Jascha Wilken

Laser-based removal of irregularly shaped space debris

Abstract. While the feasibility of laser space debris removal by high energy lasers has been shown in concept studies and laboratory proofs of principle, we address the question of the effectiveness and responsibility associated with this technique. The large variety of debris shapes poses a challenge for predicting amount and direction of the impulse imparted to the target. We present a numerical code that considers variation of fluence throughout the target surface with respect to the resulting local momentum coupling. Simple targets as well as an example for realistic space debris are investigated with respect to momentum generation. The predictability of the imparted momentum is analyzed in a Monte Carlo study. It was found that slight variations of the initial debris position and orientation may yield large differences of the modified trajectories. We identify highly cooperative targets, e.g., spheres, as well as targets that are strongly sensitive to orientation, e.g., plates, and exhibit a poor performance in laser debris removal. Despite limited predictability for the motion of a particular debris object, the laser-based approach appears to be suitable for space debris removal, albeit not with a deterministic but rather with a probabilistic treatment of the resulting trajectory modifications.

Experimental verification of high energy laser-generated impulse for remote laser control of space debris

Walking along a beach one may notice debris being washed ashore from the vast oceans. Then, turning your head up at night you even might noticed a shooting star or a bright spot passing by. Chances are, that you witnessed space debris, endangering future space flight in lower earth orbit. If it was possible to turn cm-sized debris into shooting stars the problem might be averted. Unfortunately, these fragments counting in the 100 thousands are not controllable. To possibly regain control we demonstrate how to exert forces on a free falling debris object from a distance by ablating material with a high energy ns-laser-system. Thrust effects did scale as expected from simulations and led to speed gains above 0.3 m/s per laser pulse in an evacuated micro-gravity environment.

Advanced Simulations of Reusable Hypersonic Rocket-Powered Stages

After successful completion of the MRR, technical progress of the SpaceLiner ultra-high-speed rocket-propelled passenger transport is achieved in Phase A conceptual design work. Following geometry refinement the structural design is maturing based on extensive trade-offs. Aerodynamics are investigated by numerical CFD-simulations of the two winged stages and will be supported by windtunnel tests. Aerodynamic control surfaces of the passenger cabin and rescue capsule and its subsystems are defined. Alternative options for the capsule with innovative morphing shapes are critically investigated taking into account system aspects, structural design, and advanced CFD-simulations. Potential intercontinental flight routes, considering range-safety and sonic boom constraints as well as good reachability from major business centers, are evaluated and flight guidance schemes are established. Extensions to this trajectory model are implemented to investigate the attitude dynamics and related controllability issues of the asymmetric launcher configuration. The space transportation role of the SpaceLiner concept as a TSTO-launcher is now addressed in technical detail.

SpaceLiner Cabin Escape System Design and Simulation of Emergency Separation from its Winged Stage

The SpaceLiner is a visionary concept of a hypersonic passenger transportation system with two parallel winged stages based on rocket propulsion. This fully reusable system has been studied by the German Aerospace Center (DLR) for over a decade and has entered its project phase A in 2017. Since it is supposed to transport up to 50 passengers on suborbital trajectories, high standards for safety and reliability have to be applied to this system. Hence, an emergency capsule (SpaceLiner Capsule) accommodating the passengers is foreseen that shall safely eject from the SpaceLiner passenger stage in case of a critical emergency. This paper focuses on the separation process and investigates the baseline capsule ejection procedure such as the cabin and separation motor design. Furthermore, the status and recent developments of the SpaceLiner are presented.

Evaluation of European Reusable VTVL Booster Stages

Reusability of launch systems has the potential to strongly impact the launch service market if sufficient reliability and low refurbishment costs can be achieved. This study focuses on the vertical takeoff and vertical landing (VTVL) method as currently used by SpaceX. The goal of this study is to determine the impact of this method on a technical, operational and economic level and to identify its potential for a future European reusable launch system. Therefore, different propellant combinations, stagings and engine cycles were considered for a launch system with a reusable VTVL booster stage and a payload capability of 7 tons to GTO (geostationary transfer orbit). Several concepts were subjected to a preliminary design phase and are presented in this paper. The most promising concept will be selected to enter a second, more detailed design phase to obtain a feasible reusable VTVL launcher with the potential to become a future European launch vehicle.