Website of Herb Yeates



  Rapatronic photographs  

Developed by Dr. Harold Edgerton in the 1940s, the Rapatronic photographic technique allowed very early times in a nuclear explosion's fireball growth to be recorded on film. The exposures were often as short as 10 nanoseconds, and each Rapatronic camera would take exactly one photograph.

A bank of four to ten or more such cameras were arranged at tests to record different moments of early fireball growth. 

They provide technical information about the device's disassembly. In some of the images shown below, accelerating bomb debris 'splashes' on a relatively slower growing fireball surface, creating irregularities and mottling.

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Rapatronic shutter mechanism. The 'business end' of a Rapatronic camera. Early bomb light passed through this cell, which precisely gated the inbound light stream for exposure on photographic film. Photos courtesy of Mr. Calvin Smith. Click images for a better view.

The Rapatronic's images are peculiar in their own right; both for the subject matter and the vanishingly small fragments of time recorded.


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Shot George from Operation Greenhouse (225KT, 1951). 10 ms after detonation.

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Shot George from Operation Greenhouse (225KT, 1951). 20 ms after detonation. The bright band near the base is the emerging Mach stem, an area of maximum shock.

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Shot George from Operation Greenhouse (225KT, 1951). 30 ms after detonation. Mach stem continues to grow.

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Unidentified shot from Operation Tumbler-Snapper (1952; kiloton range). Roughly 1 ms after detonation. Visible along the bottom of the fireball's surface are what have been referred to as 'rope tricks'. Absorption of thermal energy by the tower's guy wires result in such spike-like extensions. Further discussion of this phenomenon is available here.

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Shot Lea from Operation Hardtack II (1958, 1.4KT)
This test was a "fizzle" in yield, and suspended from a balloon 1500 feet above surface. The balloon's mooring cables absorbed thermal energy ahead of the fireball and created the three 'spikes' visible.

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Unidentified shot from Operation Upshot-Knothole (1953, kiloton range).

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Mohawk shot from Operation Redwing (1956, 360KT). A thermonuclear test, the 'black stick' towards the lower right of the picture is a 300-foot tower, on which the device rested. The remains of the shot cab form the 'pimple' on the right.