Ammonium dinitramide

Ammonium dinitramide (ADN) is an inorganic compound with the chemical formula [NH₄][N(NO₂)₂]. It is the ammonium salt of dinitraminic acid HN(NO₂)₂. It consists of ammonium cations [NH₄]⁺ and dinitramide anions ⁻N(NO₂)₂. ADN decomposes under heat to leave only nitrogen, oxygen, and water.

It makes an excellent solid rocket oxidizer with a slightly higher specific impulse than ammonium perchlorate and, more importantly, does not leave corrosive hydrogen chloride fumes. This property is also of military interest because halogen-free smoke is harder to detect. It decomposes into low-molecular-mass gases, which contributes to higher performance without creating excessive temperatures if used in gun or rocket propellants. However, the dinitramide salt is more prone to detonation under high temperatures and shock compared with the perchlorate.

The Eurenco Bofors company produced LMP-103S as a 1-to-1 substitute for hydrazine by dissolving 65% ammonium dinitramide, [NH₄]N(NO₂)₂, in 35% water solution of methanol and ammonia. LMP-103S has 6% higher specific impulse and 30% higher impulse density than hydrazine monopropellant. Additionally, hydrazine is highly toxic and carcinogenic, while LMP-103S is only moderately toxic. LMP-103S is UN Class 1.4S, allowing for transport on commercial aircraft, and was demonstrated on the Prisma satellite in 2010. Special handling is not required. LMP-103S could replace hydrazine as the most commonly used monopropellant.

The ADN-based monopropellant FLP-106 is reported to have improved properties relative to LMP-103S, including higher performance (ISP of 259 s vs. 252 s) and density (1.362 g/cm³ vs. 1.240 g/cm³).