We have created an exciting design project that integrates engineering design with cryptography. In this project, students design a model rocket that will be launched from underwater. The first goal of the project is to chose the mass and shape of the payload (a clay nose-cone molded by the students and oven-fired) and the rocket motor that will maximize the ratio of the maximum potential energy to the stored energy for a launch through a water column between 0.75m and 2.5m high (shown to the right). The students simulate their design and predict the height at which the rocket payload will just break the surface of the water column. Finally, after taking a workshop on basic cryptography, the students go head-to-head deciphering a launch code (shown below). If the team who designed the rocket deciphers the launch code first, the rocket is automatically launched and the peak of the rocket's trajectory is measured and recorded. If the opposing team deciphers the launch code first, the the launch is blocked until a judge manually overrides the system to cause the launch so that the peak of the rocket's trajectory can be measured and recorded. The final score in the competition takes into consideration each phase of the competition, including: (i) the performance of the design, based on the ratio of the maximum potential energy measured during the launch to the stored energy in the motor (extra points are given to the designs that break the surface of the water) (ii) modeling of the design, based on the percent error between the predicted and observed height of the launched rocket (extra points are given for the aesthetics of the rocket) and (iii) code breaking, based on the time to decipher the code for launch and launch prevention.
We have successfully used this project at the Midwest Undergraduate Private Engineering Colleges (MUPEC) conference. At this conference, students from 11 different schools majoring in a variety of science, math, and engineering disciplines were assigned into four interdisciplinary teams to participate in the design competition. Three of the four teams selected the correct motor that would produce the maximum efficiency. All of the teams were capable of deciphering the coded message, although some teams were faster than others. The head-to-head competition produced an exciting close to the design experience. As a result of this design experience, many students felt they gained confidence in their ability to apply Newton's second law and deal with drag forces in a rectilinear particle motion problem. In addition, this design experience pointed out the difficult nature of open-ended design problems and using computational software to solved nonlinear differential equations.
To aid other institutions in using this project or a similar project, we have included a detailed list of all materials, equipment, and software that was used during the competition and to develop the launch apparatus. On the Competition Materials page, you can download the problem statement, the grade sheet, the correct solution to the problem, and the cryptography workshop materials. On the Equipment and Software page, you can download schematics, mechanical drawings, and software used to create the apparatus that tested the rockets in the competition.