UK confirms it is developing Astraea nuclear warhead

The British Ministry of Defense has confirmed that the country is developing a new nuclear warhead model codenamed Project Astraea. This is part of the "Strategic Defense Review 2025" program deployed by London to strengthen its nuclear deterrence capabilities.

In response to a question period in the British Parliament , British Defence Secretary Luke Pollard said: “The budget for the Astraea project is estimated at £15 billion during the current parliamentary term .”

The Mk4A nuclear warhead is currently being fitted by the UK on Trident II D5 missiles.

However, part of this budget is also used to maintain the existing Mk4A warhead and modernize infrastructure at the UK Ministry of Defence's Nuclear Weapons Engineering Establishment (AWE).

Mr Pollard stressed that the UK Ministry of Defence would not make public the expected cost of Astraea “to ensure national security.”

The Astraea project, designated A21/Mk7, is being designed, developed and manufactured in the UK and is being delivered by AWE.

Astraea will replace the Holbrook warhead currently used on the Trident II D5 missile equipped on Vanguard-class submarines and their successors to the Dreadnought class.

The system was developed in conjunction with the US W93 program, sharing some non-nuclear components such as the Mk7 hull under established treaty frameworks, to ensure continued compatibility with the Trident system.

Trident II D5 missile with 6 nuclear warheads in service with the Royal Navy.

The UK's Strategic Defence Review 2025 states that the sovereign warhead programme will create around 9,000 jobs in the defence nuclear sector. Astraea is expected to enter service in the 2030s, when the Holbrook warhead reaches the end of its operational life.

According to official documents, Astraea will incorporate improved safety and performance measures, including hard-to-detonate explosives and technologies developed through the UK–US Joint Technology Demonstration program.

According to estimates by the Stockholm International Peace Research Institute (SIPRI), Britain currently has about 225 nuclear warheads, ranking 9th on the list of countries possessing nuclear weapons.

If the warhead is completed, the UK can only deploy it directly into service without going through an actual test. Because the UK is currently a signatory to the Comprehensive Nuclear Test Ban Treaty.