Space proximity missions essentially need on the ground hardware in the loop (HIL) testing of sensors, algorithms, and actuators. Such testing would surpass that of software only simulations and would mature hardware and software to vastly reduce risk of close proximity operations. Simulation of interaction dynamics in proximity operations is very difficult. An active pendulum system can be used to simulate these important contact dynamics. The pendulum system can be commanded to track trajectories which represent plausible contact dynamic motions. The pendulum system can also be used to investigate unknown contact dynamics. With an external robot to simulate spacecraft motion, a payload on the gantry system can be subjected to contact forces. The pendulum system actively moves the payload to simulate planar space-like contact dynamics throughout and after the interaction. This thesis develops high fidelity and first principle based controllers to allow for simulation of both prescribed and unknown planar contact dynamics. A linear quadratic integral controller is designed for trajectory tracking. This controller is compared with a nonlinear trajectory tracking controller developed using partial feedback linearization. To simulate unknown contact dynamics a controller is developed using uncollocated partial feedback linearization. The three controllers are analyzed and compared using several test cases in software simulation. The nonlinear trajectory tracking controller is shown to outperform the linear controller. Simulation results also indicate that the unknown contact dynamics controller outperforms the trajectory tracking controllers in the neighborhood surrounding interactions.