Thesis

Modeling the shape control of a solar sail

Space traveling is still in its infancy. The idea that one can traveling throughout space is intriguing. The idea of a solar sail to travel or "sail" through space using just sunlight as a propulsion system is still a fairly new field. This thesis is a theoretical modeling of the shape control of a square shape solar sail. The angle at which the sunlight hits the solar sail helps navigate the solar sail through space. The various solar sail designs today has a control system in place that tilts the solar sail and helps change the angle at which the sunlight hits the solar sail. If we can control the shape of a solar sail, it can somehow be used to help navigate the solar sail through space. To control the shape of the solar sail, we propose the idea of bonding piezoelectric actuators onto the booms of a solar sail. The booms are what makes the solar sail rigid and gives it its structure. When a voltage is applied across piezoelectric material, it makes a tiny change in shape. This voltage can be supplied by the solar cells that are on the solar sail. This will help bend the booms and in the process help change the shape of the whole sail. Finite elements of beams and a membrane are used to achieve what shapes we will obtain when a certain amount of voltage is supplied to the piezoelectric actuators. Using the principle of virtual work and obtaining generalized forces that is produced by the piezoelectric, we can solve for the displacements across our system. For simplicity, we will only theoretically model the booms and the sail. We will concentrate on the steady state system to see what shape is obtained. We use our program to show displacements of a 20 m solar sail when voltage is applied to the PVDF piezoelectric actuators. With 1000V applied to the actuators, a tip displacement of 5 cm is achieved. Parameters chosen for our example are from work that has been done with boom design and PVDF actuators for controlling space antennas. Results show that the actuators can help displace the solar sail.

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