Japanese submarine Ro-15

Ro-15, originally named Submarine No. 24, was an Imperial Japanese Navy Kaichū-Type submarine of the Kaichū II subclass. She was commissioned in 1921 and operated in the waters of Japan. She was stricken in 1933.

Design and description
The submarines of the Kaichu II sub-class were larger and had a greater range than the preceding Kaichu I subclass, but they had the same powerplant, so their greater size resulted in a loss of some speed. They also had a modified conning tower, bow, and stern, and the stern was overhanging. They displaced 740 LT surfaced and 1003.1 LT submerged. The submarines were 70.10 m long and had a beam of 6.10 m and a draft of 3.68 m. They had a diving depth of 30 m.

For surface running, the submarines were powered by two 1,450 bhp Sulzer Mark II diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600 hp electric motor. They could reach 16.5 kn on the surface and 8.5 kn underwater. On the surface, they had a range of 6,000 nmi at 10 kn; submerged, they had a range of 85 nmi at 4 kn.

The submarines were armed with six 450 mm torpedo tubes, four internal tubes in the bow and two external tubes mounted on the upper deck, and carried a total of ten Type 44 torpedoes. They were also armed with a single 76.2 mm deck gun mounted aft of the conning tower.

Construction and commissioning
Ro-15 was laid down as Submarine No. 24 on 12 June 1920 by the Kure Naval Arsenal at Kure, Japan. Launched on 14 October 1920, she was completed and commissioned on 30 June 1921.

Service history
Upon commissioning, Submarine No. 24 was attached to the Kure Naval District, to which she remained attached throughout her career. She was assigned to Submarine Division 15 — in which she spent the rest of her career — and to the Kure Defense Division on 1 July 1921. On 19 July 1921, a fire broke out in her galley due to faulty electrical wiring and spread to the adjacent torpedo room. She was flooded to extinguish it, but not before much of her interior was burned out. There were no casualties, and she was repaired and returned to service.

Submarine Division 15 served in the Kure Defense Division until 1 December 1921 and again from 1 December 1922 to 1 December 1923. While cruising off Moji, Japan, on 29 July 1924, Submarine No. 24 collided with a steamer, suffering no casualties.

Submarine No. 24 was renamed Ro-15 on 1 November 1924. On 1 December 1926, Submarine Division 15 began another assignment to the Kure Defense Division that lasted through the end of Ro-15′s active service.

Ro-15 was stricken from the Navy list on 1 September 1933. She remained moored at Kure as a hulk after that, and was renamed Training Hulk No. 3036 on 7 March 1934. She served on training duties through the end of World War II in August 1945, and was scrapped in September 1948.