German submarine U-639

German submarine U-639 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II. She was laid down on 31 October 1941 at Blohm & Voss in Hamburg as yard number 615, launched on 22 July 1942 and went into service on 10 September 1942. U-639 spent her entire career operating out of Norway. Over the course of four patrols she neither sank nor damaged any ships, and was sunk by the SOVIET SUBMARINE S-101 in the Kara Sea while on a minelaying mission.

Design
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-639 had a displacement of 769 t when at the surface and 871 t while submerged. She had a total length of 67.10 m, a pressure hull length of 50.50 m, a beam of 6.20 m, a height of 9.60 m, and a draught of 4.74 m. The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2800 to 3200 PS for use while surfaced, two BBC GG UB 720/8 double-acting electric motors producing a total of 750 PS for use while submerged. She had two shafts and two 1.23 m propellers. The boat was capable of operating at depths of up to 230 m.

The submarine had a maximum surface speed of 17.7 kn and a maximum submerged speed of 7.6 kn. When submerged, the boat could operate for 80 nmi at 4 kn; when surfaced, she could travel 8500 nmi at 10 kn. U-639 was fitted with five 53.3 cm torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.8 cm SK C/35 naval gun, 220 rounds, and one twin 2 cm C/30 anti-aircraft gun. The boat had a complement of between forty-four and sixty.