In 1961, President John F. Kennedy proposed that the United States commit itself to landing a human on the Moon by the end of the decade. NASA undertook three manned programs -- Mercury, Gemini, and Apollo -- and a series of robotic missions throughout the 1960's. These efforts culminated in the Apollo 11 moon landing on July 20, 1969, in which astronauts Neil Armstrong and Edwin Aldrin walked on the Sea of Tranquility.
The American triumph in the "Moon Race" is a well known and much celebrated accomplishment. What is less well known is that the Soviet Union also had an aggressive lunar program that lasted from 1959 until the mid-1970's. The program included an ambitious, and largely successful, series of robotic missions that included orbiters, landers, surface rovers, and sample-return spacecraft.
The Soviets also undertook an unsuccessful effort during this period to land humans on the lunar surface. Although the program failed in its goal, it did complete several automated lunar flybys and pioneered development of technologies that were useful in other manned and robotic programs. The program featured a failed attempt to develop a super booster to rival the Saturn 5 rocket used in the Apollo program.
The Soviet Union began in 1959 with a Moon mission. On January 2, the USSR launched Luna 1 on a course to impact on the lunar surface. However, the spacecraft missed the moon by 5,000 kilometers (3,100 miles) and went into solar orbit.
They had better luck nine months later with Luna 2. Launched on September 12, the 390-kilogram (860-pound) probe scored a direct hit, crashing about 800 kilometers (500 miles) north of the visual center of the Moon. This marked the first time that a man-made object had reached another planetary body. The spacecraft's instrumentation revealed that the moon lacked a strong magnetic field and radiation belts. Luna 2 was the first to photograph the Moon's far side before crashing on September 15.
The country finished out 1959 with Luna 3, which was launched on October 4 to mark the second anniversary of Sputnik 1, the first artificial satellite. The spacecraft circumnavigated the Moon, photographing about 70 percent of the far side. The probe relayed images back to Earth by television.
The second phase of the Soviet lunar program involved sending spacecraft to orbit the Moon and to land softly on the surface. However, early Soviet successes were followed by a string of failed missions that would stretch for more than six years.
Following the success of Luna 3, the country didn't make any further lunar attempts until early 1963. The Soviets ended the two-year gap in January and February, launching two Luna probes that failed to reach orbit. These spacecraft, which were not given numbers, were designed for soft landings on the lunar surface. In April 1963, the Soviets launched another lander called Luna 4, which did a lunar flyby at a distance of 8,500 kilometers (5,280 miles) and then went into solar orbit.
These flights were followed by six other failed landing missions over the next 2.5 years. In April 1964, a lunar lander was destroyed during launch. In 1965, the country made five failed landing attempts. Cosmos 60 failed to reach orbit in March. Luna 5 crashed on the Moon in May 1965 at 31° S, 8°. Its successor, Luna 6, went into solar orbit after missing the moon by 160,000 kilometers (100,000 miles). Luna 7 and Luna 8 crashed on the lunar surface in October and December 1965, respectively.
The USSR's lone successful Moon flight in 1965 occurred in July with the Zond 3 lunar flyby mission. The 905-kilogram (2,095-pound) spacecraft, launched on July 18, returned images of the remaining regions of the far side that had not been photographed.
The Soviets landing efforts succeeded in January 1966, guiding Luna 9 to the first successful soft landing on another planetary body. The 1,581-kilogram (3,490-pound) spacecraft was launched on January 31 and touched down on the Ocean of Storms on February 3. The spacecraft transmitted several medium-resolution photographs of the lunar surface before its batteries failed four days after landing. The lander also returned data on radiation levels at the landing site.
This mission was followed by another successful soft landing by Luna 13, which was launched on December 21, 1966. The spacecraft landed at 10°52'N by 62°W on December 24. It returned panoramic photographs and radiation data. The spacecraft also was outfitted with two mechanical arms, which were used to test soil consistency and density.
The other Luna spacecraft in the second series were designed strictly for orbital missions. The Soviets successfully placed Luna 10 into lunar orbit on April 3, 1966, making it the first human object to circle another world. The 245-kilogram (540-pound) spacecraft transmitted micrometeroid and radiation measurements during its 56-day mission. It also transmitted back to Earth a recording of the "Internationale," the Communist Party anthem.
The Soviets successfully launched two other orbiters, Luna 11 and Luna 12, in 1966. Luna 11 was launched on August 24 and achieved a lunar orbit with a perigee of 159 kilometers (99 miles) and an apogee of 1,200 kilometers (746 miles). Luna 12 was launched on October 22 and achieved an orbit of 100 by 1,740 kilometers (62 by 1,081 miles). It returned television pictures of the surface. Other successful orbital missions included Luna 14 (April 1968), Luna 19 (September 1971), and Luna 22 (May 1974).
During this same period, the Soviet Union accelerated its efforts to send humans to the Moon. Soviet engineers and designers worked on developing new human spacecraft and a booster capable of launching them toward the lunar surface.
Soviet efforts to reach the Moon included a series of Zond spacecraft that were sent on circum-lunar flights. The Zond vehicles were automated versions of the manned Soyuz spacecraft, which was first flown in 1967. The Zond spacecraft were precursor vehicles to eventual human flights to and landings on the Moon.
Zond spacecraft had an instrument module that included solar cells, a propulsion unit, fuel tanks, and avionics. The Zond series also included a descent module with an improved heat shield capable of surviving a return from a circum-lunar flight. Spacecraft returning from the Moon enter the atmosphere at far greater speeds than those returning from Earth orbit, generating a greater amount of heat.
The Soviets launched Zond 5 on a circum-lunar flight on September 14, 1968. The spacecraft included turtles, wine flies, meal worms, plants, seeds, bacteria, and other living matter. These specimens were used to investigate radiation and other potential hazards in lunar space. The spacecraft passed 1,950 kilometers (1,210 miles) behind the moon on September 18, and entered the Earth's atmosphere three days later. Soviet naval forces recovered the re-entry module in the Indian Ocean, marking the first recovery of a spacecraft from a lunar mission.
On November 10, 1968, the Soviet Union launched Zond 6 on a similar mission. Seven days later, it entered the atmosphere and was successfully retrieved by recovery forces. A significant element of this flight was that it used a double re-entry. The spacecraft dipped into the atmosphere, skipped off and then entered a second time. This type of re-entry lessened the force of gravity, testing a technique that would make it easier for humans to return from the moon. Zond 4 experienced forces of 10 to 15 times normal gravity (10 to 15 G's), while Zond 6 experienced only 4 to 7 G's.
The USSR's success with the Zond missions helped to accelerate NASA's Apollo program. American officials were concerned that the Soviet might reach the Moon first, perhaps as early as December 1968. American surveillance satellites took photographs of a massive moon rocket, dubbed the G-1, on the launch pad at the Soviet Baikonur launch facility.
NASA launched the first manned Apollo mission in October 1968. The 11-day Apollo 7 flight was a complete success, giving the agency much confidence in its new spacecraft. NASA had hoped to test the first lunar module in Earth orbit on the following flight; however, it was not ready to fly. Weighing these factors, and mindful of the Soviet Zond program, NASA elected to send Apollo 8 to the Moon. Astronauts Frank Borman, Jim Lovell, and William Anders spent Christmas Eve 1968, making 10 orbits of the lunar surface.
The Zond flights resumed on August 7, 1969, about three weeks after the Apollo 11 moon landing. Zond 7 flew around the Moon and returned to Earth on August 14, using the same skip re-entry profile used by its immediate predecessor. The spacecraft returned the first color photographs of the moon ever taken by a Soviet spacecraft.
The Zond program was completed in October 1970 by Zond 8. It was launched on October 20, and was recovered seven days later after circling the moon. It made a single re-entry similar to Zond 5.
During this same period, Soviet engineers were developing a large lunar booster, which Western experts labeled the G-1. This rocket, which was designed to rival the Saturn 5, was plagued by technical problems, explosions and launch failures between 1968 and 1972. The Soviets eventually abandoned the program in the wake of the successful Apollo missions.
The Soviet Union also developed prototypes of a lunar lander that would have been used by cosmonauts. However, the landers were apparently never flown.
Soviet officials would later deny that they ever planned to send humans to the Moon. Instead, they focused on a series of lunar rovers and sample return missions that they flew during the first half of the 1970's. It was not until the late 1980's that discussion about the lunar missions was allowed.
Although the lunar program was unsuccessful, the Zond program provided useful operating experience for other lunar missions. The Zonds also helped Soviet engineers to perfect operations for the similar Soyuz spacecraft. The Soyuz, first flown in 1967, is still in operation today as a human transport to the space station Mir.
During the same period they were undertaking the Zond missions, Soviet engineers were working on an advanced series of landers. These sophisticated spacecraft were designed to return soil samples to Earth and to deploy Lunokhod rovers that would explore the surface.
In 1969 and 1970, the Soviets attempted six flights in this series under the designation Luna or Cosmos. All six efforts failed due to mechanical problems. Luna 15 crashed onto the moon in July 1969, just days after the Apollo 11 landing. The exact mission is unknown, but experts believe it was either a rover mission or a sample return vehicle intended to return to Earth before the Apollo 11 crew.
Luna 16, launched on September 12, 1970, was the first successful automated sample-return mission. After landing on the Sea of Fertility, the spacecraft deployed a drill that bore 35 centimeters (1 foot) into the surface. The soil sample, which weighed 100 grams (.22 pounds), was transferred to a return vehicle that landed in the Soviet Union on September 24.
Luna 17 saw the introduction of the first rover mission. The spacecraft, launched on November 10, 1970, touched down on the Sea of Rains and deployed the sophisticated Lunokhod 1 rover. This eight-wheel vehicle was controlled by radio from the ground and included two cameras and various other sampling instruments.
Lunokhod 1 covered 10.5 kilometers (6.5 miles) during a mission that lasted 10.5 months. The rover's cameras transmitted more than 20,000 photographs, including 200 panoramic shots. Instruments on the vehicle analyzed the physical and mechanical properties of the soil at more than 500 locations. Other instruments analyzed the chemical composition of the soil at 25 sites. Lunokhod 1 also housed a retro-reflector mirror that allowed scientists on Earth to conduct laser experiments that determined the distance between the Earth and Moon to an accuracy of 40 centimeters (15 inches).
This flight was followed on September 2, 1971, by Luna 18, a soil sample-return mission that crashed on the surface. Luna 19, launched 26 days later, successfully orbited the Moon but was not designed to land.
Luna 20, launched on February 14, 1972, was a successful sample-return mission. The vehicle landed in a mountainous region between the Sea of Fertility and the Sea of Crises. The return capsule successfully landed on Earth with 50 grams (.11 pounds) of lunar soil.
Luna 21, launched in January 1973, carried the Lunokhod 2 rover to the Le Monnier crater in the Sea of Serenity. The 840-kilogram (1,852-pound) rover traveled 37 kilometers (23 miles) during a four-month lifetime. The rover took many photographs and conducted experiments during its mission.
The following three Luna spacecraft were designed as soil return. Luna 23 was damaged during a landing after it was launched in October 1974. Another Luna mission, launched almost a year later, failed to achieve orbit.
The last lunar mission was Luna 24, which was launched on August 9, 1976. The spacecraft landed in the southeast region of the Sea of Crises and drilled to a depth of 2 meters (6.5 feet). The spacecraft returned 170 grams (.37 pounds) of soil for analysis.
The Soviet Union never returned to the moon after 1976. During the 1980's, the country focused its attention on launching spacecraft to Venus and Mars. When the USSR dissolved in 1991, Russia inherited most of its space program. The nation has experienced economy problems, and its future plans for lunar exploration are uncertain.
Collins, Michael, Liftoff: The Story of America's Adventure in Space, Grove Press, New York, 1988.
Clark, Phillip, The Soviet Manned Space Program, Salamander Books, New York, 1988.
Gatland, Kenneth, consultant and chief author, The Illustrated Encyclopedia of Space Technology, Harmony Books, New York, 1981.
Planetary Science Database, National Space Science Data Center, National Aeronautics and Space Administration, Greenbelt, Maryland. World Wide Web: http://nssdc.gsfc.nasa.gov/nssdc/nssdc_home.html.