The orange-brown smoke seen in the exhaust of some missiles, particularly those using hydrazine-based fuels, is primarily due to the presence of nitrogen dioxide (NO2). This reddish-brown gas is a byproduct of the breakdown of dinitrogen tetroxide (N2O4), which is often used as an oxidizer in these rocket engines. When N2O4 decomposes, it forms NO2, which is responsible for the distinctive color of the exhaust plume.
— Seen on the internet. Now my head hurts.
