Design of a dual-expander aerospike nozzle rocket engine

The University of Alabama’s Aerospace Engineering and Mechanics Department is developing a computational dual-expander aerospike nozzle (DEAN) upper stage rocket engine to demonstrate the engine’s performance capabilities and to establish a model by which the DEAN can be built. This research expands the base model developed by the Air Force Institute of Technology to more accurately represent the physics involved in both the fluid flow and geometrical properties of the engine. The DEAN engine was modeled using NASA’s Numerical Propulsion System Simulation (NPSS) and Chemical Equilibrium with Applications (CEA) software. The methodology implemented in this research was validated by modeling the RL-10A-3-3A upper stage engine in NPSS and comparing resulting outputs with NASA’s ROCket Engine Transient Simulator (ROCETS) analysis. The DEAN uses liquid oxygen and liquid hydrogen as its propellant and is being designed to produce a thrust of 30,000 [lbf] and a specific impulse of at least 465.5 [s], at an oxidizer-to-fuel ratio of 5.88, while also remaining within the size envelope of the RL-10B-2 upper stage engine. The performance and size objectives were established to meet the National Aeronautics and Space Administration’s (NASA) Advanced Upper Stage Engine Program (AUSEP) need for an upper stage rocket engine to replace the aging RL-10 series engines that have been in production since the 1960s. Results indicate that optimal performance for the feasible solution space examined in this research occurs at an expansion ratio of 30, a throat area of 23 [in2], and a characteristic length, L*, of 90 [in]. The optimal DEAN design point was shown to achieve a thrust of more than 5,000 [lbf] greater than the RL-10B-2, a Isp of 1.8 [s] greater, and a significantly reduced size envelope.