The automated Phalanx CIWS cannons aboard Britain's aircraft carriers are a final line of defence against attack, capable of filling the sky with 4,500 armour-piercing rounds a minute to defeat incoming missiles. Find a way to dodge them, and the HMS Queen Elizabeth is little more than a floating 65,000-tonne target.
It would be no surprise, then, if military chiefs are feeling a little nervous about the latest wonder weapon.
As conflict rages in Ukraine and a crisis builds in Taiwan, the world is poised to enter the age of the hypersonic missile – a weapon so fast that it can go from a distant blip on the radar to explosive death within seconds, far too quickly to stop.
A Russian bomber fired a trio of Kinzhal Mach-12 hypersonic missiles at the port city of Odessa in May, a raid which followed launches in April and March, the first known use of the weapon, and the first claimed use of hypersonic arms in a war.
China last year reportedly test-fired a hypersonic projectile around the globe, while in May a Russian warship successfully fired a Zircon cruise missile that can travel for almost 1,000 miles.
Typical missiles fly at about Mach 3. Hypersonics are defined as travelling at at least Mach 5, about 3,800mph, or five times the speed of sound.
The leap in technology to hypersonics is similar in scale to the introduction of the air-to-air missile, according to Wes Kremer, president of US arms maker Raytheon Missiles & Defense, a weapon which only became a staple during the Vietnam war and revolutionised air-to-air combat.
And in both launching its own hypersonics and protecting its forces from a hit, the West is falling behind.
“What you saw in Ukraine, reported in the press, was the first operational use of a hypersonic weapon in Ukraine," says Steve Wadey, chief executive of the arms maker QinetiQ.
"I think the technology to deal with that is certainly available in the next decade or so."
As well as being incredibly fast, hypersonic missiles have an unpredictable flight path, making them hard to track.
They come in two versions, a powered variant which uses a particularly fast type of engine called a scramjet, or a projectile launched far above the earth which then bounces off the atmosphere to reach its target.
Qinetiq is attempting to use a laser weapon, dubbed “dragonfire” to shoot down the missiles.
The development is a “growing and important area” for the UK, US and Australia, Wadey says.
The high speed at which hypersonic weapons fly brings advantages and disadvantages. The faster they are, the harder they are to stop but the more difficult they become to control, making it a challenge to strike moving targets.
Managing the heat produced is also difficult, says Simon Prince, an expert in hypersonic aerodynamics at Cranfield University, which specialises in aerospace research.
“They are better at hitting big, slow targets, which make buildings and aircraft carriers vulnerable,” he says.
“It may mean operating capital ships always in fleets with outriding warships detecting potential threats, and permanent airborne early warning.”
In terms of defending against them, lasers of the type being developed by Qinetiq offer some promise.
“Increased speed means reduced reaction time," says Prince.
"So if you can press a button and you've got a beam rather than having to fire something that often takes seconds to get there, you can see the clear benefit.”
There are broadly three ways of destroying hypersonics, Kremer says.
They can be hit directly, which is the hardest method because of the speed of the missile; they can be hit by a missile with a blast radius, which is messier because shrapnel and debris brings the danger of more destruction; or energy weapons can be used. These can theoretically work by turning the missile into a large antenna and corrupting the electronics inside.
“If you can get to the right amount of power at the right frequency, you're going to have an effect on anything that has electronics,” said Mr Kremer.
To develop a good defence against these weapons, a system must monitor a much larger area to detect and intercept them, he adds. This probably means watching missiles from space using large constellations of satellites.
Europe’s early warning infrastructure may be enough to react to a strike on the UK mainland, Prince says.
“If you've got the space, if something was headed towards us in the United Kingdom, and you've got the whole of Europe to detect it, then we could probably take it out,” he adds.
But naval ships in the ocean will not have that advantage.
While Britain is behind in developing these weapons, he says that it has the capability to be a leader in them if it chooses.
“What we identified when we studied this, is that the UK is as strong as anybody else in the world, if not leading in terms of theoretical and computational hypersonic aerodynamics," Prince says.
"Using computers to solve the relevant equations, we've got world experts in that area, that's no problem. What we lack is enough experimental expertise."
UK universities have a few suitable wind tunnels to study the science of hypersonic flows, but not of the size needed for weapons development, which must be considerably bigger to allow testing of representative complex scale models, he adds.
“A few years ago, it became clear that Russia and China were actually working on these things when we weren't,” Prince says. “The UK - but also the US as well - is behind the curve, in many respects”.
The end of the Cold War led to severe cutbacks in the defence industry, and universities suffered too. This spending drop continued into the 2010s and is only now being reversed in academia where the science itself is worked out.
A shortfall of money has not yet been properly addressed at the industrial scale to allow independent UK product development and testing, Prince adds.
“We are starting to rebuild that capability very slowly," he says.
"What we've lost is a larger scale activity where we actually do actual development of real programmes.
"This is a general problem across all of aerospace, but hypersonics is an area which is probably at the extreme end of this neglect."
A change is likely to be needed soon, or the British Navy is in danger of becoming a sitting duck.