This paper expands system of systems (S2) engineering through the addition of rapid, top‐level engineering, in a computer‐aided environment known as Rapid Computer‐Aided System of Systems Engineering (RCASSE). This process is carried out over a nominal six month period and involves ten steps: Mission Engineering Baseline Architecting Performance Assessment Specialty Engineering Interfaces/Compatibility Evaluation Software Issues/Sizing Risk Definition/Mitigation Scheduling Pre‐Planned Product Improvement Life Cycle Cost Issue Assessment Each of these steps is defined and discussed, together with supporting computer tools. Other guiding RCASSE principles and a summary are also provided.