A starship is a theoretical spacecraft designed for traveling between the stars, as opposed to a vehicle designed for orbital spaceflight or interplanetary travel. The term is mostly found in science fiction, as humanity has not yet constructed such vehicles (while the Voyager and Pioneer probes have traveled into local interstellar space, they are not generally considered starships, mainly because they are both unpowered and uncrewed). However, exploratory engineering has been undertaken on several preliminary designs and feasibility studies for starships that could be built with modern technology or technology thought likely to be available in the near future.