isolating those electrical paths from each other. A non-electrical conducting coating needed to be applied  because this was a metallic blade hinge. Eventually, the requirement to have solar cells on both sides of  the SA was deemed unnecessary and removed. This allowed the design to evolve into the final concept  with reduced complexity.  Hinge: Development Issues and Solutions  From this initial concept, the hinge design still had several design, interface, and assembly issues to  overcome. The design evolved to reduce the effects and risk of friction-causing issues. One was changing  the large hinge knuckle in favor of two smaller knuckles at the corners in order to limit the contact area of  the knuckle on the pin. The other change was to add a bushing made out of a polyimide plastic with  impregnated graphite between the hinge knuckle and pin interface. This provides a low-friction interface on  the rotating parts’ surfaces without the need for grease or liquid lubricants.  Transmitting the electrical power through the SMAs and isolating them from each other required many  design solutions. The SMA needed to be isolated over the steel hinge pin, chassis, and through the radiator.  Isolating the hinge pin from the SMAs was solved by adding a polyimide tape layer covered by a heat shrink  sleeve. The SMA was isolated from the radiator using G10 composite bushings, which isolated the terminal  bolts from the metal radiator. These isolation solutions work in the stowed configuration. However, when  deployed, the SMA bends and folds into a different shape that can contact the radiator and chassis in other  areas, causing an electrical short. This was solved by adding the polyimide tape to the radiator and chassis  in areas where the SMAs may make contact.   Designing the SMA to provide enough torque to open the array and transmit the electrical power required  many considerations. The final shape of the SMA was driven by the required torque and the available room  for installation onto the SA. The torque drove the width of the SMAs, however, that width was wider than  the available footprint to install the SMAs to the PCB and keep them isolated. This was solved by  maximizing the width of the SMA where it attaches to the radiator and over the hinge pin where the torque  is generated. Then, the SMA’s width narrows down at the installation location on the PCB. Some issues  arose during mechanical tests. The SMAs were soldered to the PCB copper substrate and the torque  generated by the SMA to open the array was enough to delaminate the copper layer from the rest of the  PCB. This issue was solved by adding a rivet close to the edge of the PCB. However, installing the rivet  caused the SMA and PCB to crack. This issue was solved by adding a washer to both sides of the rivet to  spread out the load when driven. Lastly, the design decision on how to install the SMA to meet the SMAs’  torque requirement was made. The initial SMA location was inboard under the hinge pins. This did not work  because it prevented the array from fully deploying. The final configuration chosen was to install the SMAs  outboard of the pin.  The hinge latch is provided as a backup to keep the SAs in the deployed configuration if the SMAs fail. The  latch evolved from several different concepts, but was kept as a simple hook and detent latch. Overall, the  latch worked well, although there were some special considerations performed during assembly for proper  functionality. Initially, the latch had some issues staying latched. The hook would jump out of the detent  when the array hit the hard stops and then rebound. Several mitigation methods were used to prevent this.  Proper installation of the hook is key to ensure that it is preloaded with enough force. This is done by  installing the hook in the deployed configuration. The latch design is a steel on aluminum surface. The  loading is light enough that a thin film of a MoS 2 lubricant applied to the contacting rotating surfaces is  enough to mitigate the friction concerns. However, the lubricant has to be limited to a thin film and cannot  go onto the latching surfaces in the detent or the mating surface on the hook. If it does, the hook can slip  out of the detent.  Analysis of Mechanisms  The analysis of these mechanisms was divided into three main areas: structural strength, mechanism  tolerances (critical primarily to the thermal environments), and dynamic and kinematic analysis. The  structural strength of the parts was primarily driven by the random vibration environment during ascent.  NASA/CP—2018-219887 383