From the early 1940s to the ultimate collapse of the USSR, the Soviet Navy pushed its submarine design bureaus to develop submarines specifically for troop and cargo transport. While many of these "submarine LST" concepts were not pursued, the effort offers a fascinating look at the technical challenges and strategic thought inherent in modern submarine design.
Early in World War II the Soviet Navy occasionally employed submarines as transports for small numbers of people, usually saboteurs and "agents," and limited cargo. This situation changed when German forces began the siege of the Crimean port of Sevastopol. When Soviet defenses collapsed in the Crimea in the fall of 1941, about 110,000 soldiers, sailors, and marines remained in the beleaguered port. Soviet ships and submarines, running a gauntlet of bombs and shells, brought men, munitions, and supplies into the city.
Heavy losses in surface ships led the commander of the Black Sea Fleet in April 1942 to order submarines to deliver munitions and food to Sevastopol, and to evacuate wounded troops as well as the remaining women and children. The largest available Soviet submarines of the Series XIII (L class) could carry up to 95 tons of cargo, while the smaller units delivered far less. Not only was every available space within the submarines used for cargo (including containers of gasoline), but cargo was loaded into torpedo tubes and mine chutes. Some 80 runs were made into Sevastopol by 27 submarines. They delivered 4,000 tons of supplies and munitions to Sevastopol's defenders and evacuated more than 1,300 persons. (Sevastopol fell on 3 July 1942 after a siege of 250 days.)
Based on the Sevastopol experience, the Soviet Navy's high command initiated an urgent program to build transport submarines. First, an effort was undertaken to design submarine barges for transporting cargo - solid and liquid - that could be towed by standard submarines or a specialized submarine tug (Project 605). It was envisioned that these underwater barges could be built rapidly in large numbers. According to the official Soviet submarine design history, from the beginning of the project the major complexity was not with the underwater barge itself, but with towing it by a submarine. The Navy was forced to cancel the project because of this problem.
A Tactical-Technical Elements (TTE) requirement for a small cargo submarine was issued by the Navy's shipbuilding office in July 1942, eventually designated Project 607. This was to be a submarine with a capacity of 250 to 300 tons of solid cargo not larger than 21-inch torpedoes, and also 110 tons of gasoline in four ballast tanks. Two folding cargo cranes would be fitted. The engineering plant was diesel-electric, with a single propeller shaft. No torpedo tubes would be provided, although two small deck guns were to be mounted. These cargo submarines were to use the same equipment and fittings as the small submarines of the earlier VI and VI-bis series (202 tons submerged). This approach would simplify the design and construction of the submarines, which could be built at inland shipyards.
By April 1943, blueprints were being issued. But by that time the general military situation had changed in favor of the Soviets, and the need for underwater transports disappeared; Project 607 was canceled. However, no technical or operational problems had been envisioned in the design.
While the Soviet Union built no Project 607 submarines, the concept of cargo-transport submarines continued to occupy the thoughts of Soviet submarine designers into the post-World War II era. The Soviets may also have considered ocean-going cargo submarines in this same period. According to the memoirs of the U.S. ambassador to the USSR, Admiral William H. Standley, while discussing with Josef Stalin the problems of shipping war materiél to Russia, Stalin asked:
Why don't you build cargo submarines? Cargo submarines could cross the ocean without interference from Nazi submarines and could deliver their supplies directly to our own ports without danger of being sunk.
Admiral Stanley responded that he was "sure that the question of building cargo submarines has received consideration in my country." Stalin replied, "I'm having the question of cargo submarines investigated over here."
In 1948 the design bureau TsKB-18 (later Rubin) developed a draft design for Project 621 - a landing ship-transport submarine to carry out landings behind enemy lines. This was to be a large submarine with a surface displacement of some 5,950 tons. This underwater giant - with two vehicle decks - was to carry a full infantry battalion of 745 troops plus 10 T-34 tanks, 12 trucks, 12 towed cannon, and 3 La-5 fighter aircraft. The troops and vehicles would be unloaded over a bow ramp; the aircraft would be catapulted, with the launching device fitted into the deck forward of the aircraft hangar. Both conventional diesel-electric and steam-gas turbine (closed-cycle) powerplants for both surface and submerged operation were considered for Project 621.
TsKB-18 also developed the draft for Project 626, a smaller landing ship-transport ship intended for Arctic operations. The ship would have had a surface displacement of some 3,480 tons and was intended to carry 165 troops and 330 tons of fuel or four T-34 tanks for transfer ashore.
Simultaneously, interest in specialized mine-laying submarines was renewed. In 1956, the Soviet Navy's leadership endorsed a TTE for a large minelayer capable of carrying up to 100 of the new PLT-6 mines and transporting 160 tons of aviation fuel (gasoline or kerosene) in fuel-ballast tanks. This was Project 632 at TsKB-18.
Graphic courtesy of A.D. Baker III, from Cold War Submarines
The Soviet's Project 621 was designed as a landing ship-transport submarine that could carry out landings behind enemy lines. This underwater giant had two vehicle decks, and was designed to carry a full infantry battalion of 745 troops plus 10 T-34 tanks, 12 trucks, 12 towed cannon, and three La-5 fighter aircraft.
Preliminary designs addressed carrying mines both "wet" and "dry" (i.e., within the pressure hull). Soon the heavy workload at TsKB-18 led to the transfer of design work on Project 632 - estimated to be 33 percent complete at the time - to TsKB-16 (later Volna/Malachite). The design was completed in two variants - with wet storage for 90 mines or dry storage for 88 mines. A combined wet/dry configuration could carry 110 mines. A further variant of Project 632 showed a small increase in dimensions that would permit 100 troops to be carried in the mine spaces, with the mine-laying gear designed to be removable. The latter feature was a consequence of the Sevastopol experience, which suggested that these and other large submarines should also be able to transport aviation fuels and to be reconfigurable at naval bases to transport combat troops or wounded (with medical attendants) in place of mines.
Project 632 was approved for construction in February 1958. Significantly, in October 1958, the design for a nuclear-propelled variant of the minelayer was also approved - Project 632M, employing a small O-153 reactor plant. This ship would have been some 100 to 200 tons heavier than the basic 632 design. The nuclear variant would have a submerged cruising range estimated at 20,000 nm compared to 600 to 700 nm for the conventional propulsion plant. But when the Central Committee and Council of Ministers approved the seven-year shipbuilding program in December 1958, the Project 632 submarine was missing.
In its place, a replenishment submarine was developed beginning in 1958 that would have a secondary mine-laying capability - Project 648. Designed at TsKB-16, the craft's primary mission requirement would be to replenish and re-arm submarines attacking Allied merchant shipping. Project 648 was to carry missiles (ten P-5/P-6 [NATO SS-N-3 Shaddock]) or torpedoes (40 21-inch and 20 15.75-inch) plus 34 tons of food (estimated to feed 100 personnel for 90 days), 60 tons of potable water, and 1,000 tons of diesel fuel (or the equivalent in aviation fuels).
The weapons and stores were to be trans- ferred at sea to submarines, a considerable challenge, especially with respect to the cruise missiles. Diesel fuel was to be transferred to a submarine while both were submerged. Aviation fuel would be carried for transfer to seaplanes in remote operating areas. Again, the Sevastopol experience led to the TTE including a capability to transport 120 troops and their weapons, or to evacuate 100 wounded personnel.
Meanwhile, the design for Project 648 had been approved on 10 July 1958. Because of the termination of Project 632, the new submarine was to carry up to 98 mines in place of replenishment stores. Work on Project 648 began at the Severodvinsk shipyard in the Arctic, and a section of the submarine's hull was fabricated and specialized replenishment equipment and systems installed. The project was complex and, according to Russian historians, "As it was more profitable to construct the large-series orders for atomic submarines, the shipyard's director, Ye.P. Yegorov, tried in every possible way to shift construction of the transport-minelayer submarine to another yard or shut down the project overall."
The design for Project 664 combined the characteristics of a "submarine LST" with a replenishment submarine - and it would have nuclear propulsion. This large submarine would carry 20 cruise missiles or 80 21-inch torpedoes, or 160 15.75-inch torpedoes for transfer to combat submarines. Liquid cargo would include 1,000 tons of diesel oil or aviation fuel, plus 60 tons of lubricating oil, 75 tons of potable water, and 31 tons of food. In the LST role, the submarine would carry 350 troops, although up to 500 could be carried for a five-day transit.
Graphic courtesy of A.D. Baker III, from Cold War Submarines
Six variants of the Soviet's diesel-electric submarine LST design - Project 748 - were developed, with surface displacements from 8,000 to 11,000 tons. Most variants had three separate, cylindrical pressure hulls side-by-side, encased in a single outer hull. This large submarine could carry up to 20 amphibious tanks and BTR-60P armored personnel carriers, and up to 1,200 troops. In addition to a torpedo armament of four bow 21-inch torpedo tubes with 18 to 20 torpedoes, the submarine was to be fitted with anti-aircraft guns and surface-to-air missiles. Graphic courtesy of A.D. Baker III, from Cold War Submarines.
The difficulties in replenishing submarines at sea and interest in nuclear propulsion for a replenishment submarine led to cancellation of Project 648 in June 1961. There already was a preliminary design for Project 648M in which three of the ship's silver-zinc batteries and two diesel engines would be replaced by two small O-153 nuclear plants of 6,000 horsepower each. It was estimated that the nuclear capability would increase submerged endurance from the 600 hours of diesel-electric propulsion to 1,900 hours.
The design was presented to the Navy and shipbuilding committee, but this modification of the original Project 648 design was already being overtaken by the more ambitious Project 664 submarine. Project 664 combined the characteristics of a "submarine LST" with a replenishment submarine and would have nuclear propulsion. Design work began in 1960 at TsKB-16. This would be a larger submarine, with a surface displacement of 10,150 tons, and would carry 20 cruise missiles or 80 21-inch torpedoes, or 160 15.75-inch torpedoes for transfer to combat submarines. Liquid cargo would include 1,000 tons of diesel oil or aviation fuel, plus 60 tons of lubricating oil, 75 tons of potable water, and 31 tons of food. In the LST role, the submarine would carry 350 troops, although up to 500 could be carried for a five-day transit.
There obviously was interest in replenish- ment submarines at the highest levels of the Soviet Navy. A 1961 issue of Voyennaya Mysl (Military Thought), the senior (classified) Soviet military journal, contained an article by Admiral Yuri Panteleyev looking at future submarine operations. Among the technical problems he looked to see resolved was creating "a class of special submarine tankers and submarine transports for the shipment of combat supplies, equipment, and contingents of personnel." Panteleyev also called for "... a system for all types of underwater supply, for submarines lying on the bottom at points of dispersal and at definite depths and not moving."
Construction of Project 664 began at Severodvinsk in 1964. But soon it was determined that combining three missions - replenishment, transport, and mine-laying - in a single hull caused major complications, even in a nuclear-powered submarine. Both range and operating depth were reduced. In May 1965 all work on the lead submarine was halted. The proposal was made to transfer the project to a Leningrad shipyard to make room at Severodvinsk for accelerated construction of Project 667A/Yankee SSBNs, but the project was halted completely.
Accordingly, in August 1965 TsKB-16 was directed to respond to the TTE for a large diesel-electric submarine LST - Project 748. The design bureau, realizing the limitations of conventional propulsion for this submarine's missions, additionally initiated nuclear-propelled variants.
Six variants of Project 748 were developed with surface displacements from 8,000 to 11,000 tons. Most variants had three separate, cylindrical pressure hulls side-by-side, encased in a single outer hull. The first variant met the basic TTE; the second variant carried a larger number of PT-76 amphibious tanks; the third variant had VAU-6 auxiliary nuclear power plants; the fourth variant had two OK-300 reactor plants generating 30,000 horsepower; the fifth variant had the VAU-6 system with a single pressure hull; and in the sixth variant the OK-300 plant was replaced by four VAU-6 units.
This large submarine could carry up to 20 amphibious tanks and BTR-60P armored personnel carriers, and up to 470 troops. In addition to a torpedo armament of four bow 21-inch torpedo tubes with 18 to 20 torpedoes, the submarine was to be fitted with anti-aircraft guns and surface-to-air missiles. And, of course, the submarine could serve as a minelayer.
TsKB-16 recommended proceeding with the fourth (nuclear-propelled) variant. Still, construction was not initiated because the Navy, Ministry of Shipbuilding Industry, and General Staff of the Armed Forces ordered a review of the features of Projects 632, 648, 664, and 748 in an effort to develop a "ubiquitous" or all-capable nuclear submarine. TsKB-16 (now named Volna) was directed to develop a preliminary design for the submarine - Project 717. The TTE called for the clandestine delivery of up to 800 marines and four armored vehicles; the transport of arms, munitions, fuel, and provisions, including up to 20 amphibious tanks and personnel carriers; and the evacuation of troops and wounded, as well minelaying. This was to be the world's largest submarine designed to that time, with a surface displacement of more than 17,600 tons and nuclear propulsion.
The preliminary design effort was completed early in 1969. In July the Navy and the Ministry of Shipbuilding Industry added to the TTE the requirement for "the rescue of the crews of sunken submarines with the aid of rescue apparatus." This change led to revised specifications, which were not formally approved until February 1970. Completion of the revised contract design for Project 717 was delayed until October 1971.
The Severodvinsk shipyard made prepara- tions for constructing five submarines to this design. Full-scale mockups were made of the control room, cargo spaces, and other portions of the submarine. However, this project, too, was stillborn when in the late 1970s, the available building ways at Severodvinsk were needed for the construction of nuclear submarines, especially Project 941/Typhoon SSBNs that were being developed as a counter to the U.S. TRIDENT program, i.e., the USS Ohio (SSBN-726) class.
American Design Efforts. The U.S. Navy also undertook preliminary sketches of submarine LSTs, but never pursued the concept to the extent of the Soviet design efforts. This is artist Frank Tinsley's impression of a submarine LST produced in the 1950s for
Mechanix Illustrated magazine and presented to the Navy Department. This was a 10,000-ton submarine, 720 feet long, with a beam of 124 feet that could carry 2,240 Marines, landing them by "amphibious flying platforms" that could move at 100 mph.
Thus ended the design of large minelaying/ transport/replenishment submarines in the Soviet Union. But there still was some interest in submarine tankers. In the 1960s TsKB-57 undertook the design of a large submarine tanker, Project 681, intended primarily for commercial operation. With two VM-4 nuclear reactor plants, the submarine would have a surface displacement of 24,750 tons. Subsequently, TsKB-16 began design of another nuclear-propelled submarine tanker in 1973, Project 927, but neither of these projects was pursued.
There was yet again interest in submarine tankers - and container submarines - in Russia in the 1990s. The Malachite bureau (formerly TsKB-16/143) put forward preliminary designs for a submarine capable of transporting petroleum or freight containers, especially in the Arctic region. Envisioning under-ice navigation between European and Asian ports, and possibly northern Canada, the Malachite designers noted, "Given equal cargo capacity, the efficiency of an underwater container ship is considerably higher, for example, than that of an icebreaker transport ship of the Norilsk type. The underwater tanker is competitive."
Malachite proposed tankers and container variants of the same basic nuclear submarine design employing an elliptical cross-section. The tanker variant would transport almost 30,000 tons of petroleum, which could be loaded and discharged from surface or underwater terminals. The underwater container carrier could transport 912 standard (20-foot) freight containers, loaded through a series of hatches. It was estimated to take 30 working hours to load or unload a full shipload. Large cargo hatches and an internal container-moving scheme would facilitate those operations. A single-reactor, single-shaft propulsion plant was proposed with three diesel generators for maneuvering in harbor and for ship electrical needs. Two of the diesel generators would be fitted to work as closed-cycle/Air Independent Pro-pulsion (AIP) systems for emergency under-ice operation. Thirty tons of oxygen was to be carried to provide an AIP endurance of 20 hours at a speed of seven or eight knots.
No detailed design or procurement followed as Russia fell into financial extremis during the post-Soviet era.
