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McCabe, Justin W.

Mechanical Engineering

2009

MS

NASA and the Department of Defense currently have interest in the development of new satellites several orders of magnitude smaller than those of the present day. These next generation satellites will substantially decrease launch costs, increase reliability and enable redundant flight architectures. Due to their reduced size (O[10 cm]) and mass ([less or equal to] 10 kg), these 'nanosats' will require unique propulsion systems capable of precision attitude control and orbital manuevers. To obtain the needed precision the thrust and impulse-bits must be on the order of 10 - 100 [mu]N and 100 - 1000 [mu]Ns, respectively. The significance of the work to date is in the utilization of a two-phase micro scale flow phenomena as the basis for a fuel injection system in a novel, 'discrete' monopropellant MEMS-based thruster design.
In this study we examine the formation of microscopic liquid slugs, or 'microslugs', resulting from converging flows of a simulated liquid propellant and inert gas at a four-way 90° microchannel junction. The primary goal of the current work is to obtain fundamental information which will enable the prediction of slug sizes and frequencies in terms of pressure inlet conditions thereby characterizing the microfluidic system. An experimental system was successfully designed and installed in the University of Vermont Microfluids Lab. The experimental studies show a range of slug characteristics are possible. Currently, we find that liquid slugs lengths of 50 [mu]m - 1.5mm are produced in a highly repeatable manner at frequencies as high as 325 Hz. This work is supported by the Air Force Office of Scientific Research (AFOSR).