An Orbital Debris Active Protection System for Space Stations in Low Earth Orbit

The growing number of Resident Space Objects (RSOs) in Low Earth Orbit (LEO) poses a threat to future spaceflight activities. As LEO becomes more congested, there is a need to address the increasing collision risk between spacecraft and RSOs in the 1 – 10 cm size range, which are numerous and impractical to shield against. An assessment of the capabilities of space situational awareness (SSA) networks reveals that performing collision avoidance against such RSO threats is also not feasible; In this paper, an “active protection system” (APS) to address these threats is proposed for space stations – large structures with long orbital lifespans for which crew safety is paramount. Trade studies are first performed to derive the basic APS design and mission architecture – a station-based pulsed laser optical system that will perform cued detection, tracking, and ablation of RSO threats. With this approach, RSOs on collision trajectories are first identified by ground-based sensors and then de-orbited by the APS via ablation prior to the close approach. A quantitative analysis of the laser performance is also conducted using the International Space Station (ISS) reference orbit and some optimal system parameters are derived. Finally, a feasibility study of implementation on the ISS is performed; The resulting design consists of a robotic arm interfaced to the ISS via a Power and Data Grapple Fixture (PDGF) on the S0 truss, with the laser and telescope optics attached to the end of the arm for pointing flexibility. All phases of APS active operations are expected to occur within a 500 km range, with laser burst powers of ~ 10 kW and repetition rates of ~ 100 Hz; Energy is stored in lithium- ion batteries that are recharged via the PDGF at a reasonable rate of ~ 1.2 kW for 16 minutes after each interaction. The estimated mass of the entire system is under ~ 6000 kg and should pose no substantial issues for delivery to the ISS or other future stations in LEO. It is hoped that this thesis will inform continued research on the issue of protecting space stations from orbital debris threats.