We demonstrate an application of the ontology driven methodology to develop trajectory simulations in a function-oriented style. We adopt a model based approach to software development, guided by the domain engineering process, to promote knowledge and software reuse. MATLAB Simulink (R) block definitions have been generated from the function specifications in the Trajectory Simulation Ontology, called TSONT. MATLAB implementations of the blocks have been generated from the DAVE-ML definitions of the functions, which are incorporated in TSONT. Finally, the simulation has been put together by manually connecting the blocks.