Bottle rockets and parametric design in a converging-diverging design strategy

The Sophomore Engineering Clinic covers two semesters in an eight-semester design sequence. The course integrates engineering with writing and public speaking. In the past the course has used two semester-long design projects to teach design through a series of problems of increasing complexity. Though the course has been effective at teaching students to prototype devices, it has been less effective at teaching design as evidenced by written project documentation and observation of students' decision making processes. In the fall of 2005 the course was revised to incorporate a convergent-divergent framework to teach design. In addition, the semester-long project in the fall was replaced in favor of one four-week project followed by a ten-week project. The initial four-week project was structured to formalize an approach to making choices using parametric studies in a diverging-converging design process. The design and construction of water-propelled bottle rockets from 2 L soda bottles was chosen as the initial four-week project. Students built and tested rockets which were limited in materials and construction. The limitations allowed the rockets to be characterized by three parameters: the mass of water used, the aspect ratio of fins used, and the mass of Playdoh used in a nose cone. Students generated parametric testing schedules and took data on the performance of their designs with respect to the variables in order to inform design choices. During the course, these steps towards a final design were linked to a diverging-converging framework for design thinking. At the end of the course all students had performed parametric studies of their rockets and rocket performance was improved both over the four weeks and as compared to previous years. In addition, the following ten-week project showed improvements in quantitative metrics of performance over the previous years.