The Jack-in-the-box effect refers to a specific effect of a catastrophic kill

Catastrophic kill

A catastrophic kill, K-Kill or complete kill refers to damage inflicted on a vehicle by a weapon that renders it both unusable and unrepairable whereas a "knocked out" vehicle is completely inoperable but not beyond repair...

 on a tank or other turreted armored vehicle in which an ammunition

Ammunition

Ammunition is a generic term derived from the French language la munition which embraced all material used for war , but which in time came to refer specifically to gunpowder and artillery. The collective term for all types of ammunition is munitions...

 explosion

Explosion

An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a "high explosive"...

 causes the tank's turret to be violently blown off the chassis and into the air. It is named after the child's toy, the jack-in-the-box

Jack-in-the-box

A jack-in-the-box is a children's toy that outwardly consists of a box with a crank. When the crank is turned, it plays a melody, often "Pop Goes the Weasel". At the end of the tune there is a "surprise", the lid pops open and a figure, usually a clown or jester, pops out of the box...

, in which a puppet pops up.

While relatively uncommon, it is a very visually iconic image of the complete destruction of a tank, and is thus seen often in movies, TV, and video games.

Mechanics

If an AT projectile

Anti-tank warfare

Anti-tank warfare was created by the need to seek technology and tactics to destroy tanks and their supporting infantry during the First World War...

 or shaped-charge blast

Blast

Blast or The Blast may refer to:*Explosion, a rapid increase in volume and release of energy in an extreme manner*Detonation, an exothermic front accelerating through a medium that eventually drives a shock front-Film:...

 manages to penetrate a turreted

Gun turret

A gun turret is a weapon mount that protects the crew or mechanism of a projectile-firing weapon and at the same time lets the weapon be aimed and fired in many directions.The turret is also a rotating weapon platform...

 armored vehicle's hull and subsequently its ammunition

Ammunition

Ammunition is a generic term derived from the French language la munition which embraced all material used for war , but which in time came to refer specifically to gunpowder and artillery. The collective term for all types of ammunition is munitions...

 storage area, the 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...

 or heat

Heat

In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

 and pressure

Pressure

Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 can be sufficient to cause cooking off

Cooking off

Cooking off refers to ammunition exploding prematurely due to heat in the surrounding environment. It can also refer to a technique used when throwing grenades to achieve a controlled, predictable explosion....

 or sympathetic detonation

Sympathetic detonation

A sympathetic detonation , also called flash over, is a detonation, usually unintended, of an explosive charge by a nearby explosion. Sympathetic detonation is caused by a shock wave, or impact of primary or secondary blast fragments.The initiating explosive is called donor explosive, the initiated...

 of the tank's entire load of unfired explosive shells and propellant

Propellant

A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...

. This causes a massive and instantaneous overpressure

Overpressure

The term Overpressure is applied to a pressure difference, relative to a "normal" or "ambient" pressure, in various circumstances:* In engineering: the pressure difference over the wall thickness of a pressure vessel...

 in the sealed internal compartment of the tank, until it explodes outwards through the weakest point in the otherwise homogeneous compartment, namely the turret ring, blowing the turret completely off the chassis and into the air in a gout of flame

Flame

A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...

.

The Jack-in-the-box effect is only known to occur in tanks which are "buttoned-up" (i.e. with all hatches

Trapdoor

A trapdoor is a door set into a floor or ceiling .Originally, trapdoors were sack traps in mills, and allowed the sacks to pass up through the mill while naturally falling back to a closed position....

 closed and locked), and which have internally-stored ammunition and no blow-off panels on the ammunition storage area. Tanks of the World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 era were frequently seen to have lost their turrets in this manner, largely owing to poor design (most designers had not yet recognized the need for special shielding of the ammunition storage compartments of tanks.). Also, most tanks of the era were gasoline

Gasoline

Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

-powered, adding another possible source for an overpressure detonation scenario in the event of a hull-penetrating hit, since gasoline is more volatile

Volatility (chemistry)

In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...

 and flammable than diesel fuel.

Many modern tanks (for instance, the M1 Abrams

M1 Abrams

The M1 Abrams is a third-generation main battle tank produced in the United States. It is named after General Creighton Abrams, former Army Chief of Staff and Commander of US military forces in Vietnam from 1968 to 1972. The M1 is a well armed, heavily armored, and highly mobile tank designed for...

 series) feature ammunition compartments designed to fail safely under fire as a firepower kill—when damaged, vents open to channel ignited propellant

Propellant

A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...

s and explosives away from the crew cabin.