Multi-attribute evaluation approach for small launch vehicle with multi-objective multi-discipline design optimization

In this paper, a novel synthetical multi-attribute evaluation (MAE) approach for small launch vehicles (SLVs) is proposed. In addition to traditional technical performances, other attributes, including cost, operability, manufacturability, flexibility and safety/environmental-friendly characteristics, are considered for comparison. Three chemical propulsion systems, which are solid rocket motor (SRM), liquid rocket engine (LRE), and hybrid rocket motor (HRM), are adopted for the design optimization of a SLV and comparison of the multi-attribute evaluations. Three disciplines are considered to establish the system design model of the SLV, including propulsion, structure and overall design. The Ziolkovsky formula is used to estimate the total velocity increment needed for the orbit injection. Cost models for different propulsion are established respectively. And two performance parameters, the taking-off mass and total cost of the launch vehicle, are selected as the design targets of the multi-objective optimization, which aims at the same design reference mission, 100kg payload with injection at 300km circle low earth orbit. Moreover, fuzzy decision method is adopted to quantitatively characterize expert evaluation in MAE. In order to synthetically evaluate the suitability of each propulsion system, TOPSIS multi-standard decision scheme is implemented based on entropy weight method. The results show that all MDO models acquire a series of solutions with two objectives (takeoff mass and total cost) for SLV. Aiming at the same index, SLV powered by SRM has the smallest takeoff mass, while SLV powered by HRM emerges the lowest cost. Total mass emerges significant positive correlation with total cost, while Pareto front indicates that negative correlation exists between total cost and takeoff mass at the range of whole design space. The proposed synthetical MAE approach is proved to be flexible for SLV design, and can be extended to other attributes. Otherwise the HRM is proved to have the most competitive advantages for small payload injection.