Mixed oxides of nitrogen
Mixed oxides of nitrogen are solutions of nitric oxide in dinitrogen tetroxide/nitrogen dioxide. It may be used as an oxidizing agent in rocket propulsion systems. A broad range of compositions is available, and can be denoted as MONi, where i represents the percentage of nitric oxide in the mixture. An upper limit is MON40. In Europe MON 1.3 is mostly used for rocket propulsion systems, while NASA seems to prefer MON 3. A higher percentage of NO decreases the corrosiveness of the liquid, while the costs increase and the oxidation potential is decreased.
The addition of nitric oxide also reduces the freezing point to a more desirable temperature. The freezing point of pure nitrogen tetroxide is, while MON3 is and MON25 is.
