The Contact Dynamics Simulation Laboratory ( CDSL ) of the Marshall Space Flight Center provides for refined hardware - in - the - loop real - time simulation of docking and berthing mechanisms and associated control systems . This facility is employed to verify the performance of docking / berthing mechanisms during Earth - orbit operations , determine the capture envelope of dockingherthing devices , measure contact loads at vehicle interfaces , and evaluate visual cues for man - in - the - loop operations . The CDSL has developed test verified analytical models of such systems as the ISS Common Berthing Mechanism and HST Three Point Docking Mechanism . This paper will describe the modeling and test techniques employed at the CDSL and present results from recent programs .