▁for ▁the ▁boost - g lide ▁concept ▁was ▁first ▁noticed ▁by ▁German ▁art illery ▁officers , ▁who ▁found ▁that ▁their ▁Pe en em ünd er ▁P fe il gesch os se ▁arrow ▁shell s ▁tra ve led ▁much ▁further ▁when ▁fired ▁from ▁higher ▁alt itudes . ▁This ▁was ▁not ▁entirely ▁unexpected ▁due ▁to ▁geometry ▁and ▁th inner ▁air , ▁but ▁when ▁these ▁factors ▁were ▁account ed ▁for , ▁they ▁still ▁could ▁not ▁explain ▁the ▁much ▁greater ▁ranges ▁being ▁seen . ▁Investig ations ▁at ▁Pe en em ünd e ▁led ▁them ▁to ▁discover ▁that ▁the ▁longer ▁traject ories ▁in ▁the ▁th inner ▁high - alt itude ▁air ▁resulted ▁in ▁the ▁shell ▁having ▁an ▁angle ▁of ▁attack ▁that ▁produced ▁aer od ynamic ▁lift ▁at ▁su person ic ▁spe eds . ▁At ▁the ▁time ▁this ▁was ▁considered ▁highly ▁und es irable ▁because ▁it ▁made ▁the ▁traject ory ▁very ▁difficult ▁to ▁calculate , ▁but ▁its ▁possible ▁application ▁for ▁extending ▁range ▁was ▁not ▁lost ▁on ▁the ▁obser vers . ▁ ▁In ▁June ▁ 1 9 3 9 , ▁Kurt ▁P att ▁of ▁Klaus ▁R ied el ' s ▁design ▁office ▁at ▁Pe en em ünd e ▁proposed ▁wings ▁for ▁converting ▁ro cket ▁speed ▁and ▁alt itude ▁into ▁aer od ynamic ▁lift ▁and ▁range . ▁He ▁calculated ▁that ▁this ▁would ▁roughly ▁double ▁range ▁of ▁the ▁A - 4 ▁rock ets ▁from ▁ ▁to ▁about ▁. ▁Early ▁development ▁was ▁considered ▁under ▁the ▁A - 9 ▁name , ▁although ▁little ▁work ▁other ▁than ▁wind ▁tunnel ▁studies ▁at ▁the ▁Ze ppel in