Rocket engine with an extendible nozzle

The engine has three extensible nozzle expanders displaceably arranged against each other in a longitudinal direction of the engine. Interlinking upper, middle and lower cones (1-3) are lockable with each other in an extended state. Manually lockable locking regions are automatically formed between two cones through stoppers and flexible locking elements. The stoppers are formed as annular projections that are connected with the cone through screws. The locking regions are manually locked using screws.