SSAS Verific ation  The verificati on of the S SAS was accompli shed using tolerance analysi s, FEM analy sis, com ponent  testing, syst em level de velopment te sting, ha rdware fit che cks and finally  missi on uni que dynami c  simulatio n analysis. Due to  the size of e ach truss element (roug hly 4.6 m (15 ft) in length and weig h 13.6   metric ton s (3000 0 lb)) and the fa ct the y have differ ent structu ral and mass propertie s is combined  with  the fact the mating task is accom plished in a near zero gravity environ ment with one of the two truss  element s being hel d by th e SSRMS, p erformi ng a true represent ative system  level test was deem ed not  practical. T he co st effe ctive app roach was to p erform in dividu al co mponent testing to validate the   capability for the extreme  misalig nmen t conditio ns, perfo rm limit ed sy stem le vel developm ent testing,   perform hardware fit check s to verify  installation  and finally pe rform dynam ic analysi s for ea ch of the fo ur  berthin g eve nts. Dynami c simulation s, which include test proven conta ct dyna mics ch aracteristics of  the  berthin g inte rface components, were  used to ve rify system functio nality, and p rior to  the system   developm ent test, used to determi ne the  worst-ca se initial c onditions  for the tes t.   

Captu re Lat ch Assem bly  The Captu re Latch  testin g esta blished the rea ch and preloading capability du ring an d afte r exposure  to  the pre dicted environm ents. The a ssembly su ccessfully unde rwent Ra ndom Vibration te sting and was  function ed in  a thermal v acuum cham ber at the ho t and cold extremes. Th e latch testin g verified the   capability to capture a nd pull in the capt ure ba r when anywh ere within the ca pture envelop e.   

Bolting System   The Bolting system testin g wa s perfo rmed in two phases. The  first phase establi shed the rea ch and  preloading capability during and afte r exposure to the predi cted environm ents. The assembl y successfull y  unde rwent Random Vib ration testing a nd wa s fun ctioned in a th ermal va cuum cham ber at the hot and   cold extrem es. The bolt system te sting  verified th e capability to engag e the  nut and preload  when at the  worst-ca se m isalignment condition s. Th e second phase established the capa bility to drive tog ether a cup   and cone that  are misalign ed and mo unted to stru ctures of  stiffness equivalent to  the truss ele ments.   

Simulation  FEM and  multiple dynami c model s were develop ed and validate d using dat a from the S 0, S1 (symmetri c  with P1) and P3 (symmet ric with  S3) truss stati c loads  testing, the SSAS component testing, and the  SSAS “system level” development testing. These validat ed models were refined to include the specific   parameters and mating c onditions for each of the four SSAS inte rfaces to be berthed on-orbit. The  simulatio ns were al so used to verify berthing corrido r, RTL pe rform ance and SS RMS intera ctions.   

System  Developm ent Test   The key driv er for the need of a devel opment test was due to S SAS being an over-constra ined system.  Three of the  four nut a ssemblies are h oused inside an item d efined as a “Flexu re Assembly”. The flexu re  is a flexible structu re that allows complia nce i n only o ne late ral di rection. In the  axial dire ction the flexure  has an equivalent stiffne ss to the   truss st ructu re. The thre e flexure   assembli es are p ositioned in the   passive truss eleme nt such that the   direction of complian ce all point to   the fixed cup (Figu re 8).    Direction of   ComplianceDirection of  Complian ceDirection of   Compliance Fixed Cup Direction of   ComplianceDirection of  Complian ceDirection of   Compliance Fixed Cup Figure 8. Flexure Compliance Illustration   The captu re latch i s require d to   gene rate p reload sufficient  to align  the cone  (bolt side ) with t he cup in  the flexure a ssembly. Th e issu e of  most concern wa s the on-orbit  structural-the rmal defo rmations of   the truss, whi ch create the  need for  the flexure t o move in t he lateral  plane  perpendicular to the compli ant  direction. Th ese structu ral-the rmal  308