The findings about the North’s difficulties with a re-entry vehicle came from Michael Elleman, a missile expert at the International Institute for Strategic Studies in London. He said the malfunction of the warhead as it re-entered the earth’s atmosphere “casts doubt” on the North’s ability to shield a nuclear warhead from the blistering heat and vibrations as it heads to its target at the high speeds that intercontinental ballistic missiles typically achieve.
In a news conference on Monday, Mr. Elleman said North Korea would have to conduct a minimum of two or three more ICBM test flights to make sure its rocket designers have fixed the warhead problem. Still, he said, the nation will probably be able to develop a workable missile with a reliable warhead by early next year. That would put the country within the rough time period described in recent American intelligence analyses, which predicted that sometime in 2018 all the technologies needed by the North were likely to come together in a single weapon.
Fixing the design flaw “might take them another six months,” Mr. Elleman told reporters on a conference call organized by 38 North, a research institute at the Johns Hopkins University School of Advanced International Studies. “But the key is that they’ll have to do additional flight tests.”
The need for more tests creates an opening for the Trump administration.
Under President Barack Obama, North Korean missile tests were regularly subject to cyber and electronic attacks. Among its military options, the Trump administration could accelerate those attacks, but they appeared less effective over the past six months.
The United States could also position more naval craft in international waters off the North Korean coast. That would give it the option of conducting pre-emptive attacks on missiles on their launchpads — a risky approach because it could incite a war — or trying to shoot down test missiles as they are rising through the atmosphere.
The videotape of the warhead’s breakup came from the Japanese television station NHK. An affiliate in Muroran City, a port in Hokkaido, Japan’s northernmost large island, keeps a weather camera mounted on a roof. On Friday, in a stroke of luck, the camera was trained on the area of the sky where the mock warhead appeared to plunge back to earth, about 125 miles from the Japanese coast.
The incoming mock warhead, Mr. Elleman said, should have shone brightly and continuously as it…