The Development of the Hybrid Dynamics Simulation System for Rendezvous and Docking: SATDyn

Abstract

JAXA is studying the active debris removal (ADR) technology. There are several ADR technologies, i.e. net capturing, harpoon, laser ablation, etc. One candidate for ADR in the LEO environment is capturing a large rocket body with a chaser spacecraft with mechanical aid then deorbiting the debris using the propulsion system of the chaser. The key technology is the method of capturing debris. Because debris is an uncooperative target, it has no markers or devices to grasp. To validate the navigation system and the capturing device under gravity, JAXA is developing a hybrid dynamic simulation system called the “satellite dynamics test platform for on-orbit servicing technology,” or SATDyn. The hybrid simulation system uses the same hardware as the device under test (DUT), the navigation sensors, and the capturing device. The navigation sensor's measurements and the force/torque due to contact with the debris are used as simulation inputs. The spacecraft and target dynamics are calculated by a PC with the assumption of free motion. The result of the position and attitude calculations is simulated physically using robots, on which DUTs are located. The chaser system consists of a two-axis gantry rail table, which has a 10m x 7m operational range. A 6DOF industrial level robot arm simulates the motion of the chaser and is mounted on the gantry table. A high-speed 6DOF Stewart platform is equipped at the end of the robot arm to manage high-frequency responses, such as the contact dynamics of the capturing device. The target system consists of a large 6DOF robot arm and the model targets. JAXA's ADR target candidate is the H2A upper stage. There is a scaled 4m diameter mockup of the top of H2A and 1/10- and 1/30-scale models as targets. SATDyn has already been applied to preliminary sensor tests of JAXA's ADR project, the CRD2 phase I.