Page 50 - Apollo Moonships

48 On bOard apOllO mOOnships
SERVICE MODULE STRUCTURE
Designed to operate as a storehouse, the unpressurized Service Module (SM) contained
the main engine of the Apollo mother ship, its propellant, and vital consumables such as oxygen, water, and hydrogen. The SM, a 1-inch-thick aluminum cylinder that measured 24.17 feet long and 12.83 feet in diameter, remained attached to the Command Module (CM) throughout the mission, but it was jettisoned just before the capsule reentered into the Earth’s atmosphere. The internal structure of SM consisted of a center section or tunnel surrounded by six pie-shaped sectors covered on the top and the bottom by forward and aft bulkheads. The center section housed two spherical helium tanks, and the Service Propulsion System (SPS) was endowed with a single rocket engine that produced a thrust of 20,500 pounds and used Aerozine 50 as fuel and nitrogen tetroxide (N2O4) as an oxidizer. The six pie-shaped sectors contained the oxidizer and fuel sump and storage tanks and
the Electrical Power System (EPS), composed of three fuel cells, two oxygen tanks, and two hydrogen tanks. Outside of the SM, on the upper section, were installed four reaction control thrusters, each about 92 pounds in force. These small engines were located every 90° in four clusters or quads arranged in such a way that the thrusters were on the outside and the propellant tanks and associated components (valves, regulators, etc.) were on the inside. The SM also housed a communication system, which included four antennas.
SM GENERAL ARRANGEMENT
1 Radial beam truss (6 places)
2 Forward Bulkhead (thermally insulated)
3 CM–SM umbilical connector
4 Helium tank (2)
5 Electrical Power System (EPS) radiator
6 Reaction Control System (RCS) engine
7 S–band hi gain antenna
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Environmental Control System (ECS) radiator
Propellant fill point
Service Propulsion System (SPS) nozzle extension
Aft bulkhead
Center section (tunnel)
13 Sector 1 (50°)
14 Sector 2 (70°)
15 Sector 3 (60°)
16 Sector 4 (50°)
17 Sector 5 (70°)
18 Sector 6 (60°)
SERVICE MODULE MAIN COMPONENTS
STRUCTURE
The cylinder that formed the service module was built of one-inch aluminum honeycomb panels. Its interior was divided into six sectors by radial beams made of aluminum alloy plate, arranged asymmetrically around a center section (tunnel), which measured about 3.7 feet in diameter.
SERVICE PROPULSION SYSTEM (SPS)
This component provided impulse and velocity changes to the Apollo mother ship. It was consisted of a rocket engine, a helium pressurization system, a propellant gauging system and another of propellant feed. The engine had a gimbal actuator to provide control around the Z-axis and Y-axis (yaw and pitch movements).
Nozzle extension
SPS ROCKET ENGINE
The 20,500-pound-force rocket engine was used to propel the spacecraft and put it into orbit around the moon, but also to brake it and correct its course. It was 12.72 feet long and 8.20 feet wide at the base.