The command module was a stubby, conical craft almost entirely covered with a heatshield that was thickest across its base to sustain most of the punishment of re-entry. The outer rim of the cone was packed with small tanks, thrusters, various antennae and two small ports for the ejection of waste water and urine. The apex of the cone had a removable probe mechanism to enable it to dock with the Apollo lander and a tunnel through which the crew could transfer between the two spacecraft. Parachutes were carefully packed around the outside of this tunnel, along with other paraphernalia of the Earth landing system.
The main bulk of the CM's volume was taken up by the pressure hull which accommodated three crew members and much of their electronic equipment. For lightness, the hull was constructed from two layers of aluminium sheet with an aluminium honeycomb in between. During launch and re-entry, the crew lay on couches with their backs to the aft of the spacecraft. In general, though not exclusively, at the time of launch the commander
occupied the left couch for access to most of the flight instruments; the lunar module pilot (LMP) took the right couch and took responsibility for the spacecraft's systems, as this was where many of the relevant switches and displays were located; and the command module pilot (CMP) had the middle seat, with his head next to the spacecraft hatch. For major manoeuvres in space, the CMP occupied the left seat. Directly in front of the crew and ranged around the entrance to the tunnel was the main display console - a vast panel of some 400 knobs, switches, meters and displays with which most of the flying of the spacecraft was achieved, in association with various hand controllers that sprouted from the ends of armrests. Above the console, in the eye-lines of the commander and LMP, were two small forward-facing windows. Other panels, windows and compartments were arranged around the crew. In particular, at the CMP's feet was the lower equipment bay which included all the gear he would need to navigate the spacecraft, a task for which he was responsible.
Attached to the rear of the CM was the cylindrical SM that supplied most of the consumables; electrical power, water, air and cooling. It also carried an array of parabolic antennae for deep-space communication, thrusters for attitude control and the spacecraft's main means of propulsion, an ultra-reliable service propulsion system (SPS) engine that protruded from its rear. This engine took the crew into orbit around the Moon and, when their exploration had been completed, sent them back towards Earth. Most of the service module's bulk was taken up with four large tanks that carried over 16 tonnes of propellant for this engine. Smaller tanks of oxygen and hydrogen provided the reactants for three Computer rendering of the command fuel cells where a little chemical module instrument layout. (Image magic combined these elements to courtesy of Scott Sullivan.)
provide the crew with not only electrical power, but also water good enough to drink. The oxygen tanks also supplied the CM's cabin air.
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