Analysis of ship motion response under different hull parameters in sea launch

With the rapid development of sea-based launch technology, the motion stability of launch ships in complex marine environments has become a key factor for launch safety and trajectory accuracy. Under the combined influence of waves, wind, and currents, the platform’s roll, pitch, and heave motions disturb the rocket’s launch attitude and cause thrust vector deviations, which reduce orbit insertion accuracy. Since the ship’s main dimensions (length, breadth, and molded depth) and draft are critical to motion response, this study takes a typical offshore launch ship as the research object. Dynamic models are established based on the six-degree-of-freedom motion equations under different parameter combinations. Numerical simulations are carried out to evaluate roll, pitch, and heave motions during pre-launch, launch, and post-launch phases. Results show that a longer ship reduces pitch amplitude, a wider ship suppresses roll, molded depth changes strongly affect heave, and larger draft lowers overall motion amplitude. These findings provide theoretical references for ship design and optimization, and practical guidance for improving the safety and stability of sea launch missions.