Design And Fabrication Of MEMS Based Solid Propellant Micro Thruster

MEMS based solid propellant micro thruster is a new type of micropropulsion system, which is required in microspacecraft for station keeping, attitude control, gravitation compensation and orbit adjust. Both design and fabrication of MEMS based solid propellant micro thruster are introduced in this thesis, and a prototype having a 4×4 array of micro thrusters is fabricated on a 2-inch-diameter wafer, then both the ignition test and thrust test are successfully conducted.The prototype adopts the structure of three-layer sandwich, with the ignition circuit in the bottom layer, the combustion chambers in the middle layer and the nozzles in the top layer. 4×4 array of convergent-divergent Laval micro nozzles are fabricated on a 40mm-diameter, 1mm-thick Si wafer by using the anisotropic wet etching of silicon, and the section area of the nozzle throat is about , and the divergent ratio is 4.08. Combustion chamber layer is fabricated on a 40mm-diameter, 2mm-thick microcrystalline glass wafer by using precise machining, each chamber has the diameter of 2mm and thickness of 2mm. 1mm-thick, 2inch-diameter microcrystalline glass wafer is chosen to be the substrate of the ignition circuit, and Cr is chosen to be the ignition resistor material for the first time. The Cr resistor is gained by using magnetron- sputtering, photolithography and wet etching of Cr. 4.80×10 ?7 m2The glow characteristics of Cr resistor are studied on two different wafers (Si wafer and microcrystalline glass wafer), noticing that the resistor on the Si wafer can't reach high temperature due to the high thermal conductivity of Si, however, the Cr resistor on the microcrystalline wafer can easily glow red and even break up. Parallel connection shape resistor is designed, which has lower resistance, bigger contact area with the propellant and bigger heating area, so the ignition success ratio is higher. ANSYS finite element software is used to simulate the temperature field distribution of the glowing resistor, and the simulating picture is very similar to the experimental results. By using the ANSYS software we notice that, under the same glowing power, the single line resistor has much higher temperature than the parallel connection resistor, and the narrower the line is, the higher temperature it will reach.BTATZ propellant, which is very sensitive to the small heating area, is chosen to be the solid propellant of the prototype, and the assembly process of the prototype is introduced. Thrust test is conducted with twelve thrusters. The ignition success ratio is 100%, the ignition voltage is less than 30V, the lowest ignition power is about 6.66W, the average thrust is about 0.20mN, and the thrust impulse is among 10~30μN?s.