that its functional motion did not inhibit the rod end from exiting the SSRD. Using the baseline designs of  the Retraction System, SSRD, Booster Adapter Assembly, and Spacecraft Bus Structure an in depth  analysis was done to determine if redundancy would be achieved at the system level. This analysis took  into account tolerances on all components as well as utilizing conservative constraints within the system.  The results of this analysis showed the baseline design would not work unless slight modifications were  made to the SSRD, Retraction System, and Booster Adapter Assembly. All modifications were  incorporated into their respective designs and redundancy testing with the Retraction System was  successfully performed during SSRD component-level qualification testing.  Test Challenges  In addition to design challenges there were several test challenges as well. These included minimizing  the shock output from the retraction system as well as characterizing the shock output from the SSRD.  During spacecraft separation, there are two distinct shock sources from the actuation of an SSRD. These  are the shock output from the SSRD unit and the shock output from the Retraction System. The shock in  an SSRD is caused by several components within the unit. These are the restraining wire unwinding, a  spool halve hitting the inside of the housing, the rod end hitting the base washer as it exits, or a  combination of these. The shock from the Retraction System is caused by the preload bolt hitting the top  of the bolt catcher can. These two shock sources dictated a course of action: minimize the shock output  from the Retraction System and characterize the shock output from the SSRD.  As described earlier, the Retraction System consists of a retraction spring that pulls the preload bolt and  spherical rod end out of the SSRD. The spring force is sized to ensure retraction of the Preload Bolt and  Spherical Rod End; however, this force also causes a sizeable impact of the Preload Bolt into the Bolt  Catcher Can Cover. In order to minimize the impact and associated shock output, a shock absorbing  material was incorporated into the Bolt Catcher Can design. A development test effort was undertaken to  determine the type of material to be used as well as optimize the design. Initially, two candidate shock  absorbing materials were considered: Poron and Aluminum Honeycomb. Preliminary test results showed  the Poron to be a poor shock absorbing material; however, favorable results were shown for the  aluminum honeycomb. The test setup consisted of a Bolt Catcher Can, Spring Retainer, Retraction  Spring and a rod and nut of roughly the same mass as the flight designed hardware. The aluminum  honeycomb test specimen was cut to the same inner diameter as the Bolt Catcher Can and placed inside  the cover at the end of the can. The test specimen was a 2.5-cm nominal piece of aluminum honeycomb  pre-crushed to a thickness of 2.22 cm. Tri-axial accelerometers were mounted at the base in two  locations 90" apart and on top of the Bolt Catcher Can. Figure 5 shows the test setup.  I.  Figure 5. Internal and External View of the Aluminum Honeycomb Shock Test  153