A multi physical digital representation of the space capsule splashdown event in the Simcenter environment to accelerate analysis of impact condition, structural design and human body loading.
Creators: name:  M. UNGER 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: ASTRONAUTICS
ADVANCED PERFORMANCES ENGINEERING
SIMULATIONS

description: The landing of a reentering space craft into the water, the capsule splashdown, is a key critical physical loading condition of the astronauts in a space mission. A multi physical digital representation of the load case within the Simcenter environment is presented that allowed fast evaluations of the impact parameters like speed, impact angle, sea state and the effects on the final loadings on the astronauts body and capsule structure. The methodology combined cutting edge simulation technologies of three different engineering streams: CFD, structural and occupant simulations. Previous publications [1,2] on free falling lifeboats had shown the value of the simulation methods in a similar kind of loading case that now had been enhanced and demonstrated on the capsule splashdown. In the first step, the water impact of the vehicle was modelled within Simcenter STAR CCM+ that used hybrid modeling technology of the multiple phases involved. Starting from the CAD data and initial impacting conditions the overall motion of the vehicle and the pressure distribution loading on the structure was calculated over time. In the next step, the propagation of the impact loading required a structural dynamics analysis to assess the structural integrity and the specific motion of the structural parts that interacted with the occupant and restraint system. An FE analysis was performed with Simcenter 3D by file exchange through CGNS (CFD General Notation System) and used same time step as the CFD. For the safety performance of the vehicle, the motion of the floor and seat connection points were derived. These were the key structural parts that interacted with occupant and safety system. Additionally, structural loading was analyzed to assess the safe egression of the occupants and water entry. In the third step the human body dynamics of the occupants was calculated using efficient multi-body (MB) dynamics analysis in combination with explicit FE analysis of the restraint systems. A Simcenter Madymo model was build that includes occupant (MB), seat (MB) and a safety belt (FE). From the Simcenter Madymo model database the active human body model was selected as occupant model which represents a 50th %ile average male. This model includes muscle controllers that stabilize its position just like the human reaction. Then the loading condition was added by importing the 3d motion data of the floor and seat connection points from the previous steps. After the simulation, injury values for neck, lumbar spine and head were assessed according to the industry safety standards in aviation, automotive and lifeboats. Finally, a parametric study was executed on the effects of muscle strength reduction, due to long space travels in combination with a variation in landing conditions and safety system parameters. By using HEEDS the previously described steps were combined in an automated process. The presented methodology in the Simcenter environment showed to be an efficient and robust simulation tool chain for capsule splash down analysis that accelerates capsule design optimization and minimize the injury risks for the astronauts. [1] Morch, H.J., Enger, S., Milovan PERI, ?., Schreck, E. (2008). Simulation of lifeboat launching under storm conditions. [2] P A Forbes, L van Rooij, C Rodarius, K H Tan, M Philippens, R Corbeij, R Skaeveland, Occupant Safety in Freefall Lifeboats: Numerical Simulation of Full Scale Drop Conditions, ICrash 2008