China PADJ-X Software May Have Exposed B-21 Raider Design Vulnerabilities

The US's most advanced stealth bomber might not be as invisible as it seems. Chinese researchers have developed a powerful aerospace simulation tool that reportedly exposed potential vulnerabilities in the design of the B-21 Raider. This breakthrough suggests that the shadow war between the two superpowers is increasingly being fought with code and algorithms rather than just hardware.

China PADJ-X Simulation: Unmasking the B-21 Raider

The "all-in-one" PADJ-X software system, based on adjoint optimization technology, was unveiled in December 2025 in a paper published by the peer-reviewed 'Acta Aeronautica et Astronautica Sinica'. According to reports, this system might be the world's first fully integrated, multidisciplinary platform specifically designed for the evaluation and optimization of stealth aircraft.

Advanced Adjoint Optimization and Stealth Design

Unlike traditional simulation methods, PADJ-X uses adjoint technology to calculate how small changes in shape affect overall radar cross-section and aerodynamic performance simultaneously. The researchers claim they used this to simulate the B-21 and found specific parameters where its stealth capabilities could be compromised. While the United States maintains the B-21 is the peak of survivability, this Chinese study serves as a bold sign of their growing confidence in digital defense intelligence.