Merchant ships carrying Hurricanes on catapults on the UK-Murmansk convoys were called CAM (Catapult Armed Merchant) ships. These catapults were indeed rocket powered, although I haven't seen a CAM ship with a small deck for recovery of the fighter after action. These ships were developed as a result of there not being enough escort carriers to go around at the time for the convoys. The first ones must've given the German torpedo bombers and long range maritime aircraft a shock, although the Germans later developed strategies for tricking the CAM fighters into launching and chasing a decoy. After the Hurricane had run out of fuel or ammunition and the pilot had ditche dor baled out, the main attack waves were brought into play.
If any of you are interested, heres a link to some photos of HMS Triumph and RN Fireflys, Seafires and others I have, I have used these on PPRuNe before, so apologies if youve seen them before.
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Fleet Air Arm
HMS Triumph
Kermie