Laser Controlled Solid Propellant Micro-thruster

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The ultimate goal of this study is completion of a small rocket motor for satellites (micro-thruster) having high performance, reliability and wide range of thrust. Our proposing concept towards the purpose is tried by use of solid propellants for high performance, reliability and simplicity coupled with laser for the combustion on/off and thrust level control. In the research work of this time, the fundamentals of combustion control were experimentally ascertained using an originally made strand burner. The results revealed that our proposing concept is feasible: forced combustion of fuel rich HTPB/AP composite propellants by laser have the same tendency in burning behavior as ordinary self-combustible propellant under high pressures and a disposition good for combustion control in reasonably wide range of pressures. Measurements by thermography for the temperature distribution combined with regression rates gave the heat balance near the combustion surface which in turn suggested that most of the heat transferred to the burning surface is provided by chemical reaction of the propellants and laser supplies only supplementary heat flux to compensate for insufficiency. Regarding the concept of an array type rocket, laser ignition of solid propellant (Boron/Potassium nitrate)in vacuum has been realized using 1W laser diode system. This rocket system can provide an impulse of 30 mNs-1Ns using 30 mg-1 g B/KNO propellants. Mixture ratio suitable for the operation of the array type rocket system was experimentally determined to optimize its performance. This rocket system successfully operated after 2-month exposure in vacuum, showing its high reliability that can be used in actual space missions.