> Early helmet visors (early 60's) were made of plexiglas, but by the
> time of Apollo, they were using Lexan. I saw a demonstration once
> which showed a sample of each being hit by a hammer. The plexiglas
> cracked, but the lexan didn't. I was a TA in shop during undergrad
> and worked with the stuff and can attest to its virtual
> indestructibility.
> You can't break it by falling on it, even in Earth gravity.
>
> Later
> Teresa