Laydown delivery is a mode of deploying a free-fall nuclear weapon

Nuclear weapon

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...

 in which the bomb's fall is slowed by parachute

Parachute

A parachute is a device used to slow the motion of an object through an atmosphere by creating drag, or in the case of ram-air parachutes, aerodynamic lift. Parachutes are usually made out of light, strong cloth, originally silk, now most commonly nylon...

 so that it actually lands on the ground before detonating

Detonation

Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases...

. Laydown delivery requires that the weapon's case be reinforced so that it can survive the impact, and generally involves a time-delay fuze to trigger detonation

Detonation

Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases...

. Laydown mode can be used to increase the effect of the weapon's blast on built-up targets such as submarine pen

Submarine pen

A submarine pen is a bunker which is designed to protect submarines from air attack.The term is generally applied to submarine bases constructed during World War II, particularly in Germany and the occupied countries which were also known as U-boat pens .-Background:Amongst the first...

s, or to transmit a shock wave

Shock wave

A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...

 through the ground to attack deeply buried targets.
It has the additional advantage of allowing the carrier aircraft to fly very low – in order to avoid enemy defences – and still get away without being destroyed in the detonation. This is particularly important where high-yield nuclear weapons such as the B53 nuclear bomb

B53 nuclear bomb

The Mk/B53 was a high-yield bunker buster thermonuclear weapon developed by the United States during the Cold War. Deployed on Strategic Air Command bombers, the B53, with a yield of , was the most powerful weapon in the U.S...

 are concerned.

See also

• Nuclear bunker buster
  Nuclear bunker buster
  Bunker-busting nuclear weapons, also known as earth-penetrating weapons , are a type of nuclear weapon designed to penetrate into soil, rock, or concrete to deliver a nuclear warhead to a target. These weapons would be used to destroy hardened, underground military bunkers buried deep in the ground...
  
  
• B53 nuclear bomb
  B53 nuclear bomb
  The Mk/B53 was a high-yield bunker buster thermonuclear weapon developed by the United States during the Cold War. Deployed on Strategic Air Command bombers, the B53, with a yield of , was the most powerful weapon in the U.S...
  
   - a 9 MT
  TNT equivalent
  TNT equivalent is a method of quantifying the energy released in explosions. The ton of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT...
  
  nuclear weapon designed for laydown delivery