A model was developed to predict the set of flow rates and preheat temperatures required to initiate decomposition of the [Emim][EtSO4]-HAN monopropellant in a platinum microtube. The model used a one step Arrhenius reaction rate mechanism derived from empirical data from a previous study and predicted decomposition to occur in less than 10 mm at a preheat temperature of 100°C for an isothermal platinum microtube and 15 μL/s propellant flow rate. The pressure generated by the decomposition, the flow rate required to avoid flashback, and the upper limit on preheat temperature were also considered to complete the full 'startbox'. An experiment was conducted to verify this model and ignition was not observed up to 450°C as measured at the center of the microtube. At 500°C ignition was observed, but in the cooler (∼100°C) inlet section. This 10 mm section was insulated by a layer of PEEK, resulting in a closer to isothermal section and is thus explained by the modeling results.