There are other problems with the Vanguard and its three sister ships. There is, as yet, no certainty that they will be replaced when they wear out in the next 15 years or so. There is some work under way to design and build a new generation of British SSBNs. Four years ago Britain hired an American submarine builder (General Dynamics) to design a Common Missile Compartment (CMC) for Britain’s next class of SSBN, which are to begin replacing the current Vanguard class boats in the 2020s. The Vanguard boats are 150 meters (465 feet) long, displace 14,000 tons, have a crew of 135, and entered service in the 1990s. They carry 16 Trident II missiles, weighing 59 tons, with a range of 11,300 kilometers and carrying up to eight warheads. A new class of SSBNs is expected to be about the same size but that will cost up to $30 billion, and there is growing support in Britain for doing away with their SSBNs altogether.
The U.S. Navy will use the CMC for its next class of SSBNs. This makes sense because Britain buys the ballistic missiles for its SSBNs from the United States. It would be too expensive for Britain to design and build its own SSBN ballistic missiles. Thus the CMC will have to be designed by an American firm, with access to data on the characteristics (especially the dimensions) of future missiles for SSBNs.
Britain and the United States have long cooperated on designing nuclear submarines, especially SSBNs. The U.S. and Britain are designing two different SSBNs. But each sub will have many common features, like the CMC, and that will save a lot of money for both nations. The 18 U.S. Ohio class SSBNs were built between 1979 and 1997. The 16,000 ton Ohios were built to serve for twenty years, but that has been extended at least 15 and possibly 30 years. In the next 5-10 years work on a new class of U.S. SSBNs will have to begin. One option Britain may consider is simply buying four of the new American SSBNs, although such boats would be full of British designed and built equipment.