Otto Robert Frisch was a key physicist in the early understanding of nuclear fission. Working with his aunt Lise Meitner he helped explain that when a heavy nucleus splits it releases a huge amount of energy. He also helped give this process its name which is still used today.
Frisch work showed clearly what happens inside an nucleaus during fission. He explained that the nucleus breaks into two parts and releases both energy and fast moving particles. This simple explanation helped scientists finally understand the true nature of nuclear chain reactions.
Later Frisch worked with Rudolf Peierls on a very important report known as the Frisch Peierls Memorandum. In this paper they showed that a nuclear bomb could be built using only a small amount of uranium 235. Before this many scientists believed a bomb would need an unrealistically large amount of material.
This report changed everything. It proved that a bomb was not only possible but practical. These ideas were passed to the Allied governments and became part of the scientific foundation of the Manhattan Project led by J Robert Oppenheimer.
Otto Frisch did not design the bomb itself but his work built the bridge between theory and real world application. He explained what fission was and showed that it could be used in a powerful way. His ideas helped guide the scientists who later turned theory into reality during the Second World War.