▁case ▁where ▁the ▁decay ▁releases ▁the ▁fragments ▁" front " ▁and ▁" re ar ", ▁the ▁rear ward ▁moving ▁fragment ▁generates ▁thrust ▁directly , ▁while ▁the ▁front ward ▁moving ▁one ▁is ▁absor bed ▁in ▁the ▁front ▁half ▁of ▁the ▁sail ▁with ▁no ▁net ▁contribution ▁to ▁thrust . ▁The ▁sail ▁is ▁not ▁a ▁nuclear ▁re actor , ▁and ▁re lies ▁on ▁natural ▁decay ▁rates ▁for ▁energy ▁release . ▁The ▁thrust ▁from ▁such ▁a ▁system ▁will ▁always ▁be ▁very ▁low , ▁al beit ▁extremely ▁efficient . ▁ ▁For ward ▁proposed ▁the ▁system ▁as ▁an ▁" add ▁on " ▁to ▁existing ▁solar ▁s ails . ▁Close ▁to ▁stars ▁where ▁the ▁light ▁density ▁is ▁high ▁the ▁s ails ▁work ▁fine , ▁but ▁as ▁they ▁move ▁past ▁about ▁ 2 ▁A U ▁their ▁thrust ▁is ▁too ▁low ▁to ▁be ▁useful . ▁For ward ▁suggested ▁that ▁co ating ▁the ▁sail ▁with ▁f ission able ▁material ▁would ▁provide ▁thrust ▁in ▁this ▁region , ▁where ▁man eu ver ing ▁is ▁no ▁longer ▁as ▁important . ▁Such ▁a ▁system ▁would ▁acceler ate ▁and ▁man eu ver ▁based ▁on ▁solar ▁energy ▁for ▁the ▁start ▁of ▁its ▁flight , ▁and ▁then ▁continue ▁to ▁acceler ate ▁at ▁a ▁lower ▁rate ▁for ▁long ▁periods ▁of ▁time . ▁ ▁Category : N uc lear ▁space craft ▁prop ulsion <0x0A> </s> ▁Esc oul ou bre ▁ ▁is ▁a ▁commune ▁in ▁the ▁A ude ▁department ▁in ▁southern ▁France . ▁ ▁Population ▁ ▁See ▁also ▁Comm unes ▁of ▁the ▁A ude ▁department ▁ ▁References ▁IN SEE ▁ ▁Category : Comm