U.S. Navy Submarines - Analyzing the fleet using data from the Naval Vessel Registry
Updated: Feb 9, 2021
Written by: Evan Hubener
During recent defense department funding negotiations, representatives from the U.S. House and Senate agreed to fund a second Virginia-class submarine for the year. The Virginia-class program transition to two per year production during the Block III contract and the Navy is exploring the scenario of moving to a three per year rate of production. The 30-year shipbuilding plan outlines the target of a 355-ship Navy and notes on-going efforts to examine the goal of more consistent procurement of three attack submarines (SSNs) per year.
These developments raise two important questions. First, how does the current build rate, whether two or three per year, compare to historical averages in submarine construction? Second, how urgent is it that the U.S. Navy maintain, or potentially expand, submarine production?
One publicly available data source that can help answer these questions is the Naval Vessel Register (NVR). The NVR is the official inventory of the U.S. Naval Ships, and it includes past, current, and planned ships. In addition to basic ship statistics, like propulsion, displacement, and crew capacity, the NVR contains data on the commissioning and decommissioning dates, which can be used to examine and illustrate the age of the fleet and where it is in its lifecycle.
Notes on the analysis
In all, the NVR contains information on 296 U.S Navy submarines. The submarines built prior to the Cold War were diesel electric powered, and for the sake of comparison, this analysis focuses the post-World War II nuclear submarines. Observations not including a commission date (this includes planned ships not yet under construction) are also excluded.
Nuclear Submarines – how long do they last?
First, let’s examine the age of submarines at the time of decommissioning. This is illustrated below in figure 1.
In examining figure 1, it is clear that prior to 2000, there is not much change over time in the age of the submarines at decommissioning. A few ships are outside of the norm, but most subs were decommissioned after 20-30 years. However, for Los-Angeles class submarines, which are the fast-attack submarines that the current batch of Virginia-class boats are replacing, the age at decommissioning has been trending upwards over the past 25 years. Recent efforts, which include refueling, are being made to extend the service life of LA-class submarines, in order to keep up the number of SSNs until more Virginia-class boats are in service. The first crop of LA-class boats to be retired were not even 20 years old, but the retirement age has been creeping up, and the ships retired in the past five years were all around 35 years old.
Replacing a rapidly aging fleet
This brings us to our second question. How urgent is it that the U.S. Navy maintain, or potentially expand, the build rate? The in-service fleet of submarines is illustrated in figure 2, presented by year of commission.
Upon examination, figure 2 illustrates two problems. First, most of the submarine fleet is aging, and it is aging rapidly. The second of three Seawolf-class submarines was commissioned in 1998, and only 20 ships of the 77 noted in the NVR as in-service have been commissioned since (1 Seawolf-class and 19 Virginia-class). Submarines have traditionally been retired before 30 years old (which would be all ships commissioned prior to 1990), and, despite the aforementioned efforts to keep older boats in service, maintaining an older fleet does introduce higher maintenance costs.
Second, the build rate is considerably lower than it was a generation ago. In the 1980s and into the 1990s, submarines were commissioned at the average rate of 3 per year. Production was then halted, and since resuming, it has been at the rate of one per year, with a couple recent years at two per year commissioning. The U.S. industrial base has supported a higher level of submarine production in the past, but it is unclear if capacity is large enough at the shipyards. If the U.S. Navy wants to maintain the fleet size, a higher build rate is imperative.
The aging fleet will continue to be a challenge for the U.S. for some years to come. The number of ships that will need to be retired each year over the coming decade is higher than the current replacement rate, even including the upcoming 12 Columbia-class submarines, with one per year beginning in 2026. The Navy has already shown that it can hold costs under the general inflation level, but if the fleet size is to be maintained, the rate of production must increase.