When the crew is ready to land, two of the three astronauts enter the LM and undock it, leaving the third to pilot the command module. After touchdown on the Moon, the astronauts exit through the door above the ladder. The silver and black ascent stage, containing the astronauts’ pressurized compartment and the clusters of rockets that control the spacecraft, fits on top of the shiny gold descent stage that actually touches down on the Moon. The descent stage contains a main, centrally located rocket engine. This segment of the craft remains on the Moon as the crew lifts off in the ascent stage to rejoin the command module. After the crew transfers to the command module, the ascent stage is also left behind as the three crew members start their return journey. The LM is displayed just as it would look during a moon-landing mission. The gold and black materials insulate the spacecraft’s inner structure from temperature extremes and protect it from micrometeoroids. Thin sheets of both materials are used in “blankets” to accomplish the necessary protection in a foreign environment. The black material is heat-resistant nickel-steel alloy. Each sheet is only .002 millimeters (1/12,000 of an inch) thick. These absorb heat and radiate it back into the blackness of space. The shiny gold material on the descent stage is aluminum that is thinly coated over plastic film. The thin sheets of plastic and aluminum are used in blankets of up to 25 layers for protection and insulation of the spacecraft. Prime contractor for the lunar module was Grumman Aerospace Corporation. The lunar module on exhibit is from the National Aeronautics and Space Administration. Height 7 m. (22 ft., 11 in.), legs extended Diameter 9.4 m. (31 ft.) diagonally across landing gear Weight Earth launch 14,700 kg. (32,400 lb.) LM (dry) 3900 kg. (8600 lb.) Volume Pressurized 6.7 cu. m. (235 cu. ft.) Habitable 4.5 cu. m. (160 cu. ft.) [Illustration: 41. Lunar Module Center Instrument Panel in the ascent stage.] Lunar Orbiter [Illustration: 42. Lunar Orbiter.] Directional Antenna Velocity Control Rocket Engine Fuel Tank Nitrogen Gas Reaction Jets Oxidizer Tank Lenses Micrometeoroid Detectors Flight Programmer Photographic Subsystem Sun Sensor (located under equipment deck) Solar Panel Canopus Star Tracker Inertial Reference Unit Omni Directional Antenna The Lunar Orbiter project was initiated in 1963 as part of the U.S. Apollo program to land men on the Moon during the decade of the nineteen sixties.