Relevant to this story is this passage from Ignition!: On December 29, 1953, a technician at Edwards Air Force Base was examining a set of titanium samples imm

Relevant to this story is this passage from Ignition!: On December 29, 1953, a technician at Edwards Air Force Base was examining a set of titanium samples immersed in RFNA, when, absolutely without warning, one or more of them detonated, smashing him up, spraying him with acid and flying glass, and filling the room with NO₂. The technician, probably fortunately for him, died of asphyxiation without regaining consciousness. There was a terrific brouhaha, as might be expected, and JPL undertook to find out what had happened. J. B. Rittenhouse and his associates tracked the facts down, and by 1956 they were fairly clear. Initial intergranular corrosion produced a fine black powder of (mainly) metallic titanium. And this, when wet with nitric acid, was as sensitive as nitroglycerine or mercury fulminate. (The driving reaction, of course, was the formation of TiO₂.) Not all titanium alloys behaved this way, but enough did to keep the metal in the doghouse for years, as far as the propellant people were concerned. (RFNA is a mixture of NTO and anhydrous nitric acid).