Abstract
The space debris problem poses a huge threat to operational satellites and has to be addressed. Multiple removal methods have been proposed to keep Earth’s orbit stable. Flexible connection capturing methods, such as the harpoon system, tether–gripper system and the net system, are potential candidate methods for space debris removal in the future. However, the tethered system is usually assumed as a dumbbell model where two end masses are connected by a rigid bar. This traditional model is not accurate enough to predict the motion of the target, neither the whole system. In this paper, three models, namely the modified dumbbell model, lumped-mass model and the ANCF model, to describe a tethered post-capture system for space debris removal are described and compared. Moreover, modal analysis of the tethered system is performed, and an analytical solution of the system’s natural frequency is derived. In addition, two configurations of the tethered system, namely the single tether configuration and the sub-tether configuration are simulated and compared based on three models, respectively. Finally, the influence on the chaser satellite by the initial angular velocity of the target is analyzed.
Highlights
With the development of space technology, the number of yearly launches is dramatically increasing, which brings the side-effect of the space debris problem
Φq where Me and Mr are the constant Absolute Nodal Coordinates Formulation (ANCF) mass matrix and rigid bodies mass matrix, respectively; Qe is the generalized elastic force associated with absolute nodal coordinates e, and Qr is the external force applied on the rigid bodies which is governed by its coordinates qr ; here, λ represents the Lagrange multiplier; Φq is the Jacobin matrix of the constraint equations Φ (Equation (16)); γ is obtained by differentiating the constraint equations twice with respect to time
To establish the theoretical model of the tether for modal analysis and to determine the optimal number of segments, the tether is divided in the simulation, the main tether is assumed as an elastic rod, and two end bodies are assumed as two mass points for analysis
Summary
With the development of space technology, the number of yearly launches is dramatically increasing, which brings the side-effect of the space debris problem. To remove a space debris object from orbit, multiple methods have been proposed by researchers, including robotic arm, net capturing, harpoon, tentacle capture, etc. The net, harpoon and tethered-gripper capture method are all examples of the flexible connection method by definition (see Figure 2). Golebiowski et al have developed a simulator based on the Cossrat rod theory and validated their model using a zero-gravity parabolic flight experiment [12]. Many exciting results have been achieved for the first two phases of capturing a space debris object; the recent research focus has switched to the dynamics analysis of a tethered post-capture system. O’Connor has applied a modified dumbbell model to describe a tethered system and proposed a wave-based control method to detumble a spinning target [24]. By running the simulations of different tethered systems under each model, three models are cross-verified and their initial condition influences are analyzed
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