Presentation Abstract for the 2024 ESI SimulationX User Forum
Mr. Kaname Kawatsu - Associate Researcher R&D dept. Japan Aerospace Exploration Agency in collaboration with NewtonWorks Corp. Japan
"In order to realize future space missions that are unprecedented and difficult, such as landing of reusable rockets and automatic docking of spacecraft, it is important to determine feasibility and technical risks at an early stage. Furthermore, there are issues with the reproducibility of the actual operating environment and the costs involved in ground tests, making comprehensive evaluation difficult. Therefore, in addition to ground tests using conventional hardware, efficient model-based evaluation is required. Therefore, JAXA had introduced multidisciplinary concurrent approach for mission feasibility and safety evaluation by focusing on the interaction of complex physical domains and using models that integrate multiple elements (mechanisms, control, propulsion systems, etc.) to realize future space missions.
Reusable launch vehicles of the future are expected to drastically reduce space transportation costs. Realizing a radical reduction in cost for space transportation requires not only reusable design efforts for longer life but also technologies that will improve reusable launch vehicle readiness, reliability and safety. In evaluating system feasibility during concept studies, it is necessary to identify important characteristics and bottle-neck technologies that contribute significantly to capacity and mass regarding design specifications and operational conditions. Furthermore, from the perspective of robustness against weather conditions during operation, it is necessary to evaluate sensitivity and understand optimization trends through parametric study.
During altitude control or landing phase, both vehicle reorientation and drag from atmospheric flight incite large amplitude propellant slosh that may affect vehicle stability. Landing mechanical load transfer to the vehicle body is key of structure design and stability is important. Each phenomenon needs to be evaluated certainly and has strong interaction through such as vehicle attitude, position, and velocity during landing phase. Therefore, achieving optimized design require a multi-physics system-level evaluation with affordable evaluation cost which enables parametric study considering vehicle specification, constraint, and variation of condition.
Rendezvous docking (RVD) is a key technique for space activities and missions, including in-orbit servicing and planetary exploration missions. This technology is gaining importance because it makes a wide range of space activities and missions possible. These activities include orbital supply and replacement services, and assembly of large space structures that cannot be launched as a whole. In fact, the RVD is one of the crucial technologies in the International Space Station (ISS) program to provide physical connection for the crew and resources.
One of the planned missions of the HTV-X, successor to the HTV, is a demonstration of automatic docking system. After transporting cargoes and leaving the ISS, the HTV-X can be used as a platform for technical demonstration. The docking system needs to achieve a high level of reliability and safety. However, there are many scenarios for safety measures of the time-variant actuator states on both the vehicle and the docking mechanism. The HTV-X vehicle must integrate the altitude control system and the automatic docking system during design evaluation and safety assessment.
For safe autonomous docking with the target spacecraft, it is essential to evaluate the interaction of the host vehicle and the automated docking mechanism regarding failures and other off-nominal events to ensure that the system is trustworthy. However, it is difficult to comprehensively evaluate and verify the system only by ground testing because of the difficulty of reproducing the operating conditions in space.
Therefore, this study applied a model-based approach to the design evaluation and risk assessment of the automatic docking system, aiming to simulate normal and off-nominal scenarios under accidents or failures accurately."
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