The Cord Mat Sail - Concept, Mechanics, and Design Example

Abstract

A joint effort by industry and government (L’Garde, Inc., NASA Jet Propulsion Laboratory, Ball Aerospace, and NASA Langley Research Center) is currently under way to mature to Technical Readiness Level 6 a 10,000 m 2 class “scalable” solar sail for the Solar Sentinel and similar missions in the solar system. One key innovation feature in this sail is the accommodation of very low film tension by surface support with arrays of cords (the “cord mat”) in each quadrant. Besides enabling operation with negligible film tension, the cord mat also defines load paths to well approximate the stripped architecture (a hypothetical upper limit on weight efficiency for diagonally supported square sails), thereby reducing structural loads in more than one way. Another innovative solution is the used of a spreader system on only one side of the compressive columns — a solution to increase weight efficiency at the cost of accommodating light pressure from one side of the sail only, still permitting operation for the Solar Sentinel mission. This architecture, and some of its further details, was initially developed, studied, and proposed in 2001 and 2002 by the first author for the L’Garde‐Encounter solar sail mission by Team Encounter, and was subsequently refined in 2003. The surface fold pattern to match the architecture, as well as sophisticated analytical and design relations and tools for preliminary design, were also developed. This pioneering work, previously documented in technical reports only, is summarized in the present paper. A high level review of the design concept, its history and key mechanical features, is presented. Structural mechanics is discussed in detail, with key design and analytic relations derived. A point design to quantitatively illustrate the design is also presented. Nomenclature