An interstellar ark is a spaceship designed for interstellar travel. This can be used for long-term space missions as a generation or sleeper ship. This is also a potential habitat to preserve civilization and knowledge in the event of a global catastrophe.
Directly propelled by a series of explosions of atomic fission bombs behind the craft (nuclear pulse propulsion), designed initially for Mars and back, and a trip to one of the moons of Saturn. Freeman Dyson then analyzed on how to reach Alpha Centauri, the nearest star system to the Sun. He considered the use of one megaton deuterium fusion explosions. He considered both an energy limited and momentum limited pusher plate design, with a pulse rate of one explosion every three seconds, which would achieve 3.3% of the speed of light and reach Alpha Centauri in 133 years.
Later studies indicated that a nuclear pulse drive starship powered by fusion-antimatter catalyzed nuclear pulse propulsion units would be in the 10% range and pure Matter-antimatter annihilation rockets would be theoretically capable of obtaining a velocity between 50% to 80% of the speed of light. At 0.1c, Orion thermonuclear starships would require a flight time of at least 44 years to reach Alpha Centauri. Carl Sagan suggested that this would be an excellent use for current stockpiles of nuclear weapons.
The largest spacecraft design analyzed in Project Orion had a 400 m diameter and weighed approximately 8 million tons. It could be large enough to host a city of 100,000 or more people.
Project Prometheus was established in 2003 by NASA to develop nuclear-powered systems for long-duration space missions. The project was planned to design, develop, and fly multiple deep space missions to the outer planets. It was cancelled due to lack of funding.
It used nuclear electric propulsion to generate electricity which would then be used to run ion engines. If the project continued it could have been been the basis for a possible interstellar journey.
Fusion-powered, supporting a crew of 200 with extra space for expansion, on multi-year journeys at subluminal speeds to nearby star systems. A three million ton ball of frozen deuterium would fuel nuclear fusion rocket engines contained in a cylindrical section behind that ball with the crew quarters. The projected speed is anywhere from 9% to perhaps 30% of the speed of light. Astronomy Magazine called it the "Slow Boat to Centauri.”
Generation ship
A spacecraft on which a crew is living on-board for at least several decades, such that it comprises multiple generations. Several sub-categories of generation ships are distinguished: sprinter; slow boat; colony ship; world ship. The largest and likely the slowest might take centuries to thousands of years to reach even nearby stars, as the original occupants of a generation ship would grow old and die, leaving their descendants to continue traveling.
A generation ship would have to be entirely self-sustaining, providing energy, food, air, and water for everyone on board. It must also have reliable systems that could be maintained by the ship's inhabitants over long periods of time. Systems could also be enhanced by AI that would not require sustenance or sleep.
Generation ships would have to anticipate possible biological, social and morale problems, and would also need to deal with sociological matters of self-worth and purpose for the crews. Generation ships travelling for long periods of time may see breakdowns in social structures.
It would have to be large enough to support a community of humans and a fully recycling ecosystem. However, a spacecraft of such a size would require a lot of energy to accelerate and decelerate. A smaller spacecraft, while able to accelerate more easily and thus make higher cruise velocities more practical, would reduce exposure to cosmic radiation and the time for malfunctions to develop in the craft, but would have challenges with resource metabolic flow and ecologic balance.
In this ship, most or all of the crew spend the journey in some form of hibernation or suspended animation. This could be through embryo cryopreservation, or suspended animation, or cryonics (cryostasis) with resurrection at the end of the journey.
Sleeper and generation ships could be improved by the addition of AI systems or androids that could maintain systems and take over in cases of emergencies that could affect the humans on board. In Raised by Wolves, two androids escape a war-ravaged Earth, taking with them twelve human embryos. Their spacecraft reaches the planet Kepler-22b where the "mother" android hooks herself up to artificial umbilical cords to allow six fetuses to grow.
Examples:
The Discovery in Space Odyssey is an interplanetary sleeper ship
In Mass Effect Andromeda, humans and other races travel to the Andromeda Galaxy aboard a series of arks, with the aim of colonizing a series of new home worlds. The travel time is only 600 years due to the discovery of a form of faster-than-light travel that cuts down the time to traverse the 2.5 million light years between galaxies.
In the Alien Universe, the Hypersleep Chamber on the Nostromo is where people are cryogenically frozen (in cryosleep or hypersleep) to survive the very long trips. It is capable of suspending the body’s autonomic functions while maintaining the health of each individual cell during stasis.
