The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...

that was flown between

lunar orbit In astronomy, lunar orbit (also known as a selenocentric orbit) is the orbit of an object around the Moon. As used in the space program, this refers not to the orbit of the Moon about the Earth, but to orbits by spacecraft around the Moon. The ...

and the Moon's surface during the United States' Apollo program. It was the first crewed spacecraft to operate exclusively in the airless vacuum of space, and remains the only crewed vehicle to land anywhere beyond Earth. Structurally and aerodynamically incapable of flight through Earth's atmosphere, the two-stage lunar module was ferried to lunar orbit attached to the

Apollo command and service module The Apollo command and service module (CSM) was one of two principal components of the United States Apollo spacecraft, used for the Apollo program, which landed astronauts on the Moon between 1969 and 1972. The CSM functioned as a mother ship ...

(CSM), about twice its mass. Its crew of two flew the complete lunar module from lunar orbit to the Moon's surface. During takeoff, the spent descent stage was used as a launch pad for the ascent stage which then flew back to the command module, after which it was also discarded. Overseen by

Grumman The Grumman Aircraft Engineering Corporation, later Grumman Aerospace Corporation, was a 20th century American producer of military and civilian aircraft. Founded on December 6, 1929, by Leroy Grumman and his business partners, it merged in 1994 ...

, the LM's development was plagued with problems that delayed its first uncrewed flight by about ten months and its first crewed flight by about three months. Still, the LM became the most reliable component of the Apollo–Saturn

space vehicle A space vehicle is the combination of a spacecraft and its launch vehicle which carries it into space. The earliest space vehicles were expendable launch systems, using a single or multistage rocket to carry a relatively small spacecraft in p ...

. The total cost of the LM for development and the units produced was $21.3 billion in 2016 dollars, adjusting from a nominal total of $2.2 billion using the NASA New Start Inflation Indices. Ten lunar modules were launched into space. Of these, six were landed by humans on the Moon from 1969 to 1972. The first two flown were tests in

low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...

Apollo 5 Apollo 5 (launched January 22, 1968), also known as AS-204, was the uncrewed first flight of the Apollo Lunar Module (LM) that would later carry astronauts to the surface of the Moon. The Saturn IB rocket bearing the LM lifted off from C ...

, without a crew; and

Apollo 9 Apollo 9 (March 313, 1969) was the third human spaceflight in NASA's Apollo program. Flown in low Earth orbit, it was the second crewed Apollo mission that the United States launched via a Saturn V rocket, and was the first flight of the ful ...

with a crew. A third test flight in low lunar orbit was

Apollo 10 Apollo 10 (May 18–26, 1969) was a human spaceflight, the fourth crewed mission in the United States Apollo program, and the second (after Apollo8) to orbit the Moon. NASA described it as a "dress rehearsal" for the first Moon landing, and ...

, a dress rehearsal for the first landing, conducted on

Apollo 11 Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon. Commander Neil Armstrong and lunar module pilot Buzz Aldrin landed the Apollo Lunar Module ''Eagle'' on July 20, 1969, at 20:17 UTC, an ...

. The

Apollo 13 Apollo 13 (April 1117, 1970) was the seventh crewed mission in the Apollo space program and the third meant to land on the Moon. The craft was launched from Kennedy Space Center on April 11, 1970, but the lunar landing was aborted aft ...

lunar module functioned as a lifeboat to provide life support and propulsion to keep the crew alive for the trip home, when their CSM was disabled by an oxygen tank explosion en route to the Moon. The six landed descent stages remain at their landing sites; their corresponding ascent stages crashed into the Moon following use. One ascent stage (Apollo 10's ''Snoopy'') was discarded in a

heliocentric orbit A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun i ...

after its descent stage was discarded in lunar orbit. The other three LMs were burned up in the Earth's atmosphere: the four stages of

and

each re-entered separately, while Apollo 13's ''Aquarius'' re-entered as a unit.

Operational profile

At launch, the lunar module sat directly beneath the

command and service module The Apollo command and service module (CSM) was one of two principal components of the United States Apollo spacecraft, used for the Apollo program, which landed astronauts on the Moon between 1969 and 1972. The CSM functioned as a mother sh ...

(CSM) with legs folded, inside the Spacecraft-to-LM adapter (SLA) attached to the

S-IVB The S-IVB (pronounced "S-four-B") was the third stage on the Saturn V and second stage on the Saturn IB launch vehicles. Built by the Douglas Aircraft Company, it had one J-2 (rocket engine), J-2 rocket engine. For lunar missions it was fired twi ...

third stage of the

Saturn V Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with multistage rocket, three stages, and powered with liquid-propellant r ...

rocket. There it remained through Earth parking orbit and the

trans-lunar injection A trans-lunar injection (TLI) is a propulsive maneuver used to set a spacecraft on a trajectory that will cause it to arrive at the Moon. History The first space probe to attempt TLI was the Soviet Union's Luna 1 on January 2, 1959 which wa ...

(TLI) rocket burn to send the craft toward the Moon. Soon after TLI, the SLA opened; the CSM performed a maneuver whereby it separated, turned around, came back to dock with the lunar module, and extracted it from the S-IVB. During the flight to the Moon, the docking hatches were opened and the lunar module pilot entered the LM to power up temporarily and test all systems except propulsion. The lunar module pilot performed the role of an engineering officer, monitoring the systems of both spacecraft. After achieving a lunar parking orbit, the commander and LM pilot entered and powered up the LM, replaced the hatches and docking equipment, unfolded and locked its landing legs, and separated from the CSM, flying independently. The commander operated the flight controls and engine throttle, while the lunar module pilot operated other spacecraft systems and kept the commander informed about systems status and navigational information. After the command module pilot visually inspected the

landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for takeoff or landing. For aircraft it is generally needed for both. It was also formerly called ''alighting gear'' by some manufacturers, such as the Glenn L. Martin ...

, the LM was withdrawn to a safe distance, then rotated until the descent engine was pointed forward into the direction of travel. A 30-second descent orbit insertion burn was performed to reduce speed and drop the LM's

perilune An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

to within about of the surface, about uprange of the landing site. Earth, Moon and Lunar Module, AS11-44-6643

As the craft approached perilune, the descent engine was started again to begin powered descent. During this time, the crew flew on their backs, depending on the computer to slow the craft's forward and vertical velocity to near zero. Control was exercised with a combination of engine throttling and attitude thrusters, guided by the computer with the aid of landing radar. During braking, the LM descended to about , then, in the final approach phase, down to about . During final approach, the vehicle pitched over to a near-vertical position, allowing the crew to look forward and down to see the lunar surface for the first time. Astronauts flew Apollo spacecraft manually only during the lunar approach. The final landing phase began about uprange of the targeted landing site. At this point, manual control was enabled for the commander, who had enough

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...

to hover for up to two minutes to survey where the computer was taking the craft and make any necessary corrections. If necessary, landing could have been aborted at almost any time by jettisoning the descent stage and firing the ascent engine to climb back into orbit for an emergency return to the CSM. Finally, one or more of three probes extending from footpads on the legs of the lander touched the surface, activating the contact indicator light which signaled the commander to shut off the descent engine, allowing the LM to settle onto the surface. On touchdown, the probes would be bent as much as 180 degrees, or even break off. The original design used the probes on all four legs, but starting with the first landing (LM-5 on Apollo 11), the one at the ladder was removed out of concern that the bent probe after landing might puncture an astronaut's suit as he descended or stepped off the ladder. The original

extravehicular activity Extravehicular activity (EVA) is any activity done by an astronaut in outer space outside a spacecraft. In the absence of a breathable Earthlike atmosphere, the astronaut is completely reliant on a space suit for environmental support. EVA in ...

plan, up through at least 1966, was for only one astronaut to leave the LM while the other remained inside "to maintain communications". Communications were eventually deemed to be reliable enough to allow both crew members to walk on the surface, leaving the spacecraft to be only remotely attended by Mission Control. Beginning with

Apollo 14 Apollo 14 (January 31, 1971February 9, 1971) was the eighth crewed mission in the United States Apollo program, the third to land on the Moon, and the first to land in the lunar highlands. It was the last of the " H missions", landings at s ...

, extra LM propellant was made available for the powered descent and landing, by using the CSM engine to achieve the perilune. After the spacecraft undocked, the CSM raised and circularized its orbit for the remainder of the mission. When ready to leave the Moon, the LM's ascent engine fired, leaving the descent stage on the Moon's surface. After a few course correction burns, the LM rendezvoused with the CSM and docked to transfer the crew and rock samples. Having completed its job, the ascent stage was separated. The Apollo 10 ascent stage engine was fired until its fuel was used up, sending it past the Moon into a

. The

ascent stage was left in lunar orbit to eventually crash; all subsequent ascent stages (except for Apollo 13) were intentionally steered into the Moon to obtain readings from seismometers placed on the surface.

History

The Lunar Module (originally designated the Lunar Excursion Module, known by the

acronym An acronym is a word or name formed from the initial components of a longer name or phrase. Acronyms are usually formed from the initial letters of words, as in ''NATO'' (''North Atlantic Treaty Organization''), but sometimes use syllables, as ...

LEM) was designed after NASA chose to reach the Moon via

Lunar Orbit Rendezvous Lunar orbit rendezvous (LOR) is a process for landing humans on the Moon and returning them to Earth. It was utilized for the Apollo program missions in the 1960s and 1970s. In a LOR mission, a main spacecraft and a smaller lunar lander travel to ...

(LOR) instead of the

direct ascent Direct ascent is a method of landing a spacecraft on the Moon or another planetary surface directly, without first assembling the vehicle in Earth orbit, or carrying a separate landing vehicle into orbit around the target body. It was proposed as ...

or Earth Orbit Rendezvous (EOR) methods. Both direct ascent and EOR would have involved landing a much heavier, complete Apollo spacecraft 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 and ascending back to lunar orbit.

Contract letting

In July 1962, eleven firms were invited to submit proposals for the LEM. Nine companies responded in September, answering 20 questions posed by the NASA RFP in a 60-page limited technical proposal.

was awarded the contract officially on November 7, 1962. Grumman had begun lunar orbit rendezvous studies in the late 1950s and again in 1961. The contract cost was expected to be around $350 million. There were initially four major subcontractors: Bell Aerosystems ( ascent engine),

Hamilton Standard Hamilton Standard was an American aircraft propeller parts supplier. It was formed in 1929 when United Aircraft and Transport Corporation consolidated Hamilton Aero Manufacturing and Standard Steel Propeller into the Hamilton Standard Propeller C ...

(environmental control systems),

Marquardt Marquardt is a surname of German origin. Notable people with the surname include: * August F. Marquardt (1850–1925), American politician *Bridget Marquardt (born 1973), American television personality, glamour model, and actress *Christel Marquard ...

(reaction control system) and

Rocketdyne Rocketdyne was an American rocket engine design and production company headquartered in Canoga Park, California, Canoga Park, in the western San Fernando Valley of suburban Los Angeles, California, Los Angeles, in southern California. The Rocke ...

( descent engine). The Primary Guidance, Navigation and Control System (PGNCS) was developed by the

MIT Instrumentation Laboratory Draper Laboratory is an American non-profit research and development organization, headquartered in Cambridge, Massachusetts; its official name is The Charles Stark Draper Laboratory, Inc (sometimes abbreviated as CSDL). The laboratory specialize ...

; the

Apollo Guidance Computer The Apollo Guidance Computer (AGC) was a digital computer produced for the Apollo program that was installed on board each Apollo command module (CM) and Apollo Lunar Module (LM). The AGC provided computation and electronic interfaces for guidan ...

was manufactured by

Raytheon Raytheon Technologies Corporation is an American multinational aerospace and defense conglomerate headquartered in Arlington, Virginia. It is one of the largest aerospace and defense manufacturers in the world by revenue and market capitaliza ...

(a similar guidance system was used in the command module). A backup navigation tool, the Abort Guidance System (AGS), was developed by TRW.

Design phase

The Apollo Lunar Module was chiefly designed by Grumman aerospace engineer Thomas J. Kelly. The first LEM design looked like a smaller version of the Apollo command and service module (a cone-shaped cabin atop a cylindrical propulsion section) with folding legs. The second design invoked the idea of a helicopter cockpit with large curved windows and seats, to improve the astronauts' visibility for hover and landing. This also included a second, forward docking port, allowing the LEM crew to take an active role in docking with the CSM. As the program continued, there were numerous redesigns to save weight, improve safety, and fix problems. First to go were the heavy cockpit windows and the seats; the astronauts would stand while flying the LEM, supported by a cable and pulley system, with smaller triangular windows giving them sufficient visibility of the landing site. Later, the redundant forward docking port was removed, which meant the Command Pilot gave up active control of the docking to the Command Module Pilot; he could still see the approaching CSM through a small overhead window. Egress while wearing bulky extra-vehicular activity spacesuits was eased by a simpler forward hatch (). The configuration was frozen in April 1963, when the ascent and descent engine designs were decided. In addition to Rocketdyne, a parallel program for the descent engine was ordered from Space Technology Laboratories (TRW) in July 1963, and by January 1965 the Rocketdyne contract was canceled. Power was initially to be produced by

fuel cell A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requ ...

s built by

Pratt and Whitney Pratt & Whitney is an American aerospace manufacturer with global service operations. It is a subsidiary of Raytheon Technologies. Pratt & Whitney's aircraft engines are widely used in both civil aviation (especially airlines) and military av ...

similar to the CSM, but in March 1965 these were discarded in favor of an all-battery design. The initial design had three landing legs, the lightest possible configuration. But as any particular leg would have to carry the weight of the vehicle if it landed at a significant angle, this was also the least stable configuration 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, however, was too heavy and the designers compromised on four landing legs. In June 1966, the name was changed to Lunar Module (LM), eliminating the word ''excursion''. According to

George Low George Michael Low (born Georg Michael Löw, June 10, 1926 – July 17, 1984) was an administrator at NASA and the 14th president of Rensselaer Polytechnic Institute. Low was one of the senior NASA officials who made numerous decisions as m ...

, Manager of the Apollo Spacecraft Program Office, this was because NASA was afraid that the word ''excursion'' might lend a frivolous note to Apollo. Despite the name change, the astronauts and other NASA and Grumman personnel continued to pronounce the abbreviation as () instead of the letters "L-M".

Astronaut training

Lunar Landing Research Vehicle in Flight - GPN-2000-000215

Comparing landing on the Moon to "a hovering operation",

Gus Grissom Virgil Ivan "Gus" Grissom (April 3, 1926 – January 27, 1967) was an American engineer, pilot in the United States Air Force, and member of the Mercury Seven selected by National Aeronautics and Space Administration's (NASA) as Project Mercur ...

said in 1963 that although most early astronauts were fighter pilots, "now we're wondering if the pilot making this first moon landing shouldn't be a highly experienced helicopter pilot". To allow astronauts to learn lunar landing techniques, NASA contracted Bell Aerosystems in 1964 to build the

Lunar Landing Research Vehicle The Bell Aerosystems Lunar Landing Research Vehicle (LLRV, nicknamed the Flying Bedstead) was a Project Apollo era program to build a simulator for the Moon landings. The LLRVs were used by the FRC, now known as the NASA Armstrong Flight Resear ...

(LLRV), which used a gimbal-mounted vertical jet engine to counter five-sixths of its weight to simulate the Moon's gravity, in addition to its own hydrogen peroxide thrusters to simulate the LM's descent engine and attitude control. Successful testing of two LLRV prototypes at the

Dryden Flight Research Center The NASA Neil A. Armstrong Flight Research Center (AFRC) is an aeronautical research center operated by NASA. Its primary campus is located inside Edwards Air Force Base in California and is considered NASA's premier site for aeronautical rese ...

led in 1966 to three production Lunar Landing Training Vehicles (LLTV) which along with the LLRV's were used to train the astronauts at the Houston Manned Spacecraft Center. This aircraft proved fairly dangerous to fly, as three of the five were destroyed in crashes. It was equipped with a rocket-powered ejection seat, so in each case the pilot survived, including the first man to walk on the Moon,

Neil Armstrong Neil Alden Armstrong (August 5, 1930 – August 25, 2012) was an American astronaut and aeronautical engineer who became the first person to walk on the Moon in 1969. He was also a naval aviator, test pilot, and university professor. ...

Development flights

LM-1 was built to make the first uncrewed flight for propulsion systems testing, launched into low Earth orbit atop a

Saturn IB The Saturn IB (also known as the uprated Saturn I) was an American launch vehicle commissioned by the NASA, National Aeronautics and Space Administration (NASA) for the Apollo program. It uprated the Saturn I by replacing the S-IV second stage (, ...

. This was originally planned for April 1967, to be followed by the first crewed flight later that year. But the LM's development problems had been underestimated, and LM-1's flight was delayed until January 22, 1968, as

. At that time, LM-2 was held in reserve in case the LM-1 flight failed, which did not happen. LM-3 now became the first crewed LM, again to be flown in low Earth orbit to test all the systems, and practice the separation, rendezvous, and docking planned for Apollo 8 in December 1968. But again, last-minute problems delayed its flight until

on March 3, 1969. A second, higher Earth orbit crewed practice flight had been planned to follow LM-3, but this was canceled to keep the program timeline on track.

launched on May 18, 1969, using LM-4 for a "dress rehearsal" for the lunar landing, practicing all phases of the mission except powered descent initiation through takeoff. The LM descended to above the lunar surface, then jettisoned the descent stage and used its ascent engine to return to the CSM.

Production flights

Apollo 11 Lunar Module Eagle in landing configuration in lunar orbit from the Command and Service Module Columbia

The first crewed lunar landing occurred on July 20, 1969, in the

LM-5 ''Eagle''. Four days later, the Apollo 11 crew in the command module ''Columbia'' splashed down in the Pacific Ocean, completing President John F. Kennedy's goal: "...before this decade is out, of landing a man on the Moon and returning him safely to the Earth". This was followed by landings by

Apollo 12 Apollo 12 (November 14–24, 1969) was the sixth crewed flight in the United States Apollo program and the second to land on the Moon. It was launched on November 14, 1969, by NASA from the Kennedy Space Center, Florida. Commander Pete Conra ...

(LM-6 ''Intrepid'') and

(LM-8 ''Antares''). In April 1970, the

LM-7 ''Aquarius'' played an unexpected role in saving the lives of the three astronauts after an oxygen tank in the

service module A service module (also known as an equipment module or instrument compartment) is a component of a crewed space capsule containing a variety of support systems used for spacecraft operations. Usually located in the uninhabited area of the spacec ...

ruptured, disabling the CSM. ''Aquarius'' served as a "lifeboat" for the astronauts during their return to Earth. Its descent stage engine was used to replace the crippled CSM Service Propulsion System engine, and its batteries supplied power for the trip home and recharged the Command Module's batteries critical for reentry. The astronauts splashed down safely on April 17, 1970. The LM's systems, designed to support two astronauts for 45 hours (including twice depressurization and repressurization causing loss of oxygen supply), actually stretched to support three astronauts for 90 hours (without depressurization and repressurization and loss of oxygen supply). Hover times were maximized on the last four landing missions by using the Service Module engine to perform the initial descent orbit insertion burn 22 hours before the LM separated from the CSM, a practice begun on Apollo 14. This meant that the complete spacecraft, including the CSM, orbited the Moon with a perilune, enabling the LM to begin its powered descent from that altitude with a full load of descent stage propellant, leaving more reserve propellant for the final approach. The CSM would then raise its perilune back to the normal .

Extended J-class missions

The Extended Lunar Module (ELM) used on the final three "J-class missions" —

Apollo 15 Apollo 15 (July 26August 7, 1971) was the ninth crewed mission in the United States' Apollo program and the fourth to Moon landing, land on the Moon. It was the first List of Apollo missions#Alphabetical mission types, J mission, with a ...

, 16, and 17 — was upgraded to land larger payloads and stay longer on the lunar surface. The descent engine thrust was increased by the addition of a extension to the engine bell, and the descent propellant tanks were enlarged. A waste storage tank was added to the descent stage, with plumbing from the ascent stage. These upgrades allowed stays of up to 75 hours on the Moon. The

Lunar Roving Vehicle The Lunar Roving Vehicle (LRV) is a battery-powered four-wheeled rover used on the Moon in the last three missions of the American Apollo program ( 15, 16, and 17) during 1971 and 1972. It is popularly called the Moon buggy, a play on the t ...

was folded up and carried in Quadrant 1 of the descent stage. It was deployed by the astronauts after landing, allowing them to explore large areas and return a greater variety of lunar samples.

Specifications

Weights given here are an average for the original pre-ELM spec vehicles. For specific weights for each mission, see the individual mission articles.

Ascent stage

The ascent stage contained the crew cabin with instrument panels and flight controls. It contained its own

Ascent Propulsion System The ascent propulsion system (APS) or lunar module ascent engine (LMAE) is a fixed-thrust hypergolic rocket engine developed by Bell Aerosystems for use in the Apollo Lunar Module ascent stage. It used Aerozine 50 fuel, and oxidizer. Rocketdyn ...

(APS) engine and two

hypergolic propellant A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. Th ...

tanks for return to lunar orbit and rendezvous with the

. It also contained a Reaction Control System (RCS) for

attitude Attitude may refer to: Philosophy and psychology * Attitude (psychology), an individual's predisposed state of mind regarding a value * Metaphysics of presence * Propositional attitude, a relational mental state connecting a person to a pro ...

and

translation Translation is the communication of the Meaning (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...

control, which consisted of sixteen hypergolic thrusters similar to those used on the Service Module, mounted in four quads, with their own propellant supply. A forward extravehicular activity hatch provided access to and from the lunar surface, while an overhead hatch and docking port provided access to and from the Command Module. Internal equipment included an environmental control (life support) system; a VHF communications system with two antennas for communication with the Command Module; a

unified S-band The Unified S-band (USB) system is a tracking and communication system developed for the Apollo program by NASA and the Jet Propulsion Laboratory (JPL). It operated in the S band portion of the microwave spectrum, unifying voice communications, ...

system and steerable

parabolic dish antenna A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or p ...

for communication with Earth; an extravehicular activity antenna resembling a miniature parasol which relayed communications from antennas on the astronauts'

Portable Life Support System A primary (or portable or personal) life support system (or subsystem) (PLSS), is a device connected to an astronaut or cosmonaut's spacesuit, which allows extra-vehicular activity with maximum freedom, independent of a spacecraft's life support ...

s through the LM; primary (PGNCS) and backup (AGS) guidance and navigation systems; an Alignment Optical Telescope for visually determining the spacecraft orientation; rendezvous radar with its own steerable dish antenna; and a system for active thermal control. Electrical storage batteries, cooling water, and breathing oxygen were stored in amounts sufficient for a lunar surface stay of 48 hours initially, extended to 75 hours for the later missions. During rest periods while parked on the Moon, the crew would sleep on hammocks slung crosswise in the cabin. The return payload included the lunar rock and soil samples collected by the crew (as much as on Apollo 17), plus their exposed

photographic film Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin photographic emulsion, emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of th ...

. * Crew: 2 * Crew cabin volume: * Habitable volume: * Crew compartment height: * Crew compartment depth: * Height: * Width: * Depth: * Mass, dry: * Mass, gross: * Atmosphere: 100% oxygen at * Water: two storage tanks * Coolant: of

ethylene glycol Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odo ...

/ water solution * Thermal Control: one active water-ice sublimator * RCS propellant mass: * RCS thrusters: sixteen x in four quads * RCS propellants:

Aerozine 50 __NOTOC__ Aerozine 50 is a 50:50 mix by weight of hydrazine and unsymmetrical dimethylhydrazine (UDMH), originally developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II ICBM rocket e ...

fuel /

Dinitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russia rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

(N₂O₄) oxidizer * RCS

specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse i ...

: * APS propellant mass: stored in two propellant tanks * APS engine:

Bell Aerospace The Bell Aircraft Corporation was an American aircraft manufacturer, a builder of several types of fighter aircraft for World War II but most famous for the Bell X-1, the first supersonic aircraft, and for the development and production of many i ...

LM Ascent Engine (LMAE) and

LMAE Injectors * APS thrust: * APS propellants: Aerozine 50 fuel / Dinitrogen Tetroxide oxidizer * APS pressurant: two helium tanks at * APS

: * APS

delta-V Delta-''v'' (more known as "change in velocity"), symbolized as ∆''v'' and pronounced ''delta-vee'', as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as ...

: *

Thrust-to-weight ratio Thrust-to-weight ratio is a dimensionless ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine that is an indicator of the performance of the engine or vehicle. The instantaneous thrust-to- ...

at liftoff: 2.124 (in lunar gravity) * Batteries: two 28–32 volt, 296

ampere hour An ampere hour or amp hour (symbol: A⋅h or A h; often simplified as Ah) is a unit of electric charge, having dimensions of electric current multiplied by time, equal to the charge transferred by a steady current of one ampere flowing for on ...

Silver-zinc batteries A silver zinc battery is a secondary cell that utilizes silver(I,III) oxide and zinc. Overview Silver zinc cells share most of the characteristics of the silver-oxide battery, and in addition, is able to deliver one of the highest specific ener ...

; each * Power: 28 V DC, 115 V 400 Hz AC

Descent stage

The descent stage's primary job was to support a powered landing and surface extravehicular activity. When the excursion was over, it served as the launch pad for the ascent stage. Its octagonal shape was supported by four folding landing gear legs, and contained a

throttle A throttle is the mechanism by which fluid flow is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term ''throttle'' ...

able

Descent Propulsion System The descent propulsion system (DPS - pronounced 'dips') or lunar module descent engine (LMDE), internal designation VTR-10, is a variable-throttle hypergolic rocket engine invented by Gerard W. Elverum Jr. and developed by Space Technology Labo ...

(DPS) engine with four

tanks. A

continuous-wave A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency, typically a sine wave, that for mathematical analysis is considered to be of infinite duration. It may refer to e.g. a laser or particl ...

Doppler radar A Doppler radar is a specialized radar that uses the Doppler effect to produce velocity data about objects at a distance. It does this by bouncing a microwave signal off a desired target and analyzing how the object's motion has altered the f ...

antenna was mounted by the engine

heat shield In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...

on the bottom surface, to send altitude and rate of descent data to the guidance system and pilot display during the landing. Almost all external surfaces, except for the top, platform, ladder, descent engine and heat shield, were covered in amber, dark (reddish) amber, black, silver, and yellow aluminized

Kapton Structure of poly-oxydiphenylene-pyromellitimide Kapton insulating pads for mounting electronic parts on a heat sink Kapton is a polyimide film used in flexible printed circuits (flexible electronics) and space blankets, which are used on spac ...

foil blankets for thermal insulation. The number 1 (front) landing leg had an attached platform (informally known as the "porch") in front of the ascent stage's extravehicular activity hatch and a ladder, which the astronauts used to ascend and descend between the cabin to the surface. The footpad of each landing leg incorporated a surface contact sensor probe, which signaled the commander to switch off the descent engine. (The probe was omitted from the number 1 leg of every landing mission, to avoid a suit-puncture hazard to the astronauts, as the probes tended to break off and protrude upwards from the surface.) Equipment for the lunar exploration was carried in the Modular Equipment Stowage Assembly (MESA), a drawer mounted on a hinged panel dropping out of the lefthand forward compartment. Besides the astronaut's surface excavation tools and sample collection boxes, the MESA contained a television camera with a tripod; as the commander opened the MESA by pulling on a lanyard while descending the ladder, the camera was automatically activated to send the first pictures of the astronauts on the surface back to Earth. A

United States flag The national flag of the United States of America, often referred to as the ''American flag'' or the ''U.S. flag'', consists of thirteen equal horizontal stripes of red (top and bottom) alternating with white, with a blue rectangle in the ca ...

for the astronauts to erect on the surface was carried in a container mounted on the ladder of each landing mission. The Early Apollo Surface Experiments Package (later the Apollo Lunar Surface Experiments Package), was carried in the opposite compartment behind the LM. An external compartment on the right front panel carried a deployable S-band antenna which, when opened looked like an inverted umbrella on a tripod. This was not used on the first landing due to time constraints, and the fact that acceptable communications were being received using the LM's S-band antenna, but was used on Apollo 12 and 14. A hand-pulled

Modular Equipment Transporter The Modular Equipment Transporter (MET) was a two-wheeled, hand-pulled vehicle that was used as an equipment hauling device on traverses across the lunar surface. Designed after Apollo 12 astronauts Pete Conrad and Alan Bean had difficulties lugg ...

(MET), similar in appearance to a golf cart, was carried on Apollo 13 and 14 to facilitate carrying the tools and samples on extended moonwalks. On the extended missions (

and later), the antenna and TV camera were mounted on the

, which was carried folded up and mounted on an external panel. Compartments also contained replacement

(PLSS) batteries and extra lithium hydroxide canisters on the extended missions. * Height: (plus landing probes) * Width/depth, minus landing gear: * Width/depth, landing gear extended: * Mass including propellant: * Water: one storage tank * DPS propellant mass: stored in four propellant tanks * DPS engine: TRW LM descent engine (LMDE) * DPS thrust: , throttleable between 10% and 60% of full thrust * DPS propellants: Aerozine 50 fuel / nitrogen tetroxide oxidizer * DPS pressurant: one supercritical helium tank at * DPS

: 311 s (3,050 N⋅s/kg) * DPS

: * Batteries: four (Apollo 9–14) or five (Apollo 15–17) 28–32 V, 415 A⋅h silver-zinc batteries; each

Lunar modules produced

Proposed derivatives

Apollo Telescope Mount

One proposed Apollo application was an orbital solar telescope constructed from a surplus LM with its descent engine replaced with a telescope controlled from the ascent stage cabin, the landing legs removed and four "windmill" solar panels extending from the descent stage quadrants. This would have been launched on an uncrewed Saturn 1B, and docked with a crewed

, named the Apollo Telescope Mission (ATM). This idea was later transferred to the original

wet workshop A wet workshop is a space station made from a spent liquid-propellant rocket stage. Such a rocket stage contains two large, airtight propellant tanks; it was realized that the larger tank could be retrofit into the living quarters of a space s ...

design for the ''

Skylab Skylab was the first United States space station, launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three separate three-astronaut crews: Skylab 2, Skylab 3, and Skylab 4. Major operations in ...

'' orbital workshop and renamed the

Apollo Telescope Mount The Apollo Telescope Mount, or ATM, was a crewed solar observatory that was a part of Skylab, the first American space station. It could observe the Sun in wavelengths ranging from soft X-rays, ultra-violet, and visible light. The ATM was man ...

to be docked on a side port of the workshop's multiple docking adapter (MDA). When Skylab changed to a "dry workshop" design pre-fabricated on the ground and launched on a Saturn V, the telescope was mounted on a hinged arm and controlled from inside the MDA. Only the octagonal shape of the telescope container, solar panels and the Apollo Telescope Mount name were kept, though there was no longer any association with the LM.

LM Truck

The Apollo LM Truck (also known as Lunar Payload Module) was a stand-alone LM descent stage intended to deliver up to of payload to the Moon for an uncrewed landing. This technique was intended to deliver equipment and supplies to a permanent crewed

lunar base A moonbase is a facility on the surface of the Moon, enabling human activity on the Moon. As such, it is different from a lunar space station in orbit around the Moon, like the planned Lunar Gateway of the Artemis program. Moonbases can be fo ...

. As originally proposed, it would be launched on a Saturn V with a full Apollo crew to accompany it to lunar orbit and guide it to a landing next to the base; then the base crew would unload the "truck" while the orbiting crew returned to Earth.Apollo LM Truck on Mark Wade's Encyclopedia Astronautica
– Description of adapted LM descent stage for the uncrewed transport of cargo to a permanent lunar base. In later AAP plans, the LPM would have been delivered by an uncrewed lunar ferry vehicle.

Depiction in film and television

The 1995 Ron Howard film ''

'', a dramatization of that mission starring

Tom Hanks Thomas Jeffrey Hanks (born July 9, 1956) is an American actor and filmmaker. Known for both his comedic and dramatic roles, he is one of the most popular and recognizable film stars worldwide, and is regarded as an American cultural icon. Ha ...

Kevin Bacon Kevin Norwood Bacon (born July 8, 1958) is an American actor. His films include the musical-drama film '' Footloose'' (1984), the controversial historical conspiracy legal thriller '' JFK'' (1991), the legal drama '' A Few Good Men'' (1992), t ...

, and

Bill Paxton William Paxton (May 17, 1955 – February 25, 2017) was an American actor and filmmaker. He appeared in films such as '' Weird Science'' (1985), ''Aliens'' (1986), ''Near Dark'' (1987), '' Tombstone'' (1993), ''True Lies'' (1994), '' Apollo 13 ...

, was filmed using realistic spacecraft interior reconstructions of the ''Aquarius'' and the Command Module ''Odyssey''. The development and construction of the lunar module is dramatized in the 1998 miniseries ''

From the Earth to the Moon ''From the Earth to the Moon: A Direct Route in 97 Hours, 20 Minutes'' (french: De la Terre à la Lune, trajet direct en 97 heures 20 minutes) is an 1865 novel by Jules Verne. It tells the story of the Baltimore Gun Club, a post-American Civil W ...

'' episode entitled "Spider". This is in reference to LM-3, used on Apollo 9, which the crew named ''Spider'' after its spidery appearance. The unused LM-13 stood in during the teleplay to depict LM-3 and LM-5, ''Eagle'', used by Apollo 11. The Apollo 11 Lunar Module ''Eagle'' is depicted in the 2018 film '' First Man'', a biopic of

Media

File:AP11 FINAL APPROACH.ogv,

lands the

Lunar Module ''Eagle'' on the Moon, July 20, 1969, creating

Tranquility Base Tranquility Base ( la, Statio Tranquillitatis) is the site on the Moon where, in July 1969, humans landed and walked on a celestial body other than Earth for the first time. On July 20, 1969, Apollo 11 crewmembers Neil Armstrong and Buzz Aldrin ...

. Starts approximately 6200 feet from the surface. File:Apollo 15 landing on the Moon.ogg,

David Scott David Randolph Scott (born June 6, 1932) is an American retired test pilot and NASA astronaut who was the seventh person to walk on the Moon. Selected as part of the third group of astronauts in 1963, Scott flew to space three times and c ...

lands

Lunar Module ''Falcon'' on the Moon on July 30, 1971, seen from the perspective of the Lunar Module Pilot. Starts at approximately 5000 feet from the surface. File:Apollo 15 liftoff from the Moon.ogg, Apollo 15 Lunar Module ''Falcon'' lifts off from the Moon, August 2, 1971. View from TV camera on the

. File:Apollo 15 liftoff from inside LM.ogg, Apollo 15 Lunar Module liftoff. View from inside ''Falcon''. File:Ap17-ascent.ogv,

Apollo 17 Apollo 17 (December 7–19, 1972) was the final mission of NASA's Apollo program, the most recent time humans have set foot on the Moon or traveled beyond low Earth orbit. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on ...

Lunar Module ''Challenger'' liftoffs from the Moon on December 14, 1972. View from TV camera on the Lunar Roving Vehicle. File:Lunar Module Equipment Locations 1 of 2.jpg, Equipment location plans (1 of 2) File:Lunar Module Equipment Locations 2 of 2.jpg, Equipment location plans (2 of 2) File:Lunar Module Control Displays.jpg, Controls plans File:Lunar Module Landing Gear plans.jpg, Landing Gear plans

References

External links

NASA Lunar Module Documentation
Lunar Surface Journal
Google Moon overview of Apollo landing sites

NASA catalog: Apollo 14 Lunar Module

Demonstration of the Lunar Excursion Module and explanation of its systems
(1966, Thomas Kelly at Grumman plant on Long Island, episode of ''Science Reporter'', MIT film posted to YouTube)

– A site "dedicated to the men and women that designed, built and tested the Lunar Module at Grumman Aerospace Corporation, Bethpage, New York"

By D.C. Agle, ''Air & Space Magazine'', September 1, 2001 - Overview of LM descent
Apollo 11 LM Structures handout for LM-5
(PDF) – Training document given to astronauts which illustrates all discrete LM structures
Apollo Operations Handbook, Lunar Module (LM 10 and Subsequent), Volume One. Subsystems Data
(PDF) Manufacturers Handbook covering the systems of the LM.
Apollo Operations Handbook, Lunar Module (LM 11 and Subsequent), Volume Two. Operational Procedures
Manufacturers Handbook covering the procedures used to fly the LM.

– Checklist detailing how to prepare the LM for activation and flight during a mission

video

Games

Perilune
3D Procedural Lunar Lander Simulation
Lander
On-line 2D Lunar Module Landing Simulation Game
Easy Lander
3D Lunar Module Landing Simulation Game {{Authority control American inventions 1969 in spaceflight 1970 in spaceflight 1971 in spaceflight 1972 in spaceflight Crewed spacecraft Soft landings on the Moon Apollo program hardware VTVL rockets Articles containing video clips Spacecraft launched by Saturn rockets Spacecraft that orbited the Moon