▁This ▁enables ▁Z PM s ▁to ▁offer ▁a ▁new ▁way ▁to ▁perform ▁space craft ▁rot ations . ▁Un like ▁eigen axis ▁smallest ▁angle ▁rot ations , ▁Z PM s ▁are ▁larger ▁angle ▁but ▁minimum ▁fuel ▁rot ations . ▁Un like ▁eigen axis ▁fixed ▁axis ▁and ▁man eu ver ▁rate ▁rot ations , ▁Z PM ▁rot ations ▁vary ▁the ▁rotation ▁axis ▁and ▁man eu ver ▁rate ▁during ▁the ▁man eu ver . ▁Just ▁like ▁eigen axis ▁rot ations , ▁Z PM ▁rot ations ▁can ▁be ▁generated ▁by ▁command ing ▁the ▁space craft ▁with ▁a ▁time ▁varying ▁attitude ▁and ▁rate ▁command . ▁However , ▁Z PM ▁rot ations ▁require ▁significantly ▁more ▁time ▁than ▁eigen axis ▁rot ations . ▁ ▁Z PM ▁traject ories ▁can ▁also ▁be ▁used ▁to ▁reduce ▁prop ell ant ▁consumption ▁even ▁when ▁the ▁space craft ▁uses ▁thrust ers ▁instead ▁of ▁momentum ▁storage ▁devices . ▁This ▁application ▁is ▁referred ▁to ▁as ▁a ▁Red u ced ▁Prop ell ant ▁M ane u ver ▁( R PM ) ▁since ▁even ▁though ▁prop ell ant ▁use ▁is ▁minim ized ▁some ▁prop ell ant ▁will ▁have ▁to ▁be ▁used . ▁ ▁Theory ▁A ▁Z PM ▁is ▁a ▁non - e igen axis ▁attitude ▁traject ory ▁that ▁explo its ▁the ▁space craft ▁environmental ▁dynamics ▁( e . g . ▁gravity ▁gradient , ▁solar ▁pressure , ▁aer od ynam ics ▁etc .) ▁to ▁eliminate ▁the ▁need ▁for ▁mass ▁exp ulsion ▁actu ators ▁during ▁rot ational ▁operations . ▁ ▁Z PM s ▁are ▁developed ▁by ▁solving ▁a ▁specific ▁non linear