Delivering the Bomb

After the Castle Bravo test, Russian scientists were inspired to improve upon their own "layer cake" design. Sakharov is also credited with coming up with the next idea, using radiation compression to initiate the fusion reaction.

In November of 1955, at the Semipalatinsk test site, the Soviets tested this design with success. They had replaced some of the fusion fuel with a "passive material" to cut the explosive power in half. The result was a smaller 1.6 megaton blast, but an inversion layer in the atmosphere reflected a large part of the energy back toward the ground increasing the force of the blast. Three people were killed when a building collapsed a few miles from the test site. After this bomb test, Kurchatov withdrew himself from any supervisory role at future tests.

This test was the first Soviet thermonuclear bomb to be dropped from an airplane.