Soviet and Russian Lunar Exploration

The Ye-8-5
Luna 15 was the first of the third-generation Ye-8 spacecraft to succeed in leaving
Earth orbit. Because it was pushing the performance of the Proton rocket to the limit,
it took a fairly lengthy trajectory to the moon, in the order of 103 hours, much longer
than previous moon probes. It was a tense outward journey, for telemetry indicated
that the ascent stage fuel tank was overheating, threatening an explosion. Only when
they turned the tank away from the sun did temperatures stabilize.
The mission profile was for a four-day coast to the moon, followed by entry into a
circular 100 km lunar orbit. After a day, the orbit would be altered to bring the low
point down to 16 km, right over the intended landing point. After another day, the
inclination would be adjusted - probably a small manoeuvre - to ensure the lander
came in over its landing site at the right angle. Sixteen hours later, after 80 hours in
lunar orbit, an engine dead-stop manoeuvre would take place, after which Luna 15
would be right over the landing spot and then make a gentle final descent. After