el ▁N ike ▁Ze us ▁failed ▁to ▁be ▁a ▁cred ible ▁defence ▁in ▁an ▁era ▁of ▁rapidly ▁increasing ▁IC B M ▁counts ▁due ▁to ▁its ▁ability ▁to ▁attack ▁only ▁one ▁target ▁at ▁a ▁time . ▁Additionally , ▁significant ▁concerns ▁about ▁its ▁ability ▁to ▁successfully ▁intercept ▁war head s ▁in ▁the ▁presence ▁of ▁high - alt itude ▁nuclear ▁explos ions , ▁including ▁its ▁own , ▁lead ▁to ▁the ▁conclusion ▁that ▁the ▁system ▁would ▁simply ▁be ▁too ▁cost ly ▁for ▁the ▁very ▁low ▁amount ▁of ▁protection ▁it ▁could ▁provide . ▁ ▁By ▁the ▁time ▁it ▁was ▁cancel led ▁in ▁ 1 9 6 3 , ▁potential ▁up gr ades ▁had ▁been ▁expl ored ▁for ▁some ▁time . ▁Among ▁these ▁were ▁rad ars ▁capable ▁of ▁sc anning ▁much ▁greater ▁volumes ▁of ▁space ▁and ▁able ▁to ▁track ▁many ▁war head s ▁and ▁launch ▁several ▁miss iles ▁at ▁once . ▁These , ▁however , ▁did ▁not ▁address ▁the ▁problems ▁identified ▁with ▁rad ar ▁black outs ▁caused ▁by ▁high - alt itude ▁explos ions . ▁To ▁address ▁this ▁need , ▁a ▁new ▁miss ile ▁with ▁extreme ▁performance ▁was ▁designed ▁to ▁attack ▁incoming ▁war head s ▁at ▁much ▁lower ▁alt itudes , ▁as ▁low ▁as ▁ 2 0   km . ▁The ▁new ▁project ▁en comp ass ing ▁all ▁of ▁these ▁up gr ades ▁was ▁launched ▁as ▁N ike - X . ▁ ▁The ▁main ▁miss ile ▁was ▁LIM - 4 9 ▁Spart an — a ▁N ike ▁Ze us ▁upgrad ed ▁for ▁longer ▁range ▁and ▁a ▁much ▁larger ▁