One mare failure and one last sample return, Luna 24

The next sample return attempt with spacecraft Yc-8-5M No.412, the tenth in the scries, was lost when the Block D failed during its first burn and was unable to reach parking orbit. The final attempt, with No.413, was successful. Luna 24 was launched on August 9, 1976, made a midcourse correction on the 11 th, and entered a circular lunar orbit at 115 Icm with an inclination of 120 degrees on August 14. It adjusted its orbit to 120 x 12 km on the 17th and at 02:00:00 UT on the 18th it landed in darkness at 12.75°N 62.20°E in the Sea of Crises, only about 2,400 meters from the Luna 23 lander and near the Luna 15 target. The focus of the Ye-8-5M series was to obtain a deep core from the surface of the lunar mascon in Mare Crisium. The drill was able to reach the planned depth of 2.25 meters at a slightly inclined angle that equated to a vertical penetration of 2 meters. The sample was transferred to the return capsule and then at 05:25 LIT on the 19th the ascent stage lifted off. The capsule landed 200 km southeast of Surgut in Siberia at 17:53 UT on August 22. It proved to contain a sample of 170.1 grams.

End of the Moon, but the beginning for a propulsion stage

Luna 24 was the last of the Luna series and the final Soviet lunar mission. A third rover was built and another sample return spacecraft tvas prepared, but in 1977 the

Figure 11.30 Luna 16 recovery and soil sample (below). The balloons were inflated post­landing to right the capsule for antenna exposure.

launcher for the rover was requisitioned for a communications satellite and attention swung towards the ill-fated 5M Mars sample return project. Later all lunar and Mars plans were canceled in favor of continuing the successful Venus missions.

However, the reliable Ye-S cruise stage was modified to produce the autonomous propulsion stage for the 1988 Plrobos spacecraft, and went on to become the Fregat upper stage that is currently used by Proton-K and Soyuz launchers.

Results:

The altimeter on Luna 15 returned data during the descent until loss of signal, and this provided useful in forma lion on the mean density of the lunar soil. The sample that Luna 16 got from the Sea of Fertility was a dark, powdery mare basalt similar to that obtained by Apollo 12 in the Ocean of Storms. In 1971 three grams of Luna 16 soil were exchanged with NASA for three grams of Apollo 11 samples and three grams of Apollo 12 samples. The Vernadsky Institute of Geochemistry in Moscow* conducted analyses of the soils returned from these missions. Some samples were donated to other countries including France. Austria and Czechoslovakia. Although small, the Luna 20 soil from the highlands differed significantly from the Luna 16 mare sample. It was clearly lighter in color, with larger panicles. More than half of the rock particles were ancient anorthosite compared to less than 2% in the Luna 16 sample. Tw o grams were exchanged for one gram of highlands material obtained by Apollo 15, and US scientists were able to date the Luna 20 sample at 3 billion years. The 2 meter core from Luna 24 exhibited layering that clearly indicated successive deposition. Small portions of this core were exchanged with US scientists.