Abstract: In comparison with vehicles or missiles launched from the ground, an ascending spacecraft launched from an extraterrestrial body is generally obstructed by a limited firing space for its main engine. Therefore, the main engine will be forced to stay in a non-free flow state when the generated plume shock squeezed inside the nozzle jet becomes an " adherence plume shock”, with both heating and impacting effects on the nozzle and with potential threats to the safety and reliability of the engine and its peripheral equipment. In this paper, the possible influencing factors of the generated plume on the engine under limited conditions are analyzed. By the modeling of the engine plume and the related simulation analysis, the distribution pattern and the transformation of the plume shock in the nozzle jet are proposed and testified by experiments. The results may help the design of the spacecraft configuration, the plume diversion, and the safety evaluation of the main engine for spacecraft to be lifted off from extraterrestrial bodies.