The Trafalgar class submarines were, until the introduction of the Astute class, the Royal Navy's most advanced nuclear fleet submarines (SSNs).
The Trafalgar class includes seven boats: Trafalgar (S107), Turbulent (S87), Tireless (S88), Torbay (S90), Trenchant (S91), Talent (S92), and Triumph (S93).
It is an attack submarine and is essentially a refinement of the Swiftsure class, designed six years later than its predecessor. The first Trafalgar class submarine was completed in 1983.
The major improvements include a new reactor core and the Type 2020 sonar. Internal layout is near identical to the Swiftsure, and it is only 2½ metres longer.
Rather than the seven-bladed propeller used by the Swiftsures, Trafalgar class submarines use pump-jet propulsion - a high-pitch, low-revolution propeller which is much quieter but much heavier than conventional propeller designs. Development of this system was not complete in time for installation in the class's name-ship vessel, HMS Trafalgar, and so the pump-jet was first used in the second in the class, HMS Turbulent.