Warships combine current designs with unfinished systems

Are warship designs based on technology that is already five to ten years old when the keel is laid?

Not generally. Designs use technology current at laying down, but reserve space and weight for systems still being developed, especially on modern ships with long construction periods.

A ship's baseline design and the maturity of every installed system do not share one date. The naval architecture is usually current when construction begins, while designers may reserve space, weight, and services for equipment still under development. Modern warships take longer to build than many earlier ships. Some fitted technology can therefore be newer than the date implied by the original design work.