Soviet Moon program
How many was the N1 unsuccessfully tested?
Space Race
The Soviet Union had planned to divide their lunar program into two separate manned programs: circumlunar flights in 1967 and lunar landings from 1968. The circumlunar missions were to be launched by a UR-500 rocket, later known as the Proton. The cosmonauts would be flown to the Moon in the Soyuz 7K-L1 (Zond), which made four unsuccessful unmanned flights between 1967 and 1970. One flight of the Zond was, however, successful and returned its non-human passengers (tortoises) to Earth; had it been used for a manned circumlunar mission, the flight would have carried two cosmonauts. The Soviet lunar landing missions would use spacecraft derived from the Soyuz 7K-L1. The orbital module (Soyuz 7K-L3), the ""Lunniy Orbitalny Korabl"" (LOK), had a crew of two. The LOK and a separate lunar lander, the ""Lunniy Korabl"" (LK), had 40% of the mass of the Apollo CSM/LM due to the launch vehicle's capabilities. The launch vehicle would have been the N1 rocket, which was roughly the same height and takeoff mass as the American Saturn V, exceeded its takeoff thrust by 28%, and yet had roughly half the TLI payload capability. The N1 was unsuccessfully tested four times, exploding each time due to problems with the first stage's thirty engines. The Soviet leadership cancelled the program in 1970 after the first two successful American Moon landings.