Design and fabrication of smart vaporizing liquid microthruster for Cubesat applications

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.