A starship, starcraft or interstellar spacecraft is a theoretical spacecraft designed for traveling between planetary systems, as opposed to an aerospace-vehicle designed for orbital spaceflight or interplanetary travel. The term is mostly found in science fiction, because such craft is not known to have ever been constructed. Reference to a "star-ship" appears as early as 1882 in Oahspe: A New Bible (1882).Whilst the Voyager and Pioneer probes have travelled into local interstellar space, the purpose of these unmanned craft was specifically interplanetary and they are not predicted to reach another star system (although Voyager 1 will travel to within 1.7 light years of Gliese 445 in approximately 40,000 years). Several preliminary designs for starships have been undertaken through exploratory engineering, using feasibility studies with modern technology or technology thought likely to be available in the near future. In April 2016, scientists announced Breakthrough Starshot, a Breakthrough Initiatives program, to develop a proof-of-concept fleet of small centimeter-sized light sail spacecraft, named StarChip, capable of making the journey to Alpha Centauri, the nearest extrasolar star system, at speeds of 20% and 15% of the speed of light, taking between 20 and 30 years to reach the star system, respectively, and about 4 years to notify Earth of a successful arrival.