Twenty-four spacecraft were formally given the Luna designation, although more were launched. Those that failed to reach orbit were not publicly acknowledged at the time, and not assigned a Luna number. Those that failed in low Earth orbit were usually given Cosmos designations.[2] The estimated cost of the Luna programme in 1964 was US$6–10 billion[3] (equivalent to US$45–75 billion in 2023[4]). The Luna 25 mission also continues the Luna designation, although it is considered to be a part of the Luna-Glob exploration programme.[5] The same applies to other planned missions such as Luna 26, Luna 27 and Luna 28.
Mission types
The name Luna was used to designate a variety of spacecraft designs, to achieve several types of missions:
Impactor spacecraft had the generic designation of Ye-1 (or E-1 depending on transliteration from Russian) and were designed to hit the near side of the Moon.[6][7]Luna 1 (January 1959) missed its intended impact with the Moon and became the first spacecraft to escape the Earth-Moon system.[8]Luna 2 (September 1959) mission successfully hit the Moon's surface, becoming the first man-made object to reach the Moon.[9] This was Luna's only impact success out of six tries from September 1958 to September 1959.
Flybys
A flyby is the simplest lunar spacecraft, requiring neither a propulsion device for slowing, nor a guidance system sensitive enough to hit the Moon. Flyby spacecraft had the generic designations of Ye-2 and Ye-3 (E-2 and E-3 depending on transliteration from Russian).[10][11] Their function was to transmit photographs back to Earth. Luna 3 (October 1959) rounded the Moon later that year, and returned the first photographs of its far side, which can never be seen from Earth.[9] This was Luna's only successful flyby, out of three tries from October 1959 to April 1960.
Soft landers require rocket propulsion to slow their speed sufficiently to prevent the craft's destruction. They can continue to transmit pictures from the surface, and possibly dig into the lunar soil or return other information about the lunar environment.
Luna program landers had the generic designations of Ye-6 or Ye-6M (E-6 or E-6M depending on transliteration from Russian).[12][13] Two successful soft landings were achieved out of thirteen attempts from January 1963 to December 1966.[12][13]
Luna 9 (E-6 No.13) became the first probe to achieve a soft landing on another planetary body in February 1966. It transmitted five black and white stereoscopic circular panoramas, which were the first close-up shots of the lunar surface.[8]
Orbiters
Orbiter spacecraft require less thrust and propellant than landers, but still require enough to achieve lunar orbit insertion. Luna 10 (March 1966) became the first artificial satellite of the Moon.[9] Luna program orbiters had the generic designations of Ye-6LF, Ye-6LS, Ye-6S or Ye-8LS (E-6, E-6LS, E-6S or E-8LS depending on transliteration from Russian).[14][15][16][17] Luna flew six successful orbiters out of eight attempts from March 1966 to May 1974.[14][15][16][17]
More sophisticated soft lander craft can deploy wheeled vehicles to explore a wider area of the lunar surface than the immediate landing site. Luna program landers with rovers had the generic designations of Ye-8 (E-8 depending on transliteration from Russian).[18]
The first attempted Lunokhod failed in February 1969. Luna 17 (November 1970) and Luna 21 (January 1973) carried Lunokhod vehicles, which were the first robotic wheeled vehicles to explore the Moon's terrain.[9]Lunokhod 1 travelled 10.5 kilometres (6.5 mi) in 322 days and returned more than 20,000 television images and 206 high-resolution panoramas.[19]Lunokhod 2 operated for about four months, and covered 42 kilometres (26 mi) of terrain,[20] A third Lunokhod was built and intended for launch in 1977, but never flew due to lack of launchers and funding.[21]
More complex soft lander craft can robotically scoop up a small amount of lunar material, lift off from the surface, and return the material to Earth. Luna program sample return landers had the generic designations of Ye-8-5 or Ye-8-5M (E-8-5 or E-8-5M depending on transliteration from Russian).[22][23]
Luna 16 (September 1970), Luna 20 (February 1972) and Luna 24 (August 1976), returned samples of lunar soil to Earth.[9][22][23] A total of 301 g (10.6 oz) of soil sample was returned from the three missions.
Luna 15 (July 1969) flew at the same time as the Apollo 11 mission. Neil Armstrong and Buzz Aldrin had already performed the first crewed lunar landing when Luna 15 began its descent, and the spacecraft crashed into a mountain minutes later.
Mission success rates
While the programme was active, it was Soviet practice not to release any details of missions that had failed to achieve orbit. This resulted in Western observers assigning their own designations to the missions. For example, Luna E-1 No.1, the first failure of 1958 which NASA believed was associated with the Luna programme, was known as Luna 1958A.[24]
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