- St a aken ▁company ▁would ▁be ▁carried ▁out ▁during ▁the ▁next ▁few ▁years . ▁Low - level ▁research ▁continued ▁until ▁ 1 9 4 2 ▁when ▁it ▁was ▁cancel led . ▁ ▁The ▁earliest ▁known ▁use ▁of ▁the ▁boost - g lide ▁concept ▁for ▁truly ▁long - range ▁use ▁dates ▁to ▁the ▁ 1 9 4 1 ▁Sil ber v og el ▁proposal ▁by ▁ ▁Eugen ▁S änger ▁for ▁a ▁ro cket ▁power ed ▁bom ber ▁able ▁to ▁attack ▁New ▁York ▁City ▁from ▁bases ▁in ▁Germany ▁and ▁then ▁fly ▁on ▁for ▁landing ▁somewhere ▁in ▁the ▁Pacific ▁Ocean ▁held ▁by ▁the ▁Empire ▁of ▁Japan . ▁The ▁idea ▁would ▁be ▁to ▁use ▁the ▁vehicle ' s ▁wings ▁to ▁generate ▁lift ▁and ▁pull ▁up ▁into ▁a ▁new ▁ball istic ▁traject ory , ▁exit ing ▁the ▁atmosphere ▁again ▁and ▁giving ▁the ▁vehicle ▁time ▁to ▁cool ▁off ▁between ▁the ▁ski ps . ▁It ▁was ▁later ▁demonstrated ▁that ▁the ▁he ating ▁load ▁during ▁the ▁ski ps ▁was ▁much ▁higher ▁than ▁initially ▁calculated , ▁and ▁would ▁have ▁m elt ed ▁the ▁space craft . ▁ ▁In ▁ 1 9 4 3 , ▁the ▁A - 9 ▁work ▁was ▁d usted ▁off ▁again , ▁this ▁time ▁under ▁the ▁name ▁A - 4 b . ▁It ▁has ▁been ▁suggested ▁this ▁was ▁either ▁because ▁it ▁was ▁now ▁based ▁on ▁an ▁otherwise ▁un mod ified ▁A - 4 , ▁or ▁because ▁the ▁A - 4 ▁program ▁had ▁" n ational ▁priority " ▁by ▁this ▁time , ▁and ▁placing ▁the ▁development ▁under ▁the ▁A