Originally, when Rice Eclipse was founded (then RiceX), we decided to design and build hybrid engines because they strike a balance of complexity between solid and liquid, providing a challenging but attainable first goal. Additionally, we had seen other university teams around the country successfully pursuing hybrid programs, and were enthusiastic to join their efforts and adventures.
The purpose of Mark I was twofold: it was primarily a proof of concept to ensure that we knew we could build and operate hybrid rocket engines and moreso that we could do so safely and effectively. Secondly, it was a project that we could complete despite are financial constraints. Originally, the plan was to build this test engine (the engine was always only designed to stay on the ground), and then build a second, more powerful engine later in the year that we could integrate into a rocket body. That second engine (Titan) proved to be a much more substantial endeavor than we initially realized, but we're now closer than ever to completing our first major milestones!
Like most hybrid engines, Mark I has a solid fuel and liquid oxidizer which is already at operating pressure before ignition. The liquid oxidizer moves from an external tank past a manual valve and regulator and then through a remotely actuated ball vale to the engine itself where it cools the pressure transducer line before reaching the injector plate. The injector plate rests in the bulkhead and serves to atomize the oxidizer as it is injected into combustion chamber. In the combustion chamber the oxidizer mixes with the burning fuel to create combustion gasses (mostly carbon dioxide and water) which are then accelerated by a de Laval nozzle. The fuel grain is cast in an ablative sleeve that protects the aluminum combustion chamber from overheating during the burn. The nozzle in this design was at first intended to be expendable, and stainless steel was chosen for its cost and low reactivity. We later began using graphite for our nozzles for reusability.
Mark I was designed to output around 50 lbs of thrust, and use HTPB and nitrous oxide. As of December 2016, we have fired the engine approximately 13 times, and we have always used HTPB, although we have already begun casting experimental grains to explore different fuel compositions and casting techniques. In December 2016, the original design suffered a minor explosion and prompted a Mark I redesign, now named Luna. Look to our facebook page for updates on this progress.
Mark I System - "Archimedes"
The Mark I avionics structure is built around our 'Archimedes' printed circuit board and an National Instruments myRIO. The system runs on labView software with some C modules. The system can read in and wirelessly transmit data from a load cell, pressure transducer, and several thermocouples simultaneously. The ignition sequence is initiated remotely after several mechanical and software safety checks are passed. The system shuts off a test based on time, remote manual input, or sensor safety thresholds.
Archimedes is contained in a launch control box that contains all arming capabilities, antenna, and power management systems.