WASHINGTON • As the Pentagon prepares today to conduct its first test in three years of the multibillion-dollar effort to intercept a North Korean warhead launched over the Pacific, Pyongyang has delivered a new challenge.
The North recently test-fired a series of missiles based on a technology that would give the United States little warning of an attack. The new generation of missiles uses solid fuels, enabling them to be launched in minutes. That makes intercepting them far more difficult, given that the US anti-missile system works best with early alerts from satellites.
Even more worrisome is that these missiles actually seem to be functional, unlike older ones that kept exploding or falling prematurely into the sea in past tests. Recent major tests were successful, teaching the North a lot about how to fire missiles into space and drop warheads on distant targets.
While the North has not yet flight-tested an intercontinental ballistic missile (ICBM) capable of crossing the Pacific, it has repeatedly claimed that it can strike the US with a nuclear warhead.
The test scheduled for today - an interceptor rocket set to lift off from the California coast - is of the more classic anti-missile defence and the first since US President Donald Trump took office, vowing to solve the North Korea problem. But he is discovering what former president Barack Obama had learnt: intercepting an ICBM over the Pacific is exquisitely difficult. Incoming warheads move extraordinarily fast - more than 6.4km a second.
In war, the interceptors in Alaska and California would race skyward and release speeding projectiles meant to obliterate incoming warheads by force of impact.
Estimated sum spent on effort to intercept ICBMs over the Pacific.
Failure rate of the US' interceptor system against mock warheads.
Huge amounts of cash have been spent on this challenge: more than US$330 billion (S$457 billion), estimates military analyst Stephen Schwartz at the Middlebury Institute of International Studies in Monterey, California.
The Defence Department hopes to spend billions more on the interceptors, including perhaps on a new site on the East Coast.
Since the system was moved into operational mode in 2004, it has had a failure rate of 56 per cent in tests against mock warheads. While the official tally is five misses in nine attempts, critics say a test in 2006 was only a partial success, since the interceptor only struck a glancing blow. They say the system would do worse in war as flight tests are highly scripted, noting also that no mock weapon has moved nearly as fast as a true enemy warhead.
While mock enemy missiles are always launched from Kwajalein, an atoll in the Pacific, North Korea uses large trucks to move around the ICBM it is developing, adding an element of surprise.
In the past, the North's reliance on liquid-fuelled missiles eased the targeting job for anti-missile interceptors. US military surveillance planes and satellites could track missile transporters and convoys of fuel trucks. The process of fuelling a missile takes several hours, making it vulnerable to a pre-emptive strike and giving the anti-missile systems on the West Coast time to lock in on expected trajectories.
With the new generation of weapons, the solid fuels are packed into the missile body at the factory, eliminating the need for fuelling in the field and cutting preparation time for an attack to minutes.
Defence Secretary Jim Mattis, however, argued that the US could not wait for North Korea to complete its testing programme before responding forcefully. "It is a direct threat to the United States," he said on a CBS programme on Sunday.
In all, the North has successfully tested solid-fuelled missiles four times - twice last year and twice this year. After a test on May 21, its leader Kim Jong Un declared the new medium-range missile ready to be mass produced and then deployed.
Mr John Schilling, an aerospace engineer and expert on North Korea's missile programme, predicted last year that the North might need five years or more to successfully deploy a solid-fuelled missile. Recently, he has updated his estimate, saying the North might start deployments this year.