Apollo Lunar Module
| Grumman Apollo LM | | Apollo LM on lunar surface |
| Description |
|---|
| Role: | Lunar landing |
| Crew: | 2; CDR, LM pilot |
| Dimensions |
|---|
| Height: | 20.9 ft | 6.37 m |
| Diameter: | 14 ft | 4.27 m |
| Landing gear span: | 29.75 ft | 9.07 m |
| Volume: | 235 ft3 | 6.65 m3 |
| Masses |
|---|
| Ascent module: | 10,024 lb | 4,547 kg |
| Descent module: | 22,375 lb | 10,149 kg |
| Total: | 32,399 lb | 14,696 kg |
| Rocket engines |
|---|
| LM RCS (N2O4/UDMH) x 16: | 100 lbf ea | 441 N |
Ascent Propulsion System
(N2O4/Aerozine 50) x 1: | 3,500 lbf ea | 15.6 kN |
Descent Propulsion System
(N2O4/Aerozine 50) x 1: | 9,982 lbf ea | 44.40 kN |
| Performance |
|---|
| Endurance: | 3 days | 72 hours |
| Aposelene: | 100 miles | 160 km |
| Periselene: | surface | surface |
| Spacecraft delta v: | 15,390 ft/s | 4,690 m/s |
| Apollo LM diagram |
|---|
| Apollo LM diagram (NASA) |
| Grumman Apollo LM |
|---|
|
|
The LEM flight instrumentation panel and front windows. Credit: Alexandre Sabbatini |
The
Apollo Lunar Module was the
lander portion of the
Apollo spacecraft built for the
US Apollo program to achieve the transit from
moon orbit to the surface and back. The module was also known as the
LM from the manufacturer designation (yet pronounced "LEM" from NASA's early name for it,
Lunar Excursion Module).
The module was designed to carry two crew in a 6.65 m³ space. The total module was 6.4 m high and 4.3 m across, resting on four legs. It consisted of two stages—the descent stage module and the ascent stage. The total mass of the module was 15,264 kg with the majority of that (10,334 kg) in the descent stage.
The Apollo Lunar Module came into being because NASA chose to reach the moon via a lunar orbit
rendezvous(LOR) instead of a direct ascent or Earth orbit rendezvous (EOR) (see
Choosing a mission mode for more information on the available rendezvous types). Both a direct ascent and an EOR would have involved the entire Apollo spacecraft landing on the moon; once the decision had been made to proceed using LOR, it became necessary to produce a separate craft capable of reaching the lunar surface.
The LM contract was given to
Grumman Aircraft Engineering and a number of subcontractors. Grumman had begun lunar orbit rendezvous studies in late 1950s and again in 1962. In July 1962 eleven firms were invited to submit proposals for the LM. Nine did so in September, and Grumman was awarded the contract that same month. The contract cost was expected to be around $350 million. There were initially four major subcontractors -
Bell Aerosystems (ascent engine),
Hamilton Standard (environmental control systems),
Marquardt (reaction control system) and
Rocketdyne (descent engine).
The
primary guidance, navigation and control system (PGNCS) on the LM was developed by the
MIT Instrumentation Laboratory. The
Apollo Guidance Computer was manufactured by
Raytheon. A similar guidance system was used in the
Command Module. A backup navigation tool, the Abort Guidance System (AGS), was developed by
TRW.
To learn lunar landing techniques, astronauts practiced in the Lunar Landing Research Vehicle (
LLRV), a flying vehicle that simulated the Lunar Module on earth. A 200'-tall, 400'-long gantry structure was constructed at NASA
Langley Research Center; the LLRV was suspended in this structure from a crane, and "piloted" by moving the crane. (The facility is now known as the Impact Dynamics Research Facility, and is used for aircraft crash tests.)
Configuration freeze did not start until April 1963 when the ascent and descent engine design was decided. In addition to Rocketdyne a parallel program for the descent engine was ordered from
Space Technology Laboratories in July 1963, and by January 1965 the Rocketdyne contract was cancelled. As the program continued there were numerous redesigns to save weight (including 'Operation Scrape'), improve safety, and fix problems. For example initially the module was to be powered by
fuel cells, built by
Pratt and Whitney but in March 1965 they were paid off in favor of an all battery design.
The initial design iteration had the LEM with three landing legs. It was felt that three legs, though the lightest configuration, was the least stable if one of the legs were damaged during landing. The next landing gear design iteration had five legs and was the most stable configuration for landing on an unknown terrain. That configuration was too heavy and the compromise was four landing legs.
The first LM flight was on January 22, 1968 when the unmanned LM-1 was launched on a Saturn IB for testing of propulsion systems in orbit. The next LM flight was aboard
Apollo 9 using LM-3 on March 3, 1969 as a manned flight (McDivitt, Scott and Schweickart) to test a number of systems in Earth orbit including LM and CSM crew transit, LM propulsion, separation and docking.
Apollo 10, which launched on May 18, 1969, was another series of tests, this time in lunar orbit with the LM separating and descending to within 10 km of the surface. From the successful tests the LM successfully descended and ascended from the lunar surface with
Apollo 11.
In April 1970, the lunar module Aquarius played an unexpected role in saving the lives of the three astronauts of the
Apollo 13 mission (Commander James A. Lovell Jr., CSM pilot John L. Swigert Jr., and LM pilot Fred W. Haise Jr.), after an electrical short circuit caused an oxygen tank in that mission's
service module to overheat and explode. Aquarius served as a refuge for the astronauts during their return to Earth orbit, while its batteries were used to recharge the vital re-entry batteries of the command module that brought the astronauts through the Earth's atmosphere and to a safe spashdown on
April 17,
1970. The LM's descent engine, designed to slow the vehicle during its descent to the moon, was used to accelerate the Apollo 13 spacecraft around the moon and back to Earth. After the accident, the LM's systems, designed to support two astronauts for 45 hours, actually supported three astronauts for 90 hours.
The Lunar Module was the portion of the Apollo spacecraft that landed on the moon and returned to lunar orbit. It is divided into two major parts, the Descent Module and the Ascent Module.
The Descent Modules contains the landing gear, landing radar antenna, descent rocket engine, and fuel to land on the moon. It also had several cargo compartments used to carry among other things, the Apollo Lunar Surface Experiment Packages
ALSEP, Mobile Equipment Cart (a hand pulled equipment cart—
Apollo 14), the
Lunar Rover (moon car)—
Apollo 15, 16 and 17), surface television camera, surface tools and lunar sample collection boxes. It also carried the majority of the LM's battery power and oxygen, along with the single water tank needed to both cool the electronics and provide the astronauts with enough drinking water for a 2 to 3 day stay. Also, on the ladder of the descent stage is attached a
plaque.
The Ascent Module contains the crew cabin, instrument panels, overhead hatch/docking port, forward hatch, reaction control system, radar and communications antennas, ascent rocket engine and enough fuel, battery power, and breathing oxygen to return to lunar orbit and rendezvous with the Apollo Command and Service Modules.
*
Specifications: (Baseline LM)**
Ascent Stage:***Crew: 2
***Crew cabin volume: 6.65 m³ (235 ft³)
***Height: 3.76 m (12.34 ft)
***Diameter: 4.2 m (13.78 ft)
***Mass including fuel: 4,670 kg (10,300 lb)
***Atmosphere: 100% oxygen at 250
mmHg (33 kPa)
***Water: two 19.3 kg (42.5 lb) storage tanks
***Coolant: 11.3 kg (25 lb) of
ethylene glycol/water solution
***RCS (Reaction Control System) Propellant mass: 287 kg (633 lb)
***RCS thrusters: 16 x 445 N; four quads
***RCS propellants: N2O4/UDMH
***RCS specific impulse: 2.84 kN·s/kg
***APS Propellant mass: 2,353 kg (5,187 lb)
***APS thrust: 15.6 kN (3,500 lbf)
***APS propellants: N
2O
4/
Aerozine 50 (UDMH/N2H4)
***APS pressurant: 2 x 2.9 kg helium tanks at 21 MPa
***
Engine specific impulse: 3.05 kN·s/kg
***Thrust-to-weight ratio: 0.34
***Ascent stage delta V: 2,220 m/s (7,280 ft/s)
***Batteries: 2 x 296 A·h silver-zinc batteries
***Power: 28 V DC, 115 V 400 Hz AC
Thus the thrust was less than the weight on Earth, but enough on the Moon.
**
Descent Stage:***Height: 3.2 m (10.5 ft)
***Diameter: 4.2 m (13.8 ft)
***Landing gear diameter: 9.4 m (30.8 ft)
***Mass including fuel: 10,334 kg (22,783 lb)
***Water: 1 x 151 kg storage tank
***Power: 2 x 296 A·h silver-zinc batteries (secondary system)
***Propellants mass: 8,165 kg (18,000 lb)
***DPS thrust: 45.04 kN (10,125 lbf), throttleable to 4.56 kN (1025 lbf)
***DPS propellants: N
2O
4/Aerozine 50 (UDMH/N
2H
4)
***DPS pressurant: 1 x 22 kg supercritical helium tank at 10.72 kPa.
***
Engine specific impulse: 3050 N·s/kg
***Descent stage delta V: 2,470 m/s (8,100 ft/s)
***Batteries: 4 x 400 A·h silver-zinc batteries
 |
Apollo Spacecraft: Apollo Lunar Module Diagram. |
 |
Apollo Lunar Module |
| Serial number | Use | Launch date | Current location |
|---|
| LM-1 | Apollo 5 | January 22, 1968 | Reentered Earth's atmosphere |
LM-2
| Not flown
| On display at the National Air and Space Museum, Washington, DC. (Photo).
|
| LM-3 Spider | Apollo 9 | March 3, 1969 | Reentered Earth's atmosphere |
| LM-4 Snoopy | Apollo 10 | May 18, 1969 | Descent stage impacted Moon; Ascent stage in solar orbit |
| LM-5 Eagle | Apollo 11 | July 16, 1969 | Descent stage on lunar surface; Ascent stage left in lunar orbit, eventually crashed on moon |
| LM-6 Intrepid | Apollo 12 | November 14, 1969 | Descent stage on lunar surface; Ascent stage deliberately crashed into moon |
| LM-7 Aquarius | Apollo 13 | April 11, 1970 | Reentered Earth's atmosphere over Fiji |
| LM-8 Antares | Apollo 14 | January 31, 1971 | Descent stage on lunar surface; Ascent stage deliberately crashed into moon |
LM-9
| Not flown
| On display at the Kennedy Space Center (Apollo/Saturn V Center)
|
| LM-10 Falcon | Apollo 15 | July 26, 1971 | Descent stage on lunar surface; Ascent stage deliberately crashed into moon |
| LM-11 Orion | Apollo 16 | April 16, 1972 | Descent stage on lunar surface; Ascent stage deliberately crashed into moon |
| LM-12 Challenger | Apollo 17 | December 7, 1972 | Descent stage on lunar surface; Ascent stage deliberately crashed into moon |
LM-13
| Not flown (meant for later Apollo flights)
| Partially completed by Grumman; restored and on display at Cradle of Aviation, Long Island, New York |
LM-14
| Not flown (meant for later Apollo flights)
| Never completed; unconfirmed reports claim that some parts (in addition to parts from test vehicle LTA-3) are included in LM on display at the Franklin Institute, Philadelphia (see Franklin Institute webpage.) |
LM-15
| Not flown (meant for later Apollo flights)
| Scrapped
|
| Serial number | Use | Launch date | * For the location of LMs left on the Lunar surface, see the list of artificial objects on the Moon. |
The Apollo LM Truck was a stand-alone LM descent stage intended to deliver up to five metric tons of payload to the Moon for an unmanned landing. This technique was intended to deliver equipment and supplies to a permanent manned
lunar base that was never built. As originally proposed, it would be launched on a Saturn V with a full Apollo crew to accompany it to lunar orbit and then guide it to a landing next to the base; the base crew would then unload the "truck" while the orbiting crew returned to earth.
The LM and LM Truck, using a modified mission profile, appear in
Shane Johnson's novel
Ice, about a fictional
Apollo 19 mission that takes a disastrous turn. In this scenario, the LM Truck is delivered on a
Saturn IB and makes a preprogrammed landing at the proposed landing site; a J-mission Apollo crew then lands a conventional LM next to it, in a feat of precision landing recalling that of
Pete Conrad during
Apollo 12. Also in this novel, the LM, which happens to be LM-13, fails to fire its ascent engine, stranding two astronauts on the Moon--something that never happened in Project Apollo.
In the movie
Superman 2, the film's supervillains visit the moon on their way to earth, and encounter a modernized version of the LM (still bearing an obvious resemblance), which they destroy along with its crew of three (two Americans, one Soviet).
The LM design was later incorporated into the
Apollo Telescope Mount on the successful
Skylab space station. Originally planned to be launched on an unmanned Saturn 1B rocket, similar to the unmanned
Apollo 5 test flight, NASA decided to save costs and launch the ATM with the station itself. This decision saved the station, as the ATM's "windmill" solar panels helped keep the station operation after its surviving solar panel on the station was damaged during launch (the other was ripped off).
In 2005, NASA announced that the successor to the
Space Shuttle, the
Crew Exploration Vehicle, would feature, for its lunar landing missions, a
Lunar Surface Access Module (LSAM) which is roughly based on the Apollo LM. Like the LM, it has both descent and ascent module (the latter to house the crew), but unlike the LM, it will incorporate improved computer systems, laser-range and radar tracking systems for landing, waste-management systems, and an airlock for the crew, eliminating the need to depressurize the entire cockpit and allowing the astronauts to track as little lunar dust into the cabin as possible (a problem highly associated with the last three Apollo missions, when crews went into the lunar highlands).
The LSAM will be powered by four
RL-10 engines descent stage and a single RL-10 engine in the ascent stage, both of which are fueled by liquid hydrogen (LH2) and liquid oxygen (LOX), which is more powerful than the hypergolic fuels used on the LM. This will allow the LSAM to land in the polar regions of the Moon (Apollo was limited to the equatorial regions), which is a desired location for a future lunar base.
In addition, the LSAM can be flown by an astronaut crew, or even unmanned, the latter to bring supplies to the future lunar outpost, thus the LSAM would function as the proposed "LM Truck" that was envisioned in the
Apollo Applications Program. In the unmanned configuration, the LSAM can carry as much weight as that of the LM itself.
The only major difference between the LSAM and the LM is that the LSAM will be launched separately on the
Shuttle-derived Ares V rocket, with the CEV being launched separately on the man-rated
Ares I rocket. Once in orbit, the CEV will then dock with the LSAM and then be propelled to the Moon on the
Earth Departure Stage. The LM, on the other hand, was launched along with the CSM on the
Saturn V rocket and then was retrieved after the S-IVB finished firing the trans lunar injection burn.
As an additional note, the LM was given a call sign to identify it separately from the CSM – the LSAM will possibly bear the name "Artemis," while the CEV will possibly bear the name "Altair."
*
Nasa catalogue: Apollo 14 Lunar Module*
Space/Craft Assembly & Test Remembered – A site "dedicated to the men and women that designed, built and tested the Lunar Module at Grumman Aerospace Corporation, Bethpage, New York"
*
Apollo 11 LM Structures handout for LM-5 (PDF) – Training document given to astronauts which illustrates all discrete LM structures
*
Apollo 15 LM Activation Checklist for LM-10 – Checklist detailing how to prepare the LM for activation and flight during a mission
*
Apollo LM Truck on Mark Wade's Encyclopedia Astronautica – Description of adapted LM descent stage for the unmanned transport of cargo to a permanent lunar base.
* Kelly, Thomas J. (2001).
Moon Lander: How We Developed the Apollo Lunar Module (Smithsonian History of Aviation and Spaceflight Series). Smithsonian Institution Press. ISBN 156098998X.
* Baker, David (1981).
The History of Manned Space Flight. Crown Publishers. ISBN 051754377X
* Brooks, Courtney J., Grimwood, James M. and Swenson, Loyd S. Jr (1979)
Chariots for Apollo: A History of Manned Lunar Spacecraft NASA SP-4205.
* Sullivan, Scott P. (2004)
Virtual LM: A Pictorial Essay of the Engineering and Construction of the Apollo Lunar Module. Apogee Books. ISBN 1894959140
* Stoff, Joshua. (2004)
Building Moonships: The Grumman Lunar Module. Arcadia Publishing. ISBN 0738535869
