Hermann Oberth published Wege zur Raumschiffahrt, in which he greatly elaborated on ideas presented in his 1923 book. Oberth here presented several specific designs for orbital space stations, ranging from spherical living quarters for the crew to large reflective mirrors fabricated in orbit. Among several innovations were methods for fabrication in orbit, propulsion by particle emission, and small ferry vehicles to permit travel in the vicinity of the station. Such stations could be used for a variety of purposes, ranging from scientific observation sites to military installations.