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.



Harris Tries to Thread the Needle on Gaza After Meeting with Netanyahu 

US Vice President Kamala Harris meets with Israeli Prime Minister Benjamin Netanyahu at the Eisenhower Executive Office Building on the White House grounds, in Washington, DC, US, July 25, 2024. (Reuters)
US Vice President Kamala Harris meets with Israeli Prime Minister Benjamin Netanyahu at the Eisenhower Executive Office Building on the White House grounds, in Washington, DC, US, July 25, 2024. (Reuters)
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Harris Tries to Thread the Needle on Gaza After Meeting with Netanyahu 

US Vice President Kamala Harris meets with Israeli Prime Minister Benjamin Netanyahu at the Eisenhower Executive Office Building on the White House grounds, in Washington, DC, US, July 25, 2024. (Reuters)
US Vice President Kamala Harris meets with Israeli Prime Minister Benjamin Netanyahu at the Eisenhower Executive Office Building on the White House grounds, in Washington, DC, US, July 25, 2024. (Reuters)

Vice President Kamala Harris, the likely Democratic nominee for president, is attempting to bridge divides within the party over the war in Gaza, emphasizing Israel's right to defend itself while also focusing on alleviating Palestinian suffering.

She delivered remarks after meeting with Israeli Prime Minister Benjamin Netanyahu on Thursday that reflected a delicate balancing act on one of the country's most divisive political issues. Some Democrats have been critical of President Joe Biden's steadfast support for Israel despite the increasing death toll among Palestinians, and Harris is trying to unite her party for the election battle with Republican candidate Donald Trump.

"We cannot look away in the face of these tragedies," she said. "We cannot allow ourselves to become numb to the suffering. And I will not be silent."

Harris did not deviate from the administration's approach to the conflict, including grueling negotiations aimed at ending the fighting, releasing hostages held by Hamas and eventually rebuilding Gaza. She also said nothing about military assistance for Israel, which some Democrats want to cut.

Instead, she tried to refocus the conversation around mitigating the calamity in Gaza, and she used language intended to nudge Americans toward an elusive middle ground.

"The war in Gaza is not a binary issue," she said. "But too often, the conversation is binary when the reality is anything but."

In addition, Harris made a more explicit appeal to voters who have been frustrated by the ceaseless bloodshed, which began when Hamas attacked Israel on Oct. 7.

"To everyone who has been calling for a ceasefire, and to everyone who yearns for peace, I see you, and I hear you," she said.

Harris' meeting with Netanyahu was private, and she described it as "frank and constructive." She also emphasized her longtime support for Israel, which includes raising money to plant trees in the country when she was a young girl.

Jewish Americans traditionally lean Democratic, but Republicans have tried to make inroads. Trump claimed this week that Harris "is totally against the Jewish people" because she didn't attend Netanyahu's address to a joint meeting of Congress. The vice president was traveling in Indiana during the speech.

Harris is married to a Jewish man, Doug Emhoff, who has played an outspoken role in the administration's efforts to combat antisemitism.

Netanyahu did not speak publicly after his meeting with Harris. His trip was scheduled before Biden dropped his reelection bid, but the meeting with Harris was watched closely for clues to her views on Israel.

"She is in a tricky situation and walking a tightrope where she’s still the vice president and the president really is the one who leads on the foreign policy agenda," said Dearborn Mayor Abdullah Hammoud, a Democrat whose city is home to one of the largest Arab American communities in the nation. "But as the candidate, the presumptive nominee, she has to now create the space to differentiate in order for her to chart a new course."

Protesters gathered outside Union Station on the day of Netanyahu's speech, ripping down American flags and spray painting "Hamas is coming."

Harris sharply criticized those actions, saying there were "despicable acts by unpatriotic protesters and dangerous hate-fueled rhetoric. "

"I support the right to peacefully protest, but let’s be clear: Antisemitism, hate and violence of any kind have no place in our nation," she said in a statement.

As vice president, Harris has tried to show little daylight between herself and Biden. But David Rothkopf, a foreign policy writer who has met with her, said there's been "a noticeable difference in tone, particularly in regards to concern for the plight of innocent Palestinians."

The difference was on display in Selma, Alabama, in March, when Harris commemorated the anniversary of the Bloody Sunday march for voting rights in 1965.

During her speech, Harris said that "given the immense scale of suffering in Gaza, there must be an immediate ceasefire."

The audience broke out in applause. A few sentences later, Harris emphasized that it was up to Hamas to accept the deal that had been offered. But her demand for a ceasefire still resonated in ways that Biden's comments had not.

An AP-NORC poll conducted in June found that about 6 in 10 Democrats disapproved of the way Biden is handling the conflict between the Israelis and the Palestinians. Roughly the same number said Israel's military response in Gaza had gone too far.

Israeli analysts said they doubted that Harris would present a dramatic shift in policies toward their country.

Chuck Freilich, a former Israeli deputy national security adviser and senior fellow at the Institute for National Security Studies, a Tel Aviv think tank, said Harris was from a generation of American politicians who felt they could both support Israel and publicly criticize its policies.

"The question is as president, what would she do?" Freilich said. "I think she would put considerably more pressure on Israel on the Palestinian issue overall."