Abstract: With the development of deep space probe, the space applications of nuclear energy are paid more and more attention as a kind of space energy with excellent prospect. The nuclear fission is quite popular in the ground applications and some progress has been made in space activities, but there are still technological barriers in the space applications of nuclear fusion because of its limited controllability. In this paper, we propose a new way of space applications of nuclear fusion energy. The spacecraft are fired by the nuclear fission and then driven by using the energy released in the nuclear fusion. Specifically, the nuclear fusion fuels react under the condition of high temperature and density, then the fusion energy is stored in a particular thermal carrier. By selecting suitable medium, the radiation field and the pressure field can be modulated and the boundary condition can be specified. At last, the spacecraft can be driven forward directly. The radiation protection technology about the space applications of nuclear fusion is also discussed.