On June 26, 1971, the largest non-nuclear explosion in the history of the Soviet space program tore Launch Complex 110 apart and killed two engineers. It was the third failure of the N1 booster — the Soviet counterpart to the Saturn V — and effectively ended a secret manned lunar program, conducted between 1960 and 1974, whose existence the Soviet government denied until 1989. The fourth and final N1 launch attempt in November 1972 came closest to success, lasting 107 seconds before the vehicle was lost; the lunar landing work was canceled in 1974, and the Soviet Union never landed a cosmonaut on the Moon.
The N1 stood 105.3 m tall, with a first stage powered by 30 NK-15 engines producing 45.4 meganewtons of liftoff thrust. The 30-engine article was an engineering choice forced by the lack of a high-thrust engine comparable to the American F-1; the Soviet engine program had been directed by Valentin Glushko toward clustered smaller engines and storable propellants.
The four N1 launches all failed:
- 21 February 1969: failed at 68.7 seconds.
- 3 July 1969: failed at 51 seconds (pogo oscillation).
- 26 June 1971: failed on the pad; the largest non-nuclear explosion in the Soviet space program. Two people were killed.
- 23 November 1972: failed at 107 seconds, the closest to success.
The third failure destroyed Launch Complex 110 and effectively ended the program. Sergei Korolev’s death on 14 January 1966 had already removed the program’s most experienced manager. The cancellation was not announced. The Soviet response was to redirect resources to long-duration spaceflight, producing the Salyut and Mir programs.
For the rest of Soviet space program article and the space race overview.