Integrated numerical and analytical assessment of transient heave response in single-column floaters for offshore launch platforms

A deep-draft single-column floater has been proposed for offshore launch of a space rocket. The suitability of the floater during launch and post-launch has been investigated. Time-domain CFD simulations on a scaled model (1:100) were carried out to obtain the response due to the thrust force. The response indicated that the maximum vertical displacements were close to acceptable limits, with the floater maintaining positive buoyancy and hydrostatic stability during and after launch. An analytical model, using a single-degree-of-freedom equation (in heave) subjected to a pulse load, was developed. The results from the analytical model matched well, confirming the modelling technique used for CFD simulations. Heave response is influenced by burn duration. Pulse durations corresponding to odd multiples of half of the heave period (Tn/2) lead to higher displacement than even multiples. This behavior is governed by the relative phase between thrust excitation and platform velocity. The floater returned to equilibrium after 200 seconds.