Design and fabrication of smart vaporizing liquid microthruster for Cubesat applications

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Abstract

Propulsion systems capable of providing attitude and orbit control are an essential part of small satellites. In particular, Micro-Electro-Mechanical Systems (MEMS) Vaporizing Liquid Micro- thrusters (VLM), using water as a propellant, meets the requirements for launch-safety, simplicity and cost. Moreover, MEMS technology also enables the integration of sensors to fabricate smart thrusters. This thesis reports the design and fabrications of a smart vaporizing liquid microthruster for the applications in small satellites. The thruster is fabricated with a conventional anodic bonded silicon-glass wafer stack with a glass capped microfluidic channel but the novelty here is that in-channel heaters and sensors on the glass wafer are combined with on-channel heater and sensors on the silicon wafer. For example, an on-silicon piezo resistive pressure sensor is combined with an in-channel temperature sensor. To enable close proximity and stacking of heaters and sensors, a combined front-side/back-side silicon wafer processing is applied.
Furthermore, the on-silicon heater is built in a recess on the silicon wafer to minimize thermal resistance between heater and channel. The modular designed layout allows the integration of different sensor / heater combinations in the wafer stack to meet an application specific thruster performance, which enables cost effective flexible manufacturing. A preliminary characterization was performed which showed that integration of all designed modules was successful. The proposed fabrication process could therefore be a fabrication platform for VLMs.