Contact preclusion is a
fuzing feature found in some
nuclear weapons
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions (thermonuclear bomb), producing a nuclear explosion. Both bomb ...
in which backup contact fuzes in a nuclear weapon can be disabled when the weapon is set to
air burst
An air burst or airburst is the detonation of an explosive device such as an anti-personnel artillery shell or a nuclear weapon in the air instead of on contact with the ground or target. The principal military advantage of an air burst over ...
fuzing.
When a nuclear attack is planned, the planner has the option of deciding if either air burst or
ground burst
A ground burst is the detonation of an explosive device such as an artillery shell, nuclear weapon or air-dropped bomb that explodes at ground level. These weapons are set off by fuses that are activated when the weapon strikes the ground or some ...
fuzing will be used. Air burst has a larger damage radius against soft targets such as personnel or non-hardened buildings than ground bursts due to the
Mach stem
In fluid dynamics, a Mach wave is a pressure wave traveling with the speed of sound caused by a slight change of pressure added to a compressible flow. These weak waves can combine in supersonic flow to become a shock wave if sufficient Mach waves ...
effect, however in the event the air burst fuze fails to actuate a contact fuze as backup is often included in the weapon. Though the damage radius will be reduced in this event, it is possible the target will still be destroyed.
However, ground bursts produce significant fallout that has the potential to be hazardous to civilians and friendly personnel.
Therefore, in some weapons exists the option for contact preclusion in the weapon's fuzing options. When enabled the weapon's contact fuze will not act as a backup fuze if the air burst fuze fails to actuate, precluding detonation, hence the name contact preclusion.
Weapons with contact preclusion
*
B28 nuclear bomb
The B28, originally Mark 28, was a thermonuclear bomb carried by U.S. tactical fighter bombers, attack aircraft and bomber aircraft. From 1962 to 1972 under the NATO nuclear weapons sharing program, American B28s also equipped six Europe-based ...
- Only in EX (external), IN (internal) and RE (retarded external) weapons. Preclusion must be set before takeoff.
[
*]B61 nuclear bomb
The B61 nuclear bomb is the primary thermonuclear gravity bomb in the United States Enduring Stockpile following the end of the Cold War. It is a low to intermediate-yield strategic and tactical nuclear weapon featuring a two-stage radiation imp ...
- Selectable in flight.
See also
* Air burst
An air burst or airburst is the detonation of an explosive device such as an anti-personnel artillery shell or a nuclear weapon in the air instead of on contact with the ground or target. The principal military advantage of an air burst over ...
* Ground burst
A ground burst is the detonation of an explosive device such as an artillery shell, nuclear weapon or air-dropped bomb that explodes at ground level. These weapons are set off by fuses that are activated when the weapon strikes the ground or some ...
References
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Nuclear weapons