Testing and Development of the NEA Scout Solar Sail Deployer Mechanism  Alex Few*, Tiffany Lockett*, Richard Wilson** and David Boling**  Abstract  The Near Earth Asteroid (NEA) [1] Scout is a deep space CubeSat designed to use an 86-m2 solar sail to  navigate to a near earth asteroid called VG 1991. The solar sail deployment mechanism aboard NEA Scout  has gone through numerous design cycles and ground tests since its conception in 2014. An engineering  development unit (EDU) was constructed in the spring of 2016 and since then the NEA Scout team has  completed numerous ground deployments aiming to mature the deployment system and the ground test  methods used to validate that system. Testing a large, non-rigid gossamer system in 1G environments has  presented its difficulties to numerous solar sailing programs before, but NEA Scout’s size, sail configuration,  and budget has led the team to develop new deployment techniques and uncover new practices while  improving their test methods. The program has planned and completed 5 separate full-scale sail  deployments to date, with a flight sail deployment test scheduled for FY18. The paper entitled “Design and  Development of NEA Scout Solar Sail Deployer Mechanism” [2] was presented at the 43rd Aerospace  Mechanisms Symposia. Since then, the system has matured and completed ascent vent, random vibration,  boom deployment, and sail deployment tests. This paper will discuss the lessons learned and  advancements made while working on solar sail deployment testing and mechanical redesign cycles.  Introduction  In May of 2016, the Near Earth Asteroid (NEA) Scout engineering development unit (EDU) solar sail was  prepared for a suite of environmental tests culminating in a full-scale deployment at NASA Marshall Space  Flight Center’s (MSFC) flat floor facility. The full-scale deployment premiered a fully machined EDU, flightlike motors, and a developing control system. Numerous half scale deployments and mechanical  development efforts were completed in preparation for the full-scale test.   The solar sail development team developed a test suite that would begin with an ascent vent test to simulate  the rapid depressurization during ascent on NASA’s Space Launch System. This test was performed to  indicate the viability of the sail folding pattern and verify that the vent paths were performing nominally. The  folding pattern and vent paths proved to be acceptable and no sail damage was noted due to trapped air.  After ascent vent the team prepared for a random vibration test. This test was intended to vibrate the system  in all 3 axes with intermittent, boom-only deployment tests after each axis of vibration. The team  encountered their first major lesson learned through an undersized stepper motor, which disabled the ability  to perform intermittent tests. The team proceeded with the random vibration test with the undersized stepper  motor. Post-test, an investigation into the undersized motor commenced. Causes identified included limited  design space, improper scaling of half-scale loads to full-scale designs, and poor assumptions regarding  the system’s internal friction. The redesign effort required a major system reconfiguration.  After the redesign activities, boom-only deployments and retractions tests were completed. With the new  configuration and properly sized stepper motor, the boom-only deployments demonstrated the capability  and robustness of the system during nominal operations and risk mitigation activities, such as boom  blooming characterization. The team learned several lessons that will be highlighted later in the paper.  Examples are retraction rates to remove blooming, boom buckling recovery, and deployment shape  dynamics.   *NASA Marshall Space Flight Center, Huntsville, AL ** Jacobs Engineering, Huntsville, AL Proceedings of the 44th Aerospace Mechanisms Symposium, NASA Glenn Research Center, May 16-18, 2018  NASA/CP—2018-219887 323