After decades of meteoric growth, China is vying to lead the world in a wide range of technologies—radar-evading stealth fighter jets in the air, high-speed trains on the ground, missile-armed cruisers at sea, and sophisticated satellites in space.Now Beijing is competing in a new venue: underground.A state-owned railroad company based in central China has begin transforming itself into one of the planet's top producers of high-tech tunnel-boring machines, or TBMs—in essence, giant drills that can churn through earth and rock and seamlessly lay concrete segments to produce tunnels, subway tubes and sewer lines.But there's a catch: While China is beginning to assemble its own tunnel-boring machines, it still relies on critical, foreign-made components that its own industries can't manufacture on its own.TBMs must stand up to tremendous stress, making them difficult to design and build—and that difficulty increases with the machine's size."As the face [of the borer] gets bigger it gets more dangerous," Ning Haoson, commercial manager for China Railway Engineering Equipment Group Company, told Motherboard. "Stabilizing is hard," Ning added. "All of it is a challenge." Motherboard spoke to Haoson during a visit to the firm's headquarters and factory in Zhengzhou, an industrial city 380 miles south of Beijing. The China-US Exchange Foundation, a Hong Kong-based nonprofit, sponsored the visit.See the rest of this article on MOTHERBOARD.