A rotary engine is provided. The engine has a main body that fits within a housing to form an annular chamber. A piston moves within the annular chamber along an annular path. A door assembly operates to block and unblock the annular chamber, opening to unblock the chamber as the piston approaches the door and closes to block the chamber after the piston has travelled past the door. A temporary combustion chamber is formed between the closed door and the piston as the piston moves away from the door.