International competition to develop and secure cutting-edge and innovative space-based technologies has been intensified as military and commercial significance of and dependence on space grew. Especially, the so-called Forth Industrial Revolution-disruptive innovation technologies, their converging development with existing technologies, services, and platforms, which substantially reduce costs and create new values-affects competition over space-related technologies and their innovation. This study takes a closer look at innovative developments in space technologies-space mobility, satellite technologies, and global navigation satellite system-with a focus on the U.S.-China competition in outer space. It demonstrates that this competition exacerbates space security dilemma because of the dual use nature of space technologies, the difficulties in distinguishing offensive capabilities from defensive capabilities, and the benefits of offense vis-a-vis defense. Furthermore, it might be very difficult to escape this space security dilemma due to the lack of effective space governance.