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Hwasong 8 hypersonic glide warhead

North Korea put up a massive military show the night of 27 July 2023 as it paraded its high-tech weapons including nuclear-capable intercontinental missiles, tactical weapons, and modern assault drones. The Victory Day parade, attended by the country’s leader Kim Jong Un and Russian Defence Minister Sergei Shoigu and Chinese Communist Party Politburo member Li Hongzhong in Pyongyang, celebrated the end of the Korean War, remembering it as a Victory Day for its forces on its 70th anniversary. The parade included North Korea's latest Hwasong-8 hypersonic glide weapon. Russia's defence minister also accompanied Kim Jong Un to the “Weapons and Equipment Exhibition 2023” held at Pyongyang’s Three Revolutions Exhibition House on 27 July 2023, with glimpses of the Hwasong 8 in images released by North Korea's Korean Central News Agency.

A North Korean newspaper reported the country test-fired a newly developed hypersonic missile on the morning of 28 September 2021. The ruling Workers' Party newspaper Rodong Sinmun reported the launch of "Hwasong-8." It showed an image of a missile ascending while trailing orange flames.

There was no indication that leader Kim Jong Un was on the site. In January 2021, Kim said they "finished research into developing warheads of different combat missions including the hypersonic gliding flight warheads for new-type ballistic rockets and was making preparations for their test manufacture."

The missile, called Hwasong-8, performed to its technical specifications "including the guiding maneuverability and the gliding flight characteristics of the detached hypersonic gliding warhead," state media KCNA reported. The development of the weapon system increases North Korea's defence capabilities, state media KCNA said on 29 September 2021. "In the first test-launch, national defence scientists confirmed the navigational control and stability of the missile in the active section," the report said. It said the missile, called Hwasong-8, performed to its technical specifications "including the guiding maneuverability and the gliding flight characteristics of the detached hypersonic gliding warhead."

Hypersonic missiles are more nimble than ordinary ones, making them harder for missile defence systems –– on which the US is spending billions –– to intercept. Sources had raised the possibility that it could be a part of initial tests of its hypersonic missiles specifically the hypersonic glide vehicle or HGV in which the flight vehicle of the missile's warhead separates at the missile's maximum altitude and heads downward in a glide maneuver.

Hypersonic missiles are offensive weapons that fly faster than five times the speed of sound and spend most of their flight in the Earth’s atmosphere. Those missiles are intended to be maneuverable and capable of striking targets quickly (in roughly 15 minutes to 30 minutes) from thousands of kilometers away. Both hypersonic missiles and ballistic missiles equipped with maneuverable warheads could provide the combination of speed, accuracy, range, and survivability (the ability to reach a target without being intercepted) would be useful in a variety military scenarios.

Longer ranges and higher speeds are the main attributes that distinguish the hypersonic weapons from other strike weapons. Long range and high speed are nearly always desirable characteristics for a strike weapon, but they can be expensive.

Over short to intermediate ranges, hypersonic boost-glide missiles might be slightly faster than ballistic missiles of the same range that were flying on a minimum-energy trajectory (a flight path that maximizes the range of a ballistic missile). But hypersonic boost-glide missiles would be no faster than ballistic missiles flying on a lower, or depressed, trajectory (which would require a little more power to achieve the same maximum range as a ballistic missile flying on a minimum-energy trajectory).

Intermediate-range ballistic missiles equipped with maneuverable reentry vehicles would have the same, if not longer, range than the hypersonic boost-glide weapons. The reason is that a MaRV is likely to be lighter than a hypersonic glide body.

Hypersonic missiles can neutralize long-range (midcourse) defenses because they fly inside the atmosphere, below the altitude where midcourse ballistic missile defenses typically operate. Hypersonic weapons can also maneuver unpredictably at high speeds to counter short-range defenses near a target, making it harder to track and intercept them.

Hypersonic weapons would provide a niche capability, mainly useful to address threats that were both well-defended and extremely time-sensitive (requiring a strike in 15 minutes to 30 minutes). If time was not a concern, much cheaper cruise missiles could be used. If targets were time-sensitive but were not protected by defenses that effectively intercept incoming ballistic missiles in the middle of their flight, less costly ballistic missiles with maneuverable warheads could be used.

Hypersonic flight is flight through the atmosphere below about 90 km at speeds of about Mach 5 or higher, causing very high aerodynamic heating. The severe thermal environment to which vehicles are subjected during hypersonic flight pose significant technical challenges. Hypersonic glide vehicles are launched to a high altitude on a rocket or other boost vehicle and then glide to their destinations at hypersonic speeds. Hypersonic glide vehicles have been studied since the 1930s, and extensively studied beginning in the mid-1940s. By the 1950's, balancing range and speed, hypersonic glide vehicles had emerged as the best choice over competing skip, skip-glide and ballistic trajectories for unpowered flight from above or near above the atmosphere.

Hypersonic glide vehicles are launched to a high altitude on a rocket or other boost vehicle and then glide to their destinations at hypersonic speeds. Hypersonic glide vehicles have been studied since the 1930s, and extensively studied beginning in the mid-1940s. By the 1950's, balancing range and speed, hypersonic glide vehicles had emerged as the best choice over competing skip, skip-glide and ballistic trajectories for unpowered flight from above or near above the atmosphere.

A particular factor in making those determinations was heat from aerodynamic heating, primarily the heat from atmospheric friction. For example, while skip trajectories may be more efficient in converting the kinetic energy of such vehicles into range, the increased heat and other aerodynamic loads required to achieve those efficiencies are greater than most modern materials can handle.

While skip trajectories may be more efficient in converting the kinetic energy of such vehicles into range, the increased heat and other aerodynamic loads required to achieve those efficiencies are greater than most modern materials can handle. Heat load primarily comprises instantaneous heat loading, the maximum rate of heating at any time during an entire glide trajectory and, often more importantly, the total heat load, or integrated heat load, over an entire glide trajectory.

Hypersonic glide vehicles can achieve their significant efficiencies within the limits of modern materials, but not without large amounts of heat shielding, significantly reducing available space and weight carrying capacity, and often not without additional mechanically complex heat removing systems.

A particular factor in making those determinations was heat from aerodynamic heating, primarily the heat from atmospheric friction. For example, while skip trajectories may be more efficient in converting the kinetic energy of such vehicles into range, the increased heat and other aerodynamic loads required to achieve those efficiencies are greater than most modern materials can handle. Heat load primarily comprises instantaneous heat loading, the maximum rate of heating at any time during an entire glide trajectory and, often more importantly, the total heat load, or integrated heat load, over an entire glide trajectory.

Hypersonic vehicle performance (lift-to-drag ratio) is currently limited by the temperature stability of the leading edge. Improving the range, speed, altitude (lower), and/or maneuverability of a hypersonic vehicle increases heat flux transferred to the leading edge. Thermal management systems can be grouped into active and passive systems. An actively cooled system is one that requires pumped coolant to absorb and remove heat. While necessitating either additional material or energy from the vehicle, actively cooled systems are useful for higher heat fluxes or longer operation times. Examples of active systems include convective cooling, film cooling, and transpiration cooling. Passive systems may involve a phase change but can function without additional energy or mass transfer from the vehicle for operation. Examples of passive systems include an insulated structure, a heat sink, a hot structure, an ablative structure, and a heat pipe.

Hypersonic glide vehicles can achieve their significant efficiencies within the limits of modern materials, but not without large amounts of heat shielding, significantly reducing available passenger and cargo space and weight carrying capacity, and often not without additional mechanically complex heat removing systems.

The balance between speed and range can, of course, be adjusted by periodically trading speed for altitude by alternatively increasing and decreasing angle of attack. Increasing altitude helps preserve range, but also increases drag (and resulting integrated heat load) and time to destination. Trading speed for altitude can occur naturally by so-called phugoid motion. A phugoid, pronounced “f{hacek over (e)}w-goed,” motion is an oscillating aircraft motion where the aircraft pitches up and climbs, and then pitches down and descends, accompanied by speeding up and slowing down as it goes “uphill” and “downhill.” Phugoid motion alternately trades kinetic for potential energy and back again. Phugoid motion is generally something sought to be avoided, or at least reduced.

The South Korean Ministry of National Defense said in a state audit document submitted to the National Defense Commission, regarding North Korea's test-fire of the Hwasong-8 last month, "Our military has been continuously tracking the possibility of North Korea's development and test launch of a hypersonic missile." "On the 28th of last month, "The flight trajectory was detected with the ROK-U.S. joint assets during the missile launch," he said. The Ministry of National Defense explained, “The flight trajectory detected at that time (Hwasong-8) differs from existing missiles in many ways, and unique characteristics are detected, so it is evaluated as a high possibility of a ‘hypersonic missile’.” However, the 'Hwasong-8', which North Korea test-fired last month, was detected to have recorded a speed of around Mach 3 (three times the speed of sound, about 3700 km per hour), and the South Korean military authorities consider it to be in an "early stage of development".

The late September launch was apparently not of the North's modified version of Iskander-class ballistic missiles, two of which had been launched earlier in the month with boost-glide terminal trajectories. Since there was only one missile fired, it's likely to be a new type of weapon. It's presumed to be the initial test phase of the HGV since North Korea had mentioned its development during the ruling Workers' Party Congress in January and since the missile had the characteristics of both ballistic and cruise missiles. The vernier engines appartent in the single released photo of the test suggest the booster was based on the Hwasong-14 KN-20 vehicle, earlier versions of which had been identified as KN-08 / Hwasong-13 and KN-14.

The South Korean military did not specify if the projectile is a ballistic missile and it did not initially release such details as the flight range and altitude. South Korea's Joint Chiefs of Staff said North Korea is presumed to have fired one short-range missile from its inland Jagang-do , Mupyong-ri area in an easterly direction at 6:40AM local time on 28 September 2021. This area is where the North test-fired inter-continental ballistic missiles in 2017. "The ministry is monitoring the situation as well as the motive behind North Korea's missile launch. The launch is regrettable since it was carried out during times when security stability on the Korean Peninsula is critical."

The U.S. Department of State condemned North Korea's launch of the short-range missile while urging Pyongyang to engage in dialogue. The State Department released a statement on Monday, saying the North Korean missile launch is in violation of multiple UN Security Council resolutions, which poses a threat to neighboring nations and the international community. The statement added that Washington remains committed to a diplomatic approach and called on Pyongyang to come back to the negotiating table.

Washington's labeling of the latest missile test as a violation of UN resolutions is leading to speculations that North Korea may have fired a ballistic missile strictly banned by the UN.

The timing of the launch is critical. There are experts who say the latest missile launch was likely meant to test how South Korea would respond as North Korea needs Seoul to persuade Washington to ease economic sanctions and make other concessions.

The North's latest test, which followed two previous rounds of missile tests this month, indicated that the country is returning to its tried-and-true technique of mixing weapons demonstrations and peace offers to wrest concessions amid long-stalled negotiations over its nuclear weapons program.

The North is dangling the option of declaring an end to the Korean War as Seoul suggested. The first test is to see if the South Korean government refrains from criticizing the North Korean missile test. There are going to be second, third and fourth tests waiting which are going to be much more difficult for South Korea to pull through.

Pak Jong Chon, member of the Presidium of the Political Bureau and secretary of the Central Committee of the Workers' Party of Korea, watched the test-launch with leading officials in the sector of national defence science.

The development of the hypersonic missile, one of 5 top-priority tasks of the five-year plan facing the field of strategic weapon for the development of defence science and weapon system set forth at the 8th Congress of the Party, has been pushed forward according to a sequential, scientific and reliable development process.

The development of this weapon system which has been regarded as a top priority work under the special care of the Party's Central Committee is of great strategic significance in markedly boosting the independent power of ultra-modern defence science and technology of the country and in increasing the nation's capabilities for self-defence in every way.

In the first test-launch, national defence scientists confirmed the navigational control and stability of the missile in the active section and also its technical specifications including the guiding maneuverability and the gliding flight characteristics of the detached hypersonic gliding warhead. It also ascertained the stability of the engine as well as of missile fuel ampoule that has been introduced for the first time.

The test results proved that all the technical specifications met the design requirements. Pak Jong Chon mentioned the strategic importance of the development of the hypersonic missile and its deployment for action. He also noted the military significance of turning all missile fuel systems into ampoules.

Rocket ampulization is a set of constructive and technological measures to ensure the long-term maintenance of a rocket with a liquid-propellant jet engine (LRE) in full combat readiness. The constructive measures include: protection of the missile from the external environment in order to create conditions for maintaining the operability of the equipment and the missile as a whole by placing it in a sealed transport and launch container (TPK) for a strategic missile; complete sealing of fuel tanks and lines to exclude contact of propellant components with the external environment by using only welded joints; complete isolation from aggressive components and their vapors of engines and pneumohydraulic systems due to the use of membranes and a decrease in the number of units in the tanks; elimination of the influence of atmospheric factors on the rocket (temperature fluctuations, humidity, dust, etc.) by sealing the container and the shaft.

Technological measures include: reliable control of the tightness of welded joints; refueling the rocket with fuel components saturated with nitrogen to an equilibrium state, which ensures the maintenance of the required pressure in the tanks during the entire period of combat duty; monitoring the pressure in the fuel tanks and the presence of oxidizer and fuel vapors in the dry compartments of the rocket and in the container.

The first Soviet ampulized missile was the UR-100 missile, which was put into service in 1967. At present, all Russian strategic rockets with liquid propellant rocket engines are only ampulized. In addition, missile ampulization is divided into external and internal. External ampulization is carried out by placing a TPK with a rocket in a silo launcher, which ensures the maintenance of the required temperature and humidity regime during combat duty. Internal ampulization allows storing propellant components in sealed containers filled with dry nitrogen when the rocket is put on alert, and ensuring that the required pressure is maintained in the tanks and the physical and chemical properties of the propellant components are preserved during combat duty.

He stressed the need for all the defence science research teams and workers of the munitions industry to rise up with higher spirit to implement the decisions made at the 8th Party Congress true to the Party's policy of prioritizing defence science and technology and thus make greater successes in the work of increasing the country's defence capabilities thousand-fold.