Military Wiki
Project 56
Country United States
Test site Nevada Test Site
Period November 1955–January 1956
Number of tests 4
Test type Surface
Max. yield Very slight
Previous test Operation Wigwam
Next test Operation Redwing

Project 56 was a series of open-air nuclear tests conducted by the United States in Area 11 of the Nevada Test Site between 1955 and 1956.[1]


These experiments were safety tests, the purpose of which were to determine whether a weapon or warhead damaged in an accident would detonate with a nuclear yield, even if some or all of the high explosive components burned or detonated.[2][3] The procedure for these tests was to fault the test bomb by removing a detonator wire, or perhaps all but one, for example, possibly enhancing the weapon with extra initiators or an especially enriched core, and then to fire the weapon normally (see Warhead design safety). If there is any nuclear yield in the firing, then the test is deemed a failure from a safety standpoint. A successful test will measure only the chemical explosive in the test bomb exploding, which still, of course, blasts the bomb core and causes the core material to be spread over a wide area if the test is in open air, as all the Project 56 tests were.


Over 895 acres (362 ha) of Area 11 at the NTS were contaminated with plutonium dust and fragments. The area becoming known as Plutonium Valley, and continues to be used on an intermittent basis for realistic drills in radiological monitoring and sampling operations.[2]


Test name Date Time (UT[4]) Location Elevation + Height Delivery Purpose Device Yield Note
Project 56 No. 1 November 1, 1955 22:10 NTS Area 11, 36°59′04″N 115°57′41″W / 36.98444°N 115.96151°W / 36.98444; -115.96151 1,271 metres (4,170 ft) + 0 surface one-point safety test sealed pit with extra oralloy and three initiators 0 Successful; core materials dispersed over area.
Project 56 No. 2 3 November 1955 21:15 NTS Area 11, 36°58′48″N 115°57′34″W / 36.9801°N 115.9594°W / 36.9801; -115.9594 1,263 metres (4,144 ft) + 0 surface one-point safety test W25 sealed pit, three extra initiators 0 Successful; core materials dispersed over area.
Project 56 No. 3 5 November 1955 19:55 NTS Area 11, 36°58′33″N 115°57′26″W / 36.97572°N 115.95732°W / 36.97572; -115.95732 1,260 metres (4,130 ft) + 0 surface one-point safety test TX/W28 primary with three initiators 0 Successful; core materials dispersed over area.
Project 56 No. 4 18 January 1956 21:30 NTS Area 11, 36°58′17″N 115°57′19″W / 36.97135°N 115.95539°W / 36.97135; -115.95539 1,252 metres (4,108 ft) + 0 surface one-point safety test TX/W28 primary with six initiators 10 tons Partial failure, possibly due to use of six initiators on a barely subcritical core; core materials dispersed over area.

See also


  1. "United States Nuclear Tests: July 1945 through September 1992 (Revision 15)". Department of Energy, Nevada Operations Office. December 2000. Retrieved 10/26/2013. 
  2. 2.0 2.1 National Nuclear Security Administration / Nevada Site Office, Plutonium Dispersal Tests at the Nevada Test Site, April 2010, DOE/NV-1046
  3. "Operation Wigwam and Project 56". The Nuclear Weapon Archive. 
  4. Universal Time at the Nevada Test Site is 8 hours after local time; UT dates are one day after local date for UT times after 16:00.

 This article incorporates public domain material from websites or documents of the United States Department of Energy.

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