In the satellite industry, the trend is towards decreasing the size of satellites and clustering of small satellites. Technological advancements in microelectronics have made it more economical to launch a cluster of satellites with a single vehicle rather than the traditional one satellite per vehicle. A small satellite cannot carry a large quantity of fuel or batteries for power so it will require an alternative propulsion system for station-keeping and orbital corrections. The current micro-propulsion alternatives include miniaturized versions of Hall Effect thrusters, plasma thrusters, and chemical devices. These devices are commonly fabricated as microelectromechanical system (MEMS) devices using silicon.

Low-Temperature Co-fired Ceramic (LTCC) materials are an alternative to silicon for micropropulsion applications. LTCCs offer the advantages of multi-layered channels, high-temperature capability, and the ability to embed a variety of catalyst materials. A planar nozzle and hydrogen peroxide catalyst chamber was developed in LTCC for use as a micro-propulsion application.

Three supersonic nozzle configurations were developed and tested using the LTCC materials system. An isentropic model was generated to determine the overall size of each nozzle and the nozzle curvature was defined using a Method of Characteristics approach. Each nozzle was tested using a cold gas test stand at several pressures. The experimental thrust measurement was compared to the isentropic model and several 3D computational fluid dynamics (CFD) models. The ideal model predicted the actual thrust to within 25.1%. The 3D CFD model using a Spalart-Allmaras turbulence model predicted the thrust to within 5.9%. A Schlieren visualization system was created to further validate the CFD model results. The density gradient of the nozzle plume using the Spalart-Allmaras turbulence model matched the Schlieren image of the shock locations in the nozzle exit plume.

A hydrogen peroxide catalyst chamber was modeled and constructed using the multi-layered capability of the LTCC. Four configurations were developed to determine the effect on reactor performance. The device inlet pressure and surface temperature were measured during a constant inlet mass flow rate of hydrogen peroxide propellant. An inlet pressure of 1342.4kPa and a surface temperature of 120°C were achieved at a flow rate of 14mL/min using 63% hydrogen peroxide. The multi-layer channel configurations achieved a higher inlet pressure for a given inlet flow rate compared to planar designs. The multi-layer channel reactors demonstrated a greater resistance to flooding at higher flow rates as compared to the planar design.

This work was done by Amy J. Moll, Judi Steciak, and Donald G. Plumlee of Boise State University for the Air Force Research Laboratory. For more information, download the Technical Support Package (free white paper) at under the Manufacturing & Prototyping category. AFRL-0131

This Brief includes a Technical Support Package (TSP).
Micro-Propulsion Devices Made of Low-Temperature Co-Fired Ceramics

(reference AFRL-0131) is currently available for download from the TSP library.

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This article first appeared in the June, 2010 issue of Defense Tech Briefs Magazine.

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