The Royal Navy's future submarine requirement is currently called “Maritime Underwater Future Capability” (MUFC) which originates from May 2001. MUFC, formerly known as the Future Attack Sub Marine (FASM) was originally to have been a new generation attack submarine intended to replace the last four or five of the seven Trafalgar Class nuclear powered submarines in order to maintain the ten-strong SSN force authorized by Strategic Defence Review (SDR) in 1998. The name change was designed to allow a new approach to naval forces. He said, “Changing the name of our studies from submarine to capability allows us to think more laterally.”

“Instead of considering what submarine will fill the gap after ‘Astute’, we are going back to first principles of defining the capabilities we require. We will see far more tasks being conducted remotely”. (Source: Cdre. Paul Lambert, Director of Underwater Equipment Capability, MoD).

Whatever form "future sub" takes it should be designed at Barrow in order to take advantage of the construction experience on the Astute Submarine and to further reinforce the shipyard's role as the UK's Submarine Centre of Excellence.

MUFC's intended role is to provide a versatile and affordable, sustained forward power projection and battle-space dominance capability.

The main requirements are:

The expected service entry date for the First of Class MUFC would not be earlier than 2016/17.

Manned submarines are now expected to be used for command and transport roles rather than fighting sea battles.

New technologies that are expected to be incorporated in MUFC included: