RFNA

RFNA is a rocket fuel (a storeable oxidiser): red fuming nitric acid. HNO₃ + 13% N₂O₄ and 3% H₂O. The colour of the resulting red fuming nitric acid is imparted by N₂O₄. Usually used with an inhibitor (various sometimes secret substances - then revered as IRFNA) because HNO₃ attacks most container materials.

More at: http://www.astronautix.com/props/nitidjpx.htm