An interstellar travel within a human lifetime is considered as utterly impossible. The interstellar travel used Special Relativity is well known. However, there exists the problem of the twin or time paradox. In addition, although space warp using wormhole is also well known, the size of the wormhole is smaller than the atom, and moreover, the wormhole is predicted to fluctuate theoretically due to instabilities. Assuming Hyper-Space as being characterized by imaginary time, it is shown that the limitations due to the extremely long time required for interstellar travel are removed. The Hyper-Space navigation theory discussed here would allow a starship to start at any time and from any place for an interstellar travel to the farthest star systems, the whole mission time being within human lifetime. This newly added paper introduces a realistic method of the interstellar travel (i.e., Hyper-Space navigation) based on the concept published so far by author [1-6].