In this thesis, components intended for vehicles in space and other extreme environments have been realized using microsystems technology to facilitate miniaturized, yet high-performing systems beneficial for small spacecraft and other vehicles with limited size and power.
Cold gas thrusters commonly used on spacecraft basically accelerate a gaseous propellant stored under high pressure. When miniaturized, their performance is reduced because of viscous forces. Here, with a special masking and etching scheme, making silicon micronozzles close to rotationally symmetric, this shortcoming was mitigated as indicated by schlieren imaging of the rocket exhaust and a comparison with conventionally manufactured micronozzles with rectangular cross-sections. Schlieren imaging was also used to detect leakage, quantify thrust vector deviation, and measure shock cell periods in the exhaust. Correlation was made to operational conditions.
Similarly operating zirconia thrusters with integrated heaters and flow sensors were developed to allow for higher operating temperature. Successful testing at 1000°C, suggests that the propellant efficiency could be increased by 7.5%, and also makes them candidates for chemical propulsion.
A silicon thruster operating in rarefied gas regimes was also developed. Being suspended in a silicon dioxide frame reducing heat losses, a total efficiency of 17% was reached.
Relating to the integrated micropropulsion systems, two types of flow sensors were developed. Through finite element modeling, the insertion of sensor fingers in the fluid was shown to be an interesting concept for high-pressure applications.
Utilizing the same principle, a velocity sensor for a miniaturized submersible was developed. With a power consumption below 15 mW, it was able to measure directions with an accuracy of ±8º, and speed with an error less than 22%.
To enable high-speed optical communication between spacecraft, a Free Space Optics communication system, and particularly its dual-axis beam-steering actuator, was developed. Through thermal actuation, optical angles larger than 40º were obtained. A lumped thermal model was used to study design changes, vacuum operation and feedback control.
Understanding and mastering heat transfer in microsystems have been vital in many of the studies conducted. Throughout, advanced micromachining and modeling have been used as a step towards high-performance systems for space and other extreme environments.
Uppsala: Acta Universitatis Upsaliensis, 2013. , 43 p.