It is advantageous to synthesize nano-sized energetic ingredients for the development of insensitive munitions . The method currently used to produce nano-sized particles is the rapid expansion of a supercritical solution (RESS) process (, ). In this study, an ultra-highpressure (up to 207 MPa) RESS system with viewing windows was successfully designed, fabricated, assembled, and tested. During the course of development of this useful processing facility, several major obstacles were encountered. This paper describes various innovative techniques utilized to overcome the problems experienced. The developed system has many desirable features, including: 1) proper processing of both the initial micron-sized particles and the synthesized energetic nano-particles; 2) control of particle size distributions by selecting suitable pressure and temperature conditions before expanding the supercritical solution through the expansion nozzle; 3) achieving greater solubility of energetic materials in the supercritical carbon dioxide; 4) controlled thermodynamic process in the expansion of the supercritical fluid; 5) efficient collection of nano-sized energetic particles; and 6) filtering of nano-sized particles from exhaust gas. Finally, the possibility of scaling up to production levels with some additional components is addressed.