several ca ses the effect of the chan ges in eith er planni ng or u pdated e nvironment s wa s not prop erly  asse ssed fo r its impa ct to already com pleted a nalysis and certification. Thi s resulted i n hardwa re being   operated o utside the d esign baseline. Corrective a ction included processe s to assure that op eration al and  environ menta l baselin es used in desi gn analysi s and certification p rograms were carefully mo nitored, an d  that the cog nizant desi gn group revie wed a ny cha nges to operational plan s or co ndition s. In several   cases providing ad ditional margi n in the  early d esign phase could have p rovide d additio nal fl exibility when  changes were requi red later in the prog ram 

Test   These failu res and anomal ies were attri buted to eithe r test parame ters not bei ng meet o r test procedures  not bei ng foll owed.  In either case th e flight ha rdware was subject ed to exce ssive load s or temperatures  and ha d to b e reworke d or reanalyzed.  In several in stance a compone nt had t o unde r go several repe at  acceptance t ests which was beyond the original  qualification. Other problems resulted from an inability to  perfo rm th e test as originally desi gned and specifie d. Several fail ures resulted f rom te st procedures bei ng  poorly written  and co nfusi ng to test operators.   

The imp act from this type of failure could have b een reduced with  more th oroug h revie ws and verification   of the te sts that flight hardwa re was to be expo sed too. In most certificatio n programs the qualification   environ ment i s develo ped to certify the hard ware for exposu re to a given flight environme nt and either  one o r two a cceptan ce te st cycl es. In several case s a flight unit  for variou s reason s had t o be rewo rked  and then re-acceptan ce te sted. When t he ori ginal n umber of ce rtified accepta nce cycle s was rea ched a  great d eal of  extra analy sis an d somet imes limite d retest was require d to pre vent over st ressing th e  hardware. Th is could h ave been avoide d if the orig inal qualificatio n had in cluded mo re tha n one o r two  accepta nce test e nvironm ent. This sho uld be  considered especially on compl ex system s with a higher  chance of n eeding repeated te sts. O n the ISS pro gram many compone nt lev el acceptan ce test s were   eliminated a nd repla ced with acceptan ce tests at the next higher system level.  In case s like  this a failure  of any pa rt of the system resulted in all com pone nts having to b e exposed to anothe r acceptance test  cycle. Be cause the se type s of acce ptance te st we re so critical, proce dural or operato r errors had a mu ch  more costly impact, and t hus should have had mo re rigo rous reviews a nd verification. Th e institution of  “Won’t Fail Reviews” p rior to new te sts has prove n to be a u seful tool in red ucing the se type s of failures.   A “Wo n’t Fail  Review” p rovides an i ndepend ent thor ough revie w of a pro cedure by indep endent expe rts  who fo cus on risk are as in a pro cedure. 

Special T est Equipme nt (STE)   This category was used to  captu re all fai lures whe re the root cau se was dete rmined to h ave resulte d from  a failure of th e STE, either hard ware or softwa re. Th ese failures resulted in fligh t hard ware n eedin g to be   reworked or retested. Several times lack of  quality control or f ault toleran ce in the STE resulte d in  damag ed flig ht hard ware. Poor de sign of the STE also was a contributo r to sev eral an omalie s. 

A factor in several of these cases was a la ck of detailed de sign review of the STE. Beca use STE  hardware often time s has dire ct effe ct on the  flight hardware it must h ave th e same l evel of de sign and  function al review a s the flight ha rdware . Whe re potential dam age to flight hard ware exi sts fault toleran ce  in the STE is as imp ortant as the fault to leran ce in the flight system . This is also true in the m anufa cturing  of the STE. In one case, p oor q uality co ntrol of the S TE almost re sulted in severe damage to very criti cal  and irrepl aceable flight hardwa re.  

Panel Rete ntion – Failu re of quarter tu rn or othe r captive panel fast eners   This catego ry was u sed to captu re all an omalie s with  the internal a nd external I SS panels. M ost of these  failure s were attribute d to imprope r strength of a fa stene r or improper procedures used in the o riginal  assembly o r use o n orbit. 

Again thi s category at first se ems too  simple fo r discussion, but b ecause of the number of occurre nces  and on-orbit i mpact it warrants fu rther investigatio n. Most of the panels both int ernal and ext ernal to th e  ISS are rem ovable for a ccess to main tainable h ardware or for a ssembly tasks. Difficulty in the origin al  assembly of the panel s before fli ght was not co rrectly identified as  having the potential to also be a  source of failure on -orbit. These types of failures have required a n excessive amount of crew time for  296