9 7 4 , ▁three ▁C SM s ▁fer ried ▁astr onaut s ▁to ▁the ▁orb ital ▁Sk yl ab ▁space ▁station . ▁Finally ▁in ▁ 1 9 7 5 , ▁the ▁last ▁flow n ▁C SM ▁dock ed ▁with ▁the ▁Soviet ▁craft ▁So y uz ▁ 1 9 ▁as ▁part ▁of ▁the ▁international ▁Apol lo – So y uz ▁Test ▁Project . ▁ ▁Before ▁Apol lo ▁ ▁Con cept s ▁of ▁an ▁advanced ▁man ned ▁space craft ▁started ▁before ▁the ▁Moon ▁landing ▁goal ▁was ▁announced . ▁The ▁three ▁person ▁vehicle ▁was ▁to ▁be ▁mainly ▁for ▁orb ital ▁use ▁around ▁earth . ▁It ▁would ▁include ▁a ▁large ▁press ur ized ▁auxili ary ▁orb ital ▁module ▁where ▁the ▁crew ▁would ▁live ▁and ▁work ▁in ▁for ▁weeks ▁at ▁a ▁time . ▁They ▁would ▁perform ▁space ▁station ▁type ▁activities ▁in ▁the ▁module ▁while ▁later ▁versions ▁would ▁use ▁the ▁module ▁to ▁carry ▁cargo ▁to ▁space ▁stations . ▁The ▁space craft ▁was ▁to ▁service ▁the ▁Project ▁Olymp us ▁( L OR L ), ▁a ▁single ▁launched ▁fol d able ▁rot ating ▁space ▁station ▁launched ▁on ▁a ▁single ▁Sat urn ▁V . ▁Later ▁versions ▁would ▁be ▁used ▁on ▁circum l un ar ▁fl ights ▁and ▁would ▁be ▁the ▁basis ▁for ▁a ▁direct ▁as cent ▁lun ar ▁space craft ▁as ▁well ▁as ▁use ▁on ▁inter plan et ary ▁miss ions . ▁In ▁late ▁ 1 9 6 0 , ▁NASA ▁called ▁on ▁U . S . ▁industry ▁to ▁propose ▁designs ▁for ▁the ▁vehicle . ▁On ▁May ▁ 2 5 th