Shipbuilding Intervals

(Created 20 Aug 2011
Updated 7 April 2024)

To maintain a steady number of ships in a naval service's inventory, ships must be acquired on a semi-set schedule to replace overage ones.

The (rather) simple equation for this computation is:

FL / FS = I

Where:

FL = Fleet Lifetime; the expected service life of the ship in normal service. Some known service lives are:

Nimitz CVN = 50 years
Arleigh Burke DDG = 35 years
Spruance DD = 30 years
Perry FFG = 30 years

FS = Fleet Size; the level of active ships of that type that you wish to maintain. For the US CVN fleet, this is 12 ships.

I = Interval of Replacement. How often you would need to construct a new ship to maintain force levels.

EXAMPLE #1: The US Navy commissioned the last of 27 Ticonderoga-class Cruisers in 1994. If we assume a service lifetime of 35 years; what is the interval of replacement?

35 years / 27 ships = 1.3 years in-between replacements.

EXAMPLE #2: The US Navy wants to have a force level of 12 CVNs at any one time. Given a service life of 50 years, how often do we need to build a CVN?

50 years / 12 ships = 4.16 years in-between replacements.

Obviously, all of this can be deferred; i.e. making a decision to extend CVN construction to five years interval between ships and making up the difference via extending the service lives of existing hulls, but it all comes at a price which the service may not be willing to make.