Busek proposes to develop a high performance, non-toxic storable, "green" monopropellant thruster suitable for in-space reaction control propulsion. The engine will deliver 100N (~25lbf) vacuum thrust with specific impulse exceeding 240sec. Estimated Isp-density is on the order of 348 sec-g/cc, a 48% increase from the state-of-the-art hydrazine systems. The most important feature that sets this thruster apart from other similar devices will be the use of an innovative, long-life catalyst. This proprietary catalyst, constructed without any bed plate or ceramic substrate, was recently demonstrated in Busek's 0.5N micro thruster. It has shown the ability to suppress catalyst-related performance degradation problems that often plague green monopropellant thrusters. The proposed Phase I program will focus on developing a 5N green monopropellant thruster by scaling up the long-life catalyst design from the 0.5N thruster. Both empirical and modeling works are proposed to validate the scaling theory. Thruster performance will be evaluated based on hot-firing test results that include c* and vacuum thrust measurements. The Phase I findings will lead to the design of a full-scale, 100N green monopropellant thruster to be developed in Phase II.