The protective headgear worn by astronauts, especially for extravehicular activities (EVAs).
Helmets are so critical that the Mercury helmets accounted for half of the spacesuit cost. These were made of fibreglass and had a Plexiglas visor. The communication wiring entered from the rear. Gemini helmets included two additional visors, one for protection against heat and ultraviolet light and one protecting against impact. Apollo astronauts wore a bubble-shaped helmet of polycarbonate material and a soft ‘Snoopy’ helmet beneath it to hold the communications gear.
For Apollo 17, the last Moon landing, Velcro pads were positioned inside the helmets so astronauts could scratch their noses against them. This was retained for the polycarbonate space shuttle EVA helmets, along with a device to clear blocked ears. Shuttle space walkers also have a miniature television camera and lighting mounted on a visor assembly fitting over the helmet.
Subjects: Astronomy and Astrophysics — Literature.