Titanium Sponge

Post 3 turns to titanium sponge—difficulty 8, and a true zero at production scale. USGS reporting shows no U.S. sponge production in 2025 after the last plant closed in 2024; melt shops still run, but on imported sponge and scrap. Magnesium metal as Kroll reductant is a coupled risk. Melt without sponge is incomplete sovereignty.

This page is a placeholder. Meanwhile, read Post 2: Precision Inertial Sensors or Post 1: Upstream Is the Chokepoint.