Modular self-assembling on-orbit robotic and satellite systems can be more reliable, have lower launch costs, and be more easily repaired and refueled. However, when individual modules assemble, many challenges and opportunities make the control of the assembled system complex. These issues include changes in inertial properties, and redundancy of actuators and sensors. Optimal control methods may be used to coordinate the control of the modules after assembly, insure good performance, and best utilize the combined resources of the assembly of modules. Simulation and experimental results compare this Cooperative algorithm's performance to that of an approach in which the control of the individual modules is not coordinated. Cooperative optimal control methods prove well-suited for controlling redundant, modular space systems.