An open source thermodynamic modeling package completed on behalf of NASA. The Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) package offers a MATLAB/Simulink toolbox that gives a developer the ability to create simulations of such thermodynamic systems as turbomachinery and gas turbines. Keywords: TMATS, Control System, Numerical Methods, Newton-Raphson, Jacobian Calculation, Propulsion, Aircraft Engine, Jet, Turbofan, Turbojet, Compressor, Turbine, Nozzle, Inlet, open source