Ro-100-class submarine

The Ro-100-class submarine (呂百型潜水艦) was a group of medium-sized coastal submarines built for the Imperial Japanese Navy (IJN) during World War II. The IJN official designation for this class was Ko type submarine (小型潜水艦) or Senshō type submarine (潜小型潜水艦). They are also known as Type KS submarine. The type name was shortened to Sensuikan Ko-gata (潜水艦小型).

Design and description
In 1940, the IJN designed a point-defence coastal submarine because they wanted to save their larger submarines for fleet battles. The Ro-100 class was derived from the preceding Kaichū type. They displaced 601 LT surfaced and 782 LT submerged. The submarines were 60.9 m long, had a beam of 6 m and a draft of 3.51 m. They had a double hull and a diving depth of 75 m.

For surface running, the boats were powered by two 500 bhp diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 380 hp electric motor. They could reach 14.2 kn on the surface and 8 kn underwater. On the surface, the Ro-100s had a range of 3500 nmi at 12 kn; submerged, they had a range of 60 nmi at 3 kn.

The boats were armed with four internal bow 53.3 cm torpedo tubes and carried a total of eight torpedoes. They were also armed with two single mounts for 25 mm Type 96 anti-aircraft guns or a single 76.2 mm L/40 AA gun.

Boats
18 boats were built in 1941-1944 under the Maru Rin Programme (Boat #210-218) and the Maru Kyū Programme (Boat #400-408).