Application of Origami in the Starshade Spacecraft Blanket Design

Abstract

A Starshade is a large deployable structure and sole payload of an external occulter. At 34m in diameter or more, starshades are designed to block most of the light from a nearby star so that a small orbiting space telescope can image and characterize the Earth-like exoplanets in orbit around it. The starshade resembles a sunflower with a circular central disk supporting petals that are arrayed around its periphery. The petal edges are precisely shaped to match an optical profile that prevents diffraction. The area circumscribed by the edges must be completely opaque, black, and non-reflective. The petals and ring structure are covered by specially designed deployable blankets that must remain completely opaque even if they become perforated by micrometeorites. The blankets must also not cause any significant on-orbit thermoelastic loads on the lightweight supporting ring and petal structures despite very large differential thermal strains that are developed between these Kapton blankets and the thermally stable composite ring and petal structures. There are two types of blankets: one for the deployable petals and one for the central support disc that is formed by a lightweight deployable ring truss structure. The starshade blankets cover such a large area that they must be unusually lightweight compared to conventional multi-layer insulated (MLI) spacecraft blankets. The blankets must also stow around the central hub of the spacecraft with the deployable ring and petal structures in a highly repeatable fashion. This makes them ideal candidates for origami folding schemes. Based on prior studies of large deployable rigid arrays, we began with variants on the origami flasher to fold the central ring blanket, which is a minimum of 20m in diameter. We looked at the simplest methods for integrating this large blanket with a mechanical ring truss while providing ample optical baffling and little to no thermally induced loads on the structure. Petal blankets were also developed using deployable softgoods with pseudo-mechanical and shingled designs with optically blocking folds for deployment. The design was developed iteratively utilizing a variety of prototypes to explore and demonstrate the interaction between the softgoods and rigid elements.