▁variants ▁where ▁the ▁land ers ▁and ▁main ▁space craft ▁travel ▁separately , ▁such ▁as ▁the ▁lun ar ▁landing ▁plan ▁proposed ▁for ▁Sh utt le - Der ived ▁He avy ▁L ift ▁La unch ▁Ve h icle ▁and ▁Golden ▁S pi ke , ▁are ▁also ▁considered ▁as ▁L un ar ▁Or bit ▁rende z vous . ▁ ▁Adv antages ▁and ▁dis adv antages ▁ ▁Adv antages ▁ ▁The ▁main ▁advantage ▁of ▁L OR ▁is ▁the ▁space craft ▁payload ▁saving , ▁due ▁to ▁the ▁fact ▁that ▁the ▁prop ell ant ▁necessary ▁to ▁return ▁from ▁lun ar ▁orbit ▁back ▁to ▁Earth ▁need ▁not ▁be ▁carried ▁as ▁dead ▁weight ▁down ▁to ▁the ▁Moon ▁and ▁back ▁into ▁lun ar ▁orbit . ▁This ▁has ▁a ▁multip lic ative ▁effect , ▁because ▁each ▁p ound ▁of ▁" de ad ▁weight " ▁prop ell ant ▁used ▁later ▁has ▁to ▁be ▁prop elled ▁by ▁more ▁prop ell ant ▁sooner , ▁and ▁also ▁because ▁increased ▁prop ell ant ▁requires ▁increased ▁tank age ▁weight . ▁The ▁result ant ▁weight ▁increase ▁would ▁also ▁require ▁more ▁thrust ▁for ▁lun ar ▁landing , ▁which ▁means ▁larger ▁and ▁heav ier ▁engines . ▁ ▁Another ▁advantage ▁is ▁that ▁the ▁lun ar ▁land er ▁can ▁be ▁designed ▁for ▁just ▁that ▁purpose , ▁rather ▁than ▁requiring ▁the ▁main ▁space craft ▁to ▁also ▁be ▁made ▁suitable ▁for ▁a ▁lun ar ▁landing . ▁Finally , ▁the ▁second ▁set ▁of ▁life ▁support ▁systems ▁that ▁the ▁lun ar ▁land er ▁requires ▁can ▁serve ▁as ▁a ▁backup ▁for ▁the ▁systems ▁in ▁the ▁main ▁space craft .