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Operation Greenhouse
Greenhouse George
Country United States
Test site Pacific Proving Grounds, Enewetak Atoll
Period April–May 1951
Number of tests 4
Test type Atmospheric tests
Device type Fission/Thermonuclear
Max. yield 225 kilotons of TNT (940 TJ)
Previous test Operation Ranger
Next test Operation Buster-Jangle

Operation Greenhouse was the fifth American nuclear test series, the second conducted in 1951 and the first to test principles that would lead to developing thermonuclear weapons (hydrogen bombs). Conducted at the new Pacific Proving Ground, specifically on islands of the Enewetak Atoll, all of the devices were mounted in large steel towers, to simulate air bursts. This series of nuclear weapons tests were preceded by Operation Ranger and succeeded by Operation Buster-Jangle.

Operation Greenhouse represented new and aggressive designs for nuclear weapons. The main idea was to reduce the size, weight, and most importantly, reduce the amount of fissile material necessary for nuclear weapons, while increasing the destructive power. With the Soviet Union's first nuclear test a year and half earlier, the United States had begun stockpiling the new designs before they were actually proven. Thus the success of Operation Greenhouse was vital before the development of thermonuclear weapons could continue.

A number of target buildings, including bunkers, homes and factories were built on Mujinkarikku Islet to test nuclear weapon effects.

The George explosion was the world's first thermonuclear burn, though it was just a test design, unsuitable for weaponization. Shaped like a torus, the George device had a small amount of heavy isotopes of liquid hydrogen (deuterium and tritium) placed at its center. The vast majority of its yield derived from fission. The energy output from the thermonuclear fusion in this test was insignificant in comparison. The "George" device was more like a "boosted" atomic bomb than a thermonuclear one. The small amount of heavy deuterium and tritium in this test fused, but its role was to generate a strong flurry of fast neutrons - ones that sparked more fissions in the uranium nuclei that were present, and which also caused fission in uranium-238 - which does not fission under bombardment with slow neutrons, as does uranium-235.

However, the George test validated the principles which would be used for the first full-scale thermonuclear bomb test, Ivy Mike, one year later, on 1 November 1952, at Enewetak Atoll. Item was the first boosted fission weapon, nearly doubling the normal yield of a similar non-boosted weapon.

Greenhouse Test Blasts
Name Date, Time (UT[1]) Location Elevation + Height Delivery Purpose Device Yield Notes
Dog 7 April 1951 17:33:57 Runit ("Yvonne") Island, 11°33′07″N 162°20′51″E / 11.55197°N 162.34744°E / 11.55197; 162.34744 2 metres (6 ft 7 in) + 91 metres (299 ft) tower weapon development Mark 6 70 kilotons Proof test of Mark 6, 60 point implosion.
Easy 20 April 1951 17:27:00 Engebi ("Janet") Island, 11°39′56″N 162°14′02″E / 11.66543°N 162.23379°E / 11.66543; 162.23379 2 metres (6 ft 7 in) + 91 metres (299 ft) tower weapon development and effects TX-5D 47 kilotons Proof test of Mark 5, 92 point implosion, to be used as Ivy/Mike primary.
Buildings for effects tests built on nearby Mujinkarikku Island.
George 8 May 1951 20:30:00 Ebibiru ("Ruby") Island, 11°37′37″N 162°17′47″E / 11.62703°N 162.29626°E / 11.62703; 162.29626 2 metres (6 ft 7 in) + 62 metres (203 ft) tower weapon development 225 kilotons First thermonuclear experiment, deuterium core.
Item 24 May 1951 17:16:59 Engebi ("Janet") Island, 11°39′58″N 162°14′33″E / 11.66604°N 162.24254°E / 11.66604; 162.24254 2 metres (6 ft 7 in) + 62 metres (203 ft) tower weapon development 45.5 kilotons First bomb with tritium "boosting".

See also


  1. Universal Time at the Pacific Proving Ground is 12 hours before local time; UT dates are one day before local date for UT times before 12:00.

External links

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