ISBN 9783843928205

978-3-8439-2820-5, Reihe Raumfahrt

Manuel Schmitz
Active Removal of Space Debris with Space-Based Lasers

170 Seiten, Dissertation Universität Stuttgart (2016), Softcover, A5

Zusammenfassung / Abstract

Space debris has recently become a topic of elevated interest. As the threat of an uncontrollable collision cascade among defunct space objects, known as the Kessler syndrome, is being discussed, the stakeholders and decision-makers have begun to consider the active removal of orbital debris. Thus motivated, the space community has begun conceiving and studying technical concepts for the realization. The bulk of them address the removal of larger bodies from orbit. These are catalogued and have the potential of fragmenting into a high number of new, dangerous objects. This thesis, however, treats a concept for the removal of the medium-sized (1cm to 10cm) debris objects. These are by far more numerous and are not catalogued. They have a comparable destructive potential but may be even harder to pick from their orbits.

The remediation concept treated herein employs a space-based, high-power laser. By engaging objects in the size regime of 1 cm to 10 cm, and causing laser-induced surface ablation on a substantial subset of the debris population, the objects’ perigees shall be reduced, so that they will re-enter the atmosphere quickly and eventually burn up.

Although this mission concept has been studied in the past, essential key aspects have not yet been analysed in sufficient depth. In fact, important parts have only been covered by rough estimates and rule-of-thumb calculations. Among these topics are: The number of reachable debris objects, the necessity for orbital manoeuvres to be performed by the laser, the impact of the relative motion between laser and debris in the near field, and the connection between the laser optics and orbital mechanics. This thesis determines the boundaries in which a space-based laser debris removal can be performed. It identifies the necessary assumptions and the prerequisites, and derives technical system requirements for an implementation.

For this purpose, a generic and comprehensive mission performance model is es- tablished. The model employs a discrete element approach, which is implemented as a numerical code. It allows performing case studies of individual missions as well as systematic parameter scans and optimizations. Additionally, it provides insight into the relevant mechanisms that are driving the performance: The user can tell why a particular scenario is strong or weak, and iteratively tune the mission and system parameters of the orbital debris sweeper platform. Three performance-driving quantities have been identified: The laser range, the tracking agility and the laser’s power.

This computer-based model is used to identify the constraints and the boundary conditions of the mission concept in general, framing a ‘design space’ of missions. Finally, three exemplary sweeper missions are presented as a demonstration of the model’s capabilities. Requirements for their technical implementation are estimated, along with an analysis of their remediation performance. The balanced scenario is shown to be capable of reducing the debris density in the most polluted orbital regions by 23 % in 10 years.