Aeroballistic Testing at Salton Sea

This background and history of the Salton Sea Test Base is taken from a report commissioned by the Naval Facilities Engineering Command in 1994.

In 1944 and 1945 the joint Army-Navy “Z46” group (aka Project Y) conducted aeroballistic tests at the Salton Sea Naval Test Base aka Sandy Beach.

There were two main purposes for the test atomic bomb drops at the Salton Sea Test Base: To test and evaluate ballistic and aerodynamic behavior of various weapon shapes and configurations; and to test the functional operation of internal weapon components, particularly fusing and firing systems, as the test unit fell toward the target. Telemetry was used to record the time and sequence of various operations within the test unit and other pertinent data such as pressure, temperature, vibration, and acceleration. Much of the information concerning the aeroballistic testing is classified.

Sandia used two marine targets named Site 10MA and Site 10MB (named in 1997 for identification during the site cleanup project) for aeroballistic testing at the base. The original marine target Site 10MA was located approximately 3,000 feet closer to shore than the target Site 10MB. The target was moved farther offshore after an errant test drop impacted on the tennis courts in the main base area. Sandia also constructed the Site 10LB Land Target for aeroballistic testing in the mid 1950s. The total reported number of Sandia test drops prior to cessation of testing in July 1961 averaged about 150 per year, with a peak of 223 in 1952.

Only inert test units were dropped at the Salton Sea Naval Test Base aka Sandy Beach. Information reviewed by Sandia does not indicate that any test bombs dropped at the base, with the exception of one MK-6 “fly-around” unit, contained radioactive materials. The test units typically comprised of stainless steel filled with arming, fusing, and firing components with concrete, lead, and/or stainless steel ballast. The test units may also have contained lesser amounts aluminum and lead acid and nickel cadmium battery fragments associated with the arming, fusing, and firing components. The MK6 “fly-around” unit contained 120 pounds of normal uranium. The unit was accidentally dropped at an unknown location in the Salton Sea during aerial testing of the test unit.

The delivery method for the test units employed at the Salton Sea Naval Test Base included both parachute-retarded and nonretarded (free falling) drops. The nonretarded test units fragmented on impact at both the land and marine targets. Penetrator-type weapon shapes designed to penetrate below the ground surface were reportedly also tested at the land target. Standard practice included recovery of the nonretarded test unit fragments, parachute-retarded test units, and penetrator-type test units from the site 10LB Land Target for reuse and or analysis of the fusing and firing mechanisms. Only one test unit is reported to have penetrated the ground too deeply to be recovered.

Classified memo to Norman Ramsey of The Manhattan Project, dated 1945 regarding atomic bomb test unit recovery at Salton Sea Test Base

Previously classified memo to Norman Ramsey dated 1945 regarding atomic test bomb recovery

The site 10MA and 10MB water targets were also used for practice bombing by the Strategic Air Command. Sandia and the Strategic Air Command (SAC) were responsible for testing and development of different parts of the atomic bomb. Sandia’s main responsibility was for the fusing and firing mechanisms. SAC reportedly dropped more than 2,550 test units at the water target; Sandia dropped fewer than 1,200 test bombs. Sandia provided photographic and telemetry services, communications, and scoring assistance during the SAC testing activities.

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