Table 2 Optimal HRM design and rocket performance.
Related Figures (5)
Table 1. Overall rocket mass budget and performance. the increased structural masses. The relative benefit provided by staging grows when larger accelerations of smaller payloads are sought, also because the single-stage rocket is penalized by the vanishing of the coast arc when the lowest payload is adopted. V. Conclusions An optimization procedure, which couples direct and indirect optimization methods, has been applied to the design optimization of a hybrid rocket for the acceleration of subscale models of hypersonic propulsion devices to hypersonic flight conditions. The indirect trajectory optimization method is used to evaluate the performance of different design and, when employed separately, is a useful means for a parametric analysis about the influence of the design parameters. When coupled with the direct optimization of the motor design variables, the optimal design and the corresponding performance can be rapidly obtained. Few minutes are sufficient on a standard PC. The method can be easily modified to deal with different system architectures and control laws. Results are similar to those obtained when the mixture-ratio control of liquid rocket engines is analyzed for ascent trajectories: The optimum solutions require mean mixture ratios that are larger than the value which maximizes the specific impulse, in order to reduce the structural mass. Design choices, such as the rocket aspect ratio and the presence of a constraint on the minimum value of the regression rate, greatly
