THE LANDERS: A SUMMARY

Landing a cabin on the moon proved to be much more difficult than either the United States or the Soviet Union imagined. The USSR made twelve attempts, succeeding only twice. With Ranger, the Americans made three attempts, not succeeding until Surveyor 1 in June 1966. For the Russians, the main problems turned out to be the upper stage of the rocket, the translunar course and the navigation systems more than

Table 4.1. Key events in the programme of Luna 13.

No. Date Time Event

Landing First signal

First communication session Second communication session Third communication session Fourth communication session Fifth communication session Sixth communication session Seventh communication session Eighth communication session Ninth and last communication session

the actual landing phase itself. The Ye-6 landers were more sophisticated than the Ranger landers, being able to carry out a broader range of experiments and observa­tions. They achieved the function of determining that the soil would bear a manned spacecraft and that radiation levels on the moon were acceptable. They returned detailed close-up pictures of the moonscape.

The Ye-6 design was later put to good use when the Soviet Union came to soft – land spacecraft on Mars in 1971 (Mars 3). When the American Pathfinder successfully soft-landed on Mars in 1997, it used the airbag technique developed by the Russians in the 1960s (not that this was remembered at the time). Airbags were used for the later American Mars probes Spirit and Opportunity in 2003-4. The difficulties the Americans experienced with their Mars probes also echoed some of the frustrating difficulties experienced by the Russians in the 1960s.

Ye-6, Ye-6M series 4 Jan 1963 Failure 2 Feb 1963 Failure 2 Apr 1963 Luna 4 (missed moon) 21 Mar 1964 Failure 12 Mar 1965 Failure (Cosmos 60, but some science data) 10 Apr 1965 Failure 9 May 1965 Luna 5 (crashed) 8 Jun 1965 Luna 6 (missed moon) 4 Oct 1965 Luna 7 (crashed) 3 Dec 1965 Luna 8 (crashed) 31 Jan 1966 Luna 9 (Ye-6M) 21 Dec 1966 Luna 13 (Ye-6M)

Luna 13 silhouettes

Ye-6, -6M: scientific outcomes

• Density of lunar regolith similar to medium-density Earth rock, little dust, 0.8gm/cm3.

• Well able to receive a manned lunar landing vehicle.

• Radiation level of 30mrad/day, acceptable to humans.

• Moon absorbs three-quarters of cosmic radiation.

• Characterization of local landscape in two locations.

• Temperature of lunar surface, 117°C.