▁was ▁hoped , ▁would ▁be ▁able ▁to ▁destroy ▁the ▁rail road ▁bridge ▁across ▁the ▁App om atto x ▁River ▁at ▁Petersburg , ▁Virginia , ▁and ▁to ▁clear ▁the ▁ob stru ctions ▁from ▁the ▁channel ▁of ▁the ▁James ▁below ▁D rew ry ' s ▁Bl uff . ▁Sat ellite ▁accompanied ▁the ▁sub marine , ▁which ▁was ▁later ▁named ▁, ▁up ▁the ▁river ; ▁but ▁Com dr . ▁John ▁Rod gers , ▁the ▁senior ▁naval ▁officer ▁on ▁the ▁James , ▁felt ▁that ▁the ▁sub marine ▁would ▁be ▁unable ▁to ▁perform ▁the ▁under water ▁demol ition ▁miss ions . ▁The ▁shall own ess ▁of ▁the ▁App om atto x , ▁he ▁felt , ▁would ▁prevent ▁her ▁from ▁reaching ▁the ▁bridge ▁sub mer ged ; ▁and ▁a ▁surface ▁approach ▁would ▁expose ▁the ▁vulner able ▁craft ▁to ▁destruction ▁or ▁capture . ▁In ▁Confeder ate ▁hands , ▁Rod gers ▁fe ared , ▁the ▁sub marine ▁might ▁seriously ▁threaten ▁northern ▁war ships . ▁ ▁As ▁for ▁the ▁ob stru ctions ▁in ▁the ▁James , ▁Union ▁t ugs , ▁Rod gers ▁reason ed , ▁might ▁succeed ▁in ▁pulling ▁the ▁sun ken , ▁stone - lad en ▁l igh ters ▁from ▁the ▁channel ▁of ▁the ▁James . ▁However , ▁if ▁the ▁sub marine ▁should ▁succeed ▁in ▁destroy ing ▁the ▁h ul ks , ▁their ▁cargo es ▁of ▁stone ▁would ▁remain ▁to ▁ob struct ▁navigation ▁and ▁would ▁be ▁almost ▁impossible ▁to ▁remove ▁while ▁covered ▁by ▁Confeder ate ▁guns . ▁For ▁these ▁reasons , ▁he ▁sent ▁the ▁sub marine ▁back ▁to ▁Fort ▁Mon roe