The Helmets were actually designed for the Discovery era. Interstella 5555 doesn’t feature them much since the idea for the anime was developed with TOEI in the early stages of Discovery and the helmets came after, developed by Alterian. At one point the helmet designs even had hair.
Here’s a short interview with helmet creator Tony Gardner, where you can see the hair design and explaining the process:
― ✖✖✖ (Moka), Wednesday, 24 February 2021 17:47 (three years ago) link