What is the Purpose of a Permissive Action Link?

Introduction A permissive action link (PAL) is an access control security device for nuclear weapons. Its purpose is to prevent unauthorised arming or detonation of a nuclear weapon. The United States Department of Defence definition is: A device included in or attached to a nuclear weapon system to preclude arming and/or launching until the insertion… Read More


What was the Vela Incident (1979)?

Introduction The Vela incident, also known as the South Atlantic Flash, was an unidentified double flash of light detected by an American Vela Hotel satellite on 22 September 1979 near the Prince Edward Islands in the Indian Ocean. The cause of the flash remains officially unknown, and some information about the event remains classified by… Read More

What is Exercise Spade Fork?

Introduction Federal Emergency Plan D-Minus was a plan developed by the United States of America (US) in the 1950’s to guide the federal government in the immediate aftermath of a catastrophic nuclear attack. Plan D-Minus was part of the National Plan for Emergency Preparedness, which also included Mobilisation Plan C (providing direction for federal planning… Read More

What is the Number of Nuclear Detonations?

Between 1945 and 2018, there have been “2450 nuclear detonations” (Holmes, 2018, p.46). “…the origins of Greenpeace, which started life in Vancouver as a protest against the US nuclear test on Amchitka Island, Alaska, in 1971.” (Holmes, 2018, p.46). Reference Holmes, B. (2018) The Art of Remembering. New Scientist. 05 May 2018, p.46.