38 latch feature on all of the spring cartridges allo wing the spring travel to bottom out on an existing  secondary impact spring. This design change utilized existing parts and also removed the complexity and  potential single point failures of the antenna’s latch features. The new spring cartridge design solved the  issue, met surface tolerance requirements, and wa s implemented as the baseline for the remaining  testing and subsequent antenna builds. 

Figure 8: Spring Cartridge With (Left) and Without (Right) Latch    Reflector cracking

The EDU reflector gore material developed cracks. These cracks were caused through the folding of the reflector associated with stowing. The cracks initiate d at the edge of the through holes in the gores and  once initiated ran from one hole to another. All cracking was similar in location and type on all gores of the reflector and worse in areas that were required to package tighter for stowing. This cracking was reproduced with sub-scale material samples and was sh own to be worse once exposed to thermal cycling.   The through holes were put into the gores using a drilli ng process that is standard in the flex circuit and  printed circuit board industry. Testing of samples without holes proved to  largely solve the cracking issue.  Additionally, there was no compelling requirement (air dr ag, easier to fold, lighter) to keep the holes. For  these reasons the holes were removed for the FM antenna. The copper trace width was also reduced in  an effort to improve material compliance and lower t he mass of the gores. This was a low risk change  given the RF data from the EDU testing.  Release Strap Development

A test fixture, shown in Figure 5, was developed early on in the development to address a number of  deployment strap concerns. There were concerns that special attention would need to be taken to control  the band tensioning to avoid destruction of the ribs and/or feed support through twisting or excessive and/or uneven loading. A prototype deployment strap was heavily instrumented with strain gauges  between every rib to examine the band tension unifo rmity and how easily the band slid on the Ultem band  guides. A process was developed to step the band tension up gradually and work the loading around the ribs by lifting the band off the Ultem blocks for a unifo rm distribution. A flight band tensioning procedure  was developed with expected torque values and correla ting band tensions. This early testing enabled  removal of the strain gauges for the flight unit eliminating multiple snag hazards. The strain gauges were also initially required to verify and correlate the structural analysis of band behavior and performance of  the stowed antenna during launch. Testing showed t hat uniform rib gapping force was the critical  parameter affected by band tension. This uniform rib gapping force could be maintained by controlling the band tension to ±13 N (3 lbf). Instead of using the strain gauges, a handheld force gauge was used to apply the theoretical gapping force. If the rib di d not gap under that load, the band was sufficiently  tensioned.  Upon actuation, energy stored in the Frangibolt fast ener and strap tension is released into the bands.  Initial prototype testing revealed there was sufficient energy for the two band end fittings to contact on the  opposite side of the structure and possibly tangle, th us possibly preventing a full deployment. If the bands  Latch Pins  NASA/CP-2010-216272