Merchant submarine

Deutschland had a carrying capacity of 700 tons (much of it outside the pressure hull), and could travel at 12.4 knots (14.3 mph; 23.0 km/h) on the surface and 7 knots (8.1 mph; 13.0 km/h) while submerged. It had a crew of 29 men and was commanded by Paul König, a former surface merchantman captain.[3]

On its first journey to the US, departing on the 23 June 1916, Deutschland carried 163 tons of highly sought-after chemical dyes, as well as medical drugs and mail.[2] Passing undetected through the English Channel[1] she arrived in Baltimore on 8 July 1916 and soon re-embarked with 348 tons of rubber, 341 tons of nickel, and 93 tons of tin, arriving back in Bremerhaven on 25 August 1916. She had traveled 8,450 nautical miles (9,724 mi; 15,649 km), though only 190 nmi (219 mi; 352 km) of these submerged.

The American submarine pioneer Simon Lake had unsuccessfully negotiated to construct cargo submarines for Kaiserliche Marine prior to the war, and attempted to block Deutschland's return to Germany by raising patent infringement allegations. Lake was placated when a Krupp representative and a Norddeutscher Lloyd agent suggested Lake built 5,000-ton merchant submarines for them in the United States.[4]

The profit from the journey was 17.5 million Reichsmarks, more than four times the construction cost,[2] mainly because of the high prices of the patented, highly concentrated dyes, which would have cost 26,844 US dollars per pound adjusted for inflation.[3] In return, the raw materials brought back covered the needs of the German war industry for several months.[2]

A second journey in October-December of the same year was also successful, again trading chemicals, medicines and gems for rubber, nickel, alloys and tin. However, Deutschland was lightly damaged during a collision with a tug in New London.[2] Following his return, captain Paul König wrote a book (or possibly had it ghostwritten) about the journeys of Deutschland. The book was heavily publicized, as it was intended to sway public opinion in both Germany and the US.[5]

A third journey, planned for January 1917, was aborted after the US entered the war against Germany. The declaration of war had been partly due to US anger over the actions of German submarines sinking shipping bound for Great Britain, sometimes just outside American territorial waters (See SM U-53). Deutschland was taken over by the German Imperial Navy and converted into the submarine cruiser (U-Kreuzer) U-155 (a type of submarine with added artillery to fight when surfaced). It was successful in three war cruises, sinking 43 ships. After the war it was taken to England as a war trophy in December 1918. Scrapped in 1921, the boat's history ended with five workers dying due to an explosion ripping apart the sub during dismantling.[3]

A second merchant submarine, the sister ship of Deutschland, launched its first journey in August 1916 under Karl Schwartzkopf, but never arrived in the US. Its fate was never decisively uncovered, though she may have collided with the British armed merchant cruiser HMS Mantua south of Iceland, as was theorized after the war.[6] There was also the theory that she might have hit a mine off the Orkney Islands.[7]

Six further merchant submarines were in the process of being built by the Deutsche Ozean-Reederei when the US entered the war in early 1917. The construction of the merchant submarines was subsequently halted or changed into submarine cruisers, similar to the fate of Deutschland. When hostilities between Germany and the United States halted Simon Lake's attempts to build merchant submarines for Germany, Lake approached the United States Shipping Board with a proposal to build one-hundred merchant submarines to alleviate shipping losses being suffered from unrestricted submarine warfare.[4]

In World War II, Germany used Milk Cow submarines to refuel its hunter U-boats in the Atlantic. As these boats were part of Kriegsmarine (Nazi Germany's navy), did carry light armaments (anti-aircraft guns), and never engaged in trade as such, they do not qualify as merchant submarines. However, they shared the large amounts of cargo space compared to normal submarines of their day.[8]

After large Italian submarines successfully transported supplies to North Africa avoiding British Mediterranean Fleet patrols, some of these submarines had their torpedo tubes and offensive deck gun armament removed to increase cargo capacity. Five of these converted submarines were seized in Axis ports for operation by German crews after the Italian armistice in September 1943.[9]

Germany enlarged the ocean-going type IX U-boat design to an extended range type IXD1 variant with torpedo tubes removed and battery capacity reduced to increase cargo capacity for transport of strategic materials between German and Japanese ports. After the Italian submarines were converted for this cargo role, most of the extended range design were completed as an armed type IXD2 variant.[10]

In World War II, the Soviet Union used submarines (as well as other ships) to supply the besieged Crimean port of Sevastopol. The largest could transfer up to 95 tons of cargo, loading even the torpedo tubes with supplies. Around 4,000 tons were delivered by about 80 runs of 27 submarines, though Sevastopol still eventually fell.[12]

Based on this experience, the Soviet naval high command initiated a transport submarine program. A first project (Project 605) envisaged a sub that would function as a barge, towed by a standard sub. The idea was discarded due to towing difficulties. Later, a small cargo submarine design (Project 607) with a capacity of 250-300 tons of solid cargo and two folding cargo cranes was proposed. No weapons beyond two deck guns were envisaged, and the design borrowed many existing parts from the earlier VI and VI-bis submarine series to simplify construction. However, by 1943 the strategic situation had changed, and the plans were not executed.[12]

The Soviet Union envisaged and almost realized various concepts for large cargo submarines during the 1950s and 1960s, though these would not have been counted as merchant ships, being envisaged as navy landing ships to transport troops. They would have been amongst the largest submarines of their day, had they been built.[12]

In the 1990s, the Malachite design bureau in St. Petersburg proposed submarines capable of transporting petroleum or freight containers in or through Arctic regions. It was envisaged that these ships would dive under the polar ice cap to travel directly between European and Asian ports, and possibly northern Canada, with the designers noting that:

"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."[12]

The tanker and container variants would follow the same design as standard military nuclear submarines, with the tanker variant carrying almost 30,000 tons of petroleum, to be loaded and discharged from surface or underwater terminals. The container carrier was to transport 912 standard (20-foot) freight containers, loaded within 30 hours through hatches, assisted by internal conveyance systems. However, these plans came to nothing in the hard financial straits following the Dissolution of the Soviet Union.[12]

A similar design has been proposed by the Rubin Design Bureau with the 'Submarine Cargo Vessel', a civilian redesign of the famous Typhoon-class submarine of the Cold War.[13] A submarine freight transportation system (SFTS) was suggested in 1997 by Vladimir Postnikov and is considered as a sea-going component of a global intelligent transportation system.