HMAS Orion - Design and Construction

Design and Construction

The Oberon class was based heavily on the preceding Porpoise class of submarines, with changes made to improve the vessels' hull integrity, sensor systems, and stealth capabilities. Eight submarines were ordered for the RAN, in two batches of four. The first batch was approved in 1963, and the second batch (including Orion) was approved during the late 1960s, although two of these were cancelled before construction started in 1969, with the funding redirected to the Fleet Air Arm. This was the fourth time the RAN had attempted to establish a submarine branch.

The submarine is 295.2 feet (90.0 m) long, with a beam of 26.5 feet (8.1 m), and a draught of 18 feet (5.5 m) when surfaced. At full load displacement, she displaces 2,030 tons when surfaced, and 2,410 tons when submerged. The two propeller shafts are each driven by an English Electric motor providing 3,500 brake horsepower and 4,500 shaft horsepower; the electricity for these is generated by two Admiralty Standard Range supercharged V16 diesel generators. The submarine could travel at up to 12 knots (22 km/h; 14 mph) on the surface, and up to 17 knots (31 km/h; 20 mph) when submerged, had a maximum range of 9,000 nautical miles (17,000 km; 10,000 mi) at 12 knots (22 km/h; 14 mph), and a test depth of 200 metres (660 ft) below sea level. When launched, the boat had a company of 8 officers and 56 sailors, but by the time she decommissioned, the number of sailors had increased to 60. In addition, up to 16 trainees could be carried.

The main armament of the Oberons consisted of six 21-inch (533.4 mm) torpedo tubes. The British Mark 8 torpedo was initially carried by the submarine; this was later replaced by the wire-guided Mark 23. Between 1977 and 1985, the Australian Oberons were upgraded to carry United States Navy Mark 48 torpedoes and UGM-84 Sub Harpoon anti-ship missiles. As of 1996, the standard payload of an Australian Oberon was a mix of 20 Mark 48 Mod 4 torpedoes and Sub Harpoon missiles. Some or all of the torpedo payload could be replaced by Mark 5 Stonefish sea mines, which were deployed through the torpedo tubes. On entering service, two stern-mounted, short-length 21-inch (53 cm) torpedo tubes for Mark 20 anti-submarine torpedoes were fitted. However, the development of steerable wire-guided torpedoes made the less-capable aft-firing torpedoes redundant; they were closed off, and later removed during a refit.

Orion was laid down by Scotts Shipbuilding and Engineering Company at Greenock, Scotland on 6 October 1972, launched on 16 September 1974, and commissioned into the RAN on 15 June 1977. The submarine was due to enter service in 1975, but faulty high-power electrical cabling had been installed in Orion and sister boat Otama; stripping out and replacing the cabling delayed each submarine's construction by two years. The delay meant that the two boats could be fitted with Micropuffs rangefinding sonar during construction, and have additional electronic surveillance equipment installed. Orion's name comes from the constellation Orion: although a name with strong links to the Royal Navy (with six vessels operating as HMS Orion), this was a break from the RAN's traditional use of the names of explorers and pioneers for submarines. The submarine's motto of "Orbe Circumcincto" (Latin for "All around the world") refers to the visibility of the constellation from any point on Earth.