Construction of Apollo Spacecraft

Launch escape system (LES)

It is made up of 3 solid rocket motors.

•  Launch escape motor, which consists of 4 nozzles and is located at the bottom part of the body. It carries Command Module (CM) away from booster (Booster: The first stage of a missile or rocket) during an emergency.

•  Tower jettison motor has two nozzles and is used to abandon the LES from the CM either after a normal launch or after emergency escape

•  Pitch control motor is located at the top of the body. It is used to change flight course in case of an emergency.

A control device called Q-ball is placed at the top of LES. It is made up of 8 ports that sense the flight angle by detecting changes in the atmospheric pressure.

The launch escape system activates when thrust from two or more engines is lost or when the flight angle detected by Q-ball deviates beyond set parameters. When emergency is detected within 100 seconds of the launch, LES operates automatically. After that astronauts can start it manually.  

Command module

It is the central part of Apollo spacecraft. It houses three astronauts and is the only component that return to earth.  

The command module comprises up of outer wall and cabin. The outer wall together with phenolic coating protects the inside of the ship from heat of the sun and the atmospheric friction produced during re-entry.

The thickness of outer wall varies from 0.5 inch to 2.5 inch and phenolic coating is 0.5 inch all around except at the bottom where it is 2 inch.

The cabin is built by honeycombed structure of aluminum mated with aluminum alloy.  

The cabin is filled with pure oxygen at a pressure of about 1/3 atmospheric pressure and temperature of 21-24 degree Celsius.

Service module(SM)

Service module supplies water, oxygen, electrical power and life support needed for the command module and astronauts for their trip from earth to moon. It also controls the flight path. The service propulsion subsystem (SPS) engine provides the necessary thrust for the spacecraft to leave earth orbit and to enter the lunar orbit, and to leave lunar orbit and return to earth.  

Lunar module (LM)

The lunar module has two stages: descent (lower) stage and ascent (upper) stage. When the spaceship arrives onto the moon orbit, two astronauts move in the lunar module. The LM begins its descent to the surface of the moon. It is equipped with a rocket motor to slow the rate of descent. After the exploration, the equipments are left on the surface of the moon. The ascent stage consists of the crew compartment and rocket motor to return the astronauts to the orbiting command module. After the crew enters the command module, the lunar module is abandoned.

Spacecraft-LM adapter ( SLA )

The spacecraft LM-adapter is an aluminum structure that protects LM during launch. The lunar module is attached to the SLA at four places. Besides the lunar module, SLA encloses the nozzle of the service module's service propulsion engine.

Let us see how Apollo-11 landed on the surface of moon