An Overview of the Past and Current Status of Hybrid Rocket Propulsion at the University of Brasilia
Creators: name:  A.E. DE MORAIS BERTOLDI 
name:   C.A. GURGEL VERAS 
name:   O. SHYNKARENKO 
name:   A. ANDRIANOV 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: PROPULSION PHYSICS
HYBRID PROPULSION

description: The University of Brasilia (UnB) has developed research in hybrid rocket propulsion systems since the early 2000s. This paper addresses the Chemical Propulsion Laboratory activities (CPL) and the Energy and Environment Laboratory (LEA) on hybrid rocket propulsion systems. Over the years science and technology and hundreds of tests with different hybrid rocket motors were carried out by the group in many fields, such as solid fuel regression rate using diverse fuels, injectors design, internal ballistics, combustion instability, thrust control, ignition, and thermal insulators. The university and partners have made numerous efforts to design, manufacture, and test rocket motors, from small and low-altitude, sounding hybrid rocket to a propulsive decelerator test-motor for the Brazilian space program. The LEA laboratory started the hybrid propulsion activities at the University of Brasilia, studying rocket fuels regression rate using LOX and N2O (liquid) as oxidizers and polyethylene as fuel. In late 2004 the Energy and Environment Laboratory introduces paraffin-based fuel at the university propulsion activities. Based on these scientific research results, four experimental sounding rockets, LILE1, LILE2, SD-1, and SD-2, respectively, were designed, manufactured, and tested. The SD-1 hybrid prototype was launched, and the SD-2 project stopped after the motor tests phase. The test motors design meets the modular concept requirements that ensure versatility of possible configurations, simplifying the assembly-disassembling procedure due to introducing quick-detachable clamp-type connection and accessibility to disposable components without complete disassembling of test-motor. The qualification procedure showed that the test-motor is safe in operation and feasible for further research applications. The ablation rates of various matrices (epoxies, polyurethanes, silicones) were estimated experimentally to improve heat insulation of the structural casing of the test-motor. An oxyacetylene torch has been used to characterize the thermal insulation efficiency of the silicone-reinforced composites. The CPL team has elaborated new safety measures for the hybrid propulsion systems testing, including hardware and software solutions in test preparation, execution, and termination. A feed system compatible with earlier developed engines safely and efficiently provides a liquid or gaseous oxidizer to rocket engines, allowing flow control and thrust modulation using PID and real-time flow modeling. A new highly reliable ignition system based on a CH4/O2 torch has been developed at CPL. Further, this device has been improved to test other hybrid rocket engines under development in the lab. The group also develops and tests different injector plates to be applied for rocket propulsion. Various types of injectors have been designed and tested in cold and hot fire conditions by CDF simulations and experimental investigations. Thus, this paper presents the propulsion teams main results and its contribution to developing the hybrid rocket motors technology.