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On 21 January 1968, an aircraft accident (sometimes known as the Thule affair or Thule accident (); (デンマーク語:Thuleulykken)) involving a United States Air Force (USAF) B-52 bomber occurred near Thule Air Base in the Danish-administered territory of Greenland. The aircraft was carrying four hydrogen bombs on a Cold War "Chrome Dome" alert mission over Baffin Bay when a cabin fire forced the crew to abandon the aircraft before they could carry out an emergency landing at Thule Air Base. Six crew members ejected safely, but one who did not have an ejection seat was killed while trying to bail out. The bomber crashed onto sea ice in North Star Bay, Greenland, causing the conventional explosives aboard to detonate and the nuclear payload to rupture and disperse, which resulted in radioactive contamination. The United States and Denmark launched an intensive clean-up and recovery operation, but the secondary stage of one of the nuclear weapons could not be accounted for after the operation completed. USAF Strategic Air Command "Chrome Dome" operations were discontinued immediately after the accident, which highlighted the safety and political risks of the missions. Safety procedures were reviewed and more stable explosives were developed for use in nuclear weapons. In 1995, a political scandal resulted in Denmark after a report revealed the government had given tacit permission for nuclear weapons to be located in Greenland, in contravention of Denmark's 1957 nuclear-free zone policy. Workers involved in the clean-up program have been campaigning for compensation for radiation-related illnesses they experienced in the years after the accident. == Thule Monitor Mission == In 1960, the USAF Strategic Air Command (SAC) began Operation Chrome Dome, a Cold War airborne alert program devised by General Thomas S. Power to fly nuclear-armed B-52 Stratofortresses to the borders of the Soviet Union. The flights were scheduled to ensure that twelve bombers were aloft at all times. These bombers gave SAC offensive capability in the event of a Soviet first strike, and provided a significant Cold War nuclear deterrent. Beginning in 1961, B-52 bombers also flew secret "Hard Head" missions (or "Thule Monitor Missions") over Thule Air Base with the purpose of maintaining visual surveillance of the base's strategically important Ballistic Missile Early Warning System (BMEWS), which provided early warning of Soviet missile launches. If the communication link between North American Aerospace Defense Command and the base was severed, the aircraft crew could determine if the interruption resulted from an attack or a technical failure. The monitoring mission started when the designated aircraft reached a waypoint at in Baffin Bay and entered a figure-eight holding pattern above the air base at an altitude of . In 1966, United States Secretary of Defense Robert McNamara proposed cutting "Chrome Dome" flights because the BMEWS system was fully operational, the bombers had been made redundant by missiles, and $123 million ($ as of ) could be saved. SAC and the Joint Chiefs of Staff opposed the plan, so a compromise was reached whereby a smaller force of four bombers would be on alert each day. Despite the reduced program and the risks highlighted by the 1966 Palomares B-52 crash, SAC continued to dedicate one of the aircraft to monitoring Thule Air Base. This assignment was without the knowledge of civilian authorities in the United States, who SAC determined did not have the "need to know" about specific operational points. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「1968 Thule Air Base B-52 crash」の詳細全文を読む スポンサード リンク
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