Continuous low thrust propulsion can add considerable utility to spacecraft dynamics by enabling rich new families of thrust augmented orbits. With the aim of enabling such orbits for small, low-cost spacecraft with limited on-board sensing, new families of non-Keplerian orbits are generated in the Hill-Clohessy-Wiltshire approximation using position-only feedback. The same strategy is also applied to the linearised dynamics around collinear libration points in the circular restricted three-body problem. In the Earth-Moon system, position-only feedback is used to stabilise the local dynamics, and interesting new multiply-periodic orbits are generated. The in-plane and out-of plane natural frequencies are then synchronised, allowing the generation of stable halo-type orbits of arbitrary dimensions. An application for such orbits, an Earth-Moon L2 communications relay, is also suggested. The propellant requirements for such orbits are shown to be modest and achievable with existing low thrust technology. Continuous thrust is also used to produce artificial horseshoe orbits in a two body system. Using the cylindrical-polar form of the Hill-Clohessy-Wiltshire approximation, low thrust manoeuvres are developed which allow for phased, nested constellations of spacecraft around a circular two-body orbit. Interesting new three-dimensional nested constellations can be enabled by the addition of out of-plane thrust, offering reconfigurable coverage of specific regions of the Earth. In the circular restricted three-body problem, constant thrust directed along the unit radius vector from each primary mass is applied to a spacecraft, modifying the positions and nature of the five equilibrium points, and thereby changing the region in which horseshoe orbits can occur. In the 243 Ida binary asteroid system, it is found that acceleration directed towards the two primaries results in Lyapunov-stable L4 and L5 points, permitting horseshoe orbits. In the 243 Ida system, a strategy is then proposed for finding periodic horseshoe orbits which rendezvous with the surface of the smaller primary. A search and-filter method is employed to produce initial guesses for periodic horseshoe orbits, and these guesses are then refined using a numerical shooting method to find precisely periodic orbits. However, this method misses periodic orbits with more than two crossings of the axis connecting the primaries, and is therefore modified to provide guesses for horseshoe orbits with additional crossings. Using this strategy, two thrust augmented horseshoe orbits which rendezvous with the surface of the smaller primary are found, and the speed of the spacecraft at rendezvous is shown to be small. Such orbits offer interesting new opportunities for binary asteroid touch-and-go sampling.
|Date of Award||21 Sep 2018|
- University Of Strathclyde
|Sponsors||EPSRC (Engineering and Physical Sciences Research Council) & University of Strathclyde|
|Supervisor||Malcolm Macdonald (Supervisor) & Colin McInnes (Supervisor)|