Overview and Purpose
After an anomaly with the Mark I engine, the engine was redesigned and improved to become the Luna hybrid rocket engine. Luna is used as an education and testing platform for multiple aerospace design components, such as fuel grain composition, injector plate design, nozzle design, thrust vector control (TVC), and so much more! Optimizing these components allowed the team to conduct research and learn more about hybrid engine design and operation. To that end, the purpose of the project is not to be used for competition, but rather for obtaining knowledge about hybrid rocketry and further researching the theory behind hybrid engines.
Luna is designed to be 222 N (50 lb) thrust engine with a maximum burn time of 10 s. The engine is a hybrid utilizing solid HTPB (Hydroxyl-terminated Polybutadiene) and liquid nitrous oxide. After igniting the HTPB grain in the combustion chamber, a valve will actuate, enabling self pressurizing nitrous oxide in the oxidizer tank to flow through a length of plumbing, past a pressure transducer to a bulkhead. The bulkhead houses the injector plate and is secured to the combustion chamber by bolted flanges that extend from the outer diameter of the bulkhead. The combustion chamber includes an ablative cardboard liner to aid in thermal management. The nozzle at the end of the combustion chamber includes a primarily aluminum body with a graphite insert covering the length of the converging and diverging ends of the nozzle. The nozzle bolts directly to the combustion chamber using identical flanges as the bulkhead. The nozzle is not secured directly to the test stand to allow for measurement of lateral force and to allow the combustion chamber to expand freely throughout the burn. The bulkhead is mounted directly to the test stand structure. The commercial nitrous supply and run tank is kept secured inside of a wooden box away from the engine to protect it against a potential anomaly.
The Test Stand
The purpose of the test stand is to provide a stable platform to test and record data from firing Luna. This data includes axial thrust measurements from the main engine burn as well as radial thrust measurements from the engine's nitrogen-injection thrust vector control system. The test stand supports the weight of the engine and restrain its thrust to preserve safety and provide accurate thrust measurement during testing.
Luna was tested five times to date. Each test resulted in increased duration of the burn (3, 5, 7, 10, and 9 seconds) and produced vital information for the development of the project. On the 10 and 9 second burn, gas injected thrust vector control (GITVC) was integrated with one valve in the nozzle. The result was a perfectly working vector in one direction of motion. In future tests, Luna will be tested with greater direction of motion for GITVC.