Eddy currents applied to space debris objects

Abstract

The increasing population of space debris in the near-Earth region poses a serious threat to operational satellites in-orbit. This situation has led to the development of numerous guidelines in order to mitigate the potential danger of in-orbit collisions, fragmentations and uncontrolled re-entries. Among the various recommendations, active debris removal is considered as a possible solution to help decrease the chance of the aforementioned risks. However, active debris removal has never been done in space and it still requires further development of various technologies and orbit testing before it can become a reality. One of the major challenges to overcome is how to capture rotating space debris objects. Some of these objects may have high rotational speeds which hampers their capture and subsequent controlled re-entry.

This research focuses on the analysis of the eddy current phenomenon on space debris objects by the Earth magnetic field as well as its practical application to develop a de-tumbling method for active debris removal based on the generation of eddy currents.

The first part of the project focuses on the development of a new mathematical approach which generalises the existing analytical models and simplifies the numerical methods typically employed to analyse the eddy current phenomenon. This mathematical approach, referred to as the magnetic tensor theory, is validated both numerically and experimentally. The theory is based on the discovery of a symmetric Cartesian tensor of second order with no negative eigenvalues, named the magnetic tensor. A method to evaluate this tensor based on a generic finite element method is provided as well as a particularization for a specific F.E.M. which leads to a direct formula to evaluate this tensor. This way, the eddy current torque solution may be found without the necessity to solve the classical Poisson equation with Neumann boundary conditions in each time step of the integration process of Euler’s equation. This breakthrough greatly reduces the complexity and computational time of the classical approach commonly adopted in the past.

The second part of the project focuses on the design of a contactless de-tumbling method based on the generation of eddy currents named the eddy brake method. This design delves deeper into the idea first suggested by Kadaba and Naishadham in 1995 which consists in subjecting a space debris object to an enhanced magnetic field in order to damp its rotation. The advances in high temperature superconducting materials as well as spacecraft sensors and actuators has allowed for a compelling new design to be reached within this research which may serve as a stepping stone for future ADR missions.

A thorough systems engineering design of the eddy brake is presented with special attention to the thermal and guidance, navigation and control subsystems. These subsystems have been identified as the two most relevant ones to support the operation of the eddy brake. The results show that the eddy brake is a promising solution to reduce the rotation of metallic space debris and allow for their subsequent capture.

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