The aircraft will use air conditioners to control the temperature, so that the temperature in the cabin will not be particularly low; and the rocket needs to pass through the same height safely.

The air circulation refrigeration system achieves refrigeration by adiabatic expansion of compressed air in the expander to obtain low-temperature airflow. Its ideal working process includes four processes: isentropic compression, isobaric cooling, isentropic expansion and isobaric heat absorption.

During the development of China's civil aviation, the A320 aircraft air-conditioning system frequently broke down, and the failures were repeated and complicated, which brought great inconvenience to the flight crew. In the survey results of China's major airlines, it was found that the number of aircraft air-conditioning system failures has almost reached half of the total number.