Encyclopedia Astronautica
1972.11.23 - N1 7L

Unmanned test of manned lunar mission launch vehicle serial number 7L. This article incorporated significant changes to the previous model, including roll 'steering' engines to prevent the loss of control that destroyed 6L. The rocket ascended into the sky, and the engines ran 106.93 seconds, only seven seconds before completion of first stage burnout. Programmed shutdown of some engines to prevent overstressing of the structure led to propellant line hammering, rupture of propellant lines, and an explosion of engine number 4. The vehicle disintegrated.

Kerosene fuelling completed at 01:30. Upper stages Block G and D were fuelled between 04:00 and 05:00. They were allowed to reach thermal equilibrium between 05:00 and 06:15. Between 06:45 and 07:55 all lines and umbilicals were removed from the vehicle. The tower was rolled back at 08:15. Launch was on schedule at 09:00. All was normal to T+50 seconds. Centre engine shutdown at T+94.5 seconds was normal. All was normal at T+100 seconds. Then at T+110 seconds all transmissions from the vehicle suddenly ceased. An examination of telemetry showed that the vehicle catastrophically disintegrated at T+106.94 seconds, only 7 seconds before the end of the stage one burn and separation of the second stage. Later it would be alleged the cause was a failure of the oxidiser pump in engine 4. Kozlov, Kuznetsov, and Dorofeyev all blamed the other for the failure.

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