Powered Phase

Author: Tianjiang Shuo

Website: https://cislunarspace.cn

Definition

The Powered Phase, also known as the powered flight phase, is the flight stage between liftoff from the launch pad and the shutdown of the main engines, when the vehicle transitions to free-flight. During this phase, the vehicle is subject to engine thrust, aerodynamic forces, gravitational force, and control forces, with its motion state continuously adjusted by the guidance and control system.

Core Elements

Flight Process

The typical powered-phase flight process includes three sub-phases:

  1. Vertical Ascent Segment: The vehicle stands vertically on the launch pad with main engines ignited. After thrust exceeds gravity, the vehicle lifts off and ascends vertically. Vertical launch rapidly transits through the dense atmospheric layer, reducing aerodynamic loads.

  2. Turning Segment: After reaching a certain velocity, the vehicle begins to "turn" under the control system, with thrust direction controlled in real time to meet impact point or orbit insertion requirements. The turning process must satisfy normal load factor limits and attitude stability requirements.

  3. Aiming Segment: As the vehicle approaches the end of the powered phase, it flies at a constant attitude so that the current state meets the required impact point accuracy or orbit insertion accuracy, followed by engine shutdown.

Launch Methods

  • Land-based Launch: Launched from a fixed ground launch pad or mobile launch vehicle
  • Submarine Launch: Launched from underwater ejection by a submarine, with engine ignition after surfacing
  • Air Launch: Uses a large aircraft to carry the rocket to high altitude for launch, expanding the orbital inclination range and increasing payload capacity

Key Parameters

The powered-phase endpoint parameters (velocity magnitude, velocity direction, position, etc.) directly determine the vehicle's subsequent flight trajectory. For ballistic missiles, the powered-phase endpoint parameters determine impact point accuracy; for launch vehicles, they determine orbit insertion accuracy.

Application Value

The powered phase is an unavoidable stage for all powered vehicles. Its equations of motion and characteristic analysis form one of the core topics of aerospace flight mechanics. Powered-phase trajectory design (flight program selection, thrust direction planning) directly determines mission success or failure.

References

  • 郑伟, 安雪滢, 周祥, 何睿智. 空天飞行力学[M]. 国防科技大学, 2026.
  • 贾沛然, 陈克俊, 等. 远程火箭弹道学[M]. 国防科技大学出版社.