Permissive Action Link

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 Please expand this article with text translated from the corresponding article in German Wikipedia. (December 2009)
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PAL controller

A Permissive Action Link (PAL) is a security device for nuclear weapons. Its purpose is to prevent unauthorized arming or detonation of the nuclear weapon.

The United States Department of Defense definition is:

“ A device included in or attached to a nuclear weapon system to preclude arming and/or launching until the insertion of a prescribed discrete code or combination. It may include equipment and cabling external to the weapon or weapon system to activate components within the weapon or weapon system. ”

The earliest PALs were little more than locks introduced into the control and firing systems of a nuclear weapon, that would inhibit either the detonation, or the removal of safety features of the weapon. More recent innovations have included encrypted firing parameters, which must be decrypted to properly detonate the warhead, plus anti-tamper systems which intentionally mis-detonate the weapon, destroying it without giving rise to a useful nuclear explosion. It is presumed that modern PAL designs don't include self-destruction mechanisms.

These combination locks were installed on Minuteman ICBMs in the 1960s. However, the Strategic Air Command in Omaha worried that in times of need, the codes would not be available, so they quietly decided to set them to 00000000; checking this combination was even present on the launch checklists. This was not changed until 1977.[1] In 2007 the British Government revealed that its nuclear weapons were not equipped with Permissive Action Links.[2]

PAL devices were also installed on Sergeant, Pershing, and WAC Corporal missiles as well as the Nike-Hercules, Honest John rockets, the Davy Crockett system, and 155 mm Howitzer, 6 inch howitzer rounds.

Detailed information about PAL systems design and their use are classified, although these mechanisms were offered to the Soviet Union and Pakistan for protection of their nuclear weapons.

[edit] See also

[edit] References

  1. ^ Keeping Presidents in the Nuclear Dark (Episode #1: The Case of the Missing "Permissive Action Links") - Bruce G. Blair, Ph.D
  2. ^ BBC NEWS Programmes | Newsnight | British nukes were protected by bike locks

[edit] External links

Retrieved from "http://en.wikipedia.org/wiki/Permissive_Action_Link"
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