China flags 'fatal flaw' in NASA’s hypersonic aerodynamics software

Vulcan-CFD’s issues have been highlighted in a new paper by the Hypersonic Technology Laboratory of the National University of Defence Technology. This peer-reviewed paper was published in the Chinese academic journal Acta Aerodynamica Sinicaon March 14.

Led by Professor Liu Jun, the paper explains that when an aircraft’s speed exceeds Mach 5, intense friction with the air generates sizzling temperatures that can ionize air molecules and spark chemical reactions. If not modeled accurately, this could impact the effective development of working hypersonic vehicles.

Vulcan-CFD could be flawed

These complex reactions may cause erosion on the aircraft surface and affect the surrounding air temperature or density. Inaccurate modeling data can result in significant consequences for aircraft safety and performance.

NASA’s Vulcan-CFD is a highly advanced computational fluid dynamics (CFD) software developed to simulate compressible and turbulent Navier-Stokes flows. This software is designed to handle complex simulations involving finite-rate chemistry and thermodynamic non-equilibrium processes.

Designing hypersonic vehicles is highly intricate, involving accurately modeling and understanding various physical phenomena. These phenomena include but are not limited to aerodynamic heating, chemical reactions within the flow, shock wave interactions, and boundary layer effects.

So, modeling software like Vulcan-CFD is potent in any engineering team’s toolkit. However, while Vulcan-CFD is used to design and analyze hypersonic vehicles, it is not the only tool available to aerospace engineers and researchers.

Due to its sensitive nature, Vulcan-CFD is subject to export controls, and its distribution is limited to within American borders.

However, NASA released an academic paper in 2020 introducing its working principles and some of the key equations it employs.

According to Liu and his team, the software is widely recognized within the industry. Using these, Lui and his team took a deep dive into the inner workings of Vulcan-CFD and made their alleged discoveries.

Reliance on it could be delaying American hypersonics

If true, this could explain why America’s hypersonic program seems to lag behind on the international stage. For example, on April 3, North Korea announced the successful test of a land-based hypersonic gliding missile called Mars 16B.

Meanwhile, the US Army’s Long-Range Hypersonic Weapon (LRHW) failed consecutively in 2021 and 2022, resulting in the scrapping or postponement of the subsequent three planned launches.

The U.S. Congressional Budget Office has reported that “the fundamental remaining challenge involves managing the extreme heat that hypersonic missiles are exposed to by traveling at high speeds in the atmosphere for most of their flight.”

“Shielding hypersonic missiles’ sensitive electronics, understanding how various materials perform, and predicting aerodynamics at sustained temperatures as high as 3,000 degrees Fahrenheit require extensive flight testing. Tests are ongoing, but failures in recent years have delayed progress,” it added.

If Vulcan-CFD is heavily relied upon, and the Chinese research team’s findings are correct, this could mean that U.S. hypersonic research teams may need to change strategy to catch up.