Design of the Gossamer-1 Deployment Demonstrator

Abstract

Gossamer structures for solar sails, require a technology that allows a controlled and thereby reliable deployment. This is important to stop and restart the deployment in case of failures during deployment and to prevent an entanglement of the sail with other elements based on suitable sail stowing techniques. Before employing such a technology for a dedicated science mission, it is necessary, to demonstrate its reliability with a Technology Readiness Level (TRL) of six or higher. The aim of the work presented is to provide an overview of the mission and of a system for controlled deployment. The development was conducted within the Gossamer-1 project of the German Aerospace Center (DLR). For a system based on coilable booms and coated polyimide foils the design of the deployment mechanisms and electronics required is shown. The design is based on a crossed boom configuration with four triangular sail segments. According to a stepwise development of scalable gossamer systems, the design is implemented for a five by five meter sail. The satellite has an estimated mass of about 30 kg with a compact launch configuration with a maximum width of 790 mm and a height of 500 mm. Design drivers are explained and a mission design in presented. By combining different functional principles respectively mechanisms a simultaneous deployment of the booms and the sail segments is achieved. The main innovation is to deploy the sail segments with deployment units that move away from the central satellite bus. This ensures that only a minimum amount of the sail is deployed that can be spanned between the deploying booms. By this the system is always in a mechanical stable state. The deployment can be performed in a slow and controlled manner and it can even be stopped and resumed if necessary without any risk of entanglement of the sail. An innovative stowing and deployment strategy for a controlled deployment was implemented. It offers a possible solution for the deployment of solar sails and might also be adapted for other deployable structures such as photovoltaic arrays based on flexible thin-film photovoltaics.