James E. McKevitt
Introduction
The lakes, dunes and atmosphere of Titan mapped by the Cassini-Huygens spacecraft require further exploration to understand the origin and evolution of Titan and the Saturnian system. The NASA Dragonfly mission, launching in 2026, will focus on Titan’s hard surface, but still leave the unique surface lakes unexplored. Features, especially the northern lakes like Kraken Mare, while observed in-situ, are perfect for developing our understanding of the hydrocarbon cycle, the potential for habitability in the environment and the chemical processes that occur at the surface.
Methodology
A follow-up mission, a heavier-than-air flight and plunge-diving aquatic landing spacecraft is proposed. The ASTrAEUS (Aerial Surveyor for Titan with Aquatic Operation for Extended Usability) spacecraft requires modelling of the conditions which can be expected on Titan's surface lakes. Using the multiphysics simulation software LS-DYNA, fluid-structure interaction (FSI) simulations can be performed with a coupled meshfree smoothed-particle hydrodynamics (SPH) and finite element method (FEM) approach.
Modelling
The spacecraft is simulated using a rigid body entering a finite domain free-surface without heat transfer. The liquid is modelled by an SPH, pure Lagrangian method with meshfree particles, using the Murnaghan equation of state where k0 was selected from J. Monaghan and A. Kos (1999).
Acknowledgements
This work is the result of a research project funded by the Royal Academy of Engineering and the Royal Astronomical Society. Research was conducted in, and with the support of, the Blackett Laboratory at Imperial College London and the Aeronautical Engineering department at Loughborough University.
References
J. J. Monaghan, and A. Kos. 1999. “Solitary Waves On A Cretan Beach.” Journal of Waterway, Port, Coastal and Ocean Engineering 125 (3): 155.
Liang, Jianhong, Xingbang Yang, Tianmiao Wang, Guocai Yao, and Wendi Zhao. 2013. “Design and Experiment of a Bionic Gannet for Plunge-Diving.” Journal of Bionic Engineering 10 (3): 282–91. https://doi.org/10.1016/S1672-6529(13)60224-3.
Multiphysics feasibility study of an aerial-aquatic spacecraft’s plunge into Kraken Mare
by James E. McKevitt – Loughborough University
Figure 1: Oscillation of projectile during fluid entry seen with nodal acceleration displayed. (Side-by-side comparisons of projectile approximating the spacecraft at time difference of 3.6e-3s, showing stresses on the vehicle during entry.)
Figure 2: Shockwave propagation in N/C_2 H_6/CH_4 mix with nodal acceleration displayed. (View of finite simulation area showing propagation of shockwave through liquid.)
Sponsors and partner institutions: Imperial College London, Loughborough University, Royal Academy of Engineering, Royal Astronomical Society, British Interplanetary Society.
Slide 2
The Spacecraft
Figure 3: Impression of a ‘plunge diving’ manoeuvre by an aerial-aquatic spacecraft inspired by the gannet seabird (inset). Inset adapted from Liang et al. (2013). (Shows a graphic of an aerial-aquatic spacecraft entering a Titan lake.)
Slide 3
Methodology
Figure 4: Wave development and FSI of Kraken Mare liquid and Earth water with velocity displayed. Red corresponds to a higher relative velocity. (Shows row of static images from progressing wave simulations, with waves striking vertical structure placed in fluid. Taken from side).
Figure 5: High SPH resolution, double-precision solved solution with nodes travelling over a specific velocity shown and with attached velocity vectors. (Shows nosecone of spacecraft penetrating the liquid, and SPH particles reacting by propagating away from projectile tip).
Slide 4
Results and Conclusions
Figure 6: Projectile deceleration due to water and N/C_2 H_6/〖CH〗_4 mix. Shockwave return, therefore invalid results, present at t≈5.75×10^(-3) s. (Shows graph of acceleration magnitude experienced on the projectile during fluid entry).
Figure 7: Wave-structure wake formation of Kraken Mare liquid and Earth water with velocity displayed. (Shows two top-down views of wave-structure interaction simulations, making a wake visible in Kraken Mare conditions, but not in liquid water).