Numerical Study of Disperse Monopropellant Microslug Formation at a Cross Junction

Two immiscible uids converging at microchannel cross-junction results in the for- mation of periodic, dispersed microslugs. This microslug formation phenomenon has been proposed as the basis for a fuel injection system in a novel, discrete mono- propellant microthruster design for use in next-generation nanosatellites. Previous experimental work has demonstrated the ability to repeatably generate fuel slugs with characteristics commensurate with the intended application. In this work, numerical modeling and simulation are used to further study this problem, and identify the sensitivity of the slug characteristics to key material properties including surface ten- sion, contact angle and fuel viscosity. These concerns are of practical concern for this application due to the potential for thermal variations and/or uid contamination during typical operation. For each of these properties, regions exist where the slug characteristics are essentially insensitive to property variations. Future microthruster system designs should target and incorporate these stable ow regions in their baseline operating conditions to maximize robustness of operation

Computational and Experimental Studies of Catalytic Decomposition of H2O2 Monopropellant in MEMS-based Micropropulsion Systems

The next generation of miniaturized satellites (“nanosats”) feature dramatically reduced thrust and impulse requirements for purposes of spacecraft attitude control and maneuvering. E↵orts at the University of Vermont have concentrated on developing a MEMS-based chemical micropropulsion system based on a rocket grade hydrogen peroxide (HTP) monopropellant fuel. A key component in the micropropulsion system is the catalytic reactor whose role is to chemically decompose the monopropellant, thereby releasing the fuel’s chemical energy for thrust production. The present study is a joint computational and experimental design e↵ort at developing a MEMS-based micro-reactor for incorporation into a monopropellant micropropulsion system. Numerically, 0D and simplified 2D models have been developed to validate the model and characterize heat and mass di↵usion in the channel. This model will then be extended to a 2D model including all geometric complexities of the catalyst bed geometry with the goal of optimization. Experimentally, both meso and micro scale catalyst geometries have been constructed to prove the feasibility of using RuO2 nanostructures as an in situ in a microchannel