158 Design Ideology and Testing  

Early Design  Thus far, t he AMT is  the latest  system  added to the NEA  Scout project . The surrounding systems, the solar  sail boom deployer , and avionics box  (reference Figure 2), had nearly one year’s progress made at the  onset of AMT design activities . Therefore,  the interfaces for the AMT had some definition and rigidity . AMT  had to accommodate the existing designs and make minimal impacts to these two neighboring systems  and meet all previous ly-outlined requirements . Both the avionics box and boom deployer lev ied  requirements for the wire bundle connector  locations as well as  the mechanical fastening points. In turn,  the AMT lev ied requirements onto these systems regarding the locking mechanis m location and fastening.  After the interfaces were understood, the mechanical design work commenced . 

The NEA  Scout design team performed a detailed trade of 20+ concepts of varying TRLs for controlling the  CP/CM offset . The concepts included rotation tab les, gimbals, and sail  tensioning systems, and varying  reflectance materials. Each concept was scored according to the estimated ability to meet the AMT design constraints, and the trade concluded that a translation table combined simplicity, heritage, and capability .  It quickly became clear that  a COTS  translation table could not meet the requirements for the AMT. Although  many designs exist that can produce high- precision motion in low -profile assemblies (such as those for  microscopes and other laboratory optical equipment), few designs could accommodate such a large translation envelope and none could deliver a wire feedthrough capability . Furthermore no space- qualified  systems were found that could deliver translation capabilities within the same orders of magnitude as AMT and fit into the given volume. The AMT required an in- house design.     Early design concepts took conventional translation table designs and “inverted” them by moving the motors and transition components  from a central location to the periphery of the system. Figure 3 illustrates the  “inversion” . Although this concept is not novel, the low mass requirement and translation ability made the  concept unique. This modification freed a large internal volume that could be used to house a service loop  for the feedthrough bundle, locking mechanisms, and sensing equipment . The design also allow ed a small  vertical profile , and made the AMT design much more appealing to NEA  Scout . The trade, however,  complicated the interfaces and required the stepper motors to reside one atop the other . The motors’  location and the height requi rement only allowed motors of 8- millimeter diameter or less to drive the  translation of the AMT . The small motor size constraint required considerable investigation and testing for  torque output, margins, and load capacity .  

              Common XY Translation Table Design                                                      “Inverted”  Variation                     (VELMEX, Inc. UniSlide XY Table)                                                           (NEA Scout AMT )       Figure 3.  Comparison of translation table designs