The zone of immunity (or immunity zone) around a warship is an area from which both plunging fire and direct enemy fire is less effective. The concept was a factor in battleship design and in tactics during engagements.
Warships traditionally have vertical, or near vertical, belt armour which protects against missiles (shells) travelling horizontally, and horizontal deck armour, which protects against plunging (downward) shell fire. Belt armour is generally thicker than deck armour.
A shell fired at short range will travel at a high velocity on a more or less horizontal trajectory. If it strikes a ship it will do so either at an acute angle to the belt armour or an oblique angle to the deck armour.
A shell fired at long range will travel on a parabolic trajectory, arriving at its target at a steep angle of descent and so strike the deck armour although at a velocity markedly less than its original muzzle velocity.
If a ship is too close to an adversary, shells fired horizontally may pierce inadequate vertical armour; beyond a certain range, determined by the kinetic energy of incoming projectiles, plunging shells will penetrate deck armour. The distance between these two situations, which is determined by the energy of incoming ordnance and the thickness of the armour of the target vessel, is known as the zone of immunity.
Famous quotes containing the words zone of, zone and/or immunity:
“In the zone of perdition where my youth went as if to complete its education, one would have said that the portents of an imminent collapse of the whole edifice of civilization had made an appointment.”
—Guy Debord (b. 1931)
“In the zone of perdition where my youth went as if to complete its education, one would have said that the portents of an imminent collapse of the whole edifice of civilization had made an appointment.”
—Guy Debord (b. 1931)
“There is immunity in reading, immunity in formal society, in office routine, in the company of old friends and in the giving of officious help to strangers, but there is no sanctuary in one bed from the memory of another. The past with its anguish will break through every defence-line of custom and habit; we must sleep and therefore we must dream.”
—Cyril Connolly (1903–1974)