# Reliability Assessment of Space Station Based on Multi-Layer and Multi-Type Risks
###### Abstract  
A space station is a typical phased-mission system, and assessing its reliability during its configuration is an important engineering action. Traditional methods usually require extensive data to carry out a layered reliability assessment from components to the system. These methods suffer from lack of sufficient test data, and the assessment process becomes very difficult, especially in the early stage of the configuration. This paper proposes a reliability assessment method for the space station configuration mission, using multi-layer and multi-type risks. Firstly, the risk layer and the risk type for the space station configuration are defined and identified. Then, the key configuration risks are identified comprehensively, considering their occurrence likelihood and consequence severity. High load risks are identified through risk propagation feature analysis. Finally, the configuration reliability model is built and the state probabilities are computed, based on the probabilistic risk propagation assessment (PRPA) method using the assessment probability data. Two issues are addressed in this paper: (1) how to build the configuration reliability model with three layers and four types of risks in the early stage of the configuration; (2) how to quantitatively assess the configuration mission reliability using data from the existing operational database and data describing the propagation features. The proposed method could be a useful tool for the complex aerospace system reliability assessment in the early stage.  
reliability assessment; risk propagation; PRPA; multi-layer risks; multi-type risks; space station +
Footnote †: journal: Applied Sciences  
[PERSON], 12, and [PERSON]  
[PERSON], 11, 10258. [[https://doi.org/10.3390/appl12110258](https://doi.org/10.3390/appl12110258) https://doi]([https://doi.org/10.3390/appl12110258](https://doi.org/10.3390/appl12110258) https://doi).  
and management is a very important task throughout the whole configuration process. The risks identified can describe the configuration states, and the relationships between different layers and types can represent the static and dynamic risk features. Probability data on partial risks incurred in other aerospace projects are collected in the existing operational database. So, in the early stage of the configuration, the risks can be used to assess the configuration reliability. According to the above analysis, this paper proposes a PRPA method. It combines the PRA method and risk propagation theory [23; 24] to solve the reliability assessment problems.  
The structure of this paper is organized as follows. In Section 2, the framework of the space station configuration reliability assessment is given. Then, according to the classification and stratification criteria, multi-layer and multi-type risks are identified in Section 3. Section 4 analyzes the occurrence, consequence, and propagation features of the multi-layer and multi-type risks based on the risk qualitative evaluation matrix and the Leader Rank algorithm [25; 26; 27]. The model of the space station configuration reliability is built in Section 5, and the risk data is collected in Section 6. Section 7 uses the tool QRAS [28] to quantitatively assess the space station configuration reliability based on the PRPA method. The conclusions and future works are given in Section 8.