WW2, were fitted with Schnorkel (Snort) masts. This is the Artemis

The Schnorkel was really a stop-gap for submarines, allowing them to remain undetected for longer periods. What was really needed was a new type of propulsion, one that would make a 'true' submarine - capable of remaining at depth and at speed for long periods. The nuclear submarine was in the conception stage by the late 1940s and navies cast around for cheaper alternatives. The Germans had, once again, led the way, using what was known as the Walter engine. The first Walter submarine, V80, was tested in 1940. Results were encouraging and she was followed by other experimental types but the first operational Walter boats (Type XXVI-W) were still under construction at the end of the war. The Walter concept had been under study in Germany since 1939. It was based on a single system for surface and underwater propulsion, the Walter turbine. The oxygen necessary for combustion, was provided by the spontaneous decomposition of hydrogen peroxide in the presence of permanganate of lime. This breakdown into oxygen and water vapour enabled any fuel to be burned. The Germans used sulphur-free synthetic diesel oil (does that ring a bell?) to avoid corrosion of the closed-cycle machinery. In pursuit of their single propulsion gear, the Germans also studied a type of closed-cycle diesel engine fuelled by oxygen, highly pressurised in steel containers. It never passed the experimental stage but it would have been fitted in the Type XVII-K and other developing types.

While the Walter was developing, the Germans were not slow to introduce other means of improving speed and range. They were the lightweight high-capacity batteries, the Schnorkel (as above) and better hull shapes to cut down drag and quieten the boat. These 'Elektro-boote' began trials in mid 1944. Built in two types, the large XXI and much smaller XXIII, they were equipped with good acoustic equipment which, together with high underwater speed (XXI was capable of bursts of 17.5 knots, compared with a standard 7-8 knots of most boats) allowed accurate attacks to be made from depth, and escape was potentially much easier. In the end, it is probably of great importance that the XXI made only one patrol (from Bergen) and failed to score a hit. Much damage had been done by the RAF?USAAF in bombing the dockyards of Germany and they succeeded in bringing the submarine building programme to a standstill. Nevertheless, over 100 Type XXI U-Boats had been built and we will never know the amount of damage they could have brought about if they had been ready in number one year earlier.

Some of these submarines found their way into Allied hands at the end of the war and, while the principles of streamlining, high-capacity batteries and the Schnorkel were taken up, it seems only the British took further interest in the Walter engine principle.

Eight U-boats were surrendered to Britain in 1945 and temporarily commissioned into the RN for trials. The German Type XVIIB boat U-1407 - initially scuttled at Cuxhaven in May 1945 - was rebuilt and commissioned as HMS Meteorite. To supervise the reconstruction, Professor Helmuth Walter his staff came from Germany to Barrow. Meteorite's RN service came to an end in September 1949. It still took five years for the Royal Navy to commission two experimental submarines, HMS Explorer (Mar 1954) and HMS Excalibur (Feb 1955). They were twin screw boats with two modes of propulsion - HTP (or "perhydrol") turbines (15,000 SHP, 27 kts dived) and electric motors (400 Brake Horse Power, 18.25 knots dived). Speed on the surface on diesel-electric drive was only about 6 kts. There was a single generator in the forward compartment and a battery under the accomodation space and the CR. Propulsion, the same as in the German Type XVIIB, was very quiet. Hellmuth Walter and five of his staff acted as advisors to Vickers, Barrow in Furness, during the design stage (1946-49). The two boats were disposed of in the 1960s, though the Excalibur was only sold for scrap in 1970.

Meteorite (ex-U-1407) (top left), Explorer (top right). Excalibur above - the Royal Navy's Walter (High Test Peroxide) boats

One of the other great advances, prior to the nuclear submarine, was in streamlining submarines, together with advances in the silencing, or at least noise absorption, of noisier machinery. The Germans and the Americans had, by the end of the war, evolved much quieter and faster boats, both by better propulsion and by the enclosing of miscellaneous equipment which had caused underwater drag. This included the removal of deck-guns and the enclosing of the conning tower and masts in a 'fin'. The general programme of noise reduction by hull streamlining became known as the 'Guppy' modifications, but the different variants of modified British S and T Classes would give submarine-spotters a headache throughout the 1950s!

Some streamlining was carried out in 1944 to Seraph, Sceptre, Satyr, Statesman, Selene, Solent and Sleuth.

As well as streamlining (including the removal of all gunnery) this modification gave the boats a better battery and bigger propellors, giving higher underwater speeds, to simulate the German Type XXI for training the crews of ASW ships and aircraft. The remaining S and T Classes were refitted with streamlining in the course of the '40s and '50s. The Scotsman, shown at the top of the page, was used almost exclusively for trials to propulsion and streamlining, starting as a real 'ugly duckling' and eventually emerging as an elegant swan of a submarine. (See Miscellaneous Pictures). One of the drawbacks of fitting the Schnorkel (called Snort in the RN), was that the extra topweight necessitated the removal of the deck gun. Some of the T Class were lengthened by at least 12 feet, while four of their number (Tabard, Tiptoe, Trump and Truncheon) were lengthened by 20ft. This was to accommodate an extra battery and a second pair of motors. The A Class were nearly all streamlined in the same way, though some retained their deck-gun throughout, notably the Andrew, the last British boat with fixed deck armament.

HMS/M Tabard (top), prior to streamlining and lengthening in the early 1950s, (middle) 20ft longer post-refit, and (bottom) Acheron on a visit to New York.