When the USSR won the race to the Moon, although they missed a note in The Internationale'

"The only way to slow down a spacecraft was with a retro-rocket whose thrust would have to be adjusted so that it reached the ground at almost zero speed."

"An altimeter radar would be needed to measure flight altitude, along with a computer to regulate engine thrust based on its readings."

"A one-second delay each way in sending commands was unacceptable during such critical maneuvers. That brief interval would be enough to turn an operational spacecraft into just another crater in the rugged lunar landscape."

"Soviet engineers built their spacecraft around a braking motor and its fuel tanks, with delicate components requiring reasonable temperatures and protection from direct sunlight."

The Soviet Union progressed in lunar exploration by developing a spacecraft capable of controlled descent to the Moon's surface. This required advanced technology, including a retro-rocket for slowing descent, an altimeter radar for altitude measurement, and an autonomous computer system to manage engine thrust due to communication delays. The spacecraft's design included a spherical capsule for landing, with separate boxes for sensitive equipment to protect against temperature fluctuations and sunlight. The Moon's weaker gravity facilitated descent, despite the high impact speeds of earlier probes.

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