Apollo Lunar Module

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

The module was designed to carry a crew of two and rested on four landing 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 (10,334 kg) in the descent stage. Initially unpopular because the many delays in its development significantly stretched the projected timeline of the Apollo program, the LM eventually became the most reliable component of the Apollo/Saturn system, the only one never to suffer any failure that significantly impacted a mission, ["Moon Race: The History of Apollo" DVD, Columbia River Entertainment (Portland, OR, 2007)] and in at least one instance (LM-7 "Aquarius") greatly exceeded its design requirements.

History

The Apollo Lunar Module came into being because NASA chose to reach the moon via lunar orbit rendezvous (LOR) instead of by direct ascent or Earth orbit rendezvous (EOR). Both direct ascent and 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 and ascending back to lunar orbit.

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

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

To learn lunar landing techniques, astronauts practiced in the Lunar Landing Research Vehicle (LLRV), a flying vehicle that simulated the Lunar Module on earth. A 200-foot (61 m)-tall, 400-foot (122 m)- 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.

Early configurations of the LEM included a forward docking port; initially, it was believed the LEM crew would be active in the docking with the CSM. Early designs included large curved windows. A configuration freeze did not start until 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 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, the module was initially supposed to be powered by fuel cells built by Pratt and Whitney, but in March 1965 they were discarded in favor of an all battery design.Fact|date=March 2008

The initial design iteration had the LEM with three landing legs. As any particular leg would have to carry the weight of the vehicle if it lands at any significant angle, three legs was the lightest configuration. However, it would be 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, however, was too heavy and the designers compromised on four landing legs.

The first LM flight was on January 22, 1968 when the unmanned LM-1 was launched atop 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 the first manned test flight (crew McDivitt, Scott and Schweickart) to test a number of systems in Earth orbit including LM and CSM crew transit, LM propulsion, separation and docking. "Apollo 10", launched on May 18, 1969, was another series of tests, this time in lunar orbit with the LM separating and descending to within 10 km of the surface. From the successful tests the LM successfully descended to 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 after an oxygen tank in the service module exploded. "Aquarius" served as a refuge for the astronauts during their return to Earth, while its batteries were used to recharge the vital re-entry batteries of the command module that brought the astronauts through the Earth's atmosphere and to a safe splashdown on April 17, 1970. The LM's descent engine, designed to slow the vehicle during its descent to the moon, was used to accelerate the "Apollo 13" spacecraft around the moon and back to Earth. The LM's systems, designed to support two astronauts for 45 hours, actually supported three astronauts for 90 hours.

The Lunar Modules for the final three "Apollo" missions (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 ten-inch extension to the engine nozzle, and the descent fuel tanks were increased in size. The most important cargo on these missions was the Lunar Roving Vehicle, which was stowed on Quadrant 1 of the LM Descent Stage and deployed by astronauts after landing. The upgraded capability of these "J-Mission" LMs allowed three day stays on the moon.

Lunar Module specifications

The Lunar Module was the Apollo spacecraft that landed on the moon and returned to lunar orbit. It consists of the Descent and Ascent stages.

The Descent stage contains the landing gear; EVA ladder; landing radar; descent rocket engine and fuel to land on the moon. It has several cargo compartments with replacement PLSS batteries and lithium hydroxide canisters; the Apollo Lunar Surface Experiment Packages ALSEP; Mobile Equipment Cart (a hand-pulled equipment cart used on "Apollo 14") or the Lunar Rover (used on "Apollo 15", "16", and "17"); deployable S-band antenna (Apollo 11-14); surface television camera; surface tools; and lunar sample collection boxes. The descent stage carried consumables for the lunar stay: batteries; oxygen and water for drinking and cooling. The descent stage ladder carried a plaque.

The Ascent stage contains the crew cabin; environmental control (life support) system; instrument panels; overhead hatch/docking port; forward hatch; reaction control system; rendezvous radar; VHF and S-band communications equipment and antennae; guidance and navigation systems (primary and backup); active thermal control system (an ice sublimator); ascent rocket engine; and enough fuel, battery power, and breathing oxygen to return to lunar orbit and rendezvous with the Apollo Command and Service Module. The ascent stage also carried lunar rock and soil samples back with the crew, as much as 238 pounds on "Apollo 17".

*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 33 kPa (4.8 lb/in²)
***Water: two 19.3 kg (42.5 lb) storage tanks
***Coolant: 11.3 kg (25 lb) of ethylene glycol/water solution
***Thermal Control: one active water-ice sublimator.
***RCS (Reaction Control System) Propellant mass: 287 kg (633 lb)
***RCS thrusters: 16 x 445 N; four quads
***RCS propellants: N2O4/Aerozine 50
***RCS specific impulse: 2.84 km/sec (290 "seconds")
***APS Propellant mass: 2,353 kg (5,187 lb)
***APS thrust: 15.6 kN (3,500 lbf)
***APS propellants: N₂O₄/Aerozine 50
***APS pressurant: 2 x 2.9 kg helium tanks at 21 MPa
***Engine specific impulse: 3.05 km/sec (311 "seconds")
***Thrust-to-weight ratio at liftoff: 0.34 in Earth gravity, but 2.06 on the Moon
***Ascent stage delta V: 2,220 m/s (7,280 ft/s)
***Batteries: two 28-32 volt, 296 ampere-hour silver-zinc batteries; 56.7 kg each
***Power: 28 V DC, 115 V 400 Hz AC
**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
***Propellants mass: 8,165 kg (18,000 lb)
***DPS thrust: 45.04 kN (10,125 lbf), throttleable between 10% and 60% of full thrust
***DPS propellants: N₂O₄/Aerozine 50 (UDMH/N₂H₄)
***DPS pressurant: 1 x 22 kg supercritical helium tank at 10.72 kPa.
***Engine specific impulse: 3.05 km/sec (311 "seconds")
***Descent stage delta V: 2,470 m/s (8,100 ft/s)
***Batteries: four (Apollo 9-14) or five (Apollo 15-17) 28-32V, 415 A-h silver-zinc batteries; 61.2 kg each

Lunar Modules produced

LM Truck

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.

Depiction in fiction

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 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 Pete Conrad's of "Apollo 12". Also in this novel, the LM, which happens to be [http://www.cradleofaviation.org/exhibits/space/lm-13/index.html LM-13] , fails to fire its ascent engine, stranding two astronauts on the Moon — something that never happened in Project Apollo.

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

In the 1975 Sid and Marty Krofft children's show "Far Out Space Nuts", two workers (Chuck McCann and Bob Denver) are accidentally launched into space, and their spacecraft is modeled after the LM.

Successors

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

In 2005, NASA announced that the successor to the Space Shuttle, the Orion spacecraft (itself based on the Apollo CSM), would feature, for its lunar landing missions, a Lunar Surface Access Module (LSAM) roughly based on the Apollo LM. Like the LM, it has both descent and ascent modules (the latter to house the crew), but unlike the LM, it will incorporate improved computer systems, laser ranging and radar tracking systems for landing, waste-management systems, and an airlock for the crew, eliminating the need to depressurize the entire cockpit and reducing lunar dust tracked into the cabin to a minimum (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 in the descent stage and a single RL-10 in the ascent stage, all fuelled by liquid hydrogen (LH2) and liquid oxygen (LOX), which produce greater specific impulse than the hypergolic fuels used on the LM (as well as being safer, as LH2 and LOX produces water, while hypergolics are very toxic). This will allow the LSAM to land anywhere on the Moon, although NASA has targeted the polar regions of the Moon (Apollo was limited to the equatorial regions), which is a desired location for a future lunar base.

In addition, the LSAM can be flown by an astronaut crew, or unmanned (similar in nature to the drones used by the U.S. Air Force), the latter to bring supplies to the future lunar outpost(s). Thus, the LSAM could function as the proposed, yet unflown "LM Truck" envisioned in the Apollo Applications Program. In the unmanned configuration, the LSAM's payload equals the LM's fully fuelled weight.

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

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

Media

Apollo 15 landing on the Moon seen from the perspective of the Lunar Module Pilot. Starts at about 5000 feet
Apollo 15's Lunar Module blasts off and leaves the moon. View from TV camera on Rover
Apollo 15's Lunar Module blasts off and leaves the moon. View from inside LM
Apollo 17's Lunar Module blasts off and leaves the moon. View from TV camera on Rover

See also

* Apollo Command/Service Module
* List of artificial objects on the Moon
* Lunar rover
* Project Apollo

Notes

References

* 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) [http://www.hq.nasa.gov/office/pao/History/SP-4205/cover.html "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 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

* [http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1971-008C Nasa catalogue: Apollo 14 Lunar Module]
* [http://www.ehartwell.com/LM//index.htm 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"
* [http://history.nasa.gov/alsj/a11/a11LM5structures.pdf Apollo 11 LM Structures handout for LM-5] (PDF) – Training document given to astronauts which illustrates all discrete LM structures
* [http://www.btinternet.com/~ursine/LMhandbook.pdf Apollo Operations Handbook, Lunar Module (LM 10 and Subsequent), Volume One. Subsystems Data] (PDF) Manufacturers Handbook covering the systems of the LM.
* [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710071423_1971071423.pdf Apollo Operations Handbook, Lunar Module (LM 11 and Subsequent), Volume Two. Operational Procedures] Manufacturers Handbook covering the procedures used to fly the LM.
* [http://history.nasa.gov/ap15fj/lmactindex.htm Apollo 15 LM Activation Checklist for LM-10] – Checklist detailing how to prepare the LM for activation and flight during a mission
* [http://www.astronautix.com/craft/apotruck.htm 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.
* [http://www.maniacworld.com/lem-video-2.htm Lunar Module Launch] Video
* [http://www.easylander.com Easy Lander] 3D Lunar Module Landing Simulation Game