[ckissick]

Star Trek was given an incredibly low operating budget. Everyone involved in the show was always on the lookout for junk that might make a good prop.

Once, when the studio bought new typewriters for all their secretaries, someone, maybe Roddenberry, went dumpster diving to retrieve the packaging materials that the typewriters came in. They spray painted them various colors and stuck them on walls of the Enterprise.

The 3 spheres you see in the engine room are painted soccer balls. They used sono tubes for anything cylindrical.