Apollo Lunar Module

The Apollo Lunar Module, or simply lunar module (LM, pronounced "Lem"), originally designated the lunar excursion module (LEM), was the spacecraft which was flown to and landed on the Moon. The lander spacecraft were built for the US Apollo program by Grumman Aircraft. The lunar module, consisting of a descent stage and an ascent stage, was ferried from the Earth to the Moon attached to the Apollo spacecraft command and service module (CSM), approximately twice its mass. The ascent stage carried a crew of two who flew the spacecraft from lunar orbit to the surface and later back to the command module. Designed for lunar orbit rendezvous, the Apollo Lunar Module was discarded after completing its mission. It was capable of operation only in outer space; structurally and aerodynamically it was incapable of flight through the Earth's atmosphere. The lunar module was the first manned spacecraft to operate exclusively in the airless vacuum of space. It was the first, and to date only, crewed vehicle to land anywhere beyond Earth.

The LM's development was plagued with problems which delayed its first unmanned flight by about ten months, and its first manned flight by about three months. Despite this, the LM eventually became the most reliable component of the Apollo/Saturn space vehicle, the only component never to suffer a failure that could not be corrected in time to prevent abort of a landing mission.[1]

Ten lunar modules were launched into space. Of these, six successfully landed humans on the Moon between 1969 and 1972. The first two launched were test flights in low Earth orbit—the first without a crew, the second with one. Another was used by Apollo 10 for a "dress rehearsal" flight in low lunar orbit, without landing. One lunar module functioned as a "lifeboat" for the crew of Apollo 13, providing life support and propulsion when their CSM was disabled by an oxygen tank explosion en route to the Moon, forcing the crew to abandon their landing.

The total cost of the LM for development and the units produced was $21.3B in 2016 dollars, adjusting from a nominal total of $2.2B[2] using the NASA New Start Inflation Indices.[3] The six landed descent stages remain intact where they landed and one ascent stage (Apollo 10's) is in heliocentric orbit. All the other LMs that flew either crashed into the Moon or burned up in the Earth's atmosphere.

Apollo Lunar Module
Apollo16LM
Apollo 16 LM Orion on the lunar surface
ManufacturerGrumman Aircraft
DesignerThomas J. Kelly
Country of originUnited States
OperatorNASA
ApplicationsManned lunar landing
Specifications
Design life75 hours (Extended)
Launch mass
  • 33,500 pounds (15,200 kg) std
  • 36,200 pounds (16,400 kg) Extended
Dry mass
  • 9,430 pounds (4,280 kg) std
  • 10,850 pounds (4,920 kg) Extended
Crew capacity2
Dimensions23 feet 1 inch (7.04 m) high
31 feet (9.4 m) wide
31 feet (9.4 m) deep
overall, landing gear deployed
Volume235 cubic feet (6.7 m3)
PowerBatteries
RegimeLunar
Production
StatusRetired
Built15
Launched10
Operational10
Failed0
Lost0
First launchJanuary 22, 1968
Last launchDecember 14, 1972
Last retirementDecember 15, 1972
Apollo program
LEM-linedrawing

Apollo LM diagram

Operational profile

At launch, the lunar module sat directly beneath the command and service module (CSM) with legs folded, inside the Spacecraft-to-LM adapter (SLA) attached to the S-IVB third stage of the Saturn V rocket. There it remained through Earth parking orbit and the Trans Lunar Injection (TLI) rocket burn to send the craft toward the Moon.

Soon after TLI, the SLA opened and the CSM 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 temporarily power up and test its systems (except for propulsion). Throughout the flight, he performed the role of an engineering officer, responsible for 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 on systems status and navigational information. After visual inspection of the landing gear by the Command Module Pilot, the LM was withdrawn to a safe distance, then the descent engine was pointed forward into the direction of travel to perform the 30 second descent orbit insertion burn to reduce speed and drop the LM's perilune to within approximately 50,000 feet (15 km) of the surface,[4] about 260 nautical miles (480 km) uprange of the landing site.

Earth, Moon and Lunar Module, AS11-44-6643
Eagle, the lunar module ascent stage of Apollo 11, in orbit above the Moon. Earth is visible in the distance.

At this point, the engine was started again for powered descent initiation. 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 the braking phase altitude decreased to approximately 10,000 feet (3.0 km), then the final approach phase went to approximately 700 feet (210 m). 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.[5]

Astronauts only flew Apollo spacecraft manually during the lunar approach.[6] The final landing phase began approximately 2,000 feet (0.61 km) uprange of the targeted landing site. At this point manual control was enabled for the Commander, and enough propellant reserve was allocated to allow approximately two minutes of hover time 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 67.2-inch (1.71 m) long probes extending from footpads on the legs of the lander touched the surface, activating the contact indicator light which signaled the commander to manually 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 could possibly puncture an astronaut's suit while he descended or stepped off the ladder.

The original Extra-Vehicular Activity (EVA) plan, up through at least 1966, was for only one astronaut to leave the LM while the other remained inside in order "to maintain communications".[7] Communications were eventually deemed to be reasonably reliable so that both crew members could walk on the surface, leaving the spacecraft to be only remotely attended by Mission Control.

Beginning with Apollo 14, increased LM propellant reserve was made available for the powered descent and landing, by using the CSM engine to achieve the 50,000-foot (15 km) 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 would separate the descent stage and fire the ascent engine to climb back into orbit, using the descent stage as a launch platform. After a few course correction burns, the LM would rendezvous with the CSM and dock for transfer of the crew and rock samples. Having completed its job, the ascent stage was separated. The Apollo 10 ascent stage engine was fired to fuel depletion, sending it on a trajectory past the Moon into a heliocentric orbit.[8][9] The Apollo 11 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

Joseph Francis Shea
A 1962 model of the first LEM design, docked to the command and service module, is held by Dr. Joseph F. Shea

The lunar module (originally designated the lunar excursion module, known by the acronym LEM) was designed after NASA chose to reach the Moon via Lunar Orbit Rendezvous (LOR) instead of the direct ascent 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. Grumman Aircraft was awarded the contract two months later. 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 (environmental control systems), Marquardt (reaction control system) and TRW's Space Technology Laboratories (descent engine).[10]

The Primary Guidance, Navigation and Control System (PGNCS) 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.

Design phase

Lunar Lander Model
This 1963 model depicts the second LEM design, which gave rise to informal references as "the bug".

The Apollo Lunar Module was chiefly designed by Grumman aerospace engineer Thomas J. Kelly.[11] 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 (EVA) spacesuits was eased by a simpler forward hatch (32 x 32 inches).

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 cells built by Pratt and Whitney similar to the CSM, but in March 1965 these were discarded in favor of an all-battery design.[12]

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.[13]

In June 1966, the name was changed to lunar module (LM), eliminating the word "excursion".[14][15] According to George Low, Manager of the Apollo Spacecraft Program Office, this was because NASA was afraid that the word "excursion" might lend a frivolous note to Apollo.[16] After the name change from "LEM" to "LM", the pronunciation of the abbreviation did not change, as the habit became ingrained among engineers, the astronauts, and the media to universally pronounce "LM" as "lem" which is easier than saying the letters individually.

Astronaut training

Lunar Landing Research Vehicle in Flight - GPN-2000-000215
Lunar Landing Research Vehicle (LLRV) during a test flight

To allow astronauts to learn lunar landing techniques, NASA contracted Bell Aerosystems in 1964 to build the Lunar Landing Research Vehicle (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 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.[17]

Development flights

67-H-1230 Lunar module LTA-2 R
The Apollo 6 Lunar Module Test Article (LTA-2R) shortly before being mated with the SLA

LM-1 was built to make the first unmanned flight for propulsion systems testing, launched into low Earth orbit atop a Saturn IB. This was originally planned for April 1967, to be followed by the first manned 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 Apollo 5. 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 manned 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 Apollo 9 on March 3, 1969. A second, higher Earth orbit manned practice flight had been planned to follow LM-3, but this was canceled to keep the program timeline on track.

Apollo 10 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 47,400 feet (14.4 km) above the lunar surface, then jettisoned the descent stage and used its ascent engine to return to the CSM.[18]

Production flights

The first manned lunar landing occurred on July 20, 1969 with the Apollo 11 LM 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 precision landings on Apollo 12 (Intrepid) and Apollo 14 (Antares).

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

In April 1970, the Apollo 13 lunar module Aquarius played an unexpected role in saving the lives of the three astronauts after an oxygen tank in the service module 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 9.1-nautical-mile (16.9 km) 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 60 nautical miles (110 km).[19]

Extended J-class missions

Apollo 15 Engine Bell
Decreased clearance led to buckling of the extended descent engine nozzle on the landing of Apollo 15

The extended lunar module (ELM) used on the final three "J-class missions", Apollo 15, 16 and 17, were significantly upgraded to allow for greater landing payload weights and longer lunar surface stay times. The descent engine power was improved by the addition of a 10-inch (250 mm) extension to the engine bell, and the descent propellant tanks were increased in size. A waste storage tank was added to the descent stage, with plumbing from the ascent stage. These upgrades allowed stay times of up to 75 hours on the Moon.

The Lunar Roving Vehicle was carried folded up in Quadrant 1 of the descent stage and deployed by the astronauts after landing. This allowed them to explore large areas and return a greater variety of lunar samples.

Specifications

Lunar Module diagram
Lunar module diagram
Apollo Lunar Module Inside View
Lunar module crew cabin
Apollo LM crew rest positions
Astronaut rest (sleeping) accommodation
LM illustration 02
Lunar module cutaway illustration

Note that weights varied from mission to mission; those given here are an average for the non-ELM class vehicles. See the individual mission articles for each LM's weight.

Ascent stage

The Ascent stage contained the crew cabin with instrument panels and flight controls. It contained its own Ascent Propulsion System (APS) engine and two hypergolic propellant tanks for return to lunar orbit and rendezvous with the Apollo command and service module. It also contained a Reaction Control System (RCS) for attitude and translation 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 EVA 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 system and steerable parabolic dish antenna for communication with Earth; an EVA antenna resembling a miniature parasol which relayed communications from antennas on the astronauts' Portable Life Support Systems 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 an ice sublimation 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 238 pounds (108 kg) on Apollo 17), plus their exposed photographic film.

  • Crew: 2
  • Crew cabin volume: 235 cu ft (6.7 m3)
  • Habitable volume: 160 cu ft (4.5 m3)
  • Crew compartment height: 7 ft 8 in (2.34 m)
  • Crew compartment depth: 3 ft 6 in (1.07 m)
  • Height: 9 ft 3.5 in (2.832 m)
  • Width: 14 ft 1 in (4.29 m)
  • Depth: 13 ft 3 in (4.04 m)
  • Mass, dry: 4,740 lb (2,150 kg)
  • Mass, gross: 10,300 lb (4,700 kg)
  • Atmosphere: 100% oxygen at 4.8 psi (33 kPa)
  • Water: two 42.5 lb (19.3 kg) storage tanks
  • Coolant: 25 pounds (11 kg) of ethylene glycol / water solution
  • Thermal Control: one active water-ice sublimator
  • RCS propellant mass: 633 lb (287 kg)
  • RCS thrusters: sixteen x 100 lbf (440 N) in four quads
  • RCS propellants: Aerozine 50 fuel / nitrogen tetroxide (N2O4) oxidizer
  • RCS specific impulse: 290 s (2,840 N·s/kg)
  • APS propellant mass: 5,187 lb (2,353 kg) stored in two 36-cubic-foot (1.02 m3) propellant tanks
  • APS engine: Bell Aerospace LM Ascent Engine (LMAE) & Rocketdyne LMAE Injectors
  • APS thrust: 3,500 lbf (16,000 N)
  • APS propellants: Aerozine 50 fuel / nitrogen tetroxide oxidizer
  • APS pressurant: two 6.4 lb (2.9 kg) helium tanks at 3,000 pounds per square inch (21 MPa)
  • APS specific impulse: 311 s (3,050 N·s/kg)
  • APS delta-V: 7,280 ft/s (2,220 m/s)
  • Thrust-to-weight ratio at liftoff: 2.124 (in lunar gravity)
  • Batteries: two 28–32 volt, 296 ampere-hour silver-zinc batteries; 125 lb (57 kg) each
  • Power: 28 V DC, 115 V 400 Hz AC

Descent stage

Scale model of the Apollo Lunar Module
Scale model of the Apollo Lunar Module at the Euro Space Center in Belgium

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. Octagonal, it was supported by four folding landing gear legs, and contained a throttleable Descent Propulsion System (DPS) engine with four hypergolic propellant tanks. A continuous-wave Doppler radar antenna was mounted by the engine heat shield 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 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 EVA hatch and a ladder, which the astronauts used to ascend and descend between the cabin to the surface. The footpad of each landing gear contained a 67-inch-long (1.7 m) 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 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 Experiment Package (EASEP) (later the Apollo Lunar Surface Experiment Package (ALSEP)), 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 (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 (Apollo 15 and later), the antenna and TV camera were mounted on the Lunar Roving Vehicle, which was carried folded up and mounted on an external panel. Compartments also contained replacement Portable Life Support System (PLSS) batteries and extra lithium hydroxide canisters on the extended missions.

  • Height: 10 ft 7.2 in (3.231 m) (plus 5 ft 7.2 in (1.707 m) landing probes)
  • Width/depth, minus landing gear: 13 ft 10 in (4.22 m)
  • Width/depth, landing gear extended: 31.0 ft (9.4 m)
  • Mass including propellant: 22,783 lb (10,334 kg)
  • Water: one 151 kg (333 lb) storage tank
  • DPS propellant mass: 18,000 lb (8,200 kg) stored in four 67.3-cubic-foot (1.906 m3) propellant tanks
  • DPS engine: TRW LM descent engine (LMDE)[20]
  • DPS thrust: 10,125 lbf (45,040 N), throttleable between 10% and 60% of full thrust
  • DPS propellants: Aerozine 50 fuel / nitrogen tetroxide oxidizer
  • DPS pressurant: one 49-pound (22 kg) supercritical helium tank at 1,555 psi (10.72 MPa)
  • DPS specific impulse: 311 s (3,050 N⋅s/kg)
  • DPS delta-V: 8,100 ft/s (2,500 m/s)
  • Batteries: four (Apollo 9-14) or five (Apollo 15-17) 28–32 V, 415 A⋅h silver-zinc batteries; 135 lb (61 kg) each

Lunar modules produced

Serial number Name Use Launch date Location Image
LTA-1 Unflown Cradle of Aviation Museum[21]
LTA-2R Apollo 6 April 4, 1968 Reentered Earth's atmosphere 67-H-1230 Lunar module LTA-2 R
LTA-3A Unflown Kansas Cosmosphere and Space Center[21]
LTA-3DR Unflown descent stage Franklin Institute[21]
LTA-5D Unflown NASA White Sands Test Facility[21]
LTA-8A[21] Lunar Module Test Article no.8 Thermal-vacuum tests Ground tests in 1968 Space Center Houston[21]

LTA-8A

LTA-10R Apollo 4 November 9, 1967 Reentered Earth's atmosphere[21]
MSC-16 Non-flight ascent stage Museum of Science & Industry[21]
TM-5 Non-flight Museum of Life and Science[21]
PA-1 Unflown White Sands Test Facility[21]
LM-1 Apollo 5 January 22, 1968 Reentered Earth's atmosphere Lm1 ground
LM-2 Intended for second unmanned flight, used instead for ground testing. Landing gear added for drop testing. Lacks optical alignment telescope and flight computer[22]
 
On display at the National Air and Space Museum, Washington, DC LunarLander
LM-3 Spider Apollo 9 March 3, 1969 Descent and ascent stages reentered Earth's atmosphere separately Spider Over The Ocean - GPN-2000-001109
LM-4 Snoopy Apollo 10 May 18, 1969 Descent stage hit Moon, ascent stage in heliocentric orbit. Snoopy is the only surviving flown LM ascent stage. AS10-34-5087
LM-5 Eagle Apollo 11 July 16, 1969 Descent stage on lunar surface in Sea of Tranquility, ascent stage left in lunar orbit (orbit decayed: impact location on Moon unknown) Apollo 11 Lunar Lander - 5927 NASA
LM-6 Intrepid Apollo 12 November 14, 1969 Descent stage on lunar surface at Ocean of Storms, ascent stage deliberately crashed into Moon Bean Descends Intrepid - GPN-2000-001317
LM-7 Aquarius Apollo 13 April 11, 1970 Reentered Earth's atmosphere Apollo 13 Lunar Module
LM-8 Antares Apollo 14 January 31, 1971 Descent stage on lunar surface at Frau Mauro, ascent stage deliberately crashed into Moon Antares on the Frau Mauro Highlands - GPN-2000-001144
LM-9 Not flown, intended as Apollo 15, last H-class mission
 
On display at the Kennedy Space Center (Apollo/Saturn V Center)
 
LM-9KSC
LM-10 Falcon Apollo 15, first ELM July 26, 1971 Descent stage on lunar surface at Hadley-Appenine, ascent stage deliberately crashed into Moon Apollo 15 flag, rover, LM, Irwin
LM-11 Orion Apollo 16 April 16, 1972 Descent stage on lunar surface at Descartes Highlands, ascent stage left in lunar orbit, crashed on Moon Apollo 16 LM Orion
LM-12 Challenger Apollo 17 December 7, 1972 Descent stage on lunar surface at Taurus-Littrow, ascent stage deliberately crashed into Moon Apollo 17 LM Ascent Stage
LM-13
 
Not flown, intended as Apollo 18[23]
 
Partially completed by Grumman, restored and on display at Cradle of Aviation Museum, Long Island, New York. Also used during 1998 miniseries From the Earth to the Moon.
LM-14
 
Not flown, intended as Apollo 19
 
Incomplete
LM-15
 
Not flown
 
Scrapped
 
* For the location of LMs left on the Lunar surface, see list of man-made objects on the Moon.
Apollo Spacecraft Locations World Map
World map showing locations of Apollo Lunar Modules (along with other hardware).

Proposed derivatives

Apollo Telescope Mount

Wet Workshop
Original proposed "wet workshop" Skylab with the 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 unmanned Saturn 1B, and docked with a manned command and service module, named the Apollo Telescope Mission (ATM).

This idea was later transferred to the original wet workshop design for the Skylab orbital workshop and renamed the Apollo Telescope Mount 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 11,000 pounds (5.0 t) of payload to the Moon for an unmanned landing. This technique was intended to deliver equipment and supplies to a permanent manned lunar base. 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.[24] In later AAP plans, the LPM would have been delivered by an unmanned lunar ferry vehicle.

Depiction in film and television

The Ron Howard film Apollo 13, a dramatization of that mission starring Tom Hanks, Kevin Bacon, and Bill Paxton, 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 miniseries From the Earth to the Moon 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.

Media

Lunar Module Equipment Locations 1 of 2

Equipment location plans (1 of 2)

Lunar Module Equipment Locations 2 of 2

Equipment location plans (2 of 2)

Lunar Module Control Displays

Controls plans

Lunar Module Landing Gear plans

Landing Gear plans

Apollo 15 landing on the Moon seen from the perspective of the Lunar Module Pilot. Starts at about 5000 feet.

Apollo 15 Lunar Module lifts off the Moon. View from TV camera on the Lunar Roving Vehicle.

Apollo 15 Lunar Module liftoff. View from inside LM.

Apollo 17 Lunar Module liftoff. View from TV camera on the lunar rover.

See also

References

  1. ^ Moon Race: The History of Apollo DVD, Columbia River Entertainment (Portland, Oregon, 2007)
  2. ^ Orloff, Richard (1996). Apollo by the Numbers (PDF). National Aeronautics and Space Administration. p. 22.
  3. ^ "NASA New Start Inflation Indices". National Aeronautics and Space Administration. Retrieved May 23, 2016.
  4. ^ "Apollo 11 Lunar Orbit Phase".
  5. ^ Gatland, Kenneth (1976). Manned Spacecraft, Second Revision. New York: Macmillan Publishing Co. pp. 194–196. ISBN 0-02-542820-9.
  6. ^ Agle, D.C. (September 1998). "Flying the Gusmobile". Air & Space. Retrieved 2018-12-15.
  7. ^ Landing on the Moon, 1966 episode of MIT's Science Reporter (posted to YouTube by MIT on Jan 20, 2016)
    Quote:
    "While one astronaut explores the area around the LEM, the second remains inside to maintain communications."
  8. ^ Ryba, Jeanne (ed.). "Apollo 10". NASA. Retrieved June 26, 2013.
  9. ^ "Current locations of the Apollo Command Module Capsules (and Lunar Module crash sites)". Apollo: Where are they now?. NASA. Retrieved 27 December 2014.
  10. ^ Courtney G. Brooks; James M. Grimwood; Loyd S. Swenson (September 20, 2007). "Chariots for Apollo: A History of Manned Lunar Spacecraft; Engines, Large and Small". Retrieved June 7, 2012.
  11. ^ Leary, Warren E. (27 March 2002). "T. J. Kelly, 72, Dies; Father of Lunar Module" – via NYTimes.com.
  12. ^ "LM Electrical". Encyclopedia Astronautica. Archived from the original on 2010-02-01.
  13. ^ "LM Landing Gear". Encyclopedia Astronautica. Archived from the original on 2010-02-01.
  14. ^ "SP-4402 Origins of NASA Names". NASA History. NASA. Retrieved January 16, 2015.
  15. ^ Scheer, Julian W. (Assistant Administrator for Public Affairs, NASA). Memorandum from Project Designation Committee, June 9, 1966.
  16. ^ Cortright, Edgar M. (1975). Apollo expeditions to the moon. Scientific and Technical Information Office, National Aeronautics and Space Administration. NASA.gov ch-4-2.
  17. ^ "LLRV Monograph".
  18. ^ Courtney G. Brooks; James M. Grimwood; Loyd S. Swenson (1979). "Chapter 12 Part 7". Chariots for Apollo: A History of Manned Lunar Spacecraft. NASA. ISBN 0-486-46756-2. Archived from the original on 9 February 2008. Retrieved 2008-01-29.
  19. ^ McDivitt, James A. (May 1971), "6. Trajectory", Apollo 14 Mission Report, NASA, retrieved September 24, 2012
  20. ^ "TR-201 for Delta rocket second stage derived from LMDE". 1972. Archived from the original on 2008-07-06.
  21. ^ a b c d e f g h i j https://spacecenter.org/attractions/starship-gallery/lunar-module-lta-8/
  22. ^ Maksel, Rebecca, What's real and what's not? Air & Space, June/July 2013, pp. 20-21
  23. ^ "Archived copy". Archived from the original on 2013-08-14. Retrieved 2013-10-15.CS1 maint: Archived copy as title (link) Cradle of Aviation Museum, LM-13
  24. ^ Apollo LM Truck on Mark Wade's Encyclopedia Astronautica Archived 2005-12-15 at the Wayback Machine – Description of adapted LM descent stage for the unmanned transport of cargo to a permanent lunar base.

Further reading

  • Kelly, Thomas J. (2001). Moon Lander: How We Developed the Apollo Lunar Module (Smithsonian History of Aviation and Spaceflight Series). Smithsonian Institution Press. ISBN 1-56098-998-X.
  • Baker, David (1981). The History of Manned Space Flight. Crown Publishers. ISBN 0-517-54377-X
  • Brooks, Courtney J., Grimwood, James M. and Swenson, Loyd S. Jr (1979) Chariots for Apollo: A History of Manned Lunar Spacecraft NASA SP-4205.
  • Pellegrino, Charles R. and Stoff, Joshua. (1985) Chariots for Apollo: The Untold Story Behind the Race to the Moon. Atheneum. ISBN 0-689-11559-8 (This is not the NASA history series book of the same base title, above, but a totally unrelated work.)
  • Sullivan, Scott P. (2004) Virtual LM: A Pictorial Essay of the Engineering and Construction of the Apollo Lunar Module. Apogee Books. ISBN 1-894959-14-0
  • Stoff, Joshua. (2004) Building Moonships: The Grumman Lunar Module. Arcadia Publishing. ISBN 0-7385-3586-9
  • Stengel, Robert F. (1970). Manual Attitude Control of the Lunar Module, J. Spacecraft and Rockets, Vol. 7, No. 8, pp. 941–948.

External links

Games

  • Lander On-line 2D Lunar Module Landing Simulation Game
  • Easy Lander 3D Lunar Module Landing Simulation Game
Apollo (spacecraft)

The Apollo spacecraft was composed of three parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth. The expendable (single-use) spacecraft consisted of a combined command and service module (CSM) and an Apollo Lunar Module (LM). Two additional components complemented the spacecraft stack for space vehicle assembly: a spacecraft–LM adapter (SLA) designed to shield the LM from the aerodynamic stress of launch and to connect the CSM to the Saturn launch vehicle; and a launch escape system (LES) to carry the crew in the command module safely away from the launch vehicle in the event of a launch emergency.

The design was based on the lunar orbit rendezvous approach: two docked spacecraft were sent to the Moon and went into lunar orbit. While the LM separated and landed, the CSM remained in orbit. After the lunar excursion, the two craft rendezvoused and docked in lunar orbit, and the CSM returned the crew to Earth. The command module was the only part of the space vehicle that returned with the crew to the Earth's surface.

The LES was jettisoned during launch upon reaching the point where it was no longer needed, and the SLA remained attached to the launch vehicle's upper stage. Two unmanned CSM's, one unmanned LM and one manned CSM were carried into space by Saturn IB launch vehicles for low Earth orbit Apollo missions. Larger Saturn Vs launched two unmanned CSM's on high Earth orbit test flights, the CSM on one manned lunar mission, the complete spacecraft on one manned low Earth orbit mission and eight manned lunar missions. After conclusion of the Apollo program, four CSM's were launched on Saturn IBs for three Skylab Earth orbital missions and the Apollo-Soyuz Test Project.

Apollo Docking Mechanism

The docking system of the Apollo modules was a "probe and drogue" system. The system allowed the Apollo Command/Service Module to dock with the Apollo Lunar Module, and later allowed the ASTP CSM to dock with the Docking Module (an adapter which allowed to dock with the Soyuz 19 spacecraft) and Skylab 2, Skylab 3 and Skylab 4 CSMs to dock with Skylab. There were 12 hard latches.

The Apollo system differed from the Gemini Docking Mechanism in that after locking, the probe and cone mechanism could be manually removed to allow access between the two docked craft. Ideas from this system were instrumental in creating later systems, like those used in the Space Shuttle, the International Space Station, and others.

The Apollo docking system was used successfully in thirteen missions in Earth and lunar orbits between 1969 and 1975. The only serious problems were experienced on Apollo 14 and Skylab 2, when the probe systems failed to capture the drogue receptacles during repeated docking attempts. Successful docking was eventually accomplished in both missions.

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 N2O4 oxidizer. Rocketdyne provided the injector system, at the request of NASA, when Bell could not solve combustion instability problems.

Canberra Deep Space Communication Complex

The Canberra Deep Space Communication Complex (CDSCC) is an Earth station in Australia located at Tidbinbilla in the Australian Capital Territory. Opened in 1965, the complex was used for tracking the Apollo Lunar Module. It is part of the Deep Space Network of NASA's Jet Propulsion Laboratory (JPL), managed in Australia by the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

Cape Canaveral Air Force Station Space Launch Complex 37

Cape Canaveral Air Force Station Space Launch Complex 37 (SLC-37), previously Launch Complex 37 (LC-37), is a launch complex on Cape Canaveral, Florida. Construction began in 1959 and the site was accepted by NASA to support the Saturn I program in 1963. The complex consists of two launch pads. LC-37A has never been used, but LC-37B launched unmanned Saturn I flights (1964 to 1965) and was modified and launched Saturn IB flights (1966 to 1968), including the first (unmanned) test of the Apollo Lunar Module in space. It was deactivated in 1972. In 2001 it was modified as the launch site for Delta IV, a launch system operated by United Launch Alliance.

The original layout of the launch complex featured one Mobile Service Structure which could be used to service or mate a rocket on either LC-37A or 37B, but not on both simultaneously. The Delta IV Mobile Service Tower is 330 ft (100 m) tall, and fitted to service all Delta IV configurations, including the Delta IV Heavy.

Descent propulsion system

The descent propulsion system (DPS - pronounced 'dips') or lunar module descent engine (LMDE) is a variable-throttle hypergolic rocket engine developed by Space Technology Laboratories (TRW) for use in the Apollo lunar module descent stage. It used Aerozine 50 fuel and dinitrogen tetroxide (N2O4) oxidizer. This engine used a pintle injector, a design also used later in the SpaceX Merlin engine.

Fire in the hole

"Fire in the hole" is a warning that an explosive detonation in a confined space is imminent. It originated with miners, who needed to warn their fellows that a charge had been set. The phrase appears in this sense in state mining regulations, in military and corporate procedures, and in various mining and military blasting-related print books and narratives, e.g., during bomb disposal or throwing grenades into a confined space.In common parlance it has become a catchphrase for a warning of type "Watch out!" or "Heads up!". NASA has used the term to describe a means of staging a multistage rocket vehicle by igniting the upper stage simultaneously with the ejection of the lower stage, without a usual delay of several seconds. On the Apollo 5 unmanned flight test of the first Apollo Lunar Module, a "fire in the hole test" used this procedure to simulate a lunar landing abort. Gene Kranz describes the test in his autobiography:

The fire-in-the-hole test involved shutting down the descent rocket, blowing the bolts that attached the ascent and descent stages, switching control and power to the ascent stage, and igniting the ascent rocket while still nestled to the landing stage.

Grumman Studios

Grumman Studios is a sound stage complex in Bethpage, New York that offers 160,000 square feet with seven sound stages and 30 acres of paved outdoor space.Principal owner in the project is Parviz Farahzad whose production company is Lunar Module Park, LLC. The studios are in the former Apollo Lunar Module assembly plant at the massive Grumman aircraft works in Bethpage. Farahzad founded the company in 2007. The original blue Grumman landmark dome atop the facility has been repainted red for the new studio.

Grumman Studios is one of two large sound stage complexes in Bethpage related to the original Grumman operation. The other is Gold Coast Studios which has six sound stages totaling 105,000 square feet in Steel Equities Bethpage Business Park.The studio is at 500 Grumman Road West in Bethpage.

Héroux-Devtek

Héroux-Devtek is a Canadian company based in Longueuil, Quebec, specializing in the manufacture and repair of various industrial components, energy, and aviation. The greatest achievement of this undertaking was the landing gear of the Apollo Lunar Module that put Neil Armstrong on the moon as part of the mission Apollo 11 in 1969.

Héroux-Devtek's activities include:

Landing gear & actuation

Gas turbine components

Filtration & assembliesThe firm uses various metals such as steel, aluminum, iron, and titanium. March 31, 2011, Héroux-Devtek recorded revenues of CA$357.6 million and a profit of CA$18.5 million. It employs a workforce of 1342 employees.

Kosmos 379

Kosmos 379 (Russian: Космос 379 meaning "Cosmos 379") was an unmanned test of the LK (the Soviet counterpart of the Apollo Lunar Module) in Earth orbit.

LEM

LEM may refer to:

The Lake Erie Monsters (now the Cleveland Monsters), a professional ice hockey team based in Ohio

Lamina emergent mechanism, found in pop-up books

The law of excluded middle, in classical logic

Learnable Evolution Model, an evolutionary computation method

LEM, a musical instrument brand name of Generalmusic

LEM domain-containing protein 3, a membrane protein associated with laminopathies

Liquid Elastomer Molding, a gasket technology developed by the Federal-Mogul Corporation

Lunar Excursion Module, the original designation of the Apollo Lunar Module

Lymphocyte expansion molecule

Station code for the Leyton Midland Road railway station in the United Kingdom

Lay Eucharistic Minister, in the Catholic, Episcopal or Lutheran Churches

LEROS

LEROS is a family of chemical rocket engines manufactured by Nammo at Westcott, Buckinghamshire, United Kingdom. LEROS engines have been used as primary apogee engines for telecommunications satellites such as the Lockheed Martin A2100 as well as deep space missions such as Juno.The family of engines derives from the LEROS 1 which was developed and qualified in the 1990s by Royal Ordnance. The in-space propulsion business was acquired by British Aerospace, then had a sequence of owners including American Pacific Corporation, Moog (from 2012) and Nammo (2017). The LEROS engines are made of niobium alloy, which is traditionally used for liquid rocket engines such as the main engine of the Apollo Lunar Module. As of 2011, more than 70 LEROS 1 series engines had been flown successfully.

LK (spacecraft)

The LK (Russian: ЛК, from Russian: Лунный корабль, "Lunniy korabl", meaning "lunar craft"; GRAU index: 11F94) was a piloted lunar lander developed in the 1960s as a part of the Soviet attempts at human exploration of the Moon. Its role was analogous to the American Apollo Lunar Module (LM). Several LK modules were flown without crew in Earth orbit, but no LK ever reached the Moon. The development of the N1 launch vehicle required for the Moon flight suffered setbacks (including several launch failures), and the first Moon landings were achieved by US astronauts. As a result, both the N1 and the LK programs were cancelled without any further development.

Lunar basalt 70017

The Lunar basalt 70017 is a Moon rock gathered in 1972 by astronauts Eugene Cernan and Harrison Schmitt on the Apollo 17 mission near their Apollo Lunar Module from the valley of Taurus-Littrow on the Moon and divided into 1.1 gram pieces.

Peter Bielkowicz

Peter Bielkowicz (1 February 1902 – 30 September 1993) was a physicist. He worked on designing the Apollo Lunar Module and many other projects. He developed and taught courses in many fields, including aerodynamics, flight mechanics, ballistics, mathematics, and astrodynamics. He created the Air Force Institute of Technology (AFIT)'s first courses in space mechanics and spaceflight.

He was a doctor of mathematics working in the Polish aircraft industry when Germany overran Poland. He evaded capture and made his way to France only to be overrun again by the Germans. He escaped to Spain by crossing the Pyrenees Mountains on foot and then walked through Spain. Just as he was about to step onto British soil at Gibraltar, the Spanish police arrested him. After two years in a Spanish prison, he was set free when the Allies of World War II defeated the Axis powers in Africa. He worked in the British aircraft industry for a few years after the war, and later was recruited by the United States while the United States space program was still in its infancy.

Professor Bielkowicz joined the faculty of the Air Force Institute of Technology School of Engineering in July 1953 as an Assistant Professor. He worked on designing the Apollo Lunar Module and many other projects including reusable spacecraft. He developed and taught courses in many fields, including aerodynamics, flight mechanics, ballistics, mathematics, and astrodynamics. He created AFIT's first courses in space mechanics and spaceflight. His astrodynamics courses were a central focus of the AFIT astronautics program introduced in 1958.

He also introduced orbital mechanics and familiarized his students with Moulton’s text on celestial mechanics. These classes taught missile trajectories and orbits. The missile ballistics class covered the ballistic flight solutions and various empirical solutions that had been developed.

Powered Descent Initiation

Powered Descent Initiation (PDI) is a term used during the Apollo program Moon landing missions to describe the maneuver of the Apollo Lunar Module as it descended from lunar orbit to landing. "Eagle was GO to ignite its descent engine, and Armstrong and Aldrin locked their eyes to the glowing numbers displayed before them. They were almost at an invisible junction of height, speed, range, and time when everything would join together for commitment. When the instruments told them that they were 192 miles from their projected landing site, and were precisely 50,174 radar~measured feet above the long shadows of the moon, they would unleash decelerating thrust and begin slowing their speed for the touchdown.....this was it. PDI. Powered Descent Initiate."

Pressure-fed engine

The pressure-fed engine is a class of rocket engine designs. A separate gas supply, usually helium, pressurizes the propellant tanks to force fuel and oxidizer to the combustion chamber. To maintain adequate flow, the tank pressures must exceed the combustion chamber pressure.

Pressure fed engines have simple plumbing and have no need for complex and occasionally unreliable turbopumps. A typical startup procedure begins with opening a valve, often a one-shot pyrotechnic device, to allow the pressurizing gas to flow through check valves into the propellant tanks. Then the propellant valves in the engine itself are opened. If the fuel and oxidizer are hypergolic, they burn on contact; non-hypergolic fuels require an igniter. Multiple burns can be conducted by merely opening and closing the propellant valves as needed, if the pressurization system also has activating valves. They can be operated electrically, or by gas pressure controlled by smaller electrically operated valves.

Care must be taken, especially during long burns, to avoid excessive cooling of the pressurizing gas due to adiabatic expansion. Cold helium won't liquify, but it could freeze a propellant, decrease tank pressures, or damage components not designed for low temperatures. The Apollo Lunar Module Descent Propulsion System was unusual in storing its helium in a supercritical but very cold state. It was warmed as it was withdrawn through a heat exchanger from the ambient temperature fuel.Spacecraft attitude control and orbital maneuvering thrusters are almost universally pressure-fed designs.

Examples include the Reaction Control (RCS) and the Orbital Maneuvering (OMS) engines of the Space Shuttle orbiter; the RCS and Service Propulsion System (SPS) engines on the Apollo Command/Service Module; the SuperDraco (propulsive landing) and Draco (RCS) engines on the Dragon V2; and the RCS, ascent and descent engines on the Apollo Lunar Module.Some launcher upper stages also use pressure-fed engines. These include the Aerojet AJ10 and TRW TR-201 used in the second stage of Delta II launch vehicle,

and the Kestrel engine of the Falcon 1 by SpaceX.The 1960s Sea Dragon concept by Robert Truax for a big dumb booster would have used pressure-fed engines.

Pressure-fed engines have practical limits on propellant pressure, which in turn limits combustion chamber pressure. High pressure propellant tanks require thicker walls and stronger alloys which make the vehicle tanks heavier, thereby reducing performance and payload capacity. The lower stages of launch vehicles often use either solid fuel or pump-fed liquid fuel engines instead, where high pressure ratio nozzles are considered desirable.Other vehicles or companies using pressure-fed engine:

Firefly Space Systems

OTRAG (rocket)

Quad (rocket) of Armadillo Aerospace

XCOR EZ-Rocket of XCOR Aerospace

Masten Space Systems

Aquarius Launch Vehicle

NASA's Project Morpheus prototype lander

NASA Mighty Eagle mini lunar lander

CONAE's Tronador II upper stage

Thomas J. Kelly (aerospace engineer)

Thomas Joseph Kelly (June 14, 1929 – March 23, 2002) was an American aerospace engineer. Kelly primarily worked on the Apollo Lunar Module, which earned him the name of "Father of the Lunar Module" from NASA.

Kelly graduated from Cornell University in 1951, where he was a member of the Quill and Dagger society. Afterwards, Kelly obtained his MS degree from Columbia University and Ph.D. from the Polytechnic Institute of Brooklyn.

Kelly was the project engineer, engineering manager and deputy program manager for Grumman Aircraft's Apollo Lunar Module (1962–1970). His 2001 book Moon Lander: How We Developed the Apollo Lunar Module documents the process of designing, building and flying the Lunar Module.

Kelly was portrayed by Matt Craven in the 1998 miniseries From the Earth to the Moon.

Tranquility Base

Tranquility Base (Latin: Statio Tranquillitatis) is the site on the Moon where, in 1969, humans landed and walked on another celestial body for the first time. On July 20, 1969, Apollo 11 crewmembers Neil Armstrong and Buzz Aldrin landed their Apollo Lunar Module Eagle at approximately 20:17:40 UTC. Six hours later, the two astronauts exited the spacecraft and spent 2 hours 31 minutes on the lunar surface, examining and photographing it, setting up some scientific experiment packages, and collecting 47.5 pounds (21.5 kg) of dirt and rock samples for return to Earth. They lifted off the surface on July 21 at 17:54 UTC. Tranquility Base has remained unvisited since then.

Its lunar coordinates are 00°41′15″N, 23°26′00″E, in the south-western corner of the lunar lava-plain called Mare Tranquillitatis ("Sea of Tranquility"), east of the craters Sabine and Ritter, north of the crater Moltke, and near a rille called Rimae Hypatia, but unofficially called "U.S. 1".

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