This group was later merged with another rocketry organization to become the Reactive Scientific Research Institute (RNII).

In 1937 during the Great Purge, he was fired and subsequently arrested by NKVD, along with RNII director Ivan Kleymyonov and engine designer Valentin Glushko, as a follow-up to a denunciation letter by the director of RNII liquid fuel engine laboratory, Andrei Kostikov (who subsequently took his position in the institute), in which he claimed Langemak was sabotaging the research and development progress of the new engine.

Langemak was judged by a visiting session of Military Collegium of the Supreme Court of the Soviet Union on 11 January 1938, found guilty under the article 58-7, 58-8, and 58-11, and sentenced to death by shooting with property confiscation.

Langemak and other participants in the creation of the Katyusha rocket launcher received official recognition only in 1991.

By decree of President Mikhail Gorbachev, dated 21 June 1991, Kleymyonov, Langemak, Vasily Luzhin, Boris Petropavlovsky [ru], Boris Slonimer, and Nikolai Tikhomirov were posthumously awarded the title of Hero of Socialist Labor.