Before revision: 21st Century In 2004–2007, to address strength to weight ratio issues, Akhmeteli and Gavrilin addressed choice of four materials, specifically I220H beryllium (elemental 99%), boron carbide ceramic, diamond-like carbon, and 5056 Aluminum alloy (94.8% Al, 5% Mg, 0.12% Mn, 0.12%Cr) in a honeycomb double layer.
After revision: 21st century In 2004–2007, to address strength to weight ratio issues, Akhmeteli and Gavrilin addressed choice of four materials, specifically I220H beryllium (elemental 99%), boron carbide ceramic, diamond-like carbon, and 5056 Aluminum alloy (94.8% Al, 5% Mg, 0.12% Mn, 0.12%Cr) in a honeycomb double layer.