Inclusion of Asymmetric Properties in the Single-thruster Open-Loop Slew Control Algorithms for Prolate Spinning Spacecraft

摘要

Spin-stabilised control was a pioneer spacecraft control method before a three-axis stabilised control was widely used. Spin-stabilised spacecraft, or spinner, uses this simple but robust method in controlling or manoeuvring the body in the microgravity environment. Surrey Space Centre (SSC) is currently spearheading the research in this area for a prolate shape spinner as a result of its involvement in the Moon Lightweight Interior and Telecoms Experiment (LITE) surface penetrator mission development funded by Astrium. The penetrator is a missile-shaped spacecraft used for delivering required mission equipment to the subsurface of the intended planet or celestial body. It is spin-stabilised after release from the orbiter before it is slewed to achieve a desired angle while free falling to the surface.;The work described in the thesis is the ongoing development of the slew control algorithms by SSC as mentioned above. State-of-the-art algorithms have been developed, namely the Half-Cone (HC) derived family and pulse-train family. These algorithms have been proven theoretically, but implementation in a real-time mission is yet to be done, except for the Rhumb Line slew control. In particular, this thesis addresses the issue of the asymmetric shape of the developed prolate spacecraft where, in theory, it has been assumed as perfectly symmetric. Three new algorithms based on the HC-derived family that consider this asymmetric factor are discussed. The significant improvement made by these novel algorithms is the mass reduction of the final residual nutation in an average of one tenth of the current algorithm. Further analysis is done to these new algorithms in terms of accuracy, energy efficiency, slew time, the effect of thruster response time and gravity. The performance of these new algorithms in controlling an extreme asymmetric case is described first before it is applied to a common prolate-shaped spacecraft. An attempt to develop a testbed is also discussed within the work.