LEX (French: Lithergol EXpérimentale) was a French experimental hybrid-propellant sounding rocket, developed by ONERA. It had the objective of testing a lithergol fueled rocket engine (an hybrid mixture of solid and liquid propellants - Nylon-metatolueneamine as fuel and mixture of nitric acid and nitrogen tetroxide as oxidizer). It was the first rocket in history to use this technology, flying 8 times between 1964 and 1967.