ig ation ▁measures ▁for ▁space ▁de br is ▁in ▁Earth ▁orbit . ▁ ▁Deb ris ▁growth ▁ ▁During ▁the ▁ 1 9 8 0 s , ▁NASA ▁and ▁other ▁U . S . ▁groups ▁attempted ▁to ▁limit ▁the ▁growth ▁of ▁de br is . ▁One ▁trial ▁solution ▁was ▁implemented ▁by ▁Mc D onn ell ▁Douglas ▁for ▁the ▁D elta ▁launch ▁vehicle , ▁by ▁having ▁the ▁boost er ▁move ▁away ▁from ▁its ▁payload ▁and ▁vent ▁any ▁prop ell ant ▁remaining ▁in ▁its ▁t anks . ▁This ▁elimin ated ▁one ▁source ▁for ▁pressure ▁bu il dup ▁in ▁the ▁t anks ▁which ▁had ▁previously ▁caused ▁them ▁to ▁expl ode ▁and ▁create ▁additional ▁orb ital ▁de br is . ▁Other ▁countries ▁were ▁slower ▁to ▁adopt ▁this ▁measure ▁and , ▁due ▁especially ▁to ▁a ▁number ▁of ▁launch es ▁by ▁the ▁Soviet ▁Union , ▁the ▁problem ▁grew ▁throughout ▁the ▁de cade . ▁ ▁A ▁new ▁battery ▁of ▁studies ▁followed ▁as ▁NASA , ▁N OR AD ▁and ▁others ▁attempted ▁to ▁better ▁understand ▁the ▁orb ital ▁environment , ▁with ▁each ▁adjust ing ▁the ▁number ▁of ▁pieces ▁of ▁de br is ▁in ▁the ▁critical - mass ▁zone ▁up ward . ▁Although ▁in ▁ 1 9 8 1 ▁( when ▁Sche fter ' s ▁article ▁was ▁published ) ▁the ▁number ▁of ▁objects ▁was ▁estimated ▁at ▁ 5 , 0 0 0 , ▁new ▁detect ors ▁in ▁the ▁Gr ound - based ▁Elect ro - Opt ical ▁Deep ▁Space ▁Sur ve ill ance ▁system ▁found ▁new ▁objects . ▁By ▁the ▁late ▁ 1 9