China in a searing hypersonic material science lead

beijingwalker · Oct 26, 2023

China in a searing hypersonic material science lead

Chinese researchers develop new surface material allowing for better in-flight heat protection while US struggles mightily with the issue
By GABRIEL HONRADA
OCTOBER 26, 2023

Chinese researchers may have resolved the heat problem plaguing hypersonic flight. Image: Twitter

Chinese researchers have made a material science breakthrough that could change the trajectory, pace and stakes of China’s hypersonic weapons race with the United States.

This month, the South China Morning Post (SCMP) reported that Chinese researchers from the China Academy of Aerospace Aerodynamics in Beijing have successfully tested a new surface material for hypersonic vehicles, previously thought impossible to create.

Hypersonic weapons fly at speeds of up to Mach 5 and faster and perform evasive maneuvers to defeat missile defense systems. The researchers’ findings were published last month in the Physics of Gases journal.

The SCMP report says that the thin material was applied to the surface of a “waverider” aircraft, which uses shock waves generated by its flight to improve lift.

The report says that the air around the hypersonic aircraft was then heated to thousands of degrees Celsius, with the smooth, non-ablative surface not only keeping critical components inside the aircraft cool but also allowing wireless signals to transmit freely, making target identification and communication possible throughout the flight.

That’s a significant hypersonic-enabling development. The SCMP report notes that with traditional ballistic missiles, the warhead could reach hypervelocity before it is dropped onto a target.

At the same time, the report says space shuttles and re-entry capsules have added thermal tiles that can burn and absorb heat. However, the report points out that these hypersonic flights were short, usually lasting just a few minutes.

The hypersonic race has moved into a crucial new stage with enormous strategic challenges, threats and opportunities, not least to prevailing US deterrence and nuclear policies as China surges into the race’s lead.
The US has recently revived its hypersonic weapons program but reportedly still faces difficulties in dealing with the extreme heat that hypersonic missiles are subjected to during flight caused by high speeds in the atmosphere.

Flight testing is necessary to successfully shield the sensitive electronics of hypersonic missiles, understand how different materials perform at high speeds and predict aerodynamics at sustained temperatures of up to 1,650 Celsius.

SCMP notes that China has conducted more hypersonic test flights in a year than the US did in a decade. In 2021, the Chinese military flew a hypersonic vehicle around the globe, surprising the US military with technology reportedly “defying the laws of physics.”

Materials science advancements have had a significant impact on the development of hypersonic weapons technology. In a 2021 article for Johns Hopkins Technical Digest, David Van Wie notes that using materials for hypersonic weapons will include applications in aerodynamics, propulsion, high-temperature materials and structures, thermal protection systems, guidance, navigation and control.

A 2021 Deloitte report notes that materials for hypersonic airframes are primarily built of nickel-based alloys and ceramic-based composites, the latter of which has significant limitations.

In a June 2020 article for The Bridge, Kevin Bowcutt notes that nickel-based alloys are applicable for lower-end hypersonic vehicles, which are designs that travel between Mach 4 and 6.

Bowcutt says that while nickel-based alloys can withstand temperatures between 540 to 1,080 Celsius, they are on the heavy side for airframe applications and that ceramic and carbon-based composites are needed for speeds beyond Mach 6.

Robert Yancey notes in an article for Hexcel that ceramic fibers used in ceramic matrix composites (CMC) are expensive and brittle, meaning high production costs for material that can crack and peel off during hypersonic flight.

Yancey notes ongoing research on using carbon fiber for CMCs, stressing the need for carbon fiber supply chains that can produce large quantities of the material at a lower cost than ceramic fibers.

In a 2017 article for The American Society of Mechanical Engineers, Michael Abrams says that the molds for CMCs need simple geometry to prevent the components from cracking due to brittleness.

However, he points out that researchers from the University of Manchester have used liquid metals such as zirconium and titanium to permeate the CMC composite, resulting in a coating that can withstand the temperature stresses of hypersonic flight while not being brittle and can be cast in precise shapes with microscopic accuracy.

These breakthroughs in materials science could turn hypersonic weapons from mere theoretical or experimental assets into practical weapons. At the same time, designs that can withstand high temperatures for extended periods may introduce a new level of complexity and unpredictability for deterrence and missile defense.

These developments could allow China to match the US Conventional Prompt Strike (CPS) program, which aims to develop the ability to deliver a weapon that can hit any point on the globe within an hour.

In that direction, Joseph Trevithick mentions in an article for The Warzone this month that the People’s Liberation Army (PLA) may be developing and fielding a conventionally armed intercontinental ballistic missile (ICBM) that can strike targets across the continental US, Hawaii and Alaska without resorting to nuclear weapons.

Trevithick notes that a conventional ICBM may be the next step in developing the PLA Rocket Force (PLA-RF), whose conventional capabilities started 20 years ago with short-range ballistic missiles (SRBM) with ranges of 300 to 1,000 kilometers, then advanced to medium-range ballistic missiles (MRBM) with ranges of 1,000 to 3,500 kilometers and now fields long-range ballistic missiles (LRBM) with ranges of 3,500 to 5,500 kilometers.

He also mentions that as the PLA Air Force (PLA-AF) and PLA Navy (PLA-N) are still in the process of developing capabilities that can hit the continental US, the PLA-RF is now the main branch of service tasked with hitting time-sensitive US targets.

A conventionally armed hypersonic weapon would align with that objective, eliminating the predictable trajectory of ballistic missiles that allows their interception.

In a January 2021 article for the Georgetown Journal of International Affairs, Paul Bernstein and Dain Hancock mention that China is likely to field conventionally-armed hypersonic weapons with the range to hit critical US military assets, infrastructure and other high-value targets.

Trevithick notes that a conventionally armed ICBM or hypersonic weapon can allow China to threaten critical US military assets, facilities and infrastructure without resorting to nuclear weapons, which could serve as a powerful deterrent against US conventional strikes on the Chinese mainland.

China’s JL-3 nuclear missile has a range of up to 10,000 kilometers, putting the US within closer range. Photo: Twitter / Handout / SCMP

Trevithick mentions that such conventional weapons could also significantly lower the PLA’s threshold to conduct a strategic non-nuclear strike, particularly if it believes it could escape US nuclear retaliation. However, US nuclear policy reserves the right to use nuclear weapons to retaliate against non-nuclear strikes of sufficient severity.

Trevithick also mentions the ambiguity that a conventional ICBM or hypersonic weapon might pose, as the US may not know if an incoming missile is nuclear-armed or not and would have a difficult time deciding how to react.

He says that a launch on a warning dynamic could lead to a retaliation before the incoming missile hits its target to find out if it is nuclear-armed or not. He notes China has long used this ambiguity and uncertainty as part of its deterrence strategy of using SRBMs and could scale it up to the strategic level.