The space environment is ever-changing with space structures getting larger and the orbits getting increasingly crowded with time. This creates a need for removal of large defunct satellites to avoid the disastrous Kessler syndrome, which poses a major threat to the future of space exploration. This research examines the dynamics and control involved in the active removal of a large space debris - Envisat. European Space Agency's e.deorbit mission aims to de-orbit Envisat using a chaser satellite, which synchronises, docks, detumbles and deorbits it. The presence of large flexible appendages makes the configuration prone to elastic perturbations leading to complex dynamics that cannot be represented using rigid body dynamics. Therefore, a unique multibody approach based on the absolute interface coordinates in the floating frame formulation is used to model the Flexible Multibody Dynamics. The novel method proves to provide a good balance between computation time and efficiency for the control application. The controllability characteristics of two phases of the e.deorbit mission are analysed using a linear PD controller and an Incremental Nonlinear Dynamic Inversion controller. For the first phase, both controllers successfully synchronise the chaser with the target debris tumbling at the rate of 3.5 deg/s about all axes. However, during the detumbling phase, the large appendage (14.2 m) in the stacked configuration introduces complex dynamics, which could not be stabilised completely by applied controllers. Nonetheless, interesting relationships could be established between the dynamics and control of the system, which will facilitate robust control design in future work.

The purpose of this analysis is to present the design of the complete mission involving a dual spacecraft configuration that will analyse the rings of Saturn. The two spacecraft are an orbiter that will orbit at 142,000 km from the centre of Saturn, and a hovercraft that will hover at a distance of 2-3 km fromSaturn its rings...

Spacecraft are under constant threat of structural damage from hypervelocity impacts by micrometeoroids and orbital debris. To bolster the shielding used for protection against these impacts, ballistic materials can be employed. Aramid-based materials are currently used aboard the International Space Station (ISS), but Ultra High Molecular Weight PolyEthylene (UHMWPE) fibres are a common alternative for ballistic protection on Earth. In this report, the suitability of UHMWPE-based composites for spacecraft impact shielding is investigated. Hypervelocity impact simulations using smoothed particle hydrodynamics discretisation form an essential part of the design and analysis of such protection systems. Two formulations of nonlinear orthotropic hydrocode models are proposed for this purpose, which are validated using footage from hypervelocity impact experiments on Dyneema® HB26 targets. One of the proposed models yields good prediction of residual impactor velocities, generally being within 10% of experimental data. The other reproduces both residual velocities and debris cloud shape well for the highest considered impact velocities, but suffers from decreased performance as the ballistic limit is approached. Numerical comparison between UHMWPE- and aramid-based composites shows comparable ballistic performance for the considered cases.