## 3 Structural Requirements of Manned Deep Space Exploration Pressurized Capsule  
Manned deep space exploration missions refer to extraterrestrial missions targeting the Moon, asteroids, Mars and its satellites, in which human astronauts are directly involved in the exploration. According to the different target celestial bodies for landing, manned deep space exploration can be divided into missions such as manned lunar exploration, manned Mars exploration and so on. Manned lunar exploration is the starting point and foundation of manned deep space exploration, and is a hot spot of international manned deep space exploration [6; 7]. For example, since 2004, the United States has launched the Project Constellation, Artemis and so on to develop spacecraft such as Orion, as shown in Figure 6.  
The main structure of manned lunar exploration aircraft, whether manned spacecraft or lunar module, is the pressurized capsule structure, which requires higher requirements [14; 15]. These requirements include \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Serial** & **Type** & **Spacecraft** & **Nation/Institution** & **Module Name** & **First Launch Date** & **Structure Form** \\ \hline
28 & & & China & Tianhe core module & April 2021 & WPPCS \\
29 & space station & China Space Station & China & Wentian lab module & July 2022 & WPPCS \\
30 & & & China & Mengtian lab module & October 2022 & WPPCS \\ \hline \hline \end{tabular}
\end{table} 
Table 1: \(Cont.\)  
Figure 6: A schematic diagram of the composition of Orion manned spacecraft, USA. Lower structural weight [16]  
The launch cost of manned lunar exploration is several times or even dozens of times higher than that of near-earth orbit, which requires lower weight and higher efficiency of spacecraft structures. At present, the structural weight/launch weight ratio of manned spacecraft in China is about 25-35%, which is far from meeting the structural weight requirements of manned lunar exploration missions. Therefore, structural weight reduction requirements are extremely urgent to achieve the goal of reducing this ratio to less than 20%. Longer structural life requirements  
In order to realize the in situ detection and resource development of lunar resources, the working life of manned lunar exploration aircraft in orbit will be longer than 15 years, such as for the lunar orbit residence platform, lunar base, etc. This requires that the pressurized capsule structure have a lifespan of more than 15 years under complex load environments [14]. Reusable function  
In order to reduce the mission cost and improve the economy, the manned spacecraft sealing cabins such as the space-to-ground round-trip transportation system and the space-to-moon round-trip transportation system for manned lunar exploration should have reusable functions [6,7]. More complex load conditions [7]  
During the reentry of manned spacecraft in deep space exploration, the reentry velocity increases by more than 40% as it enters the Earth, reaching the second cosmic velocity of 11.2 km/s, and the reentry overload condition becomes larger. New emergency rescue systems, such as self-escape, result in the aerodynamic load of the ascending segment acting directly on the spacecraft. Large-scale impact loads during landing, parachute opening and landing/water landing directly affect the pressurized capsule structure. Therefore, the load environment experienced by the pressurized capsule structure is extremely complex [8]. Higher spatial environmental adaptability  
The manned spacecraft extends from the near-Earth orbit manned spacecraft and space station to the manned lunar landing spacecraft, the lunar orbit station platform and the lunar base. The pressurized capsule structure of these spacecraft is subjected to complex load conditions and more demanding environmental factors, including high and low temperatures, as well as radiation.