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Above: A general architecture of the Ye-8-5M spacecraft, including Luna-24. Credit: NPO Lavochkin
The final Soviet mission to the Moon was launched in 1976 under the official name Luna-24. Its real designation within the Soviet rocket industry was Ye-8-5M (or E-8-5M in Russian). Similar to several previous missions, Luna-24's goal was to bring back samples of the lunar soil. However official Soviet sources disclosed early-on that Luna-24 sported a re-designed drilling mechanism, which was different from the one used in previous successful sample-return missions.
The Proton rocket with the Ye-8-5M No. 413 spacecraft lifted off from Baikonur's Site 81, on Aug. 9, 1976, at 18:04 Moscow Time. (400) The mission was announced as Luna-24. It was the third launch of the Ye-8-5M version of the lunar-sampling spacecraft, with two previous missions ending in failures -- one on the surface of the Moon in 1974 (announced as Luna-23) and one unannounced spacecraft lost during a launch mishap in 1975.
The KIP-10 ground station in Simpheropol served as a main control center responsible for the flight. Based on the data received from the vehicle, a trajectory correction was conducted on August 11, as the spacecraft coasted toward the Moon. (270) Three days later, the probe entered its initial lunar orbit. On August 16 and 17, orbit correction maneuvers brought Luna-24 within 12 kilometers above the lunar surface during its final orbits around the Moon.
On Aug. 18, 1976, Luna-24 fired its engine one more time to conduct a braking maneuver and to initiate its final descent onto the lunar surface. Just six minutes later, the spacecraft successfully touched down in the night-covered south-eastern region of Mare Crisium (Sea of Crisis) some 40 kilometers from the "shoreline" peaks raising 3-5 kilometers above. The landing location was "traditional" for previous Soviet sample-return missions, concentrating in the Moon's equatorial areas on eastern fringes of its visible side. (398) As it transpired later, this landing area was primarily dictated by available propulsion capabilities of Soviet lunar missions. (397)
Luna-24 apparently ended up just few hundred meters (397) from its ill-fated predecessor -- Luna-23 -- which damaged its drilling mechanism in a botched landing attempt less than two years earlier. (2) It was also the same region, where another failed mission -- Luna 15 -- was heading in 1969, in a last-ditch attempt to upstage Apollo-11 astronauts in bringing back lunar soil. Like other "sea" areas on the Moon, a slightly tilted plain where Luna-24 landed was probably created by lava flows at least 1.4 billion years ago. In the following eons, meteoroid bombardment had peppered the landscape with numerous craters. A 1.5-kilometer deep, six-kilometer wide impact crater named after English physicist Daniel Fahrenheit was located 18 kilometers to the West. The Luna-24 mission scientists believed there was a chance that blast debris ejected as a result of impacts at Fahrenheit and other craters could be found in the probe's samples. (398)
Immediately after the landing, the KIP-10 ground control station commanded a soil-sampling mechanism to initiate drilling of the surface. Luna-24 featured a new type of a rotary percussion drill designated LB-9. It was developed by the Tashkent branch of the KBOM design bureau, known as TashKBM, on the assignment from NPO Lavochkin. Unlike drills installed on Luna-16 and Luna-20 missions, the new device was able to preserve the original relative position (stratigraphy) of regolith layers. (71) The new drill also had the capability to adjust its drilling power depending on the density of the soil.
As in previous soil-return missions, telemetry relayed information to ground control on the performance of the drilling mechanism and the process of loading of the samples into the return vehicle. (393) Data showed that Luna-24's drill reached the depth of two meters under 30-degree angle toward the local vertical, penetrating 225 centimeters into the soil. (398) As a result, a 260-centimeter flexible tube with the diameter of 12 millimeters was filled regolith. The tube was then coiled in a spiral-like fashion on a special drum with the diameter of 80 millimeters, which in turn, was sealed inside a metal storage container of the reentry capsule.
After 22 hours 49 minutes on the surface of the Moon, the return craft containing precious soil lifted off on Aug. 19, 1976. The ascent engine accelerated the vehicle to a speed of about 2.7 kilometers per second for a direct flight to Earth. At the predetermined distance from Earth, ground control sent a command for the separation of the reentry capsule from the return vehicle. After reentering the Earth atmosphere, the capsule released a drogue parachute at an altitude of 15 kilometers, followed by a main chute four kilometers lower. (185) The capsule successfully touched down 200 kilometers south-east of the city of Surgut in Western Siberia, on Aug. 22, 1976. According to the official Soviet sources, the landing took place in the pre-determined area, however no other civilian missions were known to conclude in this spot either before or after Luna-24.
As with the Luna-23 mission, the descent stage functioned for several days on the lunar surface, during which ground controllers reportedly conducted a number of engineering tests, including additional operations of the drill. It is possible that those trials aimed to facilitate the development of yet another version of the sampling drill, perhaps for Martian missions. At least one unflown drill design had surfaced in the post-Soviet period, even though no mission, which was expected to carry it had been identified at the time.
Luna-24 brought back 170.1 grams of lunar soil packed in a 160-centimeter-long cylindrical column. It was more than three times the amount delivered by a previous Soviet sample-return mission -- Luna-20. (118) Samples were studied and stored at the Vernadsky Institute of Geochemistry and Analytical Chemistry, GEOKhI, of the Russian Academy of Sciences. Some samples from the Luna-24 mission were provided to the Geological institute of the Czech Academy of Sciences, as well as 0.91 grams to the British scientists. During his visit to Moscow three months after Luna-24's return to Earth, NASA scientist Dr. Michael Duke exchanged three grams of samples from Luna-24 for 0.5 grams of samples delivered by Apollo astronauts. Luna-24 samples were then studied in the lunar research institute in Houston as well as a number of US academic institutions.
The wealth of scientific information resulted from the analysis of Luna-24's soil samples by an international team of scientists was summarized in the 1980 Soviet publication, comprising more than 30 scientific papers. Soil samples showed multiple layers of diversely colored and structured material, which probably reflected a complex geological history of the region. Relatively large debris fragments were found within the sample, which mostly consisted of "sea"-type materials. The age of regolith was found to be around 300 million years. (398)
Luna-24 at a glance:
LB-9 drill characteristics onboard Luna-24:
Luna 24 mission chronology (1976):
Aug. 9, 18:04:12 Moscow Time (15:04 GMT): A Proton rocket carrying Luna-24 lifts off from the "Left" launch pad at Site 81 in Baikonur, entering an initial 188 by 243-kilometer Earth orbit with an inclination 51.54 degrees toward the Equator. The Block DM upper stage then fired to send the spacecraft toward the Moon, after which Luna-24 and its upper stage have separated.
Aug. 11: Luna-24 conducts a trajectory correction.
Aug. 14 (Aug. 13, 23:11 GMT?): Luna-24 enters an initial lunar orbit with the altitude 115 kilometers above its surface and an inclination 120 degrees toward the lunar equator. The orbital period (the time to complete each orbit) is 1 hour 59 minutes.
Aug. 16: Luna-24 conducts an orbit correction.
Aug. 17: Luna-24 conducts an orbit correction resulting in a 12 by 120-kilometer orbit above the Moon.
Aug. 18, 06:36 GMT: Luna-24 initiates a barking maneuver to descent on the lunar surface.
Aug. 18, 06:36 GMT: Luna-24 touches down successfully at 12 degrees 45 minutes North latitude, 62 degrees 12 minutes East longitude.
Aug. 19, 05:25 GMT: The return vehicle of Luna-24 lifts off from the Moon.
Aug. 23, 05:55 GMT: The reentry capsule of Luna-24 lands on Earth.
Luna 24 flight control team (GOGU):
Head - L. V. Onishenko, deputy - V. M. Nikolsky, members - I. L. Feodorov, N. M. Eremenko, V. M. Sapranov, G. G. Latypov, K. K. Davidovsky, E. G. Samal. (270)
Next chapter: Missions to Mars
Written by Anatoly Zak; last update: March 26, 2013
Last edit: June 22, 2010
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The Ye-8-5M spacecraft during pre-launch tests.
The ascent stage of the Ye-8-5M spacecraft, the LB-9 drill and the upper assembly of the descent stage.
Artist renderings of the Ye-8-5M (E-8-5M) spacecraft on the surface of the Moon. Credit: NPO Lavochkin
An artist rendering of the Ye-8-5M (E-8-5M) spacecraft's return vehicle lifting off from the Moon. Click to enlarge. Credit: NPO Lavochkin
An LB-09 soil-sampling mechanism for the Luna-24 probe (left) developed by Tashkent branch of KBOM (TashKBM) and capable of drilling to the depth of more than two meters. An unidentified follow-on device can be seen on the right. Click to enlarge. Copyright © 2002 Anatoly Zak
The processing of soil samples inside a special glove box chamber. After removal from the flight container a flexible hose containing the lunar soil was placed on a special disk with a spiral groove for initial X-ray imaging. Click to enlarge. Credit: (398)
Luna-24's descent stage sits at the edge of the crater at the end of the first decade of the 21st century, as seen by the US Lunar Reconnaissance Orbiter. Click to enlarge. Credit: NASA
Sample of lunar soil delivered by a Soviet sample-return spacecraft. Copyright © 2011 Anatoly Zak