Rocket motors monopropellant

An ethylene oxide monopropellant rocket motor is considered part of a ram rocket power plant in which the turbulent exhaust of the rocket reacts with induced air in an afterburner. The exit area of the rocket motor is 8 cm2. After testing it is found that the afterburner length must be reduced by 42.3%. What size must the exit port of the new rocket be to accomplish this reduction with the same afterburner combustion efficiency The new rocket would operate at the same chamber pressure and area ratio. How many of the new rockets would be required to maintain the same level of thrust as the original power plant ... 

Thrusters are rockets for maneuvering and controlling the attitude of space vehicles. The usual monopropellant for thrusters is catalytically decomposed Hydrazine. The usual catalysts are iridium, rhodium or ruthenium and their mixts. For a review of Hydrazine thrusters see Refs 33, 34 35. Russi (Ref 34) emphasizes that, in spite of many studies and the general acceptance and apparent success of hydrazine thrusters, new rocket motor design is still largely empirical. A biproplnt consisting of Hydrazine mixed with Hydrazine Nitrate has also been tried in thrusters but is no longer popular... 

Time Lag in a Monopropellant Rocket Motor, Fifth Symposium on Combustion, p. 164, Reinhold, New York, 1955. 

Equilibrium concentrations of carbon or ammonia are not found in short combustion chambers used in rocket motors. The reason for this non-equilibrium situation is that the rate of formation of soot is very slow and carbon does not have time to form. Similarly the dissociation of NH3 is very slow. Thus in ethylene oxide monopropellant rocket motors one finds very little carbon, whereas equilibrium considerations predict carbon as a predominant product and in hydrazine decomposition chambers one finds an excess of NH3 over that predicted by equilibrium considerations. In ethylene oxide motors carbon forms from the decomposition of methane, not the reaction represented above, thus both non-equilibrium situations give higher performance than expected, since the endothermic reactions do not have time to take place. Of course, carbon also could form in cool reactions which take place in boundary layers along the walls where velocities are slow. 

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