▁Sat urn ▁IB ▁miss ions ▁ ▁The ▁payload ▁cap ability ▁of ▁the ▁Sat urn ▁IB ▁launch ▁vehicle ▁used ▁to ▁launch ▁the ▁Low ▁Earth ▁Or bit ▁miss ions ▁( A pol lo ▁ 1 ▁( pl anned ), ▁Apol lo ▁ 7 , ▁Sk yl ab ▁ 2 , ▁Sk yl ab ▁ 3 , ▁Sk yl ab ▁ 4 , ▁and ▁Apol lo - So y uz ) ▁could ▁not ▁handle ▁the ▁ ▁mass ▁of ▁the ▁fully ▁fue led ▁C SM . ▁This ▁was ▁not ▁a ▁problem , ▁because ▁the ▁space craft ▁delta - v ▁requirement ▁of ▁these ▁miss ions ▁was ▁much ▁smaller ▁than ▁that ▁of ▁the ▁lun ar ▁mission ; ▁therefore ▁they ▁could ▁be ▁launched ▁with ▁less ▁than ▁half ▁of ▁the ▁full ▁S PS ▁prop ell ant ▁load , ▁by ▁filling ▁only ▁the ▁S PS ▁sum p ▁t anks ▁and ▁leaving ▁the ▁storage ▁t anks ▁empty . ▁The ▁C SM s ▁launched ▁in ▁orbit ▁on ▁Sat urn ▁IB ▁r anged ▁from ▁ ▁( A pol lo - So y uz ), ▁to ▁ ▁( Sk yl ab ▁ 4 ). ▁ ▁The ▁om n id irection al ▁anten nas ▁su ffic ed ▁for ▁ground ▁communic ations ▁during ▁the ▁Earth ▁orb ital ▁miss ions , ▁so ▁the ▁high - g ain ▁S - band ▁anten na ▁on ▁the ▁SM ▁was ▁omitted ▁from ▁Apol lo ▁ 1 , ▁Apol lo ▁ 7 , ▁and ▁the ▁three ▁Sk yl ab ▁fl ights . ▁It ▁was ▁restored ▁for ▁the ▁Apol lo - So y uz ▁mission