<p>In addition to the primary function of oil and gas exploration, there is a growing need for the innovative design and development of offshore platforms in space research. Offshore Triceratops has emerged as a promising maritime-based space rocket launcher candidate due to their creative and unique responsive characteristics in deep-sea environments. The form-dominant design enables dynamic equilibrium and controls the impact of the deck’s rotational motion on the effectiveness of the sea-borne launch. The current study investigates the effect of stiffened buoyant legs on the tether behaviour during the rocket launch. Rigid body dynamic analysis is conducted to obtain the hydrodynamic characteristics of the platform necessary for developing Mathieu parameters and assessing tether stability using Mathieu stability charts. Studies show that the internal stiffeners are most suitable since they reduce the forces on the buoyant legs, have lesser tether tension, and tether stability. Specifically, the analyses reveal that the inclusion of internal stiffeners preserves structural symmetry and flexibility, thereby greatly reducing wave-induced leg moments. Furthermore, it confirms stability in the vertical plane of motion, across all stiffening scenarios, with only minimal rotational response (0.08°–0.15°), demonstrating the suitability of the internal stiffener configurations. Although internal stiffening introduces an initial transient increase in tether tension, the mean tension ultimately matches the unstiffened case for tethers 1 and 2 and remains the lowest among all stiffened configurations.</p>