' s ▁first ▁artificial ▁satellite . ▁The ▁US ▁Army ▁acceler ated ▁development ▁of ▁their ▁LIM - 4 9 ▁N ike ▁Ze us ▁system ▁in ▁response . ▁Ze us ▁was ▁critic ized ▁throughout ▁its ▁development ▁program , ▁especially ▁from ▁those ▁within ▁the ▁US ▁Air ▁Force ▁and ▁nuclear ▁weapons ▁establish ments ▁who ▁suggested ▁it ▁would ▁be ▁much ▁simpler ▁to ▁build ▁more ▁nuclear ▁war head s ▁and ▁guarantee ▁mut ually ▁assured ▁destruction . ▁Ze us ▁was ▁eventually ▁cancel led ▁in ▁ 1 9 6 3 . ▁ ▁In ▁ 1 9 5 8 , ▁the ▁U . S . ▁sought ▁to ▁explore ▁whether ▁air bur st ing ▁nuclear ▁weapons ▁might ▁be ▁used ▁to ▁w ard ▁off ▁IC B M s . ▁It ▁conducted ▁several ▁test ▁explos ions ▁of ▁low - y ield ▁nuclear ▁weapons ▁— ▁ 1 . 7 kt ▁boost ed ▁f ission ▁W 2 5 ▁war head s ▁— ▁launched ▁from ▁ships ▁to ▁very ▁high ▁alt itudes ▁over ▁the ▁southern ▁Atlantic ▁Ocean . ▁Such ▁an ▁explos ion ▁releases ▁a ▁burst ▁of ▁X - ray s ▁in ▁the ▁Earth ' s ▁atmosphere , ▁causing ▁secondary ▁show ers ▁of ▁charged ▁particles ▁over ▁an ▁area ▁hundreds ▁of ▁miles ▁across . ▁These ▁can ▁become ▁tra pped ▁in ▁the ▁Earth ' ▁magnetic ▁field , ▁creating ▁an ▁artificial ▁radiation ▁bel t . ▁It ▁was ▁believed ▁that ▁this ▁might ▁be ▁strong ▁enough ▁to ▁damage ▁war head s ▁travel ing ▁through ▁the ▁layer . ▁This ▁proved ▁not ▁to ▁be ▁the ▁case , ▁but ▁Arg us ▁returned ▁key ▁data ▁about ▁a ▁related ▁effect