Assessment and applications of the conversion of chemical energy to mechanical energy using model rocket engines

Abstract

To provide the first-year engineering students with a hands-on experience in an engineering application using both chemistry and physics, this team project uses a set of chemical and physical energy concepts and MS Excel based analysis. The main objective of the project is to calculate how much of the potential maximum possible chemical energy is converted into propulsion when using model rocket engines with solid fuel. The secondary objective is to determine the effects of increasing conversion rates on the performance of a model rocket. The solid fuel or propellant used in common model rocket engines is black powder. Compared to composite and hybrid engines, engines with black powder are cheaper and easier to ignite. Affordability of this propellant has made it possible to test fire many engines of different sizes. In addition, solid model rocket engines provide a good analogy to solid rocket boosters used in some of today's launch vehicles. Rockets are momentum engines; thus, it is unusual to consider them in terms of energy, but energy is felt by observers even in model rocket launches. Total impulse is the measure of momentum imparted to the vehicle and depends on several processes including the chemical energy of the propellant and the useful kinetic energy of the exhaust. The project centers around calculation of the total energy released by the combustion of the reactants in model rocket engines of various types (A through F). The propulsion energy is a small fraction of the total energy released during combustion where a significant part of the total is lost heat. Many students enjoyed this activity as they learned how to code several sets of chemical balance and physical energy equations using MS Excel. Each team wrote a detailed technical report that explains the overall project. They used field pictures and the graphs to illustrate various parts of the project. They also included an essay on alternative propulsion means to explore the outer Solar system and beyond. An anonymous learning survey was developed, implemented, and analyzed to assess the educational effect of this project. The survey results and anecdotal evidence show this was a good and a challenging learning experience that was also too demanding for some of the students.