Three duds and a launcher review

The next three sample return attempts were lost to launcher failures. In September Ye-8-5 No.403 was stranded in parking orbit when the Block D failed to restart. An oxygen fuel valve had stuck open after the first firing and allowed all the oxidizer to escape. It was designated Cosmos 300 by the Soviets, and re-entered after 4 days. In October a programming error caused the Block D to misfire and spacecraft No.404. designated Cosmos 305, re-entered during its first orbit. In February 1970 spacecraft No.405 was lost wdien a pressure sensor command error shut down the second stage after 127 seconds of flight and the vehicle was destroyed. This precipitated a review7 of the Proton launch vehicle, w hich had a miserable record with many more failures than successes in the Ye-8 and lunar Zond series at that time. Changes w ere made as a result of this review, and in August 1970 a successful suborbital diagnostic flight was flown. The following month another sample return attempt was made and, after five successive failures in a period of 15 months, success w’as finally achieved.

Luna 16

Luna 16 was launched at 13:25:53 UT on September 12, 1970. Seventy minutes after entering parking orbit, the Block D reignited and performed the translunar injection burn. After a course correction on September 13. the spacecraft entered a nearly circular 110 x 119 km orbit at 70 degrees inclination on September 17. After gravity data had been acquired in this orbit, two orbital adjustments were made on September 18 and 19, the first into an elliptical orbit wdth its perilune 15.1 km above the landing site and an apolune of 106 km, and the second to adjust the orbit plane to 71 degrees inclination. As the spacecraft approached perilune on September 20. the extra tanks were jettisoned. The engine was ignited at perilune. 05:12 UT, and fired for 270 seconds to cancel the orbital velocity and initiate the free fall. Triggered by the radar altimeter, the engine was restarted at an altitude of 600 meters and velocity of 700 km hr. It was shut down at an altitude of 20 meters and a velocity of 2 m/s. The primary verniers were ignited for the tenninal phase, and cut off at a height of 2 meters, then the spacecraft dropped to impact at about 4.8 m/s. Touchdown occurred at 05:18 UT in the Sea of Fertility at 0.68 S 56.30 H. only 1.5 km from the planned point.

Because Luna 16 touched down 60 hours after local sunset and was not fitted w ith floodlights it did not provide any images. The drill was deployed after an hour, and in 7 minutes of operations it penetrated to a depth of 35 cm before encountering an obstacle. 1 he boom then lifted the core sample from the surface and swung it up to

the return capsule atop the ascent stage, inserting it through an open hatch that then closed. Some soil was lost from the sampler during this operation. At 07:4.1 UT on September 21, after 26 hours and 25 minutes on the Moon, the ascent stage lifted off and escaped at 2.7 krn/s. The lower stage remained on the surface and continued to transmit lunar temperature and radiation data. The ascent stage returned directly to Earth. On September 24, at a distance of 48,000 km, the straps released the return capsule. Four hours later it hit the atmosphere traveling at 11 km/s on a trajectory at 30 degrees to the vertical on a ballistic entry with a peak deceleration of 350 G. At an altitude of 14.5 km the top of the capsule was ejected and the drogue parachute deployed. At 11 km the main chute was unfurled and the beacon antennas deployed. The capsule landed at 03:26 UT on September 24, approximately 80 km southeast of the city of Dzhezkazgan in Kazakhstan.

Luna 16 proved, to contain 101 grams of lunar material. It was a triumph, and the Soviet press made the best of it, hyping the use of robots over manned missions. For the Americans, Luna 16 confirmed what they suspected about Luna 15, that it was a sample return attempt intended to upstage Apollo 11.

Luna 18

The next attempt at sample return was made one year later. Luna 18 was launched on September 2, 1971, made midcourse corrections on the 4th and 6th, and entered a 101 km circular lunar orbit inclined at 35 degrees the following day. After lowering its perilune to 18 km it was commanded to land on September 11, but the signals cut off abruptly at 07:48 UT at an altitude of about 100 meters. The main engine had run out of fuel due to excessive consumption in earlier operations, and the wreckage lies at 3.57°N 56.50°E in rugged highland terrain.

Luna 20

Luna 20 was the second attempt after Luna 18 to obtain a sample from in the lunar highlands. Launched on February 14, 1972, it was tracked by telescopes to compute an accurate trajectory, made a midcourse correction the following day and entered a 100 km circular lunar orbit at 65 degrees on February 18. It lowered its perilune to 21 km the following day. And finally, at 19:19 UT on February 21, it touched down in the Apollonius highlands near the Sea of Fertility at 3.53°N 56.55,:>E, only 1.8 km from where Luna 18 crashed. The Sun was 60 degrees above the horizon. Images of the surface were transmitted prior to the sampling operations. The drill encountered resistance, and had to be paused three times to prevent overheating. It was ultimately able to achieve a depth of only 25 cm. The recovered sample core was transferred to the return capsule.

The ascent stage lifted off at 22:58 UT on February 22, and then upon its return to Earth fell into a strong snow storm. .Although it came down over the Karkingir river 40 km north of Dzhczkazgan, when it landed at 19:19 UT on February 25 it touched down on an island. The ice, wind, and snow presented the recovery team with severe difficulties. It was recovered the following day, and when opened proved to contain only 55 grams of lunar soil.

Luna 23

The first improved Ye-8-5M sample return vehicle, No.410, became Luna 23 with a successful launch on October 28, 1974. After a midcourse correction on October 31, it entered an almost circular 94 x 104 km orbit at 138 degrees on November 2. Upon lowering its perilune to 17 km it was commanded to land on November 6. Although Luna 23 landed on target in the southern part of Sea of Crises at 12.68’N 62.28°E, it did so at 11 m/s and the impact shock wrecked the sample collection apparatus and caused other damage. No samples wjere obtained and the ascent stage was not lired. The lander continued to transmit until contact was lost on November 9.