China DENIES claims it test-fired new hypersonic missile capable of carrying ...

Intelligence sources say Beijing has tested a nuclear-capable hypersonic warhead that flew around the planet in low-Earth orbit before coming back down.

If confirmed - Beijing denies it, saying it actually tested a civilian spacecraft - then it marks a major jump in the country's nuclear programme, though the technology itself is nothing new.

The core concept of China's 'new' weapon - deliver a warhead into orbit and have it circle the globe before hitting a target - was first developed by the Soviets in the 1960s.

Called a Fractional Orbital Bombardment System, or FOBS, it was developed to evade powerful US radar arrays and missile defence systems.

Those systems work by detecting launches of ICBMs - very long-range missiles that can be tipped with nukes - and tracking them into space, then firing at the warheads as they come down in the hope of blowing them up before they hit their targets.

This is possible because ICBMs and their warheads follow a predictable trajectory that rises high into space - making them relatively easy to spot and allowing defence crews to calculate where they are aimed so they can be shot out of the sky. 

FOBS aim to negate these defences by firing their warheads along a much-flatter trajectory - assisted by Earth's gravity. 

This means they pass under the scope of many radar detection arrays and are harder to track. It also makes the warheads much harder to shoot down because their trajectory is harder to calculate.  

The use of orbit makes a warhead's range potentially unlimited, meaning it can be fired at its target from any direction. This helps to avoid radar systems which generally point at a fixed spot in the sky - in America's case, over the North Pole.

Soviet Russia had a FOBS system - comprising, at its peak, of 18 R-36O missiles - which were active from 1969 until 1983 when it scuttled the programme in response to changes in America's missile defence systems.

China now appears to be pursuing the technology anew, while coupling it with a new 'hypersonic glide vehicle' to carry the warheads.

The 'HGV' is thought to make the warhead easier to manouevre while in orbit and increase its accuracy. Despite its 'hypersonic' name, it actually travels much slower than ICMB warheads - some 3,800mph compared to 15,000mph+ for 'traditional' nukes.

Russia and the US are both developing HGVs of their own, though neither has put them to use in the same way as Beijing. 

Moscow has one that can be fitted to its latest Satan 2 ICBM, while the US is working on one that can be launched from a B-52 bomber - though two recent tests of the system have failed.