From the concept exploration for a weapon system to training simulators, from hardware-in-the-loop simulators to mission planning tools, trajectory simulations are used throughout the life cycle of a weapon system. A trajectory simulation can be defined as a computational tool to calculate the flight path and flight parameters of munitions. There is a wide span of trajectory simulations differing widely with respect to their performance and fidelity characteristics, from simple point-mass simulations to six-seven degrees of freedom hardware-in-the-loop missile simulations. From our observations, it is a common practice in the industry that developments of these simulations are carried out as isolated projects although they rely on the same body of knowledge. We envision an ontology that will capture the common knowledge in trajectory simulation domain and make domain knowledge available for reuse. Trajectory Simulation Ontology, dubbed TSONT, is being developed to realize this vision.