Design and Construction of Submarines
Some Cutting Edge Features, Technology and Tactics have their origin in the Cold War and WWII.
The following commentary is an effort to connect some dots and put into perspective some information about the Design and Construction choices of Submarines during the Cold War by the US and USSR. The text is based on extensive notes the author took from the wealth of literature USNI and Norman Polmar have published about the Design and Construction of Cold War era Submarines.
No knowledge or technology exists without precedent in history and it is especially true when we study the design and construction of submarines during the Cold War. The cutting edge features in naval submarines today are the legacy of Cold War-era technologies that were, in turn, derived from both Axis and Allied efforts from the 1930s.
Following Germany’s defeat in 1945, several advanced, state-of-the-art U-Boats were commandeered by Soviets and the western allied powers These included the newest Type XXI boats, a design that was then the most cutting edge subsurface combat vessel to go to sea. Furthermore, entire German shipyard facilities were stripped and all of their production lines along with all of their surviving equipment, blueprints, design documents, prototypes and unfinished boats were dismantled and taken away by the occupying forces, especially the Red Army, since Soviet leader Joseph Stalin had given orders to dismantle all the possible industrial infrastructure on German land for use in reconstruction in the Soviet Union. What follows is a brief survey of the key innovations that continue to define much about submarine design and construction even today.
Germany’s Distributed Production and Assembly Lines:
As devastating as the German U-boats were to allied convoys in the Atlantic in the Second World War, they were never available in adequate numbers to have won the war for the Axis powers. One of the reasons for this was the long time it took to build the boats from scratch in dry docks. Karl Dönitz, grand admiral of Germany’s navy, the Kriegsmarine, noticed this problem and sought a solution from Albert Speer, the Third Reich’s talented minister of armaments and war production. Speer recruited Otto Merker, an engineer with no ship-building experience, who was nevertheless, an expert in mass production. Merker’s solution for cutting down the man-hours required to build submarines was to build them in separate sections at various facilities and then assemble them together at shipyards. This also resulted in the ability to build larger, more sophisticated boats that were previously thought to be too difficult to make. As we saw during the Cold War, and continue to see today, modern multi-compartment high-tech warships and submarine production would be impossible if larger ships and boats were not built in separate sections that were then independently transported to a dry dock, assembled and finally launched to be fitted out.
Air Independent Propulsion (AIP):
Conventionally-powered submarines have greater endurance and can remain submerged longer when fitted with Air Independent Propulsion or AIP. This propulsion technology has a long history dating back to even before the Second World War when the Kriegsmarine experimented with Helmuth Walter’s Hydrogen Peroxide-supplemented propulsion system and the derivative Type XXI boats were later commandeered and even put into service by the US Navy and Royal Navy, as well as the Soviets. However, the superpowers soon lost interest in conventionally-powered submarines and began to focus their energies on nuclear propulsion. Things changed in the years after the Cold War, as conventional diesel-electric engines (with their subsidiary silent propulsion systems) received a boost after Sweden used Stirling AIP systems to power its Gotland class of submarines. Such designs offered solutions for smaller naval powers that have to deter far stronger and more advanced navies with prominent nuclear-powered and armed fleets.
The Iconic Cigar or Teardrop shape:
The iconic cylindrical cigar shape of a submarine hull is one of the more recognizable indicators of the progress made in submarine design endeavours during the Cold War. The teardrop shape imposes a penalty on surfaced or semi-submerged speeds due to increased drag but offers much better performance for completely submerged sailing compared to any other shape. It is curious to follow, however, how the teardrop hull shape was first conceived with early submarine designs(torpedo boats) and then the Germans regressed away from them and adopted a semi-submerged corvette like a design for their U-Boats(due to their propulsion systems not being good enough for long durations when fully submerged), which the rest of the world first followed and then ultimately moved away from, only to re-adopt proper teardrop-shaped hulls once submerged propulsion systems became good enough. The Foxtrot-class (which the Indian Navy also operated) happens to be a special case, since they also carried a fairly potent package of weapons and sonar equipment on par with more advanced Soviet submarine designs, giving them an edge over older classes with which their now obsolete basic hull shape belonged.
A tale of Deep diving combat manoeuvres and Hulls:
Submarines rely on stealth and the deeper they can dive, the higher the chance they have to outmanoeuvre and outrun enemy torpedoes. The significance of being able to operate in deeper and deeper waters has never diminished. In fact, with the advent of Ballistic Missile Submarines (SSBNs) during the Cold War, it became even more important for submarines to be able to sail and dive deep so they could remain concealed until a situation arose where their nuclear payloads carrying ballistic missiles were to be launched or another SSBN relieved them from deterrence patrol duty. As submerged propulsion systems became more efficient and allowed submarines to stay submerged for longer, the need for increased hull strength became evident. To this end, pressure hulls (which had a history dating back to Tsarist times) became an important aspect of submarine design. Eventually, the Soviet would even work on making double/multiple pressure hulls out of Titanium alloys instead of the more conventionally used steel.
Nuclear Propulsion:
Contrary to popular beliefs about nuclear propulsion it is not only limited by food and other provisions. Depending on the specific reactor design and the level of enrichment of fuel used nuclear power plants onboard naval ships and submarines require refuelling anywhere between 5-25 years, not to mention the rigorous maintenance work that has to be constantly performed at the pier, with specialised onshore equipment. Reactors also have to be periodically shut down completely. Still, in the short “on sortie“ tactical sense, ranges and combat radius are virtually “unlimited”, thanks to the efforts of one man, Admiral Hyman Rickover of the US Navy, who championed the case for nuclear propulsion over all else and was instrumental in the chain of events that lead to the world’s major naval powers ambitiously pursuing nuclear propulsion.
Arctic Capability, Unprecedented Speeds and a Tale of Extremes:
The Cold War was a truly global contest but it was the Soviet Union that had a lot of catching up to do after the Second World War, especially in the maritime domain. As is the case with most late bloomers, the Soviet Navy perhaps over-compensated in some cases to establish a clear technological edge over its Western adversaries by attempting far costlier and riskier design and construction choices.
The backdrop to this is Russia’s maritime geography, with perhaps one of the biggest areas of responsibility being the Arctic. The Soviet Navy had to adapt to operating effectively in extremely low-temperature conditions. If not patrolled constantly, the Arctic could give the Soviet’s adversaries a safe haven just off their coast where they could hide submarines that might threaten the Soviet Union’s Sea Lines of Communication (SLOC) and its homeland.
Another problem that was a thorn in the Soviet Navy’s side was the capability gap between the need for repositioning assets quickly and the maximum sailing speeds possible for said assets. To mitigate these shortcomings, cutting edge propulsion systems like the lead-bismuth cooled fast reactor of the Alfa class, which gave them the ability to rush from the Arctic to the Atlantic to the Pacific with speeds of over 40 knots, were commissioned. Apart from being perfect for intercepting targets in faraway waters, these titanium alloy-hulled submarines could outrun torpedoes thanks to a combination of both unprecedented speeds and be able to survive operating at what were then unprecedented dive depths of up to 1,300 metres.
The unprecedented top speed of over 40 knots also gave these submarines a clear edge when facing Western Carrier Battle Groups made up of fast surface combat ships that used their speed as a primary means of maintaining a healthy distance between themselves and Soviet submarines they detected before ever attempting any countermeasures or offensive manoeuvres.
In these extremes, we can observe the imprint of the strategic as well as tactical genius of Admiral Flota Sovetskogo Soyuza (Admiral of The Fleet of The Soviet Union) Sergei Gorshkov, and his plans of outclassing the enemy in the design and construction of technologically advanced platforms. These left a lasting legacy on both the Russian Federation Navy and possibly the world at large, decades after his death.
This post has been amended to remove the erroneous reference to anechoic tiles being used on Foxtrot class submarines.
These are the author’s personal views and do not necessarily reflect those of the Takshashila Institution.
