They also had a long cruising range at a speed of 12 knots (22 km/h). They were quite long and carried a crew of up to 94. This class of submarines was designed and built by Mitsubishi Corporation, between 19, as cargo carriers. In addition, 35 to 40 tons of secret documents, drawings, and strategic cargo awaited I-52 's return trip to Japan: T-5 acoustic torpedoes, a Jumo 213-A motor used on the long-nosed Focke-Wulf Fw 190D fighter, radar equipment, vacuum tubes, ball bearings, bombsights, chemicals, alloy steel, and optical glass. She was also to be fitted with a snorkel device at Lorient. (The amount of unenriched uranium oxide would not have been enough to create an atomic bomb, though if used in a nuclear reactor it could have created poisonous fission products). It has been speculated that this was for the Japanese to develop a radiological weapon (a so-called ' dirty bomb') for use against the United States. It is believed that 800 kg (1,760-lbs) of uranium oxide awaited I-52 for her return voyage at Lorient according to Ultra decrypts. There has been speculation that a peace proposal to the Allies was contained on board the I-52 as well, but this is unlikely on two counts: there is no evidence that the Japanese government was interested in peace proposals or negotiated settlements at that stage in the war and the Japanese kept an open dialogue with their diplomatic attachés via radio and diplomatic voucher through Russia, and had no need for long and uncertain transfer via a submarine bound for a Nazi-controlled area of western Europe.

She is also known as Japan's 'Golden Submarine', because she was carrying a cargo of gold to Germany as payment for matériel and technology. I-52 ( 伊号第五二潜水艦 (伊52), I Gō Dai Gojūni Sensuikan (I Gojūni), I-52 submarine (I-52)), code-named Momi ( 樅, ' fir tree') was a Type C-3 cargo submarine of the Imperial Japanese Navy used during World War II for a secret mission to Lorient, France, then occupied by Germany, during which she was sunk. I-52, code-named Momi (樅, Japanese for 'evergreen' or 'fir tree')Ģ,095 metric tons standard, 2,564 t surface, 3,644 t submergedĢ-shaft diesel and electric motor, 4,700 bhp (3,500 kW) surface, 1,200 shp (890 kW) submergedġ7.7 knots (33 km/h) surface, 6.5 knots (12 km/h) submergedĢ1,000 nautical miles (39,000 km) at 16 knots (30 km/h)Ħ x 53 cm torpedo tubes, 2 x 14 cm/40 11th Year Type naval guns, 2 x Type 96 25 mm (0.98 in) anti-aircraft guns For other ships with the same name, see Japanese submarine I-52 and Japanese ship Momi.

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