You would have wondered very often that what if the glass of astronaut helmet breaks? To find the answer to that question, let us put it under a microscope.
The Spacesuit Helmet is large; majorly plastic pressurized bubble with a ring neck that attaches it to the spacesuit upper torso piece. The helmet has a ventilation distribution pad, a purge Valve with the backup oxygen tank. The water and oxygen are drawn from the Primary Life Support Subsystem or backpack.
The helmet has the visor that protects the astronaut from harmful sun rays, along with a camera that documents the extravehicular activities EVA. The helmet itself is made up of multiple layers with the shell made of highly strengthened pellets of polycarbonate. The front part of the helmet consists of two visors; a tinted polysulfone visor, and a clear polycarbonate visor.
The materials used to make spacesuit helmets resist high impact forces; you can imagine that just by looking at the fact that polysulfone and polycarbonate are the materials often used in bullet proof glass and some of the exterior automotive parts. Polycarbonate is used in the manufacturing of motorcycle helmets, which are designed to protect the skull when the bike moving at a high speed hits the pavement. Astronauts move at a lesser speed than a human walking on earth. Yet, the helmet is constructed to withstand the impact from mini-meteoroids that astronauts may encounter on EVA. It also prevents the damage from ultraviolet and infrared radiations coming from the sun and space.
The spacesuit helmet is 5 millimeters thick and during meticulous testing at NASA, an 8-pound ball of steel was dropped on the spacesuit helmet prototype. Surprisingly, it caused no damage to the helmet, not even a scratch! It is more likely that in an attempt to bang the glass of the helmet open, the astronaut might just break his skull open, even if they were thickheaded which they are not.
Say that there was such a meteorite that punctured the helmet, making the 20 millimeters hole in the helmet’s face-plate. Then, the compressed suit will be rapidly decompressed in a Hollywood version death of the astronaut, and there will be no enough time for the astronaut to escape or be rescued.
There was, however, an incident in 2013, where the spacesuit of Italian astronaut Luca Parmitano filled with water after a leakage during an EVA; it nearly drowned him. The reason, however, for the leak was assumed to be a clogged water filter on the inside rather than outside the suit.