This, the tenth Soviet attempt to achieve a lunar soft-landing, nearly succeeded. The Blok L upper stage successfully dispatched the probe towards the Moon. After a successful mid-course correction at 19:00 UT on Dec. 4, 1965, the spacecraft headed towards its targeted landing site on the Moon without any apparent problems.
Just prior to the planned retro-fire burn, a command was sent to inflate cushioning airbags around the ALS lander probe. Unfortunately, a plastic mounting bracket appears to have pierced one of the two bags. The resulting expulsion of air put the spacecraft into a spin of 12 degrees per second.
The vehicle momentarily regained attitude, long enough for a 9-second retro-engine firing, but then lost it again. Without a full retro burn to reduce approach velocity sufficient for a survivable landing, Luna 8 plummeted to the lunar surface and crashed at 21:51:30 UT on Dec. 6, 1965 just west of the Kepler crater. Impact coordinates were 9 degrees 8 minutes north latitude and 63 degrees 18 minutes west longitude.
The Soviet news agency TASS merely reported that “the station’s systems functioned normally at all stages of the landing except the final one.”
Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.