Deng was selected in China's first astronaut group in 1998 and spent more than two decades training before his first spaceflight. His long wait became a major part of his public story in China's human-spaceflight program.

He flew Shenzhou 15 to the Tiangong space station — open definition with Fei Junlong and Zhang Lu. The mission completed a long-duration handover with Shenzhou 14 and supported station operations after China's modular station entered routine crewed use.

His Shenzhou 15 mission gave his long astronaut career its defining public chapter: a veteran from China's first astronaut class finally flying during the operational Tiangong station era.