A close review of photos from North Korea’s recent military parade revealed that the Kim regime may be closer to building a functional nuclear missile that can threaten the US mainland than previously thought.

While some experts doubt that all the missile launcher tubes driving around Pyongyang really held missiles, or really posed a much of a threat, Michael Duitsman, a research associate at the Center for Nonproliferation Studies spotted a small but troubling detail on one of the missiles.

Look at the picture below. On the right side of the missile, where the cylindrical section meets the nose, the fuselage appears to have been wrapped.

Here’s a closer look:

Duitsman told Business Insider in a phone interview that this may be wound filament reinforced plastic, a very light alternative to metal that can withstand the incredible heat of rocket motors.

“Part of the parade is them showing us what they’re working on,” said Duitsman. “Not stuff that’s operational, but stuff they’re actively working on. They’re showing us their intentions.”

Duitsman said that wound filament reinforced plastic has ten times the strength to density ration of aluminium, and could greatly reduce the weight of a missile.

“The lighter the stage is,” said Duitsman, referring to the booster portion of the missile as a stage, “the less propellant you need, and the more you can put on top of it.” In this case, the lighter missile could be used to carry a nuclear warhead.

While it seems like a small detail, Duitsman said that the Soviets and the US made similar breakthroughs when creating their ICBMs. Ultimately, if the North Koreans have advanced to composite materials and plastics in this part of their missile design, it means they’re further along in their program than many experts suspected.

Though the North Koreans would still face problems in how to launch the missile and how to steer it, Duitsman said they could begin testing an ICBM that could reach Washington in as little as two or three years.

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