The boom lengths were used as improper metrics when relating the prototype and EDU. If the booms are  examined as a spring, the deployed lengths relate to the square of the stored energy in the spool. Therefore,  the coiled EDU booms, being about 1.8 times longer than the prototype booms contained about 3.24 times  more energy. The plastic-to-plastic friction was an estimated 2x less than the EDU’s aluminum-to-aluminum  friction forces. To exacerbate this condition, the plastic would also deform more easily than the aluminum  EDU. Therefore, the differing friction and stiffness properties discredited any linear correlation between the  prototype and EDU based upon boom lengths. This correlation error played a significant role in leading to  the 5 causes described above.  When the motor was sized, the designer assumed a linear relationship between the prototype and the EDU  torque requirements. The controller board for the prototype was also used to baseline the EDU controller  board, hiding some of the control input errors. The plastic material would also hide mechanical interference  as it deformed in the presence of significant load. The friction between plastic parts was more advantageous  than aluminum. Lastly, the boom spool irregularities were hidden because the booms were shorter and less  likely to spool improperly.   Summary  All in all, the design team was inexperienced with prototyping mechanical systems with plastics and allowed  a prototype to hinder a much-needed critique. The designers should have taken the time to create either a  complete system dynamics analysis or a few simple subcomponent models to determine more realistic  friction estimates. Do not base any dynamic or loads-related mechanical performance on a printed  prototype. Volumetric data, part fit up, and interface development can and should benefit from a 3D printed  model, but “form” similarities do not indicate “function” similarities.  Sail Deployment Development and Testing  As a risk mitigation strategy, the team planned several deployment tests during the project’s design and  development phases. The goal of ground deployment tests was to demonstrate the functionality of the  deployment system. The ground tests did have two inherent flaws that were difficult to overcome – gravity  and friction. Demonstrating the SSD’s functionality in a 1G environment was taken into consideration while  developing the test plan. The team started with half-scale, 3D prototype units and transitioned to a flightlike unit for full-scale testing. The team planned to perform two full-scale engineering development unit tests  and two flight-scale tests. By the conclusion of the engineering development unit test phase, the team had  completed five full-scale development tests. The development tests did not focus on simulating the space  environment conditions during deployment and all deployment tests were conducted in an ambient  environment. The team communicated to the project management the potential for false positives and  negatives produced during the tests due to the 1G environment.   The first set of deployment tests were completed with the half-scale prototype using 4-meter booms and a  40-m2 Mylar sail. The smaller sail took less time to refold and spool, allowing for quicker turnaround between tests and kept the focus of the tests on troubleshooting the deployer system. The deployment tests were conducted in the Flight Robotics Laboratory at Marshall Space Flight Center. The test location was a major factor in the success of demonstrating the systems capabilities. Due to resource constraints, the team was unable to design and build a support structure to offset the effects of gravity. Therefore, the approach to the deployment test was simple – deploy the system on a large, flat, clean, and low friction surface with minimal human intervention and ground support equipment. The facility chosen, also known as the “Flat Floor”, allowed air bearings to float across the surface of the  epoxy floor with negligible friction. Without friction loads, the air bearings were intended to simulate two  lateral degrees of freedom in the floor’s plane and a rotational degree of freedom normal to the floor. The  team attached the deployer body and each boom tip to an air bearing and a compressed air supply  (Figure 9). The “frictionless system” was supposed to help study the SSD’s natural deployment motion,  angular rates and angular accelerations. This information would have been beneficial for the guidance and  control team’s deployment modes and models, but the forces created by the air supply hoses dominated  NASA/CP—2018-219887 330