Lunar Module

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 - a descent stage and a module and ascent stage. The total mass of the module was 15,264 kg with the majority of that (10,334 kg) in the descent stage.

History

The Apollo program was developed over a number of key decisions. Once it had been decided to use a lunar orbit rendezvous (LOR) method to reach the Moon it became necessary to produce a separate unit capable of reaching the surface.

The LM contract was given to Grumman Aircraft Engineering and a number of subcontractors. Grumman had begun lunar orbit rendezvous studies in late 1960 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.

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 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.

Lunar Module (LM) specifications

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 Module 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.

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 fuel 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 (234.84 ft³)
    • Height: 3.76 m (12.34 ft)
    • Diameter: 4.2 m (13.78 ft)
    • Mass including fuel: 4,670 kg (10,295 lb)
    • Atmosphere: 100% oxygen at 250 mmHg (33 kPa)
    • Water: 2 19.27 kg storage tanks
    • Coolant: 11.3 kg of ethylene glycol/water solution
    • RCS Propellant mass: 287 kg (633 lb)
    • APS Propellant mass: 2,353 kg (5,227 lb)
    • RCS thrusters: 16 x 445 N; four quads
    • RCS propellants: N2O4/UDMH
    • RCS specific impulse: 2844 Ns/kg
    • APS thrust: 15 kN (3,375 lbf)
    • APS propellants: N2O4/UDMH
    • APS pressurant: 2 x 2.9 kg helium tanks at 214 kg/square cm
    • Engine specific impulse: 3050 Ns/kg
    • Ascent stage delta V: 2,220 m/s (7,283 ft/s)
    • Batteries: 4 x 400 Ah silver-zinc batteries
    • Power: 26-32 V dc buses

• • 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 Ah silver-zine batteries (secondary system)
    • Propellants mass: 8,165 kg (18,000 lb)
    • DPS thrust: 45 kN (10,125 lbf), throttleable to 4.8 kN (1025 lbf)
    • DPS propellants: N2O4/UDMH
    • DPS pressurant: 1 x 22 kg supercritical helium tank at 10.72 kPa.
    • Engine specific impulse: 3050 Ns/kg
    • Descent stage delta V: 2,470 m/s (8,100 ft/s)
    • Batteries: 2 x 296 Ah silver-zinc batteries