Luna 6, or E-6 No.7 (Ye-6 series) was an uncrewed Soviet spacecraft which was intended to perform a landing on the Moon as part of the Luna program. Due to the failure of a mid-course correction manoeuvre, Luna 6 failed to land, instead flying past the Moon at a distance of 160000 km.

Launch

Luna 6 was launched by a Molniya-M carrier rocket flying from Site 1/5 at the Baikonur Cosmodrome. Liftoff occurred at 07:40 UTC on 8 June 1965, with the spacecraft and Blok L upper stage entering a low Earth parking orbit, before the upper stage propelled the spacecraft into a heliocentric orbit passing the Moon.

Failure

The Luna 6 mission proceeded as planned until a scheduled mid-course correction late on 9 June. Although the spacecraft's S5.5A main engine ignited on time, it failed to cut off and continued to fire until its propellant supply was exhausted. An investigation later determined that the problem had been due to a command which had been mistakenly sent to the timer that ordered the main engine to shut down. Despite the spacecraft being unable to land on the Moon, controllers used the spacecraft to simulate a landing; a task which was satisfactorily accomplished. Luna 6 flew past the Moon late on 11 June, with a closest approach of 159612.8 km. Contact was maintained to a distance of 600000 km from Earth.