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Lunar Module was the lander of the Apollo spacecraft which descended to the moon's surface.

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The Apollo Lunar Module was the lander portion of the Apollo spacecraft. The Lunar module was built for the US Apollo program to achieve the transit from Moon orbit to the surface and back. The Lunar module was also known as the LM from the manufacturer designation (yet pronounced "LEM" from NASA's early name for it, Lunar Excursion Module).

Lunar Module.
Lunar Module.
Apollo Lunar Module on lunar surface.
Lunar Module Description.
Role: Lunar landing
Crew: 2; CDR, LM pilot
Height: 20.9 ft 6.37 m
Diameter: 14 ft 4.27 m
Landing gear span: 29.75 ft 9.07 m
Volume: 235 ft3 6.65 m│
Ascent module: 10,024 lb 4,547 kg
Descent module: 22,375 lb 10,149 kg
Total: 32,399 lb 14,696 kg
Rocket engines
LM RCS (N2O4/UDMH) x 16: 100 lbf ea 441 N
Ascent Propulsion System
(N2O4/Aerozine 50) x 1:
3,500 lbf ea 15.6 kN
Descent Propulsion System
(N2O4/Aerozine 50) x 1:
9,982 lbf ea 44.40 kN
Endurance: 3 days 72 hours
Aposelene: 100 miles 160 km
Periselene: surface surface
Spacecraft delta v: 15,390 ft/s 4,690 m/s
Apollo Lunar Module diagram.
Lunar Module diagram.
Apollo Lunar Module diagram (NASA).
Grumman Apollo Lunar Module.
Lunar Module.
The Lunar Module flight instrumentation panel and front windows. Credit: Alexandre Sabbatini.

The 6.65 m3 Lunar Module was designed to carry a crew of two. The total Lunar Module was 6.4 m high and 4.3 m across, resting on four legs. The Lunar Module consisted of two stages - the descent stage module and the ascent stage. The total mass of the Lunar Module was 15,264 kg with the majority of that (10,334 kg) in the descent stage.

History of the Lunar Module.

The Apollo Lunar Module came into being because NASA chose to reach the moon via a lunar orbit rendezvous (LOR) instead of a direct ascent or Earth orbit rendezvous (EOR). Both a direct ascent and an EOR would have involved the entire Apollo spacecraft landing on the moon; once the decision had been made to proceed using LOR, it became necessary to produce a separate craft capable of reaching the lunar surface.

The LM contract was given to Grumman Aircraft Engineering and a number of subcontractors. Grumman had begun lunar orbit rendezvous studies in late 1950s and again in 1962. In July 1962 eleven firms were invited to submit proposals for the LM. Nine did so in September, and Grumman was awarded the contract that same month. The contract cost was expected to be around $350 million. There were initially four major subcontractors - Bell Aerosystems (ascent engine), Hamilton Standard (environmental control systems), Marquardt (reaction control system) and Rocketdyne (descent engine).

The primary guidance, navigation and control system (PGNCS) on the LM was developed by the MIT Instrumentation Laboratory. The Apollo Guidance Computer was manufactured by Raytheon. A similar guidance system was used in the command module. A backup navigation tool, the Abort Guidance System (AGS), was developed by TRW.

To learn lunar landing techniques, astronauts practiced in the Lunar Landing Research Vehicle (LLRV), a flying vehicle that simulated the Lunar Module on earth. A 200-foot-tall, 400-foot-long gantry structure was constructed at NASA Langley Research Center; the LLRV was suspended in this structure from a crane, and "piloted" by moving the crane. (The facility is now known as the Impact Dynamics Research Facility, and is used for aircraft crash tests.)

Early configurations of the LEM included a forward docking port, initially it was believed the LEM crew would be active in the docking with the CSM. Early designs included large curved windows. Configuration freeze did not start until April 1963 when the ascent and descent engine design was decided. In addition to Rocketdyne a parallel program for the descent engine was ordered from Space Technology Laboratories in July 1963, and by January 1965 the Rocketdyne contract was cancelled. As the program continued there were numerous redesigns to save weight (including "Operation Scrape"), improve safety, and fix problems. For example initially the module was to be powered by fuel cells, built by Pratt and Whitney but in March 1965 they were paid off in favor of an all battery design.

The initial design iteration had the LEM with three landing legs. It was felt that three legs, though the lightest configuration, was the least stable if one of the legs were damaged during landing. The next landing gear design iteration had five legs and was the most stable configuration for landing on an unknown terrain. That configuration was too heavy and the compromise was four landing legs.

The first LM flight was on January 22, 1968 when the unmanned LM-1 was launched on a Saturn IB for testing of propulsion systems in orbit. The next LM flight was aboard Apollo 9 using LM-3 on March 3, 1969 as a manned flight (McDivitt, Scott and Schweickart) to test a number of systems in Earth orbit including LM and CSM crew transit, LM propulsion, separation and docking. Apollo 10, launched on May 18, 1969, was another series of tests, this time in lunar orbit with the LM separating and descending to within 10 km of the surface. From the successful tests the LM successfully descended and ascended from the lunar surface with Apollo 11.

In April 1970, the lunar module Aquarius played an unexpected role in saving the lives of the three astronauts of the Apollo 13 mission (Commander James A. Lovell Jr., CSM pilot John L. Swigert Jr., and LM pilot Fred W. Haise Jr.), after an electrical short circuit caused an oxygen tank in that mission's service module to explode. Aquarius served as a refuge for the astronauts during their return to Earth, while its batteries were used to recharge the vital re-entry batteries of the command module that brought the astronauts through the Earth's atmosphere and to a safe splashdown on April 17, 1970. The LM's descent engine, designed to slow the vehicle during its descent to the moon, was used to accelerate the Apollo 13 spacecraft around the moon and back to Earth. After the accident, the Lunar Module's systems, designed to support two astronauts for 45 hours, actually supported three astronauts for 90 hours.

Lunar Module specifications.

The Lunar Module was the portion of the Apollo spacecraft that landed on the moon and returned to lunar orbit. The Lunar Module is divided into two major parts, the Descent Module and the Ascent Module.

The Descent Module contains the landing gear, landing radar antenna, descent rocket engine, and fuel to land on the moon. The Lunar Module also had several cargo compartments used to carry among other things, the Apollo Lunar Surface Experiment Packages ALSEP, Mobile Equipment Cart (a hand-pulled equipment cart used on Apollo 14), the Lunar rover (moon car) used on Apollo 15, 16 and 17), surface television camera, surface tools and lunar sample collection boxes. It also carried the majority of the Lunar Module's battery power and oxygen, along with the single water tank needed to both cool the electronics and provide the astronauts with enough drinking water for a two-to-three-day stay. Also, on the ladder of the descent stage is attached a plaque.

The Ascent Module contains the crew cabin, instrument panels, overhead hatch/docking port, forward hatch, reaction control system, radar and communications antennas, ascent rocket engine and enough fuel, battery power, and breathing oxygen to return to lunar orbit and rendezvous with the Apollo Command and Service Modules.

  • Specifications: (Baseline LM) of the Lunar Module.
    • Ascent Stage of the Lunar Module.
      • Crew: 2.
      • Crew cabin volume: 6.65 m3 (235 ft3).
      • Height: 3.76 m (12.34 ft).
      • Diameter: 4.2 m (13.78 ft).
      • Mass including fuel: 4,670 kg (10,300 lb).
      • Atmosphere: 100% oxygen at 33 kPa (4.8 lb/in2).
      • Water: two 19.3 kg (42.5 lb) storage tanks.
      • Coolant: 11.3 kg (25 lb) of ethylene glycol/water solution.
      • RCS (Reaction Control System) Propellant mass: 287 kg (633 lb).
      • RCS thrusters: 16 x 445 N; four quads.
      • RCS propellants: N2O4/UDMH.
      • RCS specific impulse: 2.84 kNĚs/kg.
      • APS Propellant mass: 2,353 kg (5,187 lb).
      • APS thrust: 15.6 kN (3,500 lbf).
      • APS propellants: N2O4/Aerozine 50 (UDMH/N2H4).
      • APS pressurant: 2 x 2.9 kg helium tanks at 21 MPa.
      • Engine specific impulse: 3.05 kNĚs/kg.
      • Thrust-to-weight ratio: 0.34 (in Earth gravity - The thrust was less than the weight on Earth, but enough on the Moon).
      • Ascent stage delta V: 2,220 m/s (7,280 ft/s).
      • Batteries: 2 x 296 Ah silver-zinc batteries.
      • Power: 28 V DC, 115 V 400 Hz AC.
    • Descent Stage of the Lunar Module.
      • Height: 3.2 m (10.5 ft).
      • Diameter: 4.2 m (13.8 ft).
      • Landing gear diameter: 9.4 m (30.8 ft).
      • Mass including fuel: 10,334 kg (22,783 lb).
      • Water: 1 x 151 kg storage tank.
      • Power: 2 x 296 Ah silver-zinc batteries (secondary system).
      • Propellants mass: 8,165 kg (18,000 lb).
      • DPS thrust: 45.04 kN (10,125 lbf), throttleable to 4.56 kN (1025 lbf).
      • DPS propellants: N2O4/Aerozine 50 (UDMH/N2H4).
      • DPS pressurant: 1 x 22 kg supercritical helium tank at 10.72 kPa.
      • Engine specific impulse: 3050 NĚs/kg.
      • Descent stage delta V: 2,470 m/s (8,100 ft/s).
      • Batteries: 4 x 400 AĚh silver-zinc batteries.

Lunar Modules produced.

Serial numberUseLaunch dateCurrent location
LM-1 Apollo 5 January 22, 1968 Reentered Earth's atmosphere
Not flown
On display at the National Air and Space Museum, Washington, DC. (Photo).
LM-3 Spider Apollo 9 March 3, 1969 Reentered Earth's atmosphere
LM-4 Snoopy Apollo 10 May 18, 1969 Descent stage impacted Moon; Ascent stage in solar orbit
LM-5 Eagle Apollo 11 July 16, 1969 Descent stage on lunar surface; Ascent stage left in lunar orbit, eventually crashed on moon
LM-6 Intrepid Apollo 12 November 14, 1969 Descent stage on lunar surface; Ascent stage deliberately crashed into moon
LM-7 Aquarius Apollo 13 April 11, 1970 Reentered Earth's atmosphere over Fiji
LM-8 Antares Apollo 14 January 31, 1971 Descent stage on lunar surface; Ascent stage deliberately crashed into moon
Not flown
On display at the Kennedy Space Center (Apollo/Saturn V Center)
LM-10 Falcon Apollo 15 26 July, 1971 Descent stage on lunar surface; Ascent stage deliberately crashed into moon
LM-11 Orion Apollo 16 April 16, 1972 Descent stage on lunar surface; Ascent stage deliberately crashed into moon
LM-12 Challenger Apollo 17 December 7, 1972 Descent stage on lunar surface; Ascent stage deliberately crashed into moon
Not flown (meant for later Apollo flights)
Partially completed by Grumman; restored and on display at Cradle of Aviation Museum, Long Island, New York. Also used during HBO's 1998 mini-series From the Earth to the Moon.
Not flown (meant for later Apollo flights)
Never completed; unconfirmed reports claim that some parts (in addition to parts from test vehicle LTA-3) are included in LM on display at the Franklin Institute, Philadelphia (see: http://www.fi.edu/qa00/attic5/" Franklin Institute web page.)
Not flown (meant for later Apollo flights)
* For the location of LMs left on the Lunar surface, see the list of artificial objects on the Moon.

Lunar Module truck.

Apollo Lunar Module Diagram.
Apollo Spacecraft: Apollo Lunar Module Diagram.
Apollo Lunar Module.
Apollo Lunar Module.
Lunar Module Space Museum.
A Lunar Module in the National Air and Space Museum.

The Apollo LM Truck was a stand-alone LM descent stage intended to deliver up to five metric tons of payload to the Moon for an unmanned landing. This technique was intended to deliver equipment and supplies to a permanent manned lunar base that was never built. As originally proposed, it would be launched on a Saturn V with a full Apollo crew to accompany it to lunar orbit and then guide it to a landing next to the base; the base crew would then unload the "truck" while the orbiting crew returned to earth.

Lunar Module in fiction.

The Lunar Module and LM Truck, using a modified mission profile, appear in Shane Johnson's novel Ice, about a fictional Apollo 19 mission that takes a disastrous turn. In this scenario, the LM Truck is delivered on a Saturn IB and makes a preprogrammed landing at the proposed landing site; a J-mission Apollo crew then lands a conventional LM next to it, in a feat of precision landing recalling that of Pete Conrad during Apollo 12. Also in this novel, the LM, which happens to be LM-13, fails to fire its ascent engine, stranding two astronauts on the Moon - something that never happened in Project Apollo.

In the movie Superman II, the film's supervillains visit the moon on their way to earth, and encounter a modernized version of the LM (still bearing an obvious resemblance), which they destroy along with its crew of three (two Americans, one Soviet).

Successors to the Lunar Module.

The Lunar Module design was later incorporated into the Apollo Telescope Mount on the successful Skylab space station. Originally planned to be launched on an unmanned Saturn 1B rocket, similar to the unmanned Apollo 5 test flight, NASA decided to save costs and launch the ATM with the station itself. This decision saved the station, as the ATM's "windmill" solar panels helped keep the station operational after damage to the station's solar panels during launch. One of the station's solar panels was damaged during launch, and the other was ripped off.

In 2005, NASA announced that the successor to the Space Shuttle, the Orion spacecraft (itself based on the Apollo CSM), would feature, for its lunar landing missions, a Lunar Surface Access Module (LSAM) which is roughly based on the Apollo LM. Like the LM, it has both descent and ascent modules (the latter to house the crew), but unlike the LM, it will incorporate improved computer systems, laser-range and radar tracking systems for landing, waste-management systems, and an airlock for the crew, eliminating the need to depressurize the entire cockpit and allowing the astronauts to track as little lunar dust into the cabin as possible (a problem highly associated with the last three Apollo missions, when crews went into the lunar highlands).

The LSAM will be powered by four RL-10 engines descent stage and a single RL-10 engine in the ascent stage, both of which are fueled by liquid hydrogen (LH2) and liquid oxygen (LOX), which are more powerful than the hypergolic fuels used on the LM (as well as being safer, as LH2 and LOX produces water, while hypergolics are very toxic). This will allow the LSAM to land anywhere on the Moon, although NASA has targeted the polar regions of the Moon (Apollo was limited to the equatorial regions), which is a desired location for a future lunar base.

In addition, the LSAM can be flown by an astronaut crew, or even unmanned (similar in nature to the unmanned aerial drones used by the U.S. Air Force), the latter to bring supplies to the future lunar outpost(s), thus the LSAM would function as the proposed, yet unflown "LM Truck" that was envisioned in the Apollo Applications Program. In the unmanned configuration, the LSAM can carry as much weight as the LM would weight itself fully fueled.

The only major difference between the LSAM and the LM is that the LSAM will be launched separately on the Shuttle-derived Ares V rocket, with the CEV being launched separately on the man-rated Ares I rocket. Once in orbit, the Orion CSM will then dock with the LSAM and then be propelled to the Moon on the Earth Departure Stage. The LM, on the other hand, was launched along with the CSM on the Saturn V rocket and then was retrieved after the S-IVB finished firing the translunar injection burn.

As an additional note, the LM was given a call sign to identify it separately from the CSM - all LSAMs will possibly bear the name "Artemis," the Greek name for the Moon goddess, as the "Orion" name has already been chosen for the orbiter. Unlike the CSM and LM, the CEV/LSAM combination will bear a dual identity number, much like the Spacelab missions associated with the Space Shuttle (i.e. STS-9/Spacelab 1) or the Salyut space stations orbited by the former Soviet Union in the 1970s and 1980's (i.e. Soyuz 11/Salyut 1).

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