Propulsive characteristics of metal fuel-rich pyrotechnics in hydro-reactive motors

In this paper, the propulsive characteristics of metal fuels in a hydro-combustion chamber are investigated in a thermodynamic approach. Using chemical equilibrium calculations, the thermochemistry of common metal fuels and water is studied and focused on magnesium. Next, the combustion temperatures and characteristic velocities of mixtures of magnesium and some important solid oxidizers are investigated. For the purpose of hydro-reactive propulsion, where it is necessary to use the water as the main oxidizer, the hydro-reaction of some fuel-rich mixtures of magnesium and sodium nitrate is studied. For such compounds, the maximum combustion temperature is estimated to be about 3100 K at different mass fractions of water. More fuel-rich mixtures offer higher characteristic velocity. It reaches about 1700 m/s for the compound with maximum magnesium value content. The characteristic velocity and combustion temperature decrease for high values of water mass fraction, while the specific impulse increases with water monotonically beyond 500 s. The analysis of hydro-reaction products shows that magnesium oxide, hydrogen, and steam are the main species formed. The magnesium oxide presents in its condensed forms. However, for a high amount of water, the main product is steam. (C) 2012 Elsevier Masson SAS. All rights reserved.