Page 76 - Apollo Moonships

74 On bOard apOllO mOOnships
ENVIRONMENTAL CONTROL SYSTEM
The unit of the Lunar Excursion Module (LEM) responsible for providing life support functions was the Environmental Control System (ECS), which consisted of four functional components placed into the cabin and peripheral equipment located
outside the cabin in the ascent and descent stages. These four components were the Atmosphere Revitalization Section (ARS), the Oxygen Supply and Cabin Pressurization Section (OSCPS), the Heat Transport Section (HTS), and the Water Management Section (WMS). Working together, these major sections allowed the ECS to pressurize the cabin and the astronauts’ spacesuits, remove heat, moisture, odors, and carbon dioxide from them, regulate the temperature of the electronic equipment, and provide a breathable internal atmosphere. The ECS also purveyed water for drinking, fire extinguishing, cooling the spacesuits, and food preparation. The gaseous oxygen tank (48-pound capacity) that fed the system during the descent and lunar stay phases were stored into the descent stage’s quadrant III. Another amount of oxygen—used during the lunar ascent and rendezvous and docking maneuvers with the Apollo mother ship—was stored in two tanks (2.43-pound capacity each) located in the aft equipment compartment of the descent stage. The water used by ECS had a similar arrangement: it was stored in one large descent tank (332-pound capacity) and two descent tanks (42-pound capacity each).
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3 4
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5
6
ECS COMPONENTS
1 ECS equipment
2 Carbon dioxide removal canisters 3 Oxygen control module
4 Suit flow controls
5 Water control module
6 Water dispenser
NAVIGATION, GUIDANCE AND CONTROL SYSTEM
Once separated from the Command-Service Module (CSM), the LEM had to descend and navigate towards the lunar surface on its own. When the mission on the moon ended, it had to take off and find its way back to the CSM parked in the lunar orbit. For this purpose, the ship carried the Lunar Primary Guidance Navigation and Control System (PGNCS), a device similar to the one used in the CSM, equipped with a computer that automatically controlled the RCS thrusters and the descent and ascent engines to maintain the right course. The LEM’s crew could also select a semiautomatic or manual PGNCS mode of operation. In the first case, they controlled the influence of the automatic system, and in
the second, they performed for themselves all PGNCS functions to guide the spaceship manually using the attitude and translation hand controllers on the cabin. To determine the LEM position, the crew used a
Receiving array
LANDING RADAR
Placed in the lower deck of descent stage, this radar transmitted constantly the altitude of the LEM relative to the lunar surface, to approach safely and perform and accurate landing.
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Doppler velocity sensor
Altimeter transmitting array
Inertial measurement unit (inside)
Attitude controller
– Y axis
Translation controller
Armrest
CABIN CONTROLS
The LEM’s astronauts use the cabin controls to select the best mode of navigation.
Alignment Optical – Z axis Telescope
PGNCS Computer