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HMS Sidon
Career
Class and type:	S-class submarine
Name:	HMS Sidon
Builder:	Cammell Laird Shipyard - Birkenhead
Laid down:	7 July 1943
Launched:	September 4, 1944
Commissioned:	23 November 1944
Fate:	wrecked by own torpedo explosion June 16, 1955 refloated, sunk as a target June 19, 1957
General characteristics
Displacement:	814-872 tons surfaced 990 tons submerged
Length:	217 ft
Beam:	23 ft 6 in
Draught:	11 ft
Speed:	14.75 knots surfaced 8 knots (15 km/h) submerged
Complement:	48 officers and men
Armament:	6 x forward 21-inch (533 mm) torpedo tubes, one aft 13 torpedoes one three-inch (76 mm) gun (four-inch on later boats) one 20 mm cannon three .303-calibre machine gun

HMS Sidon was launched in September 1944, one of the third group of S-class submarines built by Cammell Laird & Co Limited, Birkenhead.

On the morning of June 16, 1955, Sidon was moored alongside the depot ship HMS Maidstone in Portland Harbour. Two experimental torpedoes, code-named "Fancy", had been loaded aboard for testing. Fifty-six officers and crewmen were aboard.

At 0825, an explosion in one of the Fancy torpedoes (but not the warhead) burst the number-three torpedo tube it was loaded into and ruptured the forward-most two watertight bulkheads. Fire, toxic gases, and smoke accompanied the blast. Twelve men in the forward compartments died quickly and seven others were seriously injured.

The submarine started to settle by the bows with a list to starboard, and her commanding officer, Lieutenant Commander Verry, ordered the ship evacuated from the engine room and after escape hatches. Thanks to a rescue party from Maidstone, everyone not immediately killed escaped, except Maidstone's medical officer, Surgeon Lieutenant C.E Rhodes. He had gone aboard with the rescue party, assisted several survivors, and suffocated because he was using a DSEA set that he hadn't been trained to use. He was awarded the Albert Medal for putting his life in danger to save others. At about 0850 Sidon sank to the bottom of the harbour.

One week later the wreck was raised and towed into a causeway on Chesil Beach. The bodies of the 13 casualties were removed and buried with full honours in the Portland Naval Cemetery on top of the cliffs overlooking the harbour. A Court of Inquiry cleared anyone aboard Sidon for the loss of the boat. The direct cause of the accident was determined to have been malfunctioning of the "Fancy" torpedo, and that torpedo program was terminated.

A torpedo being readied for the morning test shot had begun a "hot-run" - its engine had started while it was still inside the submarine and was over-speeding, creating very high pressures in its fuel system. The "Fancy" torpedo used high test peroxide (HTP) as an oxidizer. When an oxidizer line burst, HTP sprayed onto the copper fittings inside the torpedo, decomposing into oxygen and steam. The torpedo's warhead did not detonate, but its hull burst violently, rupturing the torpedo tube and causing the flooding that destroyed the boat. Sidon was refloated, and sunk as an ASDIC target on June 14, 1957.

On the 50th Anniversay of the Sidon accident, 16th June 2005, the Dorset Branch of the Submariners Association erected a Memorial Stone to those that died. This is situated adjacent to the War Memorial at Portland, opposite the Portland Heights Motel. A number of survivors and relatives of those that died in the accident attended the ceremony

On the 18 January 2003, Deepquest Sub Sea announced that they intend to raise HMS Sidon.^[1]

• Submarines destroyed by hotrunning torpedoes: HMS Sidon (P259), USS Scorpion (SSN-589) and Russian submarine Kursk.

• Colledge, J. J. and Warlow, Ben (2006). Ships of the Royal Navy: the complete record of all fighting ships of the Royal Navy, Rev. ed., London: Chatham. ISBN 9781861762818. OCLC 67375475. 

• HMS Sidon War Memorial
• HMS Sidon War Memorial at Portland, Dorset