[citation needed] The ark has also been proposed as a potential habitat to preserve civilization and knowledge in the event of a global catastrophe.
The largest spacecraft design analyzed in Project Orion had a 400 m (1,300 ft) diameter and weighed approximately 8 million tons.
Another concern is selection of power sources and mechanisms which would remain viable for the long time spans involved in interstellar travel through the desert of space.
However, if the ship is capable of transits requiring hundreds of thousands of years, chemical and gravitational slingshot propulsion may be sufficient.
[1][2] The Enzmann starship proposed in 1964 is a large fusion-powered spacecraft that could function as an interstellar ark, supporting a crew of 200 with extra space for expansion, on multi-year journeys at subluminal speeds to nearby star systems.