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Luna 18

NSSDCA/COSPAR ID: 1971-073A

Description

Luna 18 was a planned lunar sample return mission, a follow-up of the successful Luna 16 mission. It launched on 2 September 1971 and went into lunar orbit 5 days later. Problems with maintaining the orientation of the spacecraft during the descent led to Luna 18 crashing into the Moon on September 11 near Mare Fecunditatis.

Spacecraft and Subsystems

Luna 18 was based on the Ye-8-5 spacecraft body, consisting of two attached stages, an ascent stage mounted on top of a descent stage. The lander stood 3.96 meters tall and had an unfueled landed mass of 1880 kg. With a full load of fuel its launch mass was between 5600 and 5750 kg.

The descent stage was the same as the Ye-8 lower stage for the Lunokhod rovers, a cylindrical body with four protruding landing legs, fuel tanks, a landing radar altimeter, and a dual descent engine complex. The main descent rocket, the KTDU-417, was a throttleable 1920 kg thrust engine used for mid-course corrections, orbit insertion, braking for descent to the surface, and to slow the craft until it reached a cutoff point which was determined by the onboard computer based on altitude and velocity. After cutoff a bank of lower thrust (210 and 350 kg) vernier jets was used for the final landing. The descent stage also acted as a launch pad for the ascent stage. The spacecraft descent stage was equipped with a television camera, radiation and temperature monitors, telecommunications equipment, and a 90 cm extendable arm with a drilling rig for the collection of a lunar soil sample. Communications were via a conical antenna at the end of a boom at 768 and 922 MHz (downlink) and 115 MHz (uplink).

The ascent stage was a smaller cylinder with a spherical top which replaced the Lunokhod rover and housing from the Ye-8 bus. It carried a cylindrical hermetically sealed soil sample container inside a spherical re-entry capsule, mounted on a 1920 kg thrust KRD-61 rocket. Total mass of the ascent stage was 520 kg, of which 245 kg was the nitric acid and UDMH propellant. It was 2 meters tall. The sample return cabin was 50 cm in diameter and had a mass of 39 kg. The KRD-61 could only fire once, for 53 seconds, to put it on a free return trajectory to Earth. Specific impulse of the engine was 313 seconds, it could impart a velocity of 2600 - 2700 m/s to the return craft.

Mission Profile

Luna 18 launched on 2 September 1971 at 13:40:40 UT from the Baikonur Cosmodrome on a Proton booster and Blok D upper stage. Luna 18 was placed in an Earth parking orbit after launch and was then sent towards the Moon. Mid-course corrections were made on 4 and 6 September. On September 7, 1971, it fired its retrorocket and entered lunar orbit, but the firing sequence stopped 15 seconds early. This put Luna 18 into an incorrect 100 km altitude circular orbit with an inclination of 35 degrees. An attempt to put the spacecraft into the nominal 16.9 x 123.9 km orbit failed due to a problem with one of the attitude control engines, putting it into a 93.4 x 180.3 km orbit. The spacecraft completed 85 communications sessions and 54 lunar orbits before it was sent towards the lunar surface by use of the braking rockets on September 11. The attitude control engine again failed, and the spacecraft could not maintain the correct orientation. Signals ceased at 07:47:16.5 UT, assumed to be the moment of impact, although possibly 100 meters or so above the surface. Point of impact was estimated at roughly 3 degrees 34 minutes (3.57) N, 56 degrees 30 minutes (56.50) E (selenographic coordinates) in a rugged mountainous terrain near the edge of Mare Fecunditatis (Sea of Fertility). A Lunar Reconnaissance Orbiter image shows a crater which may be the Luna 18 impact site at 3.76 N, 56.66 E, but this is unconfirmed as of February 2020.

Alternate Names

  • Lunik 18
  • 05448
  • Automatic Station Luna
  • Luna18

Facts in Brief

Launch Date: 1971-09-02
Launch Vehicle: Proton Booster Plus Upper Stage and Escape Stages
Launch Site: Tyuratam (Baikonur Cosmodrome), U.S.S.R
Mass: 5600 kg

Funding Agency

  • Unknown (U.S.S.R)

Disciplines

  • Planetary Science
  • Space Physics

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Mr. Artem IvankovGeneral ContactLavochkin Associationartem.ivankov@laspace.ru

Selected References

  • Harvey, B., The new Russian space programme from competition to collaboration, John Wiley & Sons, Chichester, England, 1996.
  • Johnson, N. L., Handbook of soviet lunar and planetary exploration - volume 47 science and technology series, Amer. Astronau. Soc. Publ., 1979.
  • Soviet space programs, 1971-75 - volume 1, Unpublished, Unnumbered, 1976.
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