▁in ▁theory ▁and ▁in ▁proof - of - con cept ▁pro tot ypes , ▁although ▁many ▁exper ts ▁consider ▁it ▁techn ically ▁feas ible . ▁ ▁It ▁has ▁been ▁reported ▁that ▁the ▁British ▁Army ▁has ▁tested ▁an ▁invisible ▁tank . ▁ ▁Pl asma ▁ste alth ▁ ▁Pl asma ▁at ▁certain ▁density ▁ranges ▁absor bs ▁certain ▁band width s ▁of ▁broad band ▁waves , ▁potentially ▁rendering ▁an ▁object ▁invisible . ▁However , ▁generating ▁pl asma ▁in ▁air ▁is ▁too ▁expensive ▁and ▁a ▁feas ible ▁alternative ▁is ▁generating ▁pl asma ▁between ▁thin ▁memb ran es ▁instead . ▁The ▁Def ense ▁Techn ical ▁Information ▁Center ▁is ▁also ▁following ▁up ▁research ▁on ▁pl asma ▁reducing ▁R CS ▁techn ologies . ▁ ▁A ▁pl asma ▁clo aking ▁device ▁was ▁pat ented ▁in ▁ 1 9 9 1 . ▁ ▁Met as creen ▁A ▁prototype ▁Met as creen ▁is ▁a ▁claimed ▁clo aking ▁device , ▁which ▁is ▁just ▁few ▁mic rom eters ▁thick ▁and ▁to ▁a ▁limited ▁extent ▁can ▁hide ▁ 3 D ▁objects ▁from ▁mic row aves ▁in ▁their ▁natural ▁environment , ▁in ▁their ▁natural ▁positions , ▁in ▁all ▁directions , ▁and ▁from ▁all ▁of ▁the ▁observer ' s ▁positions . ▁It ▁was ▁prepared ▁at ▁the ▁University ▁of ▁Texas , ▁Austin ▁by ▁Professor ▁Andrea ▁Al ù . ▁ ▁The ▁met as creen ▁consisted ▁of ▁a ▁ 6 6 ▁mic rom et re ▁thick ▁poly car bon ate ▁film ▁supporting ▁an ▁arrangement ▁of ▁ 2 0 ▁mic rom eter ▁thick ▁co pper ▁stri ps ▁that ▁res emble d ▁a