Precision landing of rocket fairings is difficult due to unmodeled wind gusts and parachute glide uncertainties
the verdict
INSUFFICIENT LEANING
refutedsupported
the weight of evidence
3 sources for · 0 against
Peer-reviewed literature notes that autonomous parafoil systems and returning rocket stages face low landing accuracy and path planning challenges due to wind disturbances and environmental factors, though specific data on rocket fairings combined with parachute glide uncertainties is only partially covered.
Abstract
Low landing accuracy of autonomous parafoil systems under wind disturbances remains a significant challenge in precision airdrop operations. To address this, there is a critical need for homing control systems with enhanced robustness and adaptability to cope with an uncertain environment. This study proposes a novel control framework that integrates the T-Approach guidance strategy with nonlinear model predictive control (NMPC) for path point correction and trajectory optimization. A nonlinear dynamic model is developed to accurately capture the system behaviour, and an adaptive tracking controller with real-time predictive correction is designed. Compared to traditional J-Approach methods, the T-Approach strategy demonstrates significantly improved wind disturbance rejection and landing accuracy under both steady and shear wind conditions. In 10,000 Monte Carlo simulations with randomized turbulent wind, the proposed approach reduces the 90% circular error probable (CEP90) by 24.4 meters, lowers energy consumption by 11%, and increases the likelihood of maintaining an upwind landing angle deviation within 1° by 43.5%. These results confirm the effectiveness of the proposed method in improving both energy efficiency and disturbance robustness, providing a reliable solution for autonomous parafoil landings in uncertain wind conditions.
The controlled atmospheric re-entry associated with the precision soft-landing of Reusable Launch Vehicles (RLVs) on Earth is very challenging as it depends on multiple parameters [1]. Over the last decade, the cost-effectiveness of such a technology has been finally demonstrated with the successful recoveries of SpaceX’s Falcon 9 first-stage rocket first [2], then followed by other companies such as the Rocket Lab’s Electron micro-launcher [3]. This breakthrough has been made possible by the development of advanced and robust computational methods able to generate in real time the flight conditions and to command the optimal vehicle's deflections accordingly to achieve a safe pinpoint landing.
Indeed, during an Earth atmospheric re-entry, the vehicle is subjected to fast system dynamics changes partly induced by external loads associated with the terrestrial environment (e.g., lift, drag, wind and gusts), but also by the actuation commands to answer the landing constraints satisfaction and the vehicle integrity preservation. All those involve uncertainties and nonlinearities, which lead to vehicle’s instability and therefore give reason why for a highly performant Guidance, Navigation and Control system implementation [4]. More particularly, one of the critical aspects is the design of a robust control strategy capable of counteracting the previously defined disturbances and uncertainties while satisfying the strict accuracy requirements associated with the pinpoint landing [5].
As demonstrated by the current state-of-the-art on control design for launchers [6-7], the classical linear control theory represents a rich heritage with a lot of applications. This choice was motivated by its relative easiness of implementation and the possibility to use gain-scheduling techniques to adapt to nonlinear systems. Nevertheless, these techniques are well-adapted to the control system design of single-input single-output systems, such as for example a reusable rocket using a
ESA GNC Conference Papers Repository ESA GNC Conference Papers Repository Go back to search form. Title: Robust Control Design via Structured H-infinity for the Atmospheric Re-entry of Reusable Launchers Authors: Alice De Oliveira, Michèle Lavagna Presented at: Sopot 2023 DOI: 10.5270/esa-gnc-icatt-2023-191 Full paper: Open paper Abstract: The controlled atmospheric re-entry associated with the precision soft-landing of Reusable Launch Vehicles (RLVs) on Earth is very challenging as it depends on multiple parameters [1].
Over the last decade, the cost-effectiveness of such a technology has been finally demonstrated with the successful recoveries of SpaceXs Falcon 9 first-stage rocket first [2], then followed by other companies such as the Rocket Labs Electron micro-launcher [3]. This breakthrough has been made possible by the development of advanced and robust computational methods able to generate in real time the flight conditions and to command the optimal vehicle's deflections accordingly to achieve a safe pinpoint landing.
Indeed, during an Earth atmospheric re-entry, the vehicle is subjected to fast system dynamics changes partly induced by external loads associated with the terrestrial environment (e.g., lift, drag, wind and gusts), but also by the actuation commands to answer the landing constraints satisfaction and the vehicle integrity preservation. All those involve uncertainties and nonlinearities, which lead to vehicles instability and therefore give reason why for a highly performant Guidance, Navigation and Control system implementation [4].
More particularly, one of the critical aspects is the design of a robust control strategy capable of counteracting the previously defined disturbances and uncertainties while satisfying the strict accuracy requirements associated with the pinpoint landing [5]. As demonstrated by the current state-of-the-art on control design for launchers [6-7], the classical linear control theory represents a rich heritage with a lot of applications. This choice was motivated by its relative easiness of implementation and the possibility to use gain-scheduling techniques to adapt to nonlinear systems.
Moreover, model uncertainties are not accurately considered in the design process, developed only with nominal conditions and stability margin requirements. For all these reasons, it results in an extensive (both in terms of time and cost) Verification and Validation campaign with many iterations and Monte-Carlo analyses to assess the performance and robustness of the control system. To overcome these drawbacks, the H-infinity family of methods, introduced a few years ago [8],
This paper studies the synthesis of a robust control system via structured H-infinity for the RLV atmospheric re-entry problem. First, the nonlinear 6-Degree-of-Freedom (6-DoF) RLV re-entry dynamics are simplified into a linear model and then linearised along a reference trajectory to get the nominal LFT of the system, then augmented with parametric uncertainties. The model covers the atmospheric re-entry and vertical landing of a first-stage rocket equipped with a TVC system and steerable planar fins. The controllers are built at different points of the re-entry trajectory, using the structured H-infinity framework through PID-like structures.
This study lies within the ASCenSIon (Advancing Space Access Capabilities - Reusability and Multiple Satellite Injection) project, an innovative training network funded within H2020. References: [1] L. Blackmore, Autonomous Precision Landing of Space Rockets, The Bridge on Frontiers of Engineering, Vol. 4, No. 46, pp. 1520 (2016). [2] M. Wall, Wow! SpaceX Lands Orbital Rocket Successfully in Historic First, SPACE.com (2015). Retrieval Date: 20-Jan-2022. URL: https://www.space.com/31420-spacex-rocket-landing-success.html [3] Rocket Lab (2017). Rocket Lab Electron 'Its a Test' flight successfully makes it to space. Retrieval Date: 20-Jan-2022.
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