Chinese scientists question ‘flaws’ in NASA’s hypersonic aerodynamics software

This small flaw in a complex equation can lead to “inevitably erroneous results” when scientists simulate and analyze important problems such as high-temperature ablation, the National University Superintendent says. said the team led by Professor Liu Jun, a researcher at the Sonic Technology Research Institute. Defense Technology was described in a peer-reviewed paper published in the Chinese academic journal Acta Aerodynamica Sinica on March 14th.

When aircraft speeds exceed Mach 5, intense friction with the air creates searing temperatures that can ionize air molecules and cause chemical reactions.

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These complex reactions can erode the aircraft’s surfaces and change the temperature and density of the surrounding air. Inaccuracies in modeling data can have a significant impact on aircraft performance and safety.

The software referred to in Liu’s paper, called Vulcan-CFD, was developed by NASA’s Langley Research Center and is widely used in the United States to develop hypersonic weapons. Therefore, it is subject to export controls and distribution is limited to U.S. borders.

In an academic paper published in 2020, the NASA software development team introduced how Vulcan works and some of the key equations used by Vulcan.

Liu and his collaborators say the software is “well known” in the industry.

Professor Liu, who has a laboratory in Changsha, Hunan province, was joined in the research by scientists from the People’s Liberation Army University of Aerospace Engineering in Beijing and the Aerodynamics Research and Development Center in Mianyang, Sichuan province. These three institutions have contributed to the rapid development of China’s hypersonic weapons technology over the past two decades.

Meanwhile, the U.S. Army’s long-range hypersonic weapon (LRHW), which is similar to North Korea’s missiles, suffered consecutive failures in 2021 and 2022, after which three planned launches were canceled or postponed.

These setbacks come at a huge cost. In fiscal year 2025 alone, the Army is asking taxpayers for $1.28 billion to “deliver experimental prototype aircraft with residual combat capability in 2024.”

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The Congressional Budget Office blamed the unfavorable progress on high temperatures.

After conducting an exhaustive review of America’s hypersonic weapons program last year, the agency said, “Fundamental challenges remain, including the high speeds that hypersonic missiles are exposed to during flight through the atmosphere. “This includes managing extreme heat,” the report said.

“Extensive flight testing is needed to protect hypersonic missiles’ sensitive electronics, understand how different materials will perform, and predict aerodynamics in sustained temperatures as high as 3,000 degrees Fahrenheit. “Trials are underway, but recent failures have slowed progress.”

Liu said his team discovered a flaw in the equations NASA used on Vulcan to describe the changing concentrations of various chemical components, such as oxygen and nitrogen, in the hot gas mixture.

This equation cannot account for the mixing and transport of components caused by small-scale turbulence when the temperature is rapidly changing or oscillating.

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Due to the complexity of hypersonic aerodynamics, some small-scale motions may be ignored by model designers due to lack of understanding or calculations that are too complex to resolve.

In their paper, Liu’s team argues that NASA’s lack of attention to this detail resulted in the software’s inability to accurately predict the chemical composition and temperature changes on the aircraft’s surfaces, which could affect the simulation, design, or analysis work on which it relies. He said it could have a serious impact. software.

NASA was one of the first agencies in the world to explore hypersonic technology.

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NASA scientists and engineers have conducted much pioneering research and flight testing in this field, but have suffered from relentless budget cuts and brain drain in recent years.

JPL laid off 530 employees in February amid funding uncertainty.

The South China Morning Post has contacted NASA for comment.