▁a ▁single ▁launch ▁vehicle ), ▁the ▁ro cket ▁required ▁would ▁have ▁to ▁be ▁extremely ▁large , ▁in ▁the ▁Nova ▁class . ▁The ▁alternative ▁to ▁this ▁would ▁have ▁been ▁Earth ▁orbit ▁rende z vous , ▁in ▁which ▁two ▁or ▁more ▁rock ets ▁in ▁the ▁Sat urn ▁class ▁would ▁launch ▁parts ▁of ▁the ▁complete ▁space craft , ▁which ▁would ▁rende z vous ▁in ▁Earth ▁orbit ▁before ▁depart ing ▁for ▁the ▁Moon . ▁This ▁would ▁possibly ▁include ▁a ▁separately ▁launched ▁Earth ▁departure ▁stage , ▁or ▁require ▁on - or bit ▁ref uel ing ▁of ▁the ▁empty ▁departure ▁stage . ▁ ▁Tom ▁Dol an ▁proposed ▁the ▁alternative ▁of ▁lun ar ▁orbit ▁rende z vous , ▁which ▁had ▁been ▁studied ▁and ▁promoted ▁by ▁Jim ▁Chamber lin ▁and ▁O wen ▁May n ard ▁at ▁the ▁Space ▁Task ▁Group ▁in ▁ 1 9 6 0 ▁early ▁Apol lo ▁feas ibility ▁studies . ▁This ▁mode ▁allowed ▁a ▁single ▁Sat urn ▁V ▁to ▁launch ▁the ▁C SM ▁to ▁the ▁Moon ▁with ▁a ▁smaller ▁L un ar ▁Ex c urs ion ▁Module ▁( LE M ). ▁When ▁the ▁combined ▁space craft ▁reaches ▁lun ar ▁orbit , ▁one ▁of ▁the ▁three ▁astr onaut s ▁remains ▁with ▁the ▁C SM , ▁while ▁the ▁other ▁two ▁enter ▁the ▁LE M , ▁und ock ▁and ▁descend ▁to ▁the ▁surface ▁of ▁the ▁Moon . ▁They ▁then ▁use ▁the ▁as cent ▁stage ▁of ▁the ▁LE M ▁to ▁re join ▁the ▁C SM ▁in ▁lun ar ▁orbit , ▁then ▁disc ard ▁the ▁LE M ▁and ▁use ▁the ▁C SM ▁for