Snorkel?! Part II

The German snorkel device revolutionised undersea warfare. The once surface-bound submersible was turned into a ‘true’ submarine capable of remaining submerged almost indefinitely. This late-war innovation frustrated Allied intelligence and anti-submarine search technology, well into the age of nuclear power. After World War II the snorkel was introduced by all navies around the world, most notably in the ever-expanding Soviet submarine force. In this photograph, Engineer Emil Hymowitz, Chief of the US Navy’s Search Radar Unit, pilots a captured German snorkel mounted on a sub-simulator around the Chesapeake Bay, in 1956. The German snorkel was used to test out new radar search systems designed to locate a snorkeling submarine during the Cold War.

The Legacy

In the post-war period the United States, Great Britain and Soviet Union exploited the significant lead in technology enjoyed by wartime Germany. Not all technology was exploited universally, as it depended greatly on the country’s strategic priority. Among the most sought-after technology was German designs for rockets, avionics and U-boats. It is a known fact that the final drive against north-west Germany by General Sir Bernard Montgomery’s 21st Army Group was designed to prevent the Soviet Union from reaching Denmark and German ports in that area. The objective was to halt the Soviet advance at Wismar on the Baltic coast, which had the benefit of limiting their access to advanced German U-boat technology, specifically the Walter turbine.

Among the Western Allies it was the United Kingdom that took the lead in the exploitation of U-boats. Under the terms of Operation Eclipse, British forces occupied northern Germany to include all the U-boat production facilities and ports. They quickly gained access to engineers, captains and crewmen. Most of all surrendering U-boats fell into the hands of the Royal Navy, who initiated an immediate post-war testing programme. Among the main technological innovations studied and exploited was the snorkel. Their results were passed on to the United States Navy’s Bureau of Ships, who also evaluated the wartime German innovation with great interest.

The US Navy’s post-war assessment of the snorkel was clear. It had to be adopted, even though the Navy’s two-cycle diesel engines could not be retrofitted with the device outright, and that improvements had to be made based on German wartime experiences:

Engine must be designed for snorkelling upfront. Do not implement exhaust drive superchargers. Extensible mast as designed was technically not viable. Folding mast was better. Designs should be made to prevent periscope vibration at high snorkelling speeds. Power-operated head valve for the induction system was required. Design should minimise resistance in the raised and housed position of the snorkel mast. Apply anti-radar coverings to the snorkel head. Remove the maximum amount of moisture from the air intake. Automatic depth control was not necessary but useful to avoid crew strain during long underwater patrols.

It was the snorkel that was the prerequisite for the modern submarine, as former defence analyst and submarine historian Dr Norman Friedman wrote in his book US Submarines since 1945.

The first US submarine that tested the snorkel was the Irex (SS-482). Within eighteen months of the end of the war the US Navy had completed designs for the modern telescoping snorkel. The Irex was ordered to Portsmouth, New Hampshire, for a retrofit in December 1946, followed by operational testing of the device. The Irex conducted snorkel testing from July 1947 until February 1948. After a successful evaluation, the Irex joined Submarine Squadron 8 at New London as the US Navy’s first operational snorkel submarine.

The US Navy did in fact adopt a telescoping snorkel despite its own recommendation to pursue a folding mast design. Initially the US Navy installed two separate masts, one for induction and one for exhaust. The induction mast led into a moisture separator and then into the main engine induction valve via a 22in pipe. Each diesel engine exhaust led directly into an uptake, exiting the submarine either through a car-type muffler or the snorkel exhaust trunk. Later, the US Navy reverted to the original German snorkel design and combined induction and exhaust pipes into a single mast when they began to retrofit their own submarine fleet through the ‘Greater Underwater Propulsion Program’, otherwise known as the ‘GUPPY’. The GUPPY was the first US submarine that operated with a snorkel.

The US Navy’s 1961 edition of its submarine technical training manual known as NAVPERS 16160-B The Submarine, issued to all crew members of the new GUPPY modified submarines, offered unusually high praise to their former German enemy nearly twenty years after the end of the war with the following commentary on the snorkel. The Introduction to Chapter 15’s ‘The Snorkel System’ reads:

The theory of the snorkel had been known for several years; but, it was not until 1943 that the German Navy converted such theory into practical operation … the German Navy perfected snorkel designs and incorporated the device in their submarines. This move increased the efficiency and success of German underseas craft immeasurably.’

Contrary to almost all post-war histories of the German U-boat force and the Battle of the Atlantic, the US Navy understood the snorkel’s impact during the war and its evolutionary role in submarine warfare. The US Navy ensured their own submariners knew this as well.

The snorkel began to transform US Navy submarine operations in the Cold War era. Intelligence gathering became a new, if not critical, component to its mission. In 1949 the snorkel-retrofitted Fleet Submarines Cochino (SS-345) and Tusk (SS-426) entered the Barents Sea. Cochino was also equipped with a version of the GHG Balkon passive sonar. Its goal was to conduct the first intelligence-gathering mission close to the coast of Russia; a task that could only be accomplished by a snorkel-equipped submarine. Unfortunately, Cochino experienced a snorkel defect like some of its German U-boat counterparts did during the war. In rough seas the submarine was unable to maintain trim while snorkelling and the snorkel valve failed to close when it was submerged. Water rushed in and a series of unfortunate events unfolded that resulted in a build-up of toxic gas and a battery explosion. While the crew was rescued after a fourteen-hour fight to save the sub, the Cochino was lost. It sunk on 26 August 1949, some five years after the first German snorkel-equipped U-boat entered the English Channel.

The snorkel remained a key component of post-war submarine design even into the nuclear age (despite the counterfactual claims of Blair). The first nuclear-powered submarine, USS Nautilus, also included a snorkel as a back-up to get the submarine home without surfacing in the case the nuclear reactor failed. In the modern submarine age surfacing meant the loss of the submarine’s most critical asset – invisibility. Once a submarine breached the surface it lost the element of surprise, but a snorkel provided the ability to remain submerged even in a crisis onboard the boat. The future of submarine warfare meant never operating on the surface. This was the embodiment of Walter’s Ortungskampf (battle of location concept) he championed during the war.

The Royal Navy adopted the snorkel during the end of the war, as they saw its potential to alter the course of the U-boat campaign. They needed to understand it, and how it functioned, both technically and tactically. Before the end of the war the Admiralty ordered that one U, S, T, and A Class submarine be equipped with a snorkel. Experiments continued by the Royal Navy well into the post-war period.

The Admiralty already had an eye towards the potential Soviet threat, and they were quick to exploit German naval technology and scientists. The Royal Navy had two main exploitation priorities regarding U-boats. Like the US Navy, they were the snorkel and Type XXI design. Unlike the US Navy, which already had an eye towards nuclear power, the Royal Navy’s third priority was Walter’s hydrogen peroxide closed propulsion system.

The Royal Navy’s secret intelligence unit, the 30 Assault Group, entered Kiel and immediately located Dr Walter at his home next to his factory and design offices. Along with Walter came some 50,000 pages of microfilm recordings in six boxes that he had buried in a secret location on the north coast. The original documents had been burned. These documents covered the entire technical development of German U-boats through the war. Along with the British came US Navy Captain Albert Mumma, originally of the Alsos Mission (looking for German nuclear, chemical and biological weapons research), and in the last days of the war part of the US Navy’s Technical Mission Europe. He was one of the seventy-five-man task force that captured Kiel.

Walter was interrogated extensively after the war. He informed his interrogators that he saw no future for a submarine that operated on the surface and that all design functions must be subordinated to that purpose. It was a vision he himself set on this course with the introduction of the snorkel, the Type XXI and the Walter Prototype. The Royal Navy adopted Walter’s design.

The Admiralty moved quickly to locate and raise the U-1407 hydrogen peroxide-equipped Type XVII to keep it from the Soviets. Testing was carried out in Kiel between August and September 1945 of the Walter turbine U-boats by Walter and his staff of engineers under the watchful eyes of the Royal and U.S Naval officers. After the successful trial in Kiel harbour the British offered Walter and a small group of his trusted engineers’ contracts to go and work for them in England. U-1406 was provided to the US Navy, but they did not operate that U-boat after quickly deciding to pursue nuclear propulsion instead of the Walter turbine. The U-1407 was refitted by Vickers under the guidance of Walter himself in 1947. In 1948, U-1407 was commissioned into the Royal Navy as HMS Meteorite and went through extensive operational testing off the coast of Scotland.

The Royal Navy concluded that while the Meteorite was unstable on the surface, it was ‘outstanding’ underwater and that its high speed, which came at a high cost in fuel, was best employed in escape underwater as originally envisioned by Walter during the war. The Royal Navy went on to commission HMS Explorer and HMS Excalibur to conduct underwater speed trials based on the principles of the Type XXVI. These hydrogen peroxide submarines achieved the underwater speeds of 25 knots that Walter had theorised was possible during the war. The Royal Navy concluded on their own that the diesel submarine fleet had reached its limits of endurance and speed. Walter’s ideas had been vindicated by the very Royal Navy his designs had hoped to defeat. Admiral Creasy stated of Walter’s design that ‘we stand on the threshold of very considerable technical development …’

Despite the efforts of the British to keep the most advanced U-boat technology out of Soviet hands, they failed. The Red Army had seized two unfinished Type XXIs, U-3528 and U-3542, at Schichau on the Baltic coast, Walter’s central design office for the Type XVIIB and XXVI at Blankenburg, and the Bruchner-Kanis factory that produced the Walter turbines in Dresden and at Weinrieb in Chemnitz. It was assessed by the Western Allies that one turbine of 2,500 shaft horsepower and one of 7,500shp were acquired by the Soviets. Beyond the new U-boat designs, the Soviets captured plans for advanced German torpedoes, internal electronics, the GHG passive sonar array and German technical experts themselves. This was cause for alarm at the highest levels in the US Navy.

Under the code name Medusa, two Soviet research institutes, Andreev and Krylov, adopted the German U-boat research and begin to pursue it at an accelerated rate in 1947–48. The Soviets soon adopted the advanced German designs and specifically the snorkel apparatus in their ocean-going Whiskey and coastal Malyutka-class submarines. The Whiskey class had already been designed before the end of the war as an improvement to the existing ‘S’ class, but German U-boat technology was quickly retrofitted. The Whiskey class was produced in more numbers than any other submarine in history, surpassing even the German Type VIIC.

The Soviets went on to develop the S 99 (Project 617) in 1951, known in NATO circles as Whale, which was a near exact copy of the German U-boat Type XXVI. With the help of captured German engineers, the Leningrad-Shuvalovo shipyard developed the first 7,500hp hydrogen peroxide engine for the Soviet Navy. The first operational tests began in June 1952. It was later commissioned into the Soviet Navy in 1956 and achieved an underwater speed of 20 knots, making it the fastest submarine in the Soviet fleet at that time. An explosion on the high-pressure line ended its brief career and it was decommissioned as the Soviet Navy shifted from hydrogen peroxide to nuclear power. However, the hull form and underwater principles it derived from building Walter’s Type XXVI were all carried forward into the next generation of Soviet submarines.

The Soviet Navy took an immediate interest in adopting Alberich and furthering the concepts of acoustic camouflage. While the US and, specifically the Royal Navy, were keen to understand Alberich from the perspective of countering its capability, the technical problems of adhesive turned both western naval powers off from further pursuit. The Soviets applied their version of a rubberised coating to both their Whiskey and smaller Malyutka-class submarines. The coatings were initially applied to the exterior hull, however, the Soviets began to pursue the German innovation of applying it on internal surfaces, to include their double hull, in order to reduce the transmission of sound.

Starting with the first Soviet nuclear submarines of the Project 627/November Class, almost all Soviet combat submarines were coated with what modern naval architects call anechoic tiles. Shock absorbers were also installed to reduce engine vibrations. While acoustic dampening was not a priority, creating an atmosphere capable of supporting a crew for fifty days without surfacing was. It was an endurance objective that mirrored the submerged U-boat operations in the last year of the war achieved through the snorkel.

Soviet investment in submarine technology continued at an extraordinary rate through the 1980s. A 1988 Naval Proceedings article argued that, based on developmental trends, the Soviets would all but overtake the US in advanced designs by 2000. The fact that the Soviets had mastered the process of acoustic camouflage introduced by the Germans became evident in the recovery operations of the downed Kursk (K-141) in 2000.

On 12 August 2000 the Russian Navy’s Oscar-II class nuclear-powered cruise-missile submarine suffered a catastrophic explosion from a hydrogen peroxide-fuelled Type 65 practice torpedo. Hydrogen peroxide, it should be noted, was the key component of Walter’s closed-circuit turbine engines. Its cost and highly volatile nature when exposed to an accelerant such as oxygen were among the main reasons that both the US and Royal Navies abandoned it after 1950. The explosion collapsed the first three compartments of the submarine, sending it to the bottom in 108m of water in the Barents Sea.

British and Norwegian undersea salvage experts led the search team looking for the stricken Kursk. They were given its precise co-ordinates by the Russian Navy. At 4.26am on Sunday, 20 August an ROV was lowered down from the Seaway Eagle to 300ft, just 75ft off the seabed, and its active sonar turned on. As the ROV’s sonar began to sweep for the stricken Russian submarine the British operators could not find the Kursk. It wasn’t there. According to the ROV operator ‘the sonar received absolutely no signal. The Kursk had apparently vanished.’ Confusion reigned onboard the search vessel. Numerous search passes were made over the location of the Kursk until finally a faint ‘ping’ was returned. The seven-bladed massive twin bronze propellers, standing high off the seabed, were the only physical component of the submarine that gave away the Kursk’s location. According to the ROV operator, ‘confusion turned to amazement as the men realised that the acoustic tiles on the outer hull of the Kursk were so effective that they had been absorbing the ROV’s active sonar signals’.

The Soviet Navy enjoyed a thirty-year lead in the operational employment of Alberich, known today as ‘anechoic tiles’. The US and Royal Navies did not start applying such tiles until the 1980s. The first US submarine coated was the USS Batfish in 1980, but the US Navy did not systematically adopt the technology until 1988. Even today the US Navy faces ongoing struggles with adhesive properties, as evinced in the recent reports about the Virginia Class ‘mould-in-place’ urethane coating.

Walter’s concepts continued in the post-war Federal German Navy. The introduction of the German Type 212 class submarine in 2003 ushered in the most advanced non-nuclear submarine in operation today. This highly advanced design developed by Howaldtswerke-Deutsche Werft AG (HDW) features both diesel propulsion and an air-independent propulsion (AIP) system using Siemens proton exchange membrane (PEM) compressed hydrogen fuel cells. The Type 212A can operate at high speed on diesel power or switch to the AIP system for silent slow cruising, staying submerged for up to three weeks without surfacing or using its snorkel. According to Doug Thomes, writing in the Canadian Naval Review:

The second of class U-32 set a record in April 2006 when it conducted an uninterrupted dived transit from the Baltic to Rota Spain, a distance of 1,500 nautical miles in two weeks. These vessels are very stealthy by virtue of their lack of a need to snorkel and are much more habitable than their predecessors: the accommodation improvements have enabled the abandonment of the German practice of hot bunking for the first time and there are now dining and working spaces separated from the sleeping quarters.

The Type 212A hull design and composite material make it one of their quietest and hardest to detect submarines in the world. The X-shape stern design allows it to operate in coastal water as shallow as 17m. A direct line can be drawn to the Type 212 and subsequent 214 and 216s from the effective wartime performance of the Type XXIIIs in shallow water.

It remains a testament to German wartime innovation and engineering that almost all modern submarines, whether diesel or nuclear powered, are equipped with a version of the snorkel, and some with anechoic tiles. All strive to remain unseen and undetected in Walter’s vision of ‘Total Undersea War’ ushered in after the introduction of the snorkel into the U-boat fleet at the end of 1943.