New formulation for evaluating status of space debris capture using tether-net

The capture quality index (CQI) was previously proposed to evaluate the status of space debris captured by a tether-net. However, applying CQI to capture simulations of debris of various sizes and concave shape revealed that even if debris was not fully wrapped, the CQI may inappropriately provide an evaluation value for fully wrapped debris capture. This is because the CQI does not consider the degree of net opening against debris, the adhesion of the net to the debris, or debris with concave shapes. In this study, the net outer-edge closing motion is modeled as the decrease in the natural length of the perimeter tether with time. To overcome the drawback of the previous CQI, a new evaluation method for tether-net space debris capture, modified capture quality index (MCQI), was proposed. In MCQI, to evaluate the debris-capture status, the difference between the debris volume and the volume of debris overlapped by the tether-net convex hull, the average distance of the tether-net convex hull to the debris vertices, and the degree of net opening are considered. The numerical comparison between the MCQI and conventional CQI confirms that the newly developed method for debris-capture status evaluation resolves the problems of the previous CQI.