1. Deployment was successful in all attempts for all variants for all feasible scenarios and the choice  between full, partial and no retraction does not influence the reliability of deployments. 2. Retraction spring energy imparts notable energy into the panel deployment – the effect on hinge  bracket energy dissipation shall need further work. 3. The time for full retraction with the hard retraction spring is 6 ms corresponding to 0.3° panel  deployment. This provides margin on the spigot-cone collision which occurs at 1° deployment. 4. The light retraction spring still provides fast enough retraction time (12 ms to full); however under  1g conditions, the spring was so light that the spigot would droop under its own weight once  released, and this meant that it could be heard to make contact with the cone during deployment. 5. Spigot-cone collision does not prevent deployment provided the spigot has >2° free rotation.  This test campaign has demonstrated that all variants (partial-, full- and non-retraction HDRMs) are  suitable to ensure reliable deployment of both the DMC-UK2 and DMC-CFESAT solar arrays.  Design Finalization and Qualification Plan In true SSTL-style, the early breadboard engineering test campaigns gave opportunity to make  observations and tailor the design to final design quickly, with final flight design drawings being released 5 months after HDRM evolution kick-off. It was agreed that  the full-retraction variant was most attractive  from a mechanism-reliability perspective; this could also be done without the need for the undesirable  rigid retraction cap. Instead, the natural shoulder available on the separation nut spigot could be used to constrain the spigot in the cone to prevent full withdrawal. In this  way, the HDRM retained the low-profile  stowed volume of the non-retracting variant. An O-ring on the underside of the cone is used to dampen the impact of the spigot shoulder, to permit the  spigot to be reused to refurbishment after hard-deployments. In addition, the arrangement of the spigot,  stud and retraction spring mean that if the retraction spring were to fail, the assembly allows the spigot to retain degrees of freedom, which have been shown to provide successful deployment – giving additional  confidence to the design. The final design is shown in Figure 14 and Figure 15.  Figure 14. Sep-Nut-HDRM:  Left – CAD, Right – pa rtially-built hardware (cup assembly and cone) In order to remove and replace the separation nut on the spacecraft for hard deployments during AIT, the  actuator must be inserted from the ‘front’ of the cup only. In this configuration, the stress analysis of the  design showed that the fasteners initially used to hold the actuator body to the cup was overstressed in tension, and enough larger fasteners to cope with the stressing could not be accommodated. Therefore a  novel solution was incorporated to offload the fasteners by using a bayonet interface between the  actuator carrier and the cup as shown in Figure 16. In this way, 2 small fasteners are merely used to stop  the actuator falling out upon assembly – they do not experience any load, which instead is transferred directly through the cup body. 433