Orion class battleship

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Three Orion class battleships (from right to left: Conqueror, Monarch, Thunderer) with King George V
General characteristics
Displacement:	22,000 tons standard/25,870 tons max
Length:	581 feet (177 m)
Beam:	88 feet (27 m)
Draught:	24 feet (7 m)
Propulsion:	Steam turbines, 18 boilers, 4 shafts, 27,000 hp
Speed:	21 knots
Range:	6,730 nm at 10 knots
Complement:	750–1100
Armament:	Ten 13.5 inch guns, sixteen 4 inch guns, three 21 inch submerged torpedo tubes
Armour	Belt: 12 in Bulkheads: 10 in Barbettes: 10 in Turrets: 11 in Decks: 4 in

The Orion class battleships were four super-dreadnoughts — the first ships of that type — of the Royal Navy's. The lead ship was Orion, launched in 1910. They were the first Royal Navy dreadnoughts to have all their main guns in the centerline, although the US South Carolina class battleship had this advanced feature in their first dreadnoughts. The Orion class were almost indistinguishable from the following King George V class.

Previous British dreadnoughts had been built very much with an eye on cost. By 1909, although war still seemed unlikely, the white-hot naval rivalry had loosened the purse strings. These ships were much bigger than the preceding Colossus class.

The move to the 13.5 in gun came out of necessity. The final iteration of the 12 inch gun, 50 calibers in length and of high velocity, had been unsuccessful. It lost some of its accuracy and was subject to considerable bore erosion that limited its useful life to about 80 discharges. A lower velocity weapon was indicated, and was realized in the 13.5 in gun, of 45 calibers and with a much heavier projectile (1,250 lb or 1,400 lb vs 850 lb). The shorter range of the low-velocity gun was compensated by increasing the maximum elevation from 15 to 20 degs. The 13.5 in gun was considered a successful design, although its effectiveness was compromised by poor shell design until availability of the "Green Boy" shells in 1918. (Note that although some pre-dreadnoughts carried a 13.5 inch weapon, last carried by the 1891 Royal Sovereign class battleships, the new gun in the dreadnought era bore no resemblance to the earlier one).

The adoption of the all-centerline armament was also of necessity. The previous Colossus and Neptune classes had already adopted a superfiring pair of turrets aft in an effort to save deck space, and competing designs in the US and elsewhere had led the way in the all-centerline arrangement. The great investment in displacement and cost of a 13.5 inch turret contra-indicated wing turrets, with their limited arcs of fire and therefore limited effectiveness. Finally, the staggered arrangement of the Colossus and Neptune class complicated internal arrangements and was generally not considered a success. Unfortunately, the retention of outdated sighting hoods meant that the Orions were not able to fire the superimposed turrets over the deck turrets for fear that the blast of the guns would injure the gun crew in the lower turrets. Also, the design's relatively high centre of gravity made the Orions wicked rollers in rough seas. Both these defects were eventually cured and the improvements included in subsequent classes of British Dreadnought.

The armor belt was increased to 12 inch, in view of the general increase in caliber in potential adversaries. It is quite typical of British designs that armor thickness lagged gun size, this being the opposite design driver of German ships in which armor thickness was usually greater than the guns they carried. It is also of interest to note that adequacy of ship armor was still being judged by belt (vertical) thickness, rather than deck (horizontal) thickness which became more critical as battle ranges extended beyond approximately 12,000 yards. By the time that war broke out, all capital ships on both sides were vulnerable to "plunging" fire that crashed down from the unthinkable ranges of 18,000 to 20,000 yards (German ships were less vulnerable by virtue of having very deep belts, which kept shells away from the armor decks, and because British shells were notoriously weak at penetrating armor at an oblique angle).

The Orion class ships cost almost 1.9 million pounds to construct. All four were present at the battle of Jutland in World War I, 31 May 1916, but took no damage. They had a relatively short career, all being decommissioned in 1921 and disposed of in various ways in the 1920s, due to the Washington Naval Treaty.

[edit] Ships of the class

• Conqueror
• Monarch
• Orion
• Thunderer - After being decommissioned, she served as a cadet ship from 1922, becoming the last surviving ship of the class until she was scrapped in December 1926.

Orion-class battleship

Orion | Monarch | Conqueror | Thunderer

Preceded by: Colossus class - Followed by: King George V class

List of battleships of the Royal Navy