Mission Type: Orbiter
Launch Vehicle: N1 (no. 15003)
Launch Site: NIIP-5 / launch site 110P
Spacecraft Mass: 6900 kg
Spacecraft Instruments: Unknown
References:
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

This was the first attempted launch of the giant N1 booster as part of early test operations in the Soviet piloted lunar landing program. N1 development began in 1962 after two years of initial R&D on heavy booster designs. Although the first launch had been originally planned for 1965, a major redesign of the booster in 1964 and financial and organizational difficulties delayed the launch by four years.

On this first launch, the N1 carried a basic 7K-L1 spacecraft (openly known as Zond) modified for operations in lunar orbit (rather than for circumlunar flight). Known as the 7K-L1S, the spacecraft was equipped with an Engine Orientation Complex (DOK) for attitude control in lunar orbit. During the launch, two first-stage engines initially shut down, but the remainder of the engines operated until T+70 seconds when the control system shut them down. The booster crashed about 50 kilometers from the launch site, and the payload successfully used its launch-escape system to descend without problem 32 to 35 kilometers from the pad.

Investigators believed that booster failed when a pipe for measuring fuel pressure broke at T+23.3 seconds, setting in motion a sequence of events that led to a huge fire at T+54.5 seconds in the tail of the first stage. The fire short-circuited the control system and shut down all the engines at approximately T+70 seconds.