Design and Fabrication of LTCC Catalyst Chambers

The reduction in satellite size and mass presents the need to develop a proportionally smaller propulsion system for orbital station keeping. A liquid, monopropellant micropropulsion device made from Low Temperature Co-Fired Ceramics (LTCC) has been developed at Boise State University. This robust, simple design uses an embedded silver catalyst chamber to decompose a rocket-grade hydrogen peroxide monopropellant into a hot gas, which is then expelled out through a nozzle to generate thrust. Using LTCC eliminates the planar geometry fabrication constraint commonly found in silicon MEMS processing. This report presents the design and fabrication process of the hydrogen peroxide catalyst chamber used in these monopropellant microthrusters. Using the standard fabrication process for LTCC an initial prototype was developed. The design of this initial device was developed to measure the efficiency of the catalyst chamber by evaluating the ability of the device to decompose hydrogen peroxide. Catastrophic cracking within the device substrate was observed during initial testing. An investigation revealed thermal expansion as a possible cause to fracture surfaces. In addition, a CSAM measurement tool was used to perform internal non-destructive testing, which revealed internal fractures at the inlet and outlet manifolds. As a result of this investigation, a new, functional design was implemented that decreased the overall cross sectional area of the device, which lowered thermal stresses and corresponding failure rates. These design changes will be documented. Results from CSAM investigation and optical microscope images will be used to document the failure investigation process. Several conclusions will be presented to improve the ability to use LTCC for high temperature applications.