Rope trick effect

The "rope tricks" that protrude from the bottom of the fireball are caused by the heating, rapid vaporization and then expansion of guy wires that extend from the shot cab—the housing at the top of the bomb tower that contains the explosive device—to the ground.

These x-rays cannot travel very far in standard atmosphere before reacting with molecules in the air, so the result is a fireball that rapidly forms within about 10 metres (33 ft) in diameter and does not expand.

[citation needed] Inside the radiative fireball, the bomb itself is rapidly expanding due to the heat generated by the nuclear reactions.

At the point in the explosion captured in the adjacent photo, the shock front has passed the original radiative fireball and has about twice its size.

The various light and dark patches are caused by the varying vapor density of the material splashing against the back of the shock front.

The purpose of these trails is to record the passing of the now invisible shock wave, which causes an obvious visual effect on the smoke by compressing the air into a lens.

Nuclear explosion milliseconds after detonation. From the Operation Teapot test series in Nevada , 1955, showing fireball and rope trick effects.
Rope trick effects visible from one of Operation Tumbler–Snapper 's tower-mounted test shots in 1952, taken with a rapatronic camera
Array of sounding rockets with instruments for making scientific measurements of high-altitude nuclear tests during liftoff preparations on Johnston Island