The Trident II D5 fleet ballistic missile (FBM), developed by Lockheed Martin, was first deployed in 1990. Credit: US Strategic Command.
The Trident II D5 missile is currently carried by Ohio-class and Vanguard-class submarines. Credit: US Strategic Command.
The Trident nuclear missile has a length of 13.4m and weighs approximately 58,500kg. Credit: US Strategic Command.

The Trident II D5 fleet ballistic missile (FBM) is a three-stage, solid-propellant, inertial-guided ballistic missile developed by Lockheed Martin. The missile can carry multiple independently targeted re-entry bodies for a maximum range of more than 7,360km.

The ballistic missile is a successor to the Polaris A1, Polaris A2, Polaris A3, Poseidon C3 and Trident I C4 missiles.

Since its design completion in 1989, the missile has achieved 188 successful test flights, surpassing the record of any other large ballistic missile or space launch vehicle.

The US Navy awarded a $581m contract to Lockheed Martin for Trident II D5 missile production and deployed systems support in November 2022. This was followed by the award of another contract modification worth $29.7m in January 2023.

The Trident II D5 missile will be integrated into the US Navy’s next-generation Columbia-class submarines and the UK Royal Navy’s Dreadnought-class submarines, which will replace the existing Vanguard-class submarines.

Features of Trident II D5 missile

The Trident II is a 13.41m-long missile with a diameter of 2.11m. Weighing approximately 130,000lbs (58,500kg), the missile has a considerably larger payload capability than the Trident I (C4).

All three stages of the Trident II have lighter, stronger and stiffer graphite epoxy structures, resulting in major weight saving. The missile features an aerospike, a telescoping outward extension that reduces frontal drag by about 50% and increases the missile’s range.

The Trident II is fired by the pressure of expanding gas within the launch tube. The first stage motor ignites when the missile travels a sufficient distance from the submarine, following which the aerospike extends and the boost stage commences. The missile starts travelling at a speed of more than 20,000ft per second after about two minutes of the third stage motor setting in.

Trident II D5 missile guidance and navigation technology

The navigation subsystem of the Trident II D5 has been redesigned to achieve accuracy and maintain an extended fix interval. An electrostatically supported gyro navigator (ESGN) was adopted as the inertial navigator, while a navigation sonar system (NSS) with high capacity was added to measure velocity.

The global positioning system (GPS) replaced the old navy navigation satellite system (NAVSAT), and a digital interface with the FBM weapon system and vessel was installed.

The Trident II D5 guidance system is a stellar-aided inertial system composed of precision gyroscopes, accelerometers, stellar tracker and computer. The guidance system directs the missile on a rectified trajectory, counterbalancing for the submarine’s awkward position, in-flight effects and internal guidance calibratable parameters, upon launch of the missile.

The guidance system works as the reference for maintaining missile stability and activating the re-entry body separation for a ballistic trajectory.

Launch platforms for the Trident II D5 missile

The Trident II D5 missile is launched from a submarine. It was deployed for the first time in 1990 and is currently carried by the US Navy’s Ohio-class and the UK Royal Navy’s Vanguard-class submarines.

Each Vanguard-class submarine has 16 missile tubes and ejects missiles by using high-pressure gas. The Ohio-class submarines can carry up to 24 submarine-launched ballistic missiles (SLBMs) with multiple independently targeted warheads.

The Trident II D5 missile is considered to be the strategic weapon of these submarines, providing increased range and accuracy over its predecessor, the Trident I C4. The conversion of four US C4 submarines to carry the Trident II D5 missile began in 2000 and was completed in 2008.

The US Navy and the Royal Navy are in the process of replacing Ohio-class submarines and Vanguard-class submarines with Columbia-class submarines and Dreadnought-class submarines, respectively.

General Dynamics Electric Boat (GDEB) started construction of the first Columbia-class submarine in June 2022. It is expected to be delivered to the US Navy in 2030.

BAE Systems is building four Dreadnought-class nuclear submarines for the Royal Navy. The first new submarine is scheduled to enter service in 2030.

Trident II D5 missile warheads

Trident II missiles are capable of carrying W76 or W88 multiple independently targeted re-entry vehicles (MIRVs). The MIRV is composed of an arming, fusing and firing (AF&F) assembly, a nuclear assembly, and electronics.

The AF&F assembly protects the warhead from detonating during storage and restrains re-entry vehicle detonation until all qualifying arming inputs are received.

Propulsion for the Trident II D5 missile

The Trident II D5 missile is powered by a three-stage solid-propellant rocket. The boost motor systems for all the stages are supplied by Alliant Techsystems (ATK), a subsidiary of Northrop Grumman.

The third stage motor of the missile incorporates a low-cost high-performance propellant, a low-erosion ceramic rocket nozzle throat, and a lightweight motor case and insulator.

Contractors involved

Northrop Grumman was awarded a $40.4m contract by the US Navy in January 2007 to provide technical support for the Trident II D5 missile weapon system deployed by both the US and the UK.

Boeing was contracted in October 2018 to provide technical support for the Trident II D5 navigation subsystem.

Aerojet Rocketdyne, an aerospace and defence products developer, is engaged in producing the solid and liquid propulsion systems for the ballistic missile.

Under a $202m contract, engineering innovation company Charles Stark Draper Laboratory provides technical support and research on navigation guidance and control systems for the Trident II D5 missile.

Strategic missile launchers and control units for the Trident II D5 missile were developed by Moog, an engineering support provider for defence.