A highly volatile fuel known to the Russians as the "Devil's Venom" has been powering the success of North Korea's missile program, analysts say—and it may be too late to cut off its supply. Intelligence memos from as far back as the George W. Bush administration warn that unsymmetrical dimethyl hydrazine, or UMDH, could allow North Korean missiles to reach the US, but there was no serious effort to cut off the supply from China or Russia and officials believe the country can now produce the fuel itself, the New York Times reports. Russia has tried to avoid the potent fuel since a 1960 explosion killed more than 100 people in the worst-ever space-related disaster, and NASA switched to safer propellants decades ago.
The rare fuel—which is made from chemicals, not oil—has caused other disasters and Vann H. Van Diepen, a former State Department official who long worked to prevent the spread of weapons of mass destruction, tells the Times that Pyongyang probably dealt with a few catastrophes in the process of learning to make UMDH over the last 25 years. "My guess is that the North Korean tolerance for casualties is probably pretty high," he says. The fuel and its ingredients are not included in the sanctions whose effect President Trump boasted about on Sunday. In a tweet, he called Kim Jong Un "Rocket Man" and spoke of "long gas lines forming in North Korea." (Kim says his country is nearing military "equilibrium" with the US.)