Abstract
The re-entry trajectory of maneuvering vehicles with medium to high hypersonic lift-to-drag ratios is generally planned using quasi-equilibrium flight conditions known from Space Shuttles. They may exhibit an oscillation re-entry phenomenon termed skip re-entry when related components or sensors fail. However, conventional re-entry guidance only considers quasi-equilibrium flights and ignores the possibility of the occurrence of an unexpected skip trajectory; this may lead to the failure of the re-entry mission due to a lack of a corresponding guidance strategy. However, the detection of a skip trajectory is the necessary reference for the decision-making of calling a related guidance algorithm that helps improve the safety of vehicle re-entry. Herein, a skip re-entry detection and trajectory control solution is proposed to play an emergency role in the cases of skip re-entry. Firstly, the oscillation frequency characteristics of the linearized re-entry motion equation of a vehicle are analyzed, and an approximate analytical relationship is constructed for skip altitude estimation. Then, the residual deviation between the altitude feedback data and the estimated skip altitude is calculated and compared with the threshold to determine the occurrence of skip re-entry. In addition, a method for controlling the skip re-entry trajectory with the range extension is developed by controlling the bank angle with a fixed angle of attack profile, satisfying the path constraint requirements. The results indicate that the method effectively performs skip re-entry detection and that it can help extend the range of the vehicles in abnormal re-entry scenarios, keeping the flight within the path constraints and guiding it to the expected location.
Highlights
Experiences of the Space Shuttle provide a baseline for planning and optimizing the re-entry trajectory for vehicles with similar symmetric configurations and medium or high lift-to-drag ratios [1,2]
This paper considers an unexpected skip occurrence and expects to monitor or assist decision-making through skip trajectory detection and calls on the corresponding skip guidance algorithm to improve the safety of low Earth orbit (LEO) re-entry
This paper is dedicated to the detection of unexpected skip re-entry and active use of the natural phugoid oscillations of medium or high lift-to-drag ratio (L/D) re-entry of the vehicle to guide it to the emergency area for recovery
Summary
Experiences of the Space Shuttle provide a baseline for planning and optimizing the re-entry trajectory for vehicles with similar symmetric configurations and medium or high lift-to-drag ratios [1,2]. From low Earth orbit (LEO) back into the atmosphere, the drag-acceleration profile planning algorithm [3] is explicit and practical. Electromagnetic radiation in the near-earth space environment is very complex [10] and may cause sensor performance degradation or failure [11]. Sensor performance degradation is not easy to detect directly and will lead to a deviation of the result of the guidance algorithm calculation, which may lead to an abnormal re-entry trajectory. For commercial space launch and re-entry activities, the Federal Aviation Administration requires that the trajectory analysis for both normal and malfunction flights must characterize variability and include deviation in paragraphs
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