Asteroid deflection and active debris removal methods with spaceborne lasers

Student thesis: Doctoral Thesis

Abstract

Several deflection methods have been proposed over the years to mitigate the risk of impact between an asteroid and the Earth. Most of the strategies proposed fall into two categories: impulsive and slow-push. Impulsive strategies are usually modelled with an instantaneous change of momentum given by, for example, a nuclear explosion (nuclear interceptor) or the hypervelocity impact of a spacecraft (kinetic impactor) with the asteroid. Slow-push methods, on the other hand, allow for a more controllable deflection manoeuvre by exerting a small continuous and controllable force on the asteroid over an extended period of time.However, these methods generally rely on large propellant reserve required to rendezvous with the target and apply the deflection action. Laser ablation intends to resolve this difficulty by using the material the target is made of in order to generate the required thrust. When irradiating a target with sufficient laser intensity, an ablated mass can be ejected at high velocity,thus exerting a reaction force on the target that can be used to propel itself. By selecting the appropriate laser technology and tayloring the system parameters based on the target application, it is theoretically possible to build an efficient space-based laser system.According to our calculations, the levels of performance of such a system (in term of thrust delivered per watt invested in the process) would be on the same order of magnitude as existing Ion Engines. By taking into account the propellant consumption and considering end-to-end detection scenarios in a statistically representative sample of asteroid detection scenarios, we show that laser ablation outperform other popular slow-push detection strategies as the gravity tractor and the Ion Beam Shepherd (IBS). Extrapolation of the laser ablation method is also proposed for the case where the target is a manmade piece of debris orbiting around the Earth instead of an asteroid.In this case, pulsed lasers rather than CW lasers are considered in order to maximize the achievable laser intensity (TW/m2 can be achieved even with a few watts of average power and moderate optics) with the same available average power. The choice of a pulsed laser allows considering larger operation distances and ensures that each layer of material ablated during a laser pulse will be small enough that it will not become a new threatening piece of debris by itself. Comparison between predicted and experimental results are illustrated for several material typically encountered in space debris objects, such as metallic alloys and CFRP. The different results highlight the interest for the laser ablation method as a global strategy to manipulate both man made and natural objects and indicate its potential complementarity with other strategies such as the kinetic impactor method currently envisaged for asteroid detection.
Date of Award2 Jun 2020
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorMassimiliano Vasile (Supervisor) & Edmondo Minisci (Supervisor)

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