- PADJ-X modeled the geometry of the B-21 using only publicly available images
- Simulation claims suggest 15% improvement in aerodynamic efficiency
- Leaked files show partial validation of radar cross section simulation components
A Chinese aerospace simulation tool called PADJ X has reportedly identified aerodynamic and stability limitations of the United States’ most advanced stealth bomber, the B-21 Raider.
The software functions as an integrated platform combining five major disciplines: aerodynamics, propulsion, electromagnetism, infrared signature and sonic boom design.
According to a peer-reviewed paper published in Acta Aeronautica and Astronautica Sinica, researchers applied 288 parameters to simulate a B-21-like layout, using publicly available images rather than classified specifications.
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Claimed capabilities exceed existing Western platforms
Their analysis claimed that aerodynamic optimization could increase the plane’s lift-to-drag ratio by 15%, while reducing the effects of shock waves that degrade stealth and efficiency.
The PADJ
A Chinese researcher noted that the software “benefits from all intellectual property rights” and allows “complete optimization of aircraft aerodynamic configurations.”
Western platforms such as NASA’s FUN3D and Germany’s FLOWer solvers do not integrate as many physics disciplines into a single environment.
These legacy systems often require manual adjustments when moving optimization from one discipline to another, making multi-objective tuning slower and more fragmented.
The PADJ X’s overall approach suggests a step forward in integrated aircraft design, but its practical impact on actual stealth bombers remains to be proven.
Available data suggests a functional but unverified system
The 20 GB of leaked files associated with PADJ
Individual components of the software pipeline have been verified to work correctly, including radar cross section calculations performed in third-party tools such as Altair FEKO.
However, running a full multiparameter geometry optimization from scratch would require more computing power and time than has been publicly demonstrated.
The research papers referenced in the leak – numbers 10.7527/S1000-6893.2025.32221 and 10.7527/S1000-6893.2025.32816 – cannot currently be found anywhere, even in Chinese-language repositories.
Access to these documents appears to have been strictly restricted from the start or to have been suppressed after the leak from China’s National Supercomputing Center.
The lack of verifiable access to the final December 2025 software package leaves room for doubt, as does the convenient tale of a “mother of all leaks” that cannot be independently confirmed.
What remains to be determined is whether Chinese scientists truly exceeded the aerodynamic limits of the B-21 or whether the episode as a whole serves a different strategic objective.
Leaks may rely primarily on open source images and publicly known design constraints rather than actual espionage.
This suggests that the claims may combine real technical capability with a carefully managed narrative aimed at influencing perceptions of U.S. stealth superiority.
Via SCMP
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