Abstract: In the last decade, space solar power satellites (SSPSs) have been conceived to support net-zero carbon emissions and have attracted considerable attention. Electric energy is transmitted to the ground via a microwave power beam, a technology known as microwave power transmission (MPT). Due to the vast transmission distance of tens of thousands of kilometers, the power transmitting antenna array must span up to 1 kilometer in diameter. At the same time, the size of the rectifying array on the ground should extend over a few kilometers. This makes the MPT system of SSPSs significantly larger than the existing aerospace engineering system. To design and operate a rational MPT system, comprehensive optimization is required. Taking the space MPT system engineering into consideration, a novel multi-objective optimization function is proposed and further analyzed. The multi-objective optimization problem is modeled mathematically. Beam collection efficiency (BCE) is the primary factor, followed by the thermal management capability. Some tapers, designed to solve the conflict between BCE and the thermal problem, are reviewed. In addition to these two factors, rectenna design complexity is included as a functional factor in the optimization objective. Weight coefficients are assigned to these factors to prioritize them. Radiating planar arrays with different aperture illumination fields are studied, and their performances are compared using the multi-objective optimization function. Transmitting array size, rectifying array size, transmission distance, and transmitted power remaine constant in various cases, ensuring fair comparisons. The analysis results show that the proposed optimization function is effective in optimizing and selecting the MPT system architecture. It is also noted that the multi-objective optimization function can be expanded to include other factors in the future.

Key words: space solar power satellite (SSPS), microwave power transmission (MPT), multi-objective function, beam collection efficiency (BCE), system engineering