DIAMONDS OF DEATH

Evening Star, Issue 23496, 9 February 1940, Page 10

DIAMONDS OF DEATH

AIR BURSTS SUBMARINES The secret of the tremendous destructive power of the depth charge lies in the fact that water is practically imcompressible. If you were' to fill a email pump, say, a bicycle pump, with water and then close the outlet you would find it impossible to depress the piston; whereas, in the case of a pump full of air, the piston could be depressed to nearly halfway down (writes R. L. Hadfield, in the ‘Sydney Morning Herald ’). This incompressibility of water is used in scores of ways commercially, as, for instance, in the hydraulic ram and the power press; and now, in war, it provides one of the deadliest weapons the U-boat has to face. For the shock carried by means of the incompressible water from an explosion at a distance is so severe that the seams of a U-boat can be burst open by the explosion of a depth charge at a distance of several hundred yards. Such advantages as the U-boat may possess through being able to hide beneath the sea'it loses to a great extent when its presence is detected, through the fact that direct hits are not necessary. A surface vessel must actually be struck, often more than once, before being vitally injured; tbe submarine need not be hit at all to suffer destruction.

The larger ocean-going U-boats have a double skin, but, even this skin •is comparatively thin. It is in no sense armour, and whatever the strength of its. Construction the submarine’s greatest menace is pressure. No Submarine ever built can dive indefinitely; all have their “ bottom and. if, through accident, breakdown, or any other cause it dives too deeply the pressure of the sea bursts its seams, water rushes in, and it is lost. The effect of the depth charge is much the same. On the explosion of the charge in the vicinity of the submarine the shock, carried through the water, exerts such terrific pressure on the seams of the vessels that, in a mild case, its seams are opened and the machinery is thrown out of gear. In a severe case the sides are burst in, the vessel is instantly flooded, and it goes to the bottom.

Water pressure also fires the depth charge. Roughly the depth charge is a drum containing about 3001 b of explosive and mechanism by which pressure at any prearranged depth acts on a diaphragm, which in turn fires a detonator. The depth at which the submarine is lying or cruising having been estimated with the aid of listening gear, the depth charge is set to explode when it has reached the required depth, and the practice now adopted in the Bvi+ish Navv is to “ bracket ’’ a U-hoat within a diamond of explosions. The depth charges are dropped from the stern of the attacking vessel and are also fired from mortars on each side.

Thus a destroyer travelling at full speed can drop depth charges ahead, astern, and on each, side of the submarine. Should the enemy be actually within the diamond of explosions there is no hope for her; she.must be crushed as flat as an egg-ehell. It is, of course, impossible that all U-boats which have been depth-charged have been destroyed; but even in instances when the boat has contrived to escape the effect has been important. Many U-boats'have been so badly damaged that they have had to make their way back to tiieir bases; often the diving gear has been put out of action and they have had to ride on the surface, there probably to be destroyed or captured. ' NERVE TENSION. There is another important effect of depth-charging. It is moral. In the depths of the sea human nerves are far more tightly strung than in any surface craft,, even when not being hunted by an enemy. On the explosion of a depth-charge nearby but not sufficiently near to cause instant destruction, the lights are blown-out, seams are started, water begins to spurt in here and there, valves leak. The men crouch at their stations in the impenetrable darkness, their minds filled with the ghastly fear that at any moment another charge may burst in the walls of their vessel and they may be engulfed without hope, drowning amidst the tangled steelwork of their stricken, craft. They listen, they wait; every thump of a charge bursting near at band bursts open more seams, and increases the fearful tension in their minds. There is nothing they can do but wait, helpless and silent. Probably all machinery in the boat has been stopped Jest the sound should betray its presence to the enemy, and it may be that the U-boat must he submerged for hours, while the air becomes fouler, physical powers of resistance to shock weaker, and’ courage is ebbing. All men, however brave, are not suited to U-boat work. Efficient crews have to be carefully; chosen and expertly trained to work in. a team as one man. Scratch crews would be more a menace to themselves than any enemy; but once the most efficient man has been severely depth-charged it may be months before he is fit to go to sea in a U-boat again, if ever. This is one of the reasons why Britain is winning the campaign against the U-boats. However . hurriedly the boats may be built, finding and training crews to man them cannot be done oil mass-production lines. For every U-boat which it is known has been definitely destroyed, many more have been driven from the sea by the damage to enemy sailors’ morale.