The X-STERN EXTENDER concept is a feature which turns a relatively small vessel into a flexible subsea vessel with an extendable moon pool in the aft.

This feature increases safety in subsea operations, and the vessel’s smaller size reduces total operational costs and its environmental footprint.

The X-STERN is already an innovation which expands the operational window and offers the captain the choice of placing the stern, rather than the higher and larger bow, towards winds, waves and current when on DP. The newly developed X-STERN EXTENDER feature can be used for conversions as well as newbuilds.

The ‘X-STERN EXTENDER’ is an add-on; it is not part of the ship’s structure and not counted in the ship’s length. This is important when it comes to cutting costs. The deadweight, fuel consumption and operational costs for a fully functional subsea vessel will be reduced.

Hydrodynamic simulations (CFD) in common wave conditions for the North Sea have been carried out. The results show that the water motions inside the moon pool are reduced by 50% compared to outside the moon pool and guarantee a safety margin against green water.