Boris Chertok, 99, a Russian rocket designer who played a key role in engineering Soviet-era space programs, died Wednesday. The state-controlled RKK Energiya rocket builder where he worked as a top consultant said Mr. Chertok died Wednesday in Moscow after contracting pneumonia.

For many years, he served as a deputy to the father of the Soviet space program, Sergei Korolyov. He was closely involved in putting the world's first satellite in orbit Oct. 4, 1957, and preparing the first human flight to space by Yuri Gagarin on April, 12, 1961.

Mr. Chertok was born in Lodz, Poland, when it was still part of the Russian empire and his family moved to Moscow at the start of World War I. After graduating from the Moscow Energy Institute in 1940, he began working as an aviation engineer. When World War II ended, he was selected to lead a group of Soviet experts to travel to Germany to tap Nazi know-how in rockets. He first met Korolyov there, and the two worked closely together until Korolyov's death in 1966.

Mr. Chertok, who specialized in control systems for rockets and spacecraft, has published memoirs chronicling the rise of the Soviet space program.

He was permitted to travel abroad only in the late 1980s. His voluminous work for the first time revealed to the public details of the endeavors that had been hidden by the veil of Soviet-era secrecy.

- AP