▁and ▁a ▁T - tail . ▁It ▁was ▁power ed ▁by ▁a ▁combination ▁of ▁a ▁single ▁Arm strong ▁Sid de ley ▁Vi per ▁tur bo jet ▁engine ▁and ▁de ▁Hav ill and ▁Spect re ▁ro cket ▁engine , ▁the ▁exhaust s ▁of ▁which ▁were ▁mounted ▁one ▁at op ▁the ▁other ▁on ▁the ▁rear ▁fus el age ▁beneath ▁the ▁tail . ▁Sau nd ers - R oe ▁had ▁originally ▁proposed ▁to ▁develop ▁their ▁own ▁ro cket ▁motor ▁to ▁power ▁the ▁SR . 5 3 , ▁having ▁not ▁been ▁initially ▁pleased ▁with ▁the ▁performance ▁of ▁either ▁the ▁Spect re ▁nor ▁the ▁S cre amer ; ▁however , ▁it ▁was ▁recogn ised ▁that ▁this ▁would ▁take ▁substantial ▁development ▁work . ▁By ▁October ▁ 1 9 5 2 , ▁the ▁basic ▁outline ▁of ▁the ▁aircraft ▁had ▁been ▁final ised , ▁replacing ▁the ▁combined ▁f lap ▁and ▁a iler ons ▁of ▁earlier ▁proposed ▁with ▁sl otted ▁f laps , ▁the ▁Vi per ▁engine ▁was ▁re located ▁up wards ▁and ▁was ▁to ▁be ▁fitted ▁with ▁a ▁straight ▁jet ▁pipe ▁rather ▁than ▁a ▁b if ur c ated ▁one , ▁the ▁tail plane ▁was ▁also ▁moved ▁to ▁a ▁higher ▁position ▁at ▁the ▁top ▁of ▁the ▁fin . ▁ ▁On ▁ 3 0 ▁October ▁ 1 9 5 2 , ▁the ▁company ▁received ▁an ▁Inst ruction ▁to ▁Pro ceed ▁from ▁the ▁Ministry ▁for ▁the ▁completion ▁of ▁three ▁pro tot ypes . ▁On ▁ 1 2 ▁December ▁ 1 9 5 2 , ▁further ▁ref in ement ▁of ▁the ▁concept ▁led ▁to