HMS X1 (1923)

HMS X1 was an experimental cruiser submarine designed for the Royal Navy, to raid merchant shipping. At the time of her launch she was the largest submarine in the world.
The idea of a submarine cruiser was proposed as early as 1915, but was not really started -with the mitigated experience of the M class- from 1921. She was a replica of the projected, but never completed German U-173, a large U-kreuzer displacing more than 2 000 tons and armed with heavy guns.
The Washington Naval Treaty of 1922 did not banned submarines (to the relief of France and Italy) but prohibited their use against merchant shipping. The initial purpose of X1 was being no longer valid, she was rearmed to engage against destroyers and frigates in an escort.

Design of the class

The X1 has a hull thickness of 25 mm, divided into ten watertight compartments. The hull contained ballast tanks and fuel tanks. Maximum diving depth was first planned to be 150 m, but in practice fell to 110 m in service.
Her armament was really unique, with two twin turrets, forward and aft of the conning tower, each with a pair of 130 mm guns, capable of a maximal range of 15,000 m. A rangefinder was installed on the bridge. To deal with larger ships she had six forward 530 mm torpedo tubes adopted after the cancellation of a late L-class submarine.

Propulsion comprised two main MAN 8-cylinder diesel engines which developed 3,000 HP and two auxiliary diesel engines (rated 1,200 HP) from a war prize, the U-Kreuzer U-126. When diving the two 1,000 HP electric motors powered by three batteries groups weight more than 70 tonnes ensured quick dive and both speed and range underwater.

Commissioned in December 1925, X1 left for Gibraltar but needed fixes to her troubesome main engines. She remains in the Mediterranean Fleet and went on experiencing scores of mechanical problems, so acute that in 1928 she entered the Malta Drydock for long repairs and overhaul. Plagued by her composite German propulsion and criticized for her too cramped living spaces, she was eventually placed in reserve in 1932-33, then mothballed, discarded and decommissioned, then sold to Pembroke, Wales on December 12, 1936 to be scrapped. She served less than nine year actively and overall “cured” any Royal Navy further attmpts to produce a comparable “white elephant”. The US, France or Japan all went for the same rabbit hole, albeit for different purposes. The French Surcouf was probably the closest in concept…