There is serious doubt about whether the submarines will perform at the level it has been sold on. Open-source analysts point out that the Hangor-class boats are export versions of China’s Yuan-class, with many sensitive systems downgraded. There is serious doubt about whether the submarines will perform at the level it has been sold on. Open-source analysts point out that the Hangor-class boats are export versions of China’s Yuan-class, with many sensitive systems downgraded.