Due to increasing use by civil and federal authorities and vast commercial and amateur applications, Unmanned Aerial Systems (UAS) will be introduced into the National Air Space (NAS); the question is only how we can do this safely. NASA and the FAA are designing a new automated air traffic control system (NextGen) for all aircraft, manned or unmanned. New algorithms and tools need to be developed to enable computation of the complex questions inherent in designing such a system while proving adherence to rigorous safety standards.