While remote sensing techniques are useful in determining the composition of other worlds, the Rosetta Stone for planetary scientists is actual samples which can be subjected to a wide range of analyses in the lab much more complex than is possible with robotic explorers. The grandfather of today’s robotic sample return spacecraft is the E-8-5 series of lunar landers developed by the Soviet Union in the midst of its race to the Moon with the United States. Although NASA’s crewed Apollo missions returned hundreds of kilograms of samples from the lunar surface, the Soviet robotic sample return missions during the early 1970s managed to provide scientifically important samples from areas never visited by Apollo. The first successful robotic sample return mission was that of Luna 16 flown a half century ago in September 1970.
The New E-8 Lunar Spacecraft
The hardware that would be employed in the Soviet sample return missions can be traced back to the E-8 spacecraft family developed by the design bureau known as NPO Lavochkin. Run by Chief Designer Georgi Babakin until his death in 1971, NPO Lavochkin was given responsibility for the development and construction of unmanned lunar and planetary spacecraft in April 1965 so that OKB-1 (the ancestor of Russia’s RKK Energia, which previously had that task) could concentrate its resources on the development of the Soyuz spacecraft and the related hardware needed to send cosmonauts to the Moon in competition with Apollo. The design bureau’s very first successes included Luna 9, which became the first spacecraft to land a working payload on the Moon on February 3, 1966 (see “Luna 9: The First Lunar Landing”), and Luna 10, the first spacecraft to successfully enter orbit around the Moon two months later (see “Luna 10: The First Lunar Satellite”).
Originally the E-8 rover (later known as Lunokhod) was tasked with checking out the site for Soviet manned lunar landings. (NPO Lavochkin)
The E-8 program initially consisted of two components: The E-8 rover (which would eventually be known to the world as “Lunokhod”) and the E-8LS orbiter. Both versions of the E-8 used a standardized “correction and braking module” (known by the acronym “KT”) with a dry mass of about 1,100 kilograms which carried over 3,500 kilograms of hydrazine and nitric acid propellants internally and in four jettisonable outboard tanks. The KT carried all the consumables for its KTDU-417 main engine and attitude control thrusters. It also was equipped with an astro-orientation system and other sensors needed to support its payload while travelling in space. The rover would be brought to the surface from an intermediate lunar parking orbit by a version of the KT fitted with landing legs, a pair of ramps, and other equipment required for descent such as a radar altimeter. Originally, the mission of the rover was to perform an on-site survey of a proposed manned landing area to make sure it was safe. It would also carry a radio beacon to guide the Soviet’s manned lunar lander or “LK” (their version of the LM) towards a pinpoint landing. Later versions would be used to aid the cosmonaut’s exploration of the landing area.
Image of an E-8LS lunar orbiter. (NASA)
With only small areas of potential lunar landing sites imaged in 1966 by the E-6LF Luna 12 mission (see “Mapping the Moon: The Soviet Luna 11 & 12 Missions”), the E-8LS orbiter’s mission was to perform a more thorough orbital survey of proposed landing sites. Its variant of the KT was loaded with less propellant than the lander version but it carried more consumables, such as for attitude control, needed for its planned yearlong mission in lunar orbit. The orbiter’s primary payload was a modified E-8 rover instrument compartment, minus its wheels and other drivetrain components, equipped with high resolution cameras and other instruments to study the lunar surface and surrounding environment.
Origins of the Sample Return Mission
As 1968 unfolded, it was becoming increasingly apparent to Soviet officials that the Apollo program was going to land men on the Moon long before the Soviet equivalent would be ready to fly. Babakin and his team at NPO Lavochkin had a potential means of at least partially upstaging Apollo: an automated lunar sample return mission. As early as 1966, engineers at Lavochkin had been working on design studies for just such a missions. These engineers ultimately arrived at a simple means of doing so using the E-8 hardware then under development. The standard E-8 KT was modified to carry an 800 kilogram payload consisting of a toroidal shaped instrument compartment used to support surface operations and an ascent stage which was to return a small lunar sample.
Russian diagram showing the major components of the E-8-5 lunar sample return spacecraft. 1) Return capsule, 2) ascent stage instrument compartment, 3) propellant tanks, 4) KRD-61 engine, 5) KT instrument compartment, 6) KTDU-417 engine, 7) KT propellant tanks, 8) imaging telephotometers, 9) sampler drill and 10) sampler arm. Click on image to enlarge. (Nauka)
A simple 0.9-meter sampling arm sporting a 13.6-kilogram drill mechanism could be swung over an arc of 100° in front of the lander to a sampling site selected using stereo images provided by a pair of imaging telephotometers. Once the drill mechanism at the end of the arm secured a 38-centimeter core sample with a mass of a couple of hundred grams, the arm would swing up and place the sample inside the spherical, 50-centimeter return capsule with a mass of 35 kilograms. The entire spacecraft, known as the E-8-5, stood 3.96 meters tall and had a launch mass of about 5,700 kilograms – right at the performance limit of its Proton-D launch vehicle (see “The Largest Launch Vehicles Through History”).
A schematic showing how the sampler head (2) is moved by the arm (3) to transfer the sample from the surface to the return capsule (1). (Nauka)
While in theory the KT could deliver its payload anywhere on the Moon’s surface from its intermediate parking orbit, the E-8-5 designers had to sacrifice some flexibility in order to limit the ascent stage to a mass of 520 kilograms and maintain the tight development schedule. Dmitry Okhotsimsky, a pioneer of space ballistics at the Soviet’s Institute of Applied Mathematics, had discovered a set of trajectories from the lunar surface which allowed a returning spacecraft to follow a simple ballistic path without the need for a midcourse correction or the mass penalty of a complex guidance system. This simplest of return strategies only required the ascent stage’s guidance system to maintain a vertical ascent profile while its KRD-61 engine accelerated the returning spacecraft to a velocity of about 2,700 meters per second. When properly timed, the return capsule would literally fall straight towards the Earth with any initial aiming errors minimized by the focusing effects of Earth’s gravity. Since this approach resulted in a large error ellipse at the Earth, a radio beacon on the ascent stage as well as optical tracking during its approach would allow the landing site to be determined precisely enough to ensure ground recovery crews could locate the return capsule after landing.
Cutaway diagram of the E-6-5 return capsule showing its major components: 1) container for soil, 2) parachute compartment cover, 3) parachute compartment, 4) antennas, 5) antenna switch, 6) transmitters, 7) case of return capsule, 8) lagging, 9) battery, 10) cover. Click on image to enlarge.
Such a simple ballistic return from the near side of the Moon was only possible for landing sites in a narrow band centered just north of the lunar equator near 56° east longitude in the general area of Mare Crisium and the highlands to the south stretching to the northeastern corner of Mare Fecunditatis. The exact location of the ten-kilometer wide landing zone varied over time depending on the season, the Moon’s position in orbit, the extent of lunar librations and the location of the intended recovery site. Fortunately, much of this area of the Moon was relatively safe for landing and was scientifically interesting as well.
This was one of the better images of the 560-kilometer Mare Crisium taken by the American Lunar Orbiter 4 (and processed using modern techniques). A band stretching from the left-of-center of the basin downward into the adjacent highlands was the region accessible to the E-8-5 sample return mission. (NASA/LPI)
The First E-8-5 Launches
The successful conclusion of the Apollo 8 mission on December 27, 1968 (see “Apollo 8: Where No One Has Gone Before”) and NASA’s aggressive test flight schedule to follow meant that the first Apollo lunar landing attempt could come in the summer of 1969. With no hope of beating the American manned landing, Soviet officials shifted focus to automated lunar missions in hopes of casting some shade on NASA’s accomplishments. With the preparation of E-8-5 hardware in its advanced stages, the Soviet Military-Industrial Commission (VPK) approved the launch of the first sample return missions on December 30, 1968. This was followed on January 8, 1969 by a decree by the Council of Ministers which, in part, authorized launches of the E-8 missions.
By June of 1969, five E-8-5 sample return spacecraft were being prepared for a series of launches. The first ready was E-8-5 No. 402. With a launch date set for June 14, 1969, its planned 11-day sample return mission would be completed three weeks ahead of the scheduled launch of Apollo 11 now set to attempt the first manned lunar landing after the successful completion of the Apollo 10 rehearsal on May 26 (see “Apollo 10: The Adventure of Charlie Brown & Snoopy”). The first E-8-5 lifted off at 07:00:47 Moscow Time (04:00:47 GMT) on June 14 atop of Proton No. 238-01. Unfortunately, the Blok-D escape stage failed to ignite to place itself and the E-8-5 payload into a temporary parking orbit. Instead, the hardware was destroyed during reentry over the Pacific Ocean ending this attempt to upstage Apollo.
Next up was E-8-5 No. 401 which would be the last chance for the Soviet Union to upstage the Apollo 11 mission. Launched at 05:54:41 Moscow Time (02:54:41 GMT) on July 13 on Proton No. 242-01, this time the launch vehicle worked as intended and placed what was now designated Luna 15 on course for the Moon. Unfortunately, the only way this mission could beat Apollo 11 by returning the first lunar samples was a delay in the scheduled July 16 launch or a failure of the Apollo mission to return samples from the lunar surface.
Luna 15 entered lunar orbit at 10:00 GMT on July 17. Unfortunately, issues with the propulsion system, attitude control and navigating in the lumpy gravitational field of the Moon as well as confusing radar data caused a 21-hour delay in the landing attempt. When the landing was finally attempted during the 54th orbit on July 21 (after the crew of Apollo 11 had successfully landed on the Moon and completed their historic moonwalk), Luna 15 crashed on Mare Crisium at 15:50 GMT ending any hopes of returning a sample (see “Luna 15: The Soviet Union’s Last Lunar Gamble”).
With three more E-8-5 spacecraft ready to fly, Soviet officials continued launch attempts in the months to follow. At 17:07:36 Moscow Time(14:07:36 GMT) on September 23, 1969, Proton No. 244-01 lifted off from the Baikonur Cosmodrome carrying E-8-5 No. 403. While Earth parking orbit was achieved, an oxidizer leak caused by a faulty valve in the Blok D escape stage prevented the reignition of its engine stranding the spacecraft. The orbit of what was now designated Kosmos 300 decayed four days later.
The fourth E-8-5 launch attempt came at 17:08:59 Moscow Time (14:09:59 GMT) on October 22 when Proton No. 241-01 lifted off carrying E-8-5 No. 404. This time, a malfunction in the upper stage control system resulted in the loss of attitude control in the Blok D. The escape stage failed to reignite properly stranding what was now called Kosmos 305 in low Earth orbit.
The final launch attempt with the initial batch of E-8-5 spacecraft came at 07:16:06 Moscow Time (04:16:06 GMT) on February 6, 1970. This time a false reading from a pressure gauge resulted in the first stage of Proton No. 247-01 shutting down early after firing for only about 127 seconds. The rocket along with E-8-5 No. 405 fell back to Earth and crashed downrange ending this attempt to return lunar samples.
The Luna 16 Mission
As personnel at NPO Lavochkin were completing assembly of the next batch of E-8-series spacecraft, a thorough review of the Proton was started after the string of eight failures in ten launch attempts over the previous year. As a result, major changes were made to the Proton to improve its reliability and its performance during the spring and summer of 1970. A suborbital test flight designated 82-EV using Proton No. 246-01 was launched on August 18 validating the changes made to the troublesome launch vehicle opening the way for a September launch attempt to the Moon.
E-8-5 No. 406 shown during testing before its launch on September 12, 1970 to become Luna 16.
Proton No. 248-01 lifted off at 16:25:53 Moscow Time (13:25:53 GMT) carrying the 5,727-kilogram E-8-5 No. 406 into a 185 by 241 kilometer parking orbit with an inclination of 51.5°. After coasting for 70 minutes, the Blok D stage reignited to send what was now called Luna 16 on its way to the Moon. The changes made to the Proton during the stand down had paid off with nine successes out of ten launch attempts over the following year (including the Luna 16 launch).
A Russian diagram showing the E-8-5 mission profile: 1) Launch, 2) parking orbit, 3) translunar injection, 4) translunar trajectory, 5) trajectory correction maneuver, 6) lunar orbit injection, 7) lunar orbit, 8) maneuvers to final orbit, 9) descent, 10) ascent from lunar surface, 11) return trajectory and 12) separation of return capsule. Click on image to enlarge.
After separating from its spent escape stage, Luna 16 settled into its cruise attitude for the 107-hour transit to the Moon. The day after launch, Luna 16 fired its KTDU-417 engine for 6.4 seconds to fine tune its trajectory to the Moon. Finally, at about 01:52 GMT on September 17, Luna 16 fired its engine once again to enter its initial 110 by 119 kilometer orbit around the Moon with an inclination of 70°. After tracking the spacecraft to map the perturbations of its orbit caused by the Moon’s lumpy gravitational field, ground controllers fired the main engine on September 18 to cut the spacecraft’s velocity by 20 meters per second to enter a 15.1 by 106 kilometer orbit with the perilune or low point over the intended landing site in the northern part of Mare Fecunditatis to the south of Mare Crisium. A second orbital trim maneuver on September 18 lowered the apolune to 106 kilometers and rotated its orbit plane increasing the inclination slightly to 71°.
Russian diagram showing the final approach of the E-8-5 for landing on the lunar surface. Click on image to enlarge. (Nauka)
As Luna 16 approached what would be its final perilune on September 20, it jettisoned its nearly empty outboard propellant tanks in preparation for landing. At 05:12 GMT, the KTDU-417 engine fired for 270 seconds burning about three quarters of its onboard propellant load to negate it 1,700 meter per second orbital velocity and begin a freefall towards the lunar surface. When the onboard radar altimeter indicated an altitude of 600 meters, the KTDU-417 engine was reignited by automated systems for the final time to slow the spacecraft’s 215 meter per second descent velocity. The main engine shut down as planned at an altitude 20 meters with smaller vernier engines controlling the final approach. The vernier engines shut down as programmed at an altitude of two meters allowing Luna 16 to come gently to rest at a speed of 4.8 meters per second at 05:18 GMT. Luna 16, with a landed mass of 1,880 kilograms, had come down at 0.68° S, 56.30° E only 1.5 kilometers from its intended landing target. This was the first successful Soviet lunar landing in almost four years (see “The Mission of Luna 13: Christmas 1966 on the Moon”).
Image of Luna 16 acquired on September 2, 2009 by NASA’s Lunar Reconnaissance Orbiter (LRO). Click on image to enlarge. (NASA/GSFC/Arizona State University)
Once on the surface, Luna 16 performed a quick systems check and then proceeded to use its pair of telephotometers to acquire 300 by 6,000-pixel panoramic images to provide a stereo view of the surface accessible to the spacecraft’s sample arm as well as an image of the Earth in the sky to help provide data on the lander’s orientation. Because Luna 16 had landed 60 hours after local sunset, it was equipped with floodlights to illuminate the lunar surface for imaging. Unfortunately, the floodlights failed to activate leaving ground controllers to grope in the dark for a sample.
An hour after landing, the sampler arm was deployed and its drill proceeded to penetrate the lunar surface for 7 minutes before it hit an obstacle at a depth of 35 centimeters. The arm was then lifted from the surface and rotated to place the sample into the return capsule. Unknown to ground controllers at the time, some of the sample had fallen out of the drill during this operation resulting in a smaller than expected sample of lunar material. Meanwhile, tracking data and telemetry from Luna 16 was used to fix its position and orientation on the lunar surface to fine tune the exact time for liftoff.
The Return Home
At 07:43 GMT on September 20, the ascent stage’s KRD-60 engine was ignited lifting it off the surface of the Moon. After a predetermined velocity around 2,700 meters was reached, the engine shut down leaving the spacecraft to begin its 68-hour transit back home. The KT descent stage remained on the Moon and continued transmitting data on lunar temperatures and radiation levels until its batteries were depleted.
An artist’s depiction of the E-8-5 ascent stage lifting off from the surface of the Moon.
On September 24, the sample-laden return capsule separated from the ascent stage 48,000 kilometers above the Earth. The capsule hit the atmosphere at 11 kilometers per second and began its reentry with braking loads peaking at 350 g. At an altitude of 14.5 kilometers, the top of the return capsule separated and its drogue chute was deployed followed by the main parachute at an altitude of 11 kilometers. The Luna 16 capsule landed at 03:26 GMT about 80 kilometers southeast of Dzhezkazgan in Soviet Kazakhstan – only 30 kilometers from the center of the intended target zone. The descent capsule was located and secured by recovery crews within minutes of touchdown. The Luna 16 mission was a complete success.
A view of the Luna 16 return capsule after it had landed on September 24, 1970.
The recovery crews removed the sealed sample container from the return capsule and sent it to Moscow. There it was opened in a sterile chamber filled with inert helium at the Laboratory of Comparative Planetology at V.I. Vernadskiy Institute of Geochemistry and Analytic Chemistry where scientists found that 101 grams of lunar material had been returned. Although only a small fraction of the size of the 21.6 kilograms of material returned by Apollo 11 and the 35.4 kilograms returned by Apollo 12 in July and November, 1969, respectively, it was still of scientific importance since it came from a region unvisited by Apollo. Although the E-8-5 program failed to return lunar samples before Apollo, Soviet officials touted their program as being only 1/20th the cost of Apollo.
A closeup view of the sample Luna 16 returned from the surface of the Moon.
Initial inspection showed the sample to be an unstratified mixture of powder composed of fine and coarse grain material. Not unexpectedly, the sample was basaltic in composition similar to that found in Apollo 12 samples from Oceanus Procellarum with vitrified glass and metal-like particles present. In June of 1971, three grams of this sample were traded with NASA for a like quantity of material acquired by the crew of Apollo 12. This unique sample continues to provide important insights into lunar history and is the subject of peer-reviewed papers even after a half a century.
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Related Reading
“Luna 15: The Soviet Union’s Last Lunar Gamble”, Drew Ex Machina, July 19, 2019 [Post]
“The Last Lunar Sample Return Mission”, Drew Ex Machina, August 18, 2016 [Post]
General References
Brian Harvey, Soviet and Russian Lunar Exploration, Springer-Praxis, 2007
Wesley T. Huntress, Jr. and Mikhail Ya. Marov, Soviet Robots in the Solar System: Mission Technologies and Discoveries, Springer-Praxis, 2011
Nicholas L. Johnson, Handbook of Soviet Lunar and Planetary Exploration, Univelt, 1979
Asif A. Siddiqi, The Soviet Space Race with Apollo, University Press of Florida, 2003