Category:Command Module (CM)

The three-seater Apollo Command Module (CM) was the conical "passenger compartment" at the front end of the Apollo spacecraft, that detached at the end of the mission and underwent rentry. This was the only part of the Apollo spacecraft that returned to Earth.

Upper surface

On the launchpad, the Apollo capsule seemed to be white ... but this was because of a white protective shield that also held the emergency escape system.

In space, the upper surface of the capsule was shiny, almost mirror-finish silver, achieved by laying layers of metallised tape over the surface. This was made easier by the capsule's conical shape: a cone is topologically equivalent to a flat sheet (before we bend it), so the strips of tape, butted up against each other, didn't need and special shaping ... just simple rectangular strips taken directly from a reel of tape would do the job (with the exception of some of the "bulging" parts of the capsule, such as the hatch area).

After return, the capsule looked rather singed and more of a bronze colour due to the heat of reentry, and also because of the sacrificial heatshield material that was designed to burn off when it got too hot.

From photos, the similar-but-updated capsule used for the later Skylab missions seems to have been white.

Heatshields

The CM was covered with a honeycomb mesh with thousands of segments, each of which was filled with the heatshield compound (by hand) and allowed to set solid. Once the capsule was clad in its heat shielding (thicker on the base), it was x-rayed to try to find air-pockets that might expand during the heat of re-entry. These spots were marked, the section of heatsinking drilled out, and the holes refilled.

This meant that the bolts for key parts of the spacecraft were initially hidden: access to these bolts was achieved by drilling down to the bolts, and then plugging the holes with special bungs. If needed the bung could be removed with a special tool.

Access

There were two ways into and out of the capsule: the main side hatch, and also a "tunnel"-type arrangement set into the peak of the cone, which allowed the capsule to dock with the Lunar Module.

Landing

The capsule was designed to land on water: the capsule had an orange inflatable flotation skirt, and three parachutes were packed into the the region around the docking part, along with asymmetrically-distributed spherical orange balloons that improved the visibility of the craft for retrieval, and also helped to right it if it somehow managed to end up upside-down in the water.