Asteroid starship. Artist's impression in cut- away of a space vehicle designed to travel to other star systems. This concept uses a hollowed- out asteroid. Heat, light and propulsion would be provided by a fusion power system. Spinning the asteroid would provide an artificial gravity. The interior of the asteroid would have Earth-like flora and fauna from which the 10,000-strong population would derive their nutrition. The 50- km long, 20 billion tonne asteroid might take hundreds or thousands of years to reach its objective. Such a concept might be a useful 'lifeboat' allowing humans to colonise other star systems should our own become uninhabitable.