The present disclosure generally pertains to a rocket propulsion oxidizer compound that is a solution, is a homogenous and stable liquid at room temperature and includes nitrous oxide and nitrogen tetroxide. In addition, an apparatus is provided for burning a fuel and nitrous oxide/nitrogen tetroxide. The apparatus has a combustor, a catalyst, a nitrous oxide/nitrogen tetroxide supply passage for directing the nitrous oxide/nitrogen tetroxide to a contact position with the catalyst, and a fuel supply passage for supplying the fuel to the combustor. The catalyst acts to facilitate decomposition of the nitrous oxide/nitrogen tetroxide, while the combustor burns the fuel, the decomposed nitrous oxide/nitrogen tetroxide and/or nitrous oxide/nitrogen tetroxide decomposed in the reaction.