Explanation-What are solid-fuel missiles and why is North Korea developing them?

By Hyonhee Shin

SEOUL (Reuters) – North Korea’s Hwasong-18 intercontinental ballistic missile (ICBM), launched for the second time on Wednesday, uses solid fuel technology, allowing it to launch with little preparation.

Here are some features of solid fuel technology and how it can help the North improve its missile systems.


Solid propellants are a mixture of fuel and oxidizer. Metal powders such as aluminum are often used as fuel, and ammonium perchlorate, which is the salt of perchloric acid and ammonia, is the most common oxidizer.

The fuel and oxidizer are bound by a hard rubbery material and packed in a metal case.

As the solid propellant burns, the oxygen in the ammonium perchlorate combines with the aluminum to generate tremendous amounts of energy and temperatures of over 5,000 degrees Fahrenheit (2,760 degrees Celsius), creating thrust and lifting the missile from the launch pad.


Solid fuel dates back to fireworks developed by the Chinese centuries ago, but made dramatic progress in the mid-20th century when the United States developed more powerful propellants.

North Korea uses solid fuel in a range of smaller, shorter-range ballistic missiles.

The Soviet Union fielded its first solid-fuel ICBM, the RT-2, in the early 1970s, followed by France’s development of its S3, also known as SSBS, a medium-range ballistic missile. scope.

China began testing solid-fuel ICBMs in the late 1990s.

South Korea also said it had achieved “efficient and advanced” solid propellant ballistic missile technology, but in much smaller rockets so far.


Liquid propellants provide greater thrust and propulsive power, but require more complex technology and additional weight.

Solid fuel is dense and burns quite quickly, generating thrust over a short period of time. Solid fuel can remain stored for an extended period without degrading or breaking down – a common problem with liquid fuel.

Vann Van Diepen, a former US government weapons expert who now works with Project 38 North, said solid-fuel missiles are easier and safer to use and require less logistical support, which makes them more difficult to detect and more resistant than liquid fuel weapons. .

Ankit Panda, a senior fellow at the US-based Carnegie Endowment for International Peace, said any country that operates large-scale missile-based nuclear forces would seek out solid-propellant missiles, which don’t need be fed immediately before launch.

“These capabilities are much more responsive in times of crisis,” Panda said.

North Korea has said the development of its new solid-fuel ICBM, the Hwasong-18, will “radically boost” its nuclear counterattack capability.

After the first launch, South Korea’s Defense Ministry sought to downplay testing, saying the North would need “more time and effort” to master the technology. On Thursday, a ministry spokesperson said they were still analyzing the latest launch.

(Additional reporting by Josh Smith; Editing by Lincoln Feast.)

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