Assessment of space station on-orbit maintenance task complexity

The safe operation of a space station relies on a large amount of on-orbit maintenance. On-orbit maintenance task complexity (OOMTC) plays an important role in maintenance processes, maintenance program assessments, astronaut training and scheduling, and space station maintainability design. However, only a few studies involve on-orbit maintenance complexity assessments. We proposed an OOMTC assessments model based on graph entropy. The model framework consisted of two aspects: inherent maintenance complexity and external environmental influences. Inherent factors include: maintenance operation logic, maintenance operations, maintenance knowledge support, and maintenance of human-machine interface; external influence factors take into account tools, operating space, visual occlusion, spacesuit restrictions and time pressure. In addition, an experiment based on the space station technology verification module was designed to verify the effectiveness of the model. The data analysis shows that the maintenance task complexity value (R = 0.9244) is a good predictor of maintenance operation time. Moreover, maintenance complexity can be well classified. The proposed maintenance task complexity assessment model can provide guidance for maintenance manuals and planning assessments, astronaut crew training and staffing arrangements, cargo spacecraft launch schedules, and space station maintainability design.