神二十飞船舷窗裂纹维修，细节披露！

Core Viewpoint - The Shenzhou 20 spacecraft experienced a delay in its return due to a crack in the window caused by suspected impact from small space debris, leading to a series of tests and a subsequent unmanned return to Earth [1][4]. Group 1: Unmanned Return vs. Manned Return - The Shenzhou 20 spacecraft utilized an unmanned return process, relying entirely on ground commands, eliminating the need for manual operation by astronauts [4]. - This marks the first unmanned spacecraft return during the space station phase, with a focus on ensuring the spacecraft's stability through careful mass balance during material transfer [4]. - The search and recovery operation for the return capsule incorporated drones and unmanned ground vehicles, emphasizing resource efficiency and coordination between manned and unmanned efforts [4]. Group 2: Window Repair and Safety Measures - The window of the Shenzhou spacecraft consists of a three-layer composite glass structure, with the outer layer designed to withstand temperatures exceeding 1000 degrees Celsius during re-entry [6]. - A penetrating crack was discovered, prompting the crew to switch to Shenzhou 21 for return. Repairs were conducted from inside the capsule, enhancing thermal and sealing capabilities [6]. - Future improvements will focus on enhancing the window structure to better resist impacts from space debris, with monitoring of small debris being a priority [6]. Group 3: Cargo Returned by Shenzhou 20 - The Shenzhou 20 spacecraft returned with a record amount of cargo due to the absence of three astronauts, including an extended-use extravehicular suit and several large components for space applications [11]. - The extravehicular suit, which has been used by 11 astronauts across 8 missions, is expected to contribute to lunar suit research and may be publicly displayed after its scientific mission [11].