LUNAR MODULE.

(P-73) Lunar Module.

Function

    The lunar module carries two astronauts from lunar orbit to the surface of the moon; serves as living quarters and a base of operations on the moon, and returns the two men to the CSM in lunar orbit. The descent stage is left on the moon; the ascent stage is left in orbit around the moon.

    The LM, built by Grumman Aircraft Engineering Corp:, Bethpage, N.Y., is designed to operate for 48 hours while separated from the CM, with a maximum stay time of 35 hours on the moon. It consists of two main parts: a descent stage and an ascent stage. The former provides the means of landing on the moon, carries extra supplies, and serves as a launching platform for the liftoff from the moon. The latter contains the crew compartment in which the two astronauts will spend their time while not on the moon's surface, and the engines will return the astronauts to the CSM.

Information in this section was provided by Grumman Aircraft Engineering Corp. Complete details on the lunar module are contained in Grumman's Lunar Module News Reference.

ASCENT STAGE

    The ascent stage houses the crew compartment, the ascent engine and its propellant tanks, and all the crew controls. It has essentially the same kind of subsystems found in the command and service modules, including propulsion, environmental control, communications, reaction control, and guidance and control. Overall height of the stage is 12 feet, 4 inches; overall width, with tankage, is 14 feet, 1 inch. Its weight, without propellant, is 4,850 pounds.

    The ascent stage provides shelter and a base of operations for the two LM crewmen during their lunar stay. The crewmen use it to return to lunar orbit and rendezvous with the orbiting CSM. After the crewmen have transferred to the CM, the ascent stage is jettisoned and remains in orbit around the moon.

    The primary structural components of the ascent stage are the crew compartment, the midsection, the aft equipment bay, and tank sections.

    The cabin is 92 inches in diameter and is made of welded aluminium alloy which is surrounded by a 3-inch-thick layer of insulating material. A thin outer skin of aluminium covers the insulation. The cabin is a pressurized shell in which the two astronauts will spend about two-thirds of their time during the lunar stay. The crew compartment is pressurized to 5 psi, its temperature is controlled at about 75 degrees F, and it has a 100-percent oxygen atmosphere. It contains the displays and controls that enable the astronauts to maneuver the module during descent, landing, lunar launch and ascent, and rendezvous and docking with the CSM. It also contains crew equipment, storage bays, and provisions for sleeping, eating, and waste management.

    Astronaut stations are 44 inches apart and each man has a set of controllers and armrests but no seats. Total volume of the pressurized portion of the lunar module is 235 cubic feet; habitable volume is about 160 cubic feet.

    There are two hatches in the crew compartment the docking hatch and the forward hatch. Both open inward. The round docking hatch (32 inches in diameter) is at the upper end of the docking tunnel and is used for the transfer of crewmen back and forth from the command module. The drogue portion of the docking subsystem is located outside the hatch. The forward hatch tunnel is beneath the center instrument console. The forward hatch is rectangular and is the one through which the astronauts will go to reach the lunar surface. Outside the forward hatch is a platform and a ladder mounted to the forward landing gear strut.

    The crew compartment has three windows. The two triangular forward windows are approximately two square feet and canted down to the side to permit sideward and downward visibility. The third window, used for docking, is located on the left side of the cabin directly over the commander's position. It is about 5 inches wide and 12 inches long.

    The midsection of the ascent stage is a smaller compartment directly behind the cabin; its floor is 18 inches above the crew compartment deck. Part of the midsection is pressurized. Ascent engine plumbing and valving extends above the deck. The midsection also contains the overhead docking tunnel (32 inches in diameter and 18 inches long), docking hatch, environmental control subsystem equipment, and stowage for equipment that must be accessible to the astronauts.

    The aft equipment bay is unpressurized and is behind the midsection pressure-tight bulkhead. It contains an equipment rack with coldplates on which replaceable electronic assemblies are mounted. It also includes two oxygen tanks for the environmental control system, two helium tanks for ascent stage main propellant pressurization, and inverters and batteries for the electrical power subsystem.

    The propellant tank sections are on either side of the midsection, outside the pressurized area. The tank sections contain ascent engine fuel and oxidizer tanks, and fuel, oxidizer, and helium tanks for the reaction control subsystem.

(P-74) Ascent stage.

DESCENT STAGE

    The descent stage is a modified octagonal shape. It is 10 feet, 7 inches high (with gear extended), 14 feet, 1 inch at its widest point, and has a diameter of 31 feet diagonally across the landing gear. it consists primarily of the descent engine and its propellant tanks, the landing gear assembly, batteries, a section to house scientific equipment for use on the moon, and extra oxygen, water, and helium tanks. The stage serves as a launching platform for the ascent stage and will remain on the moon. It is constructed of aluminium alloy chemmilled to reduce weight. (Chem-milling is a process of removing metal by chemical action.)

    The descent engine provides the power for the complex manoeuvres required to take the lunar module from orbit down to a soft landing on the moon. It is a throttleable, gimballed engine which provides from 1,050 to 9,710 pounds of thrust.

    Four main propellant tanks (two oxidizer and two fuel) surround the engine. Such items as scientific equipment, the lunar surface antennas, four electrical power subsystem batteries, six portable life support system batteries, and tanks for helium, oxygen, and water are in bays adjacent to the propellant tanks.

    The landing gear is of the cantilever type and consists of four legs connected to the outriggers. The legs extend from the front, rear, and sides of the LM. Each landing gear leg consists of a primary strut and footpad, a drive-out mechanism, two secondary struts, two downlock mechanisms, and a truss. Each strut has a shock absorbing insert of crushable aluminium- honeycomb material to soften, the lancing impact. The forward landing gear has a boarding ladder on the primary strut which the astronauts will climb to and from the forward hatch.

    The landing gear is retracted until shortly after the astronauts enter the LM during lunar orbit. Extension is activated by a switch in the LM. The landing gear locks are then released by a mild explosive charge and springs in each drive-out mechanism extend the landing gear. The footpads, about 37 inches in diameter, are made of two layers of spun aluminium bonded to an aluminium honeycomb core.

(P-75) Descent stage.