Antimatter spaceship. Artwork of the antimatter spaceship concept developed for the NASA Institute for Advanced Concepts by Hbar Technologies, LLC. The spaceship would use a round sail (lower right) with a layer of uranium. Antiprotons (green) would be directed at the uranium-coated sail, and would annihilate in uranium atoms, inducing fission. The momentum of the fission products moving away from the sail would propel the spacecraft forward. Over several months, even this low acceleration would produce very high speeds. About 30 milligrams of antiprotons would be needed for a mission to the Kuiper Belt (beyond Pluto), and would be produced by particle accelerators. Probes could be sent to the nearest stars within 80 years. This study was funded in 2002 (Phase I) and 2004-5 (Phase II).