BLUF

Reduced drag, better manoeuvrability and quieter operation are just some of the design improvements of the Columbia-class submarine.

Summary

The United States has a new Columbia-class submarine currently under construction. The new subs will be the most advanced nuclear-powered submarine armed with ballistic missiles (SSBN) in the world and the largest submarine ever built by the US. One of the design changes made to the Columbia-class is the switch to an 'X-Stern' rudder/planes from the existing 'cross' shape design seen on Ohio-class SSBNs and Virginia-class SSNs. The move to an X-shaped stern control plane has the following advantages:

An X-Stern design has more manoeuvring force that allows the controls to be smaller, reducing drag. 

An X-Stern configuration reduces the chance of an accidental dive, allowing for faster speeds at lower depths. 

The X-form of the planes reduces the negative interaction between the propulsor and rudders and assists in rotating the inflow of water to the propulsor. This helps reduce the overall noise signature of the submarine. 

Not having a long rudder below the sub minimizes the chance of it hitting the sea bottom. Conversely, not having a rudder above the centreline of the sub may allow easier access by Swimmer Delivery Vehicles entering or exiting the sub's dry deck shelter.

The Columbia-class is designed to ensure they are survivable throughout their 40-year life span and remain ready, if necessary, for the precise delivery of nuclear warheads.

 

Learn more about the new Columbia-class subs currently under construction.

References

Nov 2020 Defense News US Navy inks $9.4B contract for two Columbia-class nuclear missile submarines

Jul 2021 Forbes The Navy Should Build ‘Battle Taxi’ Variants Of Columbia Class Subs To Carry Marine Commandos

Aug 2021 National Defense Magazine New Details Revealed on Next-Gen Attack Submarine