A Trident missile test-fired by a UK submarine failed. That's a lot of money down the drain.

• A test of Britain's nuclear deterrent system ended in failure for the second time. 
• The incident involved a $70 million Trident missile that both the US and UK have in their arsenal. 
• Their high price is part of the reason these missiles are rarely tested by the British Navy.

The British navy suffered an embarrassing flop after a failed test launch of a Trident nuclear missile was revealed.

The Sun newspaper, which first reported the failure, quoted an unnamed source as saying the 58-ton missile "left the submarine but it just went plop, right next to them." It said the incident occurred on January 30 during an incident off Florida.

The issue was reportedly caused by the booster rockets malfunctioning but no further details were revealed on national security grounds.

Defense Secretary Grant Shapps said in a statement: "On this occasion, an anomaly did occur, but it was event specific and there are no implications for the reliability of the wider Trident missile systems and stockpiles."

It's the second time in a row that a test launch of a Trident missile by the Royal Navy has had an unhappy ending. In the last test in 2016, the missile misfired and veered toward the US coast, before self-destructing. It was supposed to head for an area of the Atlantic Ocean off the coast of Africa.

These failures have a high price tag, given that each missile costs tens of millions of dollars. It's hard to be certain exactly how much, given figures range from about $21 million through to about $70 million a pop.

Lockheed Martin, the defense company that makes Trident, directed a query from Business Insider about their cost to the US Navy, which did not immediately respond.

'Most advanced' missile

Trident missiles are a core part of the UK's nuclear deterrent system, which also includes four Vanguard-class submarines carrying nuclear warheads.

Some 16 Trident II D5 missiles can be carried by each submarine, and each can carry up to 12 independently-targeted warheads with a maximum range of 7,400 miles. The actual number of warheads is typically closer to 40, however.

The US also deploys Trident missiles on its Ohio-class submarines.

Lockheed Martin's website states that the Trident II D5 has achieved 188 successful test launches since its design was completed in 1989. The company describes it as the world's "most advanced ballistic missile."

The ongoing servicing costs for the entire Trident system amount to 6% of Britain's defense budget, or about $3.8 billion for 2023/24.

That involves manufacturing costs, missile extension programs, replacement warheads, in-service costs, and personnel salaries.

At least one Vanguard submarine is deployed at any time as part of the UK's Continuous at Sea Deterrent.

Building the Trident system in the 1980s cost about £21 billion ($26.5 billion) in today's money, according to the Ministry of Defense.

The Campaign for Nuclear Disarmament estimates that the total cost of building and maintaining Trident has been $258 billion (£205 billion) since then.

That's still less than the total cost of the US's nuclear deterrent. The Department of Defense is expected to spend $756 billion over the 2023 to 2032 period, according to the Congressional Budget Office.

The importance of maritime strength is rising amid conflicts against the Houthis in the Red Sea, Russia and Ukraine in the Black Sea, and Chinese expansion over the Taiwan Strait.