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AbstractThe continuous development of space exploration technology requires more efficient and economical space transport systems, and there is an urgent need for propulsion systems that are more efficient than chemical propulsion. Solar thermal propulsion (STP) systems have a relatively small size and high specific impulse, thus offering performance advantages in specific space missions. An STP system is generally composed of a concentrator, heat exchanger core, nozzle, and propellant supply system. The concentrator typically uses parabolic mirrors to concentrate sunlight to heat the heat exchanger core at a focal point. The propellant is heated when it flows through the heat exchanger core and is finally expanded and accelerated by a Laval nozzle to generate thrust. In this propulsion mode, the propulsion system can generate a Newton-level thrust by using an expandable whirling-membrane concentrator with an area of approximately 10 m2 to collect solar radiation. Because hydrogen has a small molar mass and can generate a high exhaust velocity, it is an ideal propellant for solar thermal thrusters. The theoretical specific impulse of an STP using hydrogen as a propellant can reach 800 s. However, the low molar mass of hydrogen also reduces the thrust that the engine can provide, limiting the STP system to low-thrust space missions. The main applications of STP systems are orbit transfer and interplanetary exploration, which require a thrust level between 0.1 and 40 N. Figure 1.1 compares the thrust ranges and specific impulse ranges of several common propulsion methods. Chemical propulsion has a large thrust and a low specific impulse, and electric propulsion has a high specific impulse but a very small thrust. Within the size range of currently achievable spacecraft platforms, the specific impulse and thrust characteristics of STP systems are very attractive, and their high specific impulse and moderate thrust fill the gap between chemical and electric propulsion systems; as such, they are expected to be used to increase the payload ratio of orbital transfer vehicles (OTVs) or orbital maneuvering vehicles (OMVs).