What are Solid-fuel Missiles, and Why is North Korea Developing Them?

Hwasong-18 intercontinental ballistic missile is launched from an undisclosed location in North Korea in this image released by North Korea's Korean Central News Agency on July 13, 2023. KCNA via REUTERS
Hwasong-18 intercontinental ballistic missile is launched from an undisclosed location in North Korea in this image released by North Korea's Korean Central News Agency on July 13, 2023. KCNA via REUTERS
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What are Solid-fuel Missiles, and Why is North Korea Developing Them?

Hwasong-18 intercontinental ballistic missile is launched from an undisclosed location in North Korea in this image released by North Korea's Korean Central News Agency on July 13, 2023. KCNA via REUTERS
Hwasong-18 intercontinental ballistic missile is launched from an undisclosed location in North Korea in this image released by North Korea's Korean Central News Agency on July 13, 2023. KCNA via REUTERS

North Korea launched a suspected intermediate-range ballistic missile (IRBM) on Tuesday, in what South Korean officials said could be related to its development of a new solid-fuel hypersonic weapon.
The launch comes after North Korean leader Kim Jong Un oversaw a ground test of a solid-fuel engine for a new type of intermediate-range hypersonic missile to develop national defense capability, state media reported in March.
In January, North Korea test fired an IRBM that it said was equipped with a hypersonic maneuverable controlled warhead. State media did not immediately disclose details of Tuesday's launch.
Here are some characteristics of solid-fuel technology, and how it can help the nuclear-armed North improve its missile systems.
WHAT ARE SOME ADVANTAGES OF SOLID FUEL?
Solid-fuel missiles do not need to be fueled immediately ahead of launch, are often easier and safer to operate, and require less logistical support, making them harder to detect and more survivable than liquid-fuel weapons, reported Reuters.
"These capabilities are much more responsive in a time of crisis," said Ankit Panda, a senior fellow at the US-based Carnegie Endowment for International Peace.
WHAT IS SOLID-FUEL TECHNOLOGY?
Solid propellants are a mixture of fuel and oxidizer. Metallic powders such as aluminum often serve as the fuel, and ammonium perchlorate, which is the salt of perchloric acid and ammonia, is the most common oxidizer.
The fuel and oxidizer are bound together by a hard rubbery material and packed into a metal casing.
When solid propellant burns, oxygen from the ammonium perchlorate combines with aluminum to generate enormous amounts of energy and temperatures of more than 5,000 degrees Fahrenheit (2,760 degrees Celsius), creating thrust and lifting the missile from the launch pad.
WHO HAS THAT TECHNOLOGY?
Solid fuel dates back to fireworks developed by the Chinese centuries ago, but made dramatic progress in the mid-20th century, when the US developed more powerful propellants.
North Korea uses solid fuel in a range of small, shorter-range ballistic missiles, as well as in its new Hwasong-18 intercontinental ballistic missile (ICBM).
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.
China started testing solid-fuel ICBMs in the late 1990s.
South Korea has also said it has secured "efficient and advanced" solid-propellant ballistic missile technology, though in much smaller rockets so far.
SOLID VS LIQUID
Liquid propellants provide greater propulsive thrust and power, but require more complex technology and extra weight.
Solid fuel is dense and burns quite quickly, generating thrust over a short time. Solid fuel can remain in storage for an extended period without degrading or breaking down - a common issue with liquid fuel.
North Korea said the development of its solid-fuel ICBM, the Hwasong-18, would "radically promote" its nuclear counterattack capability.
After the first launch South Korea's defense ministry sought to downplay the testing, saying the North would need "extra time and effort" to master the technology.



Syria's Aviation Comeback Struggles amid Regional Turmoil

An airport worker walks on the tarmac next to a Syrian Air plane at the Damascus International Airport on January 7, 2025. (Photo by LOUAI BESHARA / AFP)
An airport worker walks on the tarmac next to a Syrian Air plane at the Damascus International Airport on January 7, 2025. (Photo by LOUAI BESHARA / AFP)
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Syria's Aviation Comeback Struggles amid Regional Turmoil

An airport worker walks on the tarmac next to a Syrian Air plane at the Damascus International Airport on January 7, 2025. (Photo by LOUAI BESHARA / AFP)
An airport worker walks on the tarmac next to a Syrian Air plane at the Damascus International Airport on January 7, 2025. (Photo by LOUAI BESHARA / AFP)

Poor infrastructure, regional conflict and sporadic Israeli airstrikes are holding back more airlines from returning to Syria, industry officials told Reuters, hampering efforts to rebuild a shattered economy after 14 years of civil war.

This month, at least 11 foreign airlines are scheduled to fly into Syria, up from just three a year ago, as sanctions are scaled back following the overthrow of long-time leader Bashar al-Assad in December 2024.

These include the world's largest international carrier, Dubai's Emirates, and the first two European Union-based airlines to fly into Syria since 2011: Romania's Dan Air and Greece's Air Mediterranean, Reuters said.

But airlines such as Royal Jordanian, FlyDubai, Turkish Airlines and Qatar Airways last month were forced to cancel many of their recently launched flights as airspace across the Middle East closed to civil air traffic due to air and missile attacks involving Israel, the US and Iran.

There are dangers closer to home too. Israel carried out strikes against Syrian government forces in southwestern Syria for a second day on Tuesday, vowing to keep the area demilitarized and to protect the Druze minority there.

At the same time, airlines are worried about the state of Syria's aviation infrastructure and management of the industry.

"Progress is needed in regulatory oversight, infrastructure investment, and compliance with international safety and operational standards," industry body the International Air Transport Association said.

Major carriers such as Lufthansa and Air France KLM, which used to fly to Syria pre-war, have visited Damascus airport to assess the infrastructure and former offices, officials at Damascus airport and Syria's aviation regulator told Reuters.

However, both airlines told Reuters they had no current interest in resuming flights.

Small Romanian airline Dan Air launched its Bucharest to Damascus route last month.

"What held back operators until now were the logistical and regulatory complexities," Dan Air CEO Matt Ian David told Reuters, adding that eased sanctions would now make Syria more accessible.

Emirates at the end of May resumed flying over Syria for the first time since the civil war, shaving up to an hour off a Dubai to Beirut flight.

However, several countries, including Britain and the United States, still advise their airlines to avoid flying over Syria. Europe's aviation regulator EASA says "there is a risk of both intentional targeting and misidentification of civil aircraft".

Syria completely reopened its airspace on June 24, its civil air authority said.

Damascus Airport's two runways were bombed during the civil war, but have been repaired. The airport was also looted during the chaos of Assad's fall.

Alaa Sallal, director of public relations at Syria's Civil Aviation Authority, told Reuters a number of airlines had been to inspect security and infrastructure at the airport.

"The airport's construction was dilapidated, the equipment was worn out and some missing," Sallal said.

Radar equipment was lacking, leaving the country reliant on Lebanese or Turkish radar to monitor air traffic, he said.

The head of Syria's General Authority for Civil Aviation earlier this month said it wanted to build new airports in Damascus, Aleppo and in the country's central region. But that will take time and money that the war-ravaged country may struggle to find on its own.

NEW AIRLINES

The mostly Iranian and Iraqi carriers that served Syria through its long conflict have largely stopped flying there, reflecting a new political landscape after Iran- and Russia-backed Assad's overthrow.

The flag carriers of Qatar and Türkiye, countries that backed Syria's rebels through the war, were the first big airlines to resume flights in January under President Ahmed al-Sharaa's new leadership.

Türkiye, a close ally of the new government, has been helping improve Syria's airports, its transport ministry has said.