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Operation Wigwam test of a Mark 90 "Betty"

The Mark 90 nuclear bomb, given the nickname "Betty", was a cold war nuclear depth charge, developed by the United States in 1952.

It had a length of 10 ft 2 in, a diameter of 2 ft 7.5 in, and a weight of 1,243 lb, and it carried a Mark 7 nuclear warhead with a yield of 5-10 kilotons. Its purpose was to serve as an anti-submarine weapon for the United States Navy.

A test of the Mark 90 was conducted in 1955, as Operation Wigwam.

All units were withdrawn from service by 1960.


On September 25, 1959, a United States Navy Martin P5M-2 Marlin (BuNo 135540, SG tailcode, '6', of VP-50) was patrolling out of NAS Whidbey Island when it was forced to ditch in the Pacific Ocean, about 100 miles west of the Washington-Oregon border.[1]

A Mark 90 depth charge casing was lost and never recovered, but it was not fitted with an active warhead.[citation needed] The ten crew members were rescued by the US Coast Guard, after ten hours in a raft. The press was not notified at the time.[2]


  1. Maggelet, Michael H., and Oskins, James C., "Broken Arrow: The Declassified History of U.S. Nuclear Weapons Accidents",, 2007, ISBN 978-1-4357-0361-2, page 128.
  2. Gibson, James N. Nuclear Weapons of the United States - An Illustrated History . Atglen, Pennsylvania.: Schiffer Publishing Ltd., 1996, Library of Congress card no. 96-67282, ISBN 0-7643-0063-6, Chapter 12, "Nuclear Anti-Submarine Weapons", page 214.

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