The High-Density Cold Gas Jet (HDCGJ) is a self-pressurizing cold-gas propulsion system, developed at the Japan Aerospace Exploration Agency (JAXA) for use in small spacecraft. The HDCGJ aims to deliver continuous thrusting capabilities using liquid-stored, green propellants. A fraction of the gas that is generated from the liquid stored propellant is used to maintain storage pressure above critical pressure. The gas expansion, after heating to supercritical state can therefore guarantee good vapour quality, without the risk of residual liquid in the gas-side of the propulsion system or thrusters. An analysis of different propellant options is performed, on the basis of a system for use in a 50 kg small satellite, capable of delivering 5 m/s of delta-v. Out of the possible options, R-116 has good overall performance related to small storage volume, relatively low mass, and low heating power requirements. At the same time, it is non-hazardous and non- ammable, making it safe and easy to handle. Based on the performed system analysis and characteristics of the HDCGJ concept, engineering model hardware has been manufactured and is currently undergoing verification tests. Results of Bread-Board Model tests confirm the expected system behaviour and completed EM tests confirm the expected performance of the HDCGJ system. As a final point, the current state of EM development and testing is described.