Page 66 - Apollo Moonships

64 On bOard apOllO mOOnships
THE ASCENT STAGE
The ascent stage was the control center of the Lunar Excursion Module (LEM) and contained the crew’s pressurized cabin, the reaction control engines that governed the spaceship attitude, the guidance and navigation systems, and a throttleable rocket engine with its associated tanks that was ignited at the end of lunar exploration to leave the moon. From the moment of takeoff, the ascent stage—which had been operated as a unit with the descent stage—functioned as a single spacecraft for rendezvous and docking with the Command-Service Module (CSM), parked into the lunar orbit (see page 54). The ascent stages comprised three main sections: the crew compartment, the midsection, and an aft equipment bay. The two first areas made up the cabin, which had an overall volume of 235 cubic feet and served as
a control center for lunar operations. The cabin also provided shelter for the astronauts while they remained on the lunar surface. For its part, the aft equipment bay was an unpressurized area that stretched from the aft midsection bulkhead up to the equipment rack assembly, a cantilevered frame packed with electronic components placed 33 inches from the bulkhead.
The ascent stage was built using aluminum alloy as the primary component and titanium for fittings and fasteners. The thickness of the walls of the cabin reaches only 0.065 inches (1.65
mm). To protect the ascent stage from temperature drops and micrometeoroids, a thermal blanket and a micrometeorroid shield covered the entire structure.
APOLLO 16 LUNAR MODULE ASCENT STAGE
The ascent stage of the Apollo 16 Lunar Module Orion approaches the Command-Service Module (CSM) Casper during the rendezvous and docking maneuver on April 23, 1972. Note the buckled thermal panels of the aft equipment bay, bent by the pressure of the ascent engine gases when the spacecraft took off from the lunar surface.
ASCENT STAGE MAIN SECTIONS Aft equipment bay
Antenna supports
1 THERMAL AND MICROMETEOROID COVER
The blanket that protected the LEM from solar radiation and the impact of micrometeoroids was made of multiple layers of aluminized mylar, a polyester film, or a plastic sheet that was only 0.00015 inches thick (0.0000038 mm).
9 TRIANGULAR WINDOWS
The two windows in the front face of the ascent stage permitted great visibility not only due to its size (2 square feet), but also to its triangular design and its canted-down disposal to the sides.
8 FORWARD HATCH
The 32-inch square hatch placed in the front
of the ascent stage was used principally for transferring astronauts and equipment between the LEM and the lunar surface. To open the hatch on the moon, the crewmen first needed to depressurize the LEM cabin..
7 MAIN PROPULSION SYSTEM TANKS
The storage propellant tanks (fuel and oxidizer) that fed the ascent engine were mounted on the outboard side of the midsection within dedicated compartments. The crew did not require access to the tanks, so the compartments were unpressurized.