Re: What is the clear part of a space helmet made of and how thick is it?

The clear portion of the space helmet (visor) is made from a plastic or polymer called polycarbonate . It is available commercially from several manufactures under different names such as Lexan from General Electric. It is often used as a replacement for glass. You can even find it in many home improvement stores. Polycarbonate is used in applications where there is a need for a strong, scratch resistant, impact resistant material that is also clear.

I could not find a technical document with specific thicknesses, but the thickness of the helmet visor should be around 1/8 inch. While that may seem thin, consider that the visor is only having to contain the pressure inside the suit which is less than 14.7 pounds per square inch. There is a need for a safety factor to ensure no minor scratches or bumps result in a failure, but the thickness can still be fairly thin.

If you want to learn first hand how tough polycarbonate is, go to a home improvement store and buy a small sheet. It should only cost a couple of dollars. Get the thinnest sheet they have avaialble. Ask the store clerk how to cut the sheet. Some of the things you can do it try to break it with a baseball to simulate a meteor impact, scratch it with steel wool to simulate abrasion and typical usage and pile up bricks on it to see how strong it is.

Good luck!