Apollo/Saturn in Earth Orbit

The configuration of the Apollo spacecraft when it reaches earth orbit is shown in the picture at left. At the top of the stack is the conical command module. The command module, or CM, is the living quarters for the three astronauts on their lunar voyage. As its name implies, the CM is the location from which the entire spacecraft is controlled.

Just below the command module is the cylindrical service module, or SM. The CM together with the SM constitute the Apollo spacecraft. The SM houses life support equipment for the CM and contains the large rocket engine used for midcourse corrections and for the burns into and out of lunar orbit. These simulated engine firings produce accurate changes in velocity as determined by the length of the burn and current spacecraft mass. The spacecraft center of gravity shifts realistically as fuel is burned.

Below the SM is the adapter section which connects the Apollo spacecraft to the Saturn upper stage used to insert the stack into earth orbit and later to send the Apollo spacecraft on a trajectory to intercept the moon. On a lunar landing mission the lunar module would be stored in the adapter section. But since this program only simulates the orbital portions of a lunar voyage, the adapter is empty just as it was for the first trip to lunar orbit on Apollo 8.