, ▁Br ass ▁Bell , ▁and ▁ultimately ▁the ▁Bo eing ▁X - 2 0 ▁D yna - So ar . ▁Ear lier ▁designs ▁were ▁generally ▁bom bers , ▁while ▁later ▁models ▁were ▁aim ed ▁at ▁reconna issance ▁or ▁other ▁roles . ▁D orn berger ▁and ▁Ehr ic ke ▁also ▁collabor ated ▁on ▁a ▁ 1 9 5 5 ▁Popular ▁Science ▁article ▁pitch ing ▁the ▁idea ▁for ▁air lin er ▁use . ▁ ▁The ▁introduction ▁of ▁successful ▁inter cont inental ▁ball istic ▁miss iles ▁( IC B M s ) ▁in ▁the ▁off ensive ▁role ▁ended ▁any ▁interest ▁in ▁the ▁skip - g lide ▁bom ber ▁concepts , ▁as ▁did ▁the ▁reconna issance ▁satellite ▁for ▁the ▁sp y plane ▁roles . ▁The ▁X - 2 0 ▁space ▁f ighter ▁saw ▁continued ▁interest ▁through ▁the ▁ 1 9 6 0 s , ▁but ▁was ▁ultimately ▁the ▁victim ▁of ▁budget ▁cut s ; ▁after ▁another ▁review ▁in ▁March ▁ 1 9 6 3 , ▁Robert ▁Mc N am ara ▁can ce led ▁the ▁program ▁in ▁December , ▁not ing ▁that ▁after ▁$ 4 0 0 ▁million ▁had ▁been ▁spent ▁they ▁still ▁had ▁no ▁mission ▁for ▁it ▁to ▁ful fill . ▁ ▁Russia ▁in ▁March ▁ 2 0 1 8 ▁un ve iled ▁hyp erson ic ▁gli de ▁vehicle ▁Av ang ard . ▁Where as ▁China ▁officially ▁un ve iled ▁the ▁D F - Z F ▁Hyp erson ic ▁G lide ▁Ve h icle ▁in ▁October ▁ 1 st , ▁ 2 0 1 9 . ▁