Abstract
Spacecraft propulsion is an important aspect of space exploration. Current in-space propulsion technologies are limited by the amount of propellant they can carry. However, to gain higher velocities and enable a new range of missions, Solar Sails can be used as an alternative. Solar Sails use the momentum exchange of impacting and reflecting photons off their sails for propulsion. Their propellantless and low cost nature enables long duration missions, and the constant light pressure gives access to new range of orbits. Most proposed Solar Sail missions rely on the sail propulsion to achieve their primary mission/science objective. Even with the successful deployment of the IKAROS sail, Solar Sails are not at the necessary technology readiness level to be used by science missions. The focus of the research presented in this thesis is to address the two main technological challenges facing the construction of a Solar Sail: sail deployment and attitude control. Most sail attitude control systems use the centre of mass, centre of pressure offset, but rely on the use of the main sail structure. By attaching actuators to the main sail, these systems increase the complications and risks involved in deployment. A novel scalable bus-based attitude control system (ACS) is proposed that makes use of bus-mounted ballast masses and reflective panels and is shown to be more practical. As a result of the decoupled nature of this ACS, the risks and complexities involved in construction of the sail deployment subsystem are reduced. The presented attitude control system, unlike others, is generic and can be used alongside any available sail deployment mechanism or system irrespective to the size of the sail. The second challenge is in-space deployment of an ultra-lightweight membrane structure. A low cost, commercial-off-the-shelf (COTS) based, four quadrant nano-Solar Sail deployment system is proposed, that uses four novel tape-spring booms to hold the sail membrane in place. Four possible membrane-folding patters are investigated and a novel “Creasing Indicator” that quantifies the effects of folding on sail membrane efficiency is proposed. Additionally, testing of a small-scaled engineering model of the deployment mechanism for a 1. 7m x 1. 7m sail is presented. Extensive ground based deployment tests of the mechanism shows the feasibility and practicality of this concept. The fundamental objective of this PhD is to improve the current state of Solar Sail technologies by enhancing the sail deployment and attitude control subsystems. These challenges will be addressed in the context of a proposed nano-Solar Sail demonstration mission, enabled by this research, called Cubesail which is being designed and built at the Surrey Space Centre.