# Hybrid-Compliant System for Soft Capture of Uncooperative Space Debris
## 6 Conclusions  
This paper proposed a one-to-many solution: a flexible, versatile capturing mechanism of class ET2 targeting a vast range of small uncooperative space debris in low Earth orbit (LEO). It incorporates a hybrid-compliant system, combining active compliance (with controlled linear actuators) and passive compliance (with legs articulated by torsional springs). Combined, they make the equivalent hybrid stiffness adjustable to a specific range of debris mass. This novel system also uses a bio-inspired dry adhesive to stick to the debris surface and keep it from being pushed away, increasing the overall reliability of the ADR mission.  
The simulation study presented in this paper revealed that a passive-compliant ADR system was incapable of targeting all the small debris. The integration of both active and passive compliance was required to enable the successful soft capturing of the whole range of small debris (up to 100 kg). It allows the system to gently welcome the debris in contact with the servicer satellite, providing the required contact time for properly capturing it. The active compliance is controlled by the developed impedance controller (IC), which adjusts the compliance parameters based on the debris that will be captured.  
This paper brings forward the research on capturing a wide range of small debris in orbit, thus contributing to a cleaner and safer space. Future work will focus on the design, development, assembly, verification, and validation (V&V) of all components of the mechanism and experimental V&V testing in the Zero-G Lab facility of SnT-University of Luxembourg.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13137968/s1](https://www.mdpi.com/article/10.3390/app13137968/s1)]([https://www.mdpi.com/article/10.3390/app13137968/s1](https://www.mdpi.com/article/10.3390/app13137968/s1)), Video S1: Simulation video of the soft capture process. Software used: NVIDIA Omniverse.  
Conceptualization, M.H.D. and O.-O.C.-L.; Software, M.H.D. and O.-O.C.-L.; Validation, C.M.; Investigation, M.H.D. and O.-O.C.-L.; Data curation, M.H.D.; Writing--original draft, M.H.D. and O.-O.C.-L.; Writing--review & editing, M.H.D., O.-O.C.-L., B.C.Y., X.L. and C.M.; Supervision, M.O.-M. and C.M. All authors have read and agreed to the published version of the manuscript.  
SnT-SpaceR has conducted this study under Luxembourg National Research Fund (FNR)--BRIDGES funding for \"High fidELity tEsteing eNvironment for Active Space Debris Removal--HELEN\", project ref: BRIDGES2021/MS/15836393, and FNR funding for \"design of a Capturing, Absorbing, SEuring system for active space Debris removal--CASED\" project FNR16678722.  
Not applicable.  
Data Availability StatementRestrictions apply to the availability of these data. Data was obtained from DISCOS (Database and Information System Characterising Objects in Space) and are available at [[https://discosweb.esoc.esa.int/objects](https://discosweb.esoc.esa.int/objects)]([https://discosweb.esoc.esa.int/objects](https://discosweb.esoc.esa.int/objects)) with the permission of ESA.  
The authors declare no conflict of interest.