reaching out approximately in all directions. This base surge could be seen from the air for about 25 minutes and the foam patch over the blast location lasting even longer. The blast yield of the nuclear device was measured to be . The Umbrella blast created a crater in diameter and in depth in the lagoon. The maximum radiation reading was found to be by an aircraft flying over the blast location. Radiation was reported to be of small portions, and re-entry was granted 30 minutes after detonation. Out of the major target ships, the highest radiation reading was logged at of the stern of the Moran. After all scientific data had been gathered from the target ships, they were restored to be seaworthy and towed back to Pearl Harbor. The Moran was concluded to be unseaworthy due to the blast and was sunk by naval gunfire near Ikuren Island. The underwater nuclear tests (Wahoo and Umbrella) gathered scientific data that helped the Department of Defense understand the effects of nuclear weapons on Navy ships. Some of the key points found were that underwater nuclear blasts create less fallout due to the absorption of radioactive material in the water and vaporized droplets. Direct gamma radiation was found to be extremely low, but the base surge was found to be highly radioactive as it passed measurement devices. Smaller radiation concentrations followed in waves mimicking the initial base surge. Almost all free-field radiation activity was found to disappear after fifteen minutes allowing for return to normal operations. The impact of shock waves was less than previously expected. The damage from the shockwave was found to be negligible on the destroyers at the ranges tested, but equipment failure from the blast could immobilize the ships. The preliminary tests of explosive tapered charges were proven to simulate the shock waves of a nuclear device according to the data gathered. List of tests References External links Details of the YUCCA balloon-borne nuclear detonation published at Stratopedia, the balloon encyclopedia Explosions in 1958 Hardtack I Hardtack I 1958 in military history 1958 in the environment 1950s in the Marshall Islands 1958 in the Trust Territory of the Pacific Islands