Validation of a Scalable Solar Sailcraft System

A T THE start of 2003, ABLE Engineering (now part of ATK Space Systems and Sensors), in parallel with other activities [1] also under the purview of the In-Space Propulsion (ISP) projects office at NASA Marshall Space Flight Center (MSFC), began developing scalable analytical tools and advanced design technologies for a solar sail system, which led to two follow-on phases for system ground demonstrator (SGD) development and validation. These efforts, led by ATK, were performed with the assistance of the Systems Technology Group of SRS Technologies (the sail assembly provider), the NASA Langley Research Center (LARC) for sail shape and dynamics modeling and test execution, Arizona State University (ASU) for attitude-control modeling, Princeton Satellite Systems (PSS) for sailcraft control software, and the NASA Marshall Space Flight Center (MSFC) space environmental effects (SEE) laboratory (materials characterization and life evaluation). In the first phase of the program (six months), activities were focused on design and analysis refinement of the initial sail system concept [2] and refinement of plans for hardware development and demonstration [3] in phases 2 and 3. The phase 2 effort encompassed design, fabrication, and validation through a series of component and system tests of a quadrant (one sail and two masts) of a 10-m system. Validation activities culminated with the demonstration of deployment, sail shape, and system dynamics measurement [4] in a vacuum at the LARC in April of 2004 [5]. Analytical correlation activities demonstrated that gossamer mast, sail subassemblies, and system behavior are predictable [6]. In phase 3, a larger and more complete sail system was designed, fabricated, and demonstrated [7], first in ambient conditions at ATK in Goleta, CA (ATK-Goleta) and later at a large vacuum-chamber facility in April and May of 2005. The 20-m sailcraft hardware represents a flightworthy full (four sails, four masts) system that includes a boom for offsetting instruments well away from the plane of the sail, a dual-purposed mechanism for deployment and attitude control, tie-down and release hardware, solar panels, and launch vehicle interfaces, which were integrated in a carbon-composite central assembly that also functions as a bus chassis. Further descriptions of the hardware are provided herein, along with a review of some of the critical design developments important to the evolution and success of the SGD efforts. Lessons learned in the development of subsystem hardware on a quadrant of a 10-m sail system, referred to herein as the 10-m quadrant, were integrated into design and analysis activities supporting the fabrication and testing of the full sail system. The evolution and integration of additional subsystems included in the 20-m sailcraft are described. Results of 20-m sailcraft system validation activities are emphasized, followed by sail-material life-testing results, discussion of scaled performance, and concluding remarks.