Ignition of Nitromethane-based Propellant Mixtures

Abstract

Hydrazine is a commonly used propellant in spacecraft and satellite propulsion, but its toxic and carcinogenic properties, and consequently the high costs associated with its handling, have led the propulsion community to seek "green" alternatives. Our research group is exploring the use of nitromethane, a low-toxicity substance and a staple laboratory solvent, as the primary ingredient for a green monopropellant. However, nitromethane's ignition is challenging, requiring a certain level of pressure for stable combustion. To improve ignition and combustion behavior, we screened additives including transition metal acetylacetonates and other organometallic compounds. Gas-tight vessels in a DSC device and single droplet combustion tests were used to measure the influence of additives on the exotherm onset and peak in nitromethane thermal decomposition. The screening showed that some transition metal acetylacetonates and other organometallic compounds effectively enhance thermal decomposition in sealed-vessel DSC measurements. Ferrocene had the most significant influence: adding 2 wt. % of this substance to nitromethane caused the decomposition peak to shift from 384 to 280 °C. In single droplet combustion tests, the addition of Ferrocene caused a quite high reduction of the total droplet life time in an oxygen-deprived atmosphere at 3 bar, making it a strong candidate for the use as an ignition and combustion catalyst in a nitromethane-based monopropellant.