Removal of Space Debris from the Low Earth Orbit using a Ground-based Multi-kJ High-Power Laser

Kurzfassung

The concept of space debris removal from the low Earth orbit (LEO) by laser-ablative recoil is analyzed using simulations of laser-matter interaction during debris passes over a high-power laser station. Laser irradiation during the ascending part of the debris transit is used for target deceleration in order to achieve lowering of the perigee of the debris orbit. To initiate drag-induced slowdown and eventually debris removal by burn-up in the upper atmosphere, an overall velocity decrement in the order of Delta-v = 150-250 m/s is required, which can be obtained over time by debris irradiation during a multitude of station transits. Laser ablation demands for large fluences in the range of 1-10 J/cm^2 and beyond at the irradiated target. However, atmospheric constraints like laser power loss due to aerosol extinction as well as laser beam broadening as a result from atmospheric turbulence have to be considered. Therefore, the usage of adaptive optics is explored in terms of a suitable transmitter configuration in combination with a laser guide star in order to compensate for turbulence effects enabling to provide such a high energy density from ground to a distant orbital object. For the simulation of debris removal using an appropriately configured high energy laser and transmitter, virtual targets with simplified geometric shapes are employed to investigate laser-matter-interaction with rocket bodies, mission-related objects and inactive payloads. In addition to related debris data from the ESA DISCOS catalogue, the NASA Standard Breakup Model serves as a reference for fragments from collisions and explosions. For these objects, located at different altitudes in the low Earth orbit, a study on laser-ablative recoil is carried out using our code EXPEDIT for laser-matter interaction with complex target geometries. The unknown orientation of the target as well as residual laser pointing errors are addressed here by a Monte Carlo approach. The simulation results are discussed in terms of imparted momentum during laser irradiation, the resulting perigee lowering and the number of required irradiation transits for removal of the debris object. Moreover, issues of operational safety regarding laser-induced thermal effects and debris object integrity aspects are discussed.