Introduction A new, less sensitive explosive, RX-55AE-5, has been prepared and subjected to physical characterization tests. RX-55AE-5 is formulated from 97.5% 2,6-diamino-3,5dinitropyrazine-1-oxide (LLM-105) and 2.5% Viton A. Some of its properties are summarized in Table 1 along with a few for LLM-105. LLM-105 has a density of 1.913 g/cm3, a Dh50 of 90-150 cm, and is insensitive to both spark and friction. It has an onset temperature for decomposition of 348˚C at a linear heating rate of 10˚C/min as measured by Dierential Scanning Calorimetry (DSC). It is generally insoluble in common organic solvents. In this work, we measure and report the thermal expansion coecient, thermal decomposition kinetics, and sensitivity to spark, friction, and impact for the RX-55-AE-5 formulation of LLM-105.