Characterization of condensed-phase chemical reactions of rdx-based propellants

A microprobe mass spectrometer was used to measure decomposition products from the subsurface region of XM39 and M43 RDX-based propellants. The microprobe was inserted into a hole drilled axially in the centerline of each propellant sample. Gaseous species released in the subsurface region were collected in the cavity and were sucked into the probe and analyzed. Tests were conducted in Ar at 1 and 3 atm, with a CO₂ laser external heat flux of 100, 200, and 300 W/cm2. An insignificant amount of solid-phase decomposition products was detected for M43, and only a very minute amount of OST was detected from XM39 at very low heat flux conditions. At the time of burn through, the major species detected had masses of 30, 28,44, and 27 amu, believed to be CH₂O, H₂CN, N₂O, and HCN. These products suggest the RDX decomposition pathway to form CH₂O and N₂O is more dominant for the condensed-phase reactions at the operating conditions studied. The binders of these two propellants showed relatively inactive behavior under the conditions tested.