Reentry Trajectory Planning Using Flight Path Angle Constraints
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Solution Overview
Problem
Existing reentry trajectory design methods, such as the Quasi Equilibrium Gliding Condition (QEGC), ignore the flight path angle and its rate of change, leading to reduced reliability and potential failure to satisfy path constraints during reentry flights.
Innovation Solution
A method for designing reentry trajectories based on flight path angle planning, which involves extracting actual operating parameters, solving for velocity-height boundaries, setting up flight-path-angle lower limits, and calculating corresponding bank angles to satisfy terminal constraints, thereby improving trajectory accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the Quasi Equilibrium Gliding Condition (QEGC) method is used to design reentry trajectory, then the design process is simplified by assuming flight path angle and its rate of change are zero, but the reliability of the trajectory is reduced and path constraints may not be satisfied
Solution Approach 1:
The method performs preliminary flight path angle planning before trajectory optimization. By pre-calculating the flight path angle profile based on process constraints (stagnation-point heat flux, dynamic pressure, overload), the method ensures that the subsequent trajectory optimization starts with a reliable flight path angle reference, thus improving trajectory reliability while maintaining design efficiency
Solution Approach 2:
The method transitions from the static QEGC assumption (flight path angle = 0) to a dynamic flight path angle planning approach. The flight path angle is no longer fixed at zero but is planned as a varying parameter throughout the reentry process, allowing the trajectory to dynamically adapt to satisfy path constraints while maintaining reliability
2Manufacturing precision
If flight path angle planning is incorporated into trajectory design, then trajectory accuracy and reliability are improved, but the design process becomes more complex
Solution Approach 1:
The trajectory design process is segmented into distinct stages: flight path angle planning stage, trajectory optimization stage, and control command generation stage. Each stage has specific inputs and outputs, allowing the complex design process to be managed systematically. The flight path angle planning stage produces a reference profile that guides the subsequent optimization, improving accuracy without overwhelming complexity
Solution Approach 2:
The flight path angle profile serves as an intermediary between the process constraints and the trajectory optimization. Instead of directly optimizing the trajectory to satisfy complex heat flux, dynamic pressure, and overload constraints, the method first translates these constraints into a flight path angle profile, which then guides the trajectory optimization. This intermediary approach improves accuracy while managing design complexity
3Productivity
If the flight path angle is assumed to be zero throughout reentry gliding stage, then calculation speed is increased, but the trajectory may fail to satisfy path constraints such as stagnation-point heat flux, dynamic pressure, and overload
Solution Approach 1:
The method performs preliminary flight path angle planning based on process constraints before trajectory optimization. By pre-calculating the flight path angle profile that satisfies heat flux, dynamic pressure, and overload constraints, the method ensures constraint satisfaction is built into the trajectory design from the outset, maintaining both speed and reliability
Solution Approach 2:
The method changes the flight path angle parameter from the fixed zero assumption to a variable profile planned based on process constraints. This parameter change allows the trajectory to satisfy path constraints (stagnation-point heat flux, dynamic pressure, overload) while maintaining calculation efficiency through systematic planning rather than iterative correction
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach accurately plans reentry trajectories, enhances reliability, and increases calculation speed and precision, ensuring compliance with path constraints and reducing the risk of trajectory failure.
Implementation Method 1
D=1⁄2ρSCDV2
Implementation Method 2
L=1⁄2ρSCLV2
Implementation Method 3
ρ=ρ0e−h/β
Implementation Method 4
g=g0(R0/(R0+h))2
Data Source
AI summary
Disclosed is a method for designing a reentry trajectory based on flight path angle planning, including the following steps: S1. extracting an actual operating parameter of an aircraft, setting a maximum dynamic pressure qmax a maximum stagnation point heat flux {dot over (Q)}max, and a maximum overload nmax according to a mission requirement, and solving for a velocity-height boundary of a reentry trajectory; S2. solving for a reentry trajectory in an initial descent stage according to differential equations of reentry motion, and setting up a flight-path-angle lower limit γmin(V) according to the reentry trajectory in the initial descent stage, the velocity-height boundary, and a target point in a velocity-height phase plane; and S3. planning, based on the flight-path-angle lower limit γmin(V), a flight path angle satisfying terminal constraints, and calculating a corresponding bank angle to obtain a reentry trajectory.