variavel0=<b>Ulisses Côrtes Oliveira</b> - ulisses@iae.cta.br Instituto de Aeronáutica e Espaço
<b>Danton José Fortes Villas Bôas</b> - danton@iae.cta.br Instituto de Aeronáutica e Espaço
<b>Abstract.</b> The present article presents some theoretical considerations about the implications due the change of the oxidizer in a bipropellant propulsion system. Preliminary analysis conducted on the NTO/UDMH 400 N engine of a roll control system shows that this engine could be capable of operation with HTP90 without significant modification in the design. The new propellant combination is less toxic, can be handled more easily, has a wider operational temperature range, and yields a more amenable thermal environment from the combustion down to the exhaustion. Even with a decrease in liquid film cooling, the HTP90/UDMH engine would present a satisfactory reduction of the combustion chamber temperature and approximately the same performance level of the original NTO/UDMH engine.
<b>Keywords.</b> Reaction Control Systems, Auxiliary Propulsion Systems, Rocket Propellants, Hydrogen Peroxide.