the inhale hose that runs over the diver’s left shoulder directly to the mouthpiece, and the breathing cycle repeats. No breathing gas is vented to the surface – it is continuously cleaned, analysed and corrected as it is rebreathed.
The right-hand cylinder holds high-pressure 100% oxygen. The left cylinder holds the ‘diluent’, the desired breathing gas – air or trimix. The small black cylinder on the left holds the diver’s drysuit inflation gas. © Bob Anderson.
Of course, too much oxygen is also a problem. If something goes wrong, say the solenoid switch sticks open and the oxygen level in your breathing gas goes above that set level, audible alarms go off and red lights blink on the heads-up display (HUD) unit that is usually mounted on the corrugated hose breathing tube just below and off to one side of your mask in your peripheral vision. Too much or too little oxygen, and the normally green lights start flashing red warnings.
I generally use a PO2 of 1.3 bar, but with deep repeat dives I back it off to 1.1 bar just to stop racking up too high levels of oxygen over a period of days. I usually manually inject oxygen in my final decompression stops to keep the PO2 at 1.4 bar and shorten decompression.
The wrist-mounted computer handset on my Inspiration Vision CCR. The top left figure reads 0.70 and confirms the pre-set PO2 set point being used. The three figures –in this picture all at0.81 – show the individual readings of the three oxygen monitoring cells that continuously analyse the breathing gas. The readings should be roughly consistent – if one figure differs wildly from the other two then it is an indicator that the cell is possibly malfunctioning.
The horizontal white rectangle at the top is the scrubber monitor: it displays how the scrubber in the back-mounted canister is performing. © Bob Anderson
A fully rigged technical diver with a shallow bailout nitrox cylinder slung beneath the right arm on the ‘oxygen’ side. In this case the cylinder holds EAN50, which has a maximum breathing depth of 20 metres – and this is clearly marked on the cylinder, to avoid the wrong gas being breathed at the wrong depth, a standard tek diving practice. To breatheEAN 50 deeper than 20 metres for a prolonged time risks an oxygen toxicity hit with possible fatal convulsions. The mask strap is under the hood,to avoid it being kicked or knocked off.© Bob Anderson
2
27 October 1914 – the first British battleship of World War I to be lost to enemy action
The 598-foot King George V-class battleship HMS Audacious is another important first in British naval history. She had the misfortune of being the first British battleship to be sunk by enemy action during World War I, on 27 October 1914, just two months into the war. She was also the only modern British dreadnought battleship to be sunk by enemy action in the war. The story of the loss of HMS Audacious also involves a famous White Star liner, RMS Olympic, which would carry out a dramatic rescue attempt.
The 23,400-ton King George V-class dreadnought battleship HMS Audacious– the first British capital ship to be sunk by the enemy during WWI. (IWM)
Audacious was one of the four dreadnought battleships of the King George V class provided for under the 1910 building programme. Battleship design had taken a dramatic leap forward in 1906 with the launch of the revolutionary HMS Dreadnought, when the Royal Navy, under the charismatic leadership of the First Sea Lord, Admiral of the Fleet Sir John Fisher, boldly embraced a risky radical alteration of the prevailing balance of naval power with the creation of a revolutionary new type of battleship. HMS Dreadnought was such a quantum leap forward in battleship design that her name would be used to define the whole class of such new battleships – dreadnoughts. Almost overnight, the generation of battleships that had gone before her was rendered virtually obsolete; they became known as pre-dreadnoughts, and although they sailed with the respective fleets in World War I, they were relegated to the end of the battle line or given other rear echelon taskings. Soon, other major naval powers raced to build their own dreadnoughts.
The new dreadnoughts were some 10 per cent bigger than the pre-dreadnoughts; they were faster, carried better armour and were better compartmentalised internally. They also dispensed with much of the smaller calibre secondary armament of the pre-dreadnoughts, and gunnery on these new all big gun ships was radically improved.
The first of the new class of dreadnoughts were equipped with ten 12-inch guns set in five twin turrets, each gun being able to fire an 850lb shell 18,500 yards – more than 10 miles. The first British dreadnoughts had three of their five big gun turrets set on the centre line of the ship; A turret forward and two turrets, X and Y, aft. P turret was situated on the port side of the bridge superstructure, with Q turret on the starboard side in a staggered wing arrangement that allowed more space on the centreline of the vessel for boilers and machinery. The new dreadnoughts also had the latest 11-inch armour and faster new engines. They were indeed a revolution in naval warfare. Being the most important ships in the fleet, these battleships and the later battlecruiser evolution were called capital ships.
Before the dreadnought era, battleships and cruisers had no centralised fire control. Each gun was fired, independently of the others, from its respective turret. From 1906 onwards, battleships, and then battlecruisers, were fitted with the latest in range-finding techniques, sighting and fire control. Crucially, for the first time, all eight guns (and ten with later classes) in a broadside could be aimed and fired by one gunnery control officer positioned in an armoured chamber at the top of the conning tower just in front of the bridge – and also by a secondary gunnery control centre towards the stern of the ship. Officers in the spotting top – halfway up the foremast – observed the fall of shot, the splashes from shells landing beside the enemy ship far away in the distance, and could give suitable corrections to walk the guns in on their target.
The development of the dreadnought by Britain in 1906 could have been a colossal own goal – by destroying her traditional naval numerical supremacy in the balanced order of the time. But taking the calculated view that British shipyards could build more of the new dreadnoughts than could the shipyards of any rival countries, the Royal Navy gambled with the launch of HMS Dreadnought. They gambled – and won.
The dreadnought race stepped up in 1910 and 1911, with Germany laying down four capital ships in each of those years, and Britain laying down five. The British initially equipped their first dreadnoughts with 12-inch guns, which had a rate of fire of approximately 2 rounds per minute per gun. At long range, it was found that the latest version of this gun, which dated back to 1893 (but now had lengthened barrels), had accuracy problems.
To solve this, beginning with the Orion class of dreadnoughts of 1910/11, the Royal Navy quickly moved to the 13.5-inch gun. This larger gun allowed for a much larger shell, which gave improved penetration. The larger shell and increase in bore allowed a lower muzzle velocity, and this gave much greater accuracy and less barrel wear. The final development of the pre-war dreadnought was a 15-inch gun, which was reliable and accurate with a low muzzle velocity that gave outstanding barrel life. The first shipboard firing of such a gun took place in 1915.
Four Orion-class battleships were built for the Royal Navy between 1909 and 1912, and they were much larger than the earlier dreadnoughts. The next class, the King George V-class dreadnoughts such as Audacious were designed as an enlarged and improved evolution of the Orion
