LONDON, Oct 9: North Korea’s next challenge after testing a nuclear warhead is to make one small enough to fit to a missile — a tricky undertaking, experts say, but one that might not take long if it has the requisite know-how.

“They’ve got to get the weight down to about 500 to 700 kg, which I would have believed is perfectly possible with knowledge that is available today,” said Duncan Lennox, editor of Jane’s Strategic Weapons Systems.

“It would be about 1.5 metres tall, a cone, with a base diameter of 0.8 to one metre.”

Such a device could be delivered to its target by one or more missile types among North Korea’s extensive arsenal.

The Scud C, with a range of up to 500 km, would be a viable choice “if they wanted to be particularly nasty to South Korea”, Lennox said.

The Rodong, with a range of up to 1,400 km (870 miles), is capable of hitting all of South Korea and most of Japan.

Another choice would be the Taepodong-2, a type tested by North Korea in July which flew for about 40 seconds before it destructed. South Korea said the test was a failure, but some experts suggest the North may have aborted it deliberately after finding out the capability of the engine.

A nuclear bomb can also be dropped from a plane, but defence analysts assume that North Korea would prefer to fit it to a missile, which reaches its target faster and is harder to shoot down.

‘MATING’ PROCESS: However, the process of “mating” a nuclear warhead to a conventional missile is complex, said Lee Willett, defence analyst at the Royal United Services Institute in London.