The Open Autonomy Kernel (OAK) is an architecture for autonomous distributed control. OAK addresses control as a three-step process: diagnosis, planning and execution. OAK is specifically designed to support "hard" control problems in which the system is complex, sensor coverage is incomplete, and distribution of control is desired. A unique combination of model-based reasoning and autonomous agents is used. Model-based reasoning is used to perform diagnosis. Observations and execution are distributed using autonomous intelligent agents. Planning is performed with some simple script or graph-spanning planners. A prototype OAK system designed to control the chilled water distribution system of a Navy surface ship has been developed and is described.