The good news is you will fly into space on a mission to save humanity. The less good news is you will abandon the rest of Earth to certain doom and live in a mud burrow with only nerds for neighbours.

Such are the quandaries that passengers will face if plans work out for an interstellar spaceship designed to serve as a lifeboat for Earth should the planet face disaster in the next century.

Architects, designers and scientists have joined forces to explore the technologies needed to build a spacecraft that could be launched within the next 100 years and sustain human life for generations.

Early designs for the ship envisage a giant 15km-wide ball filled with soil that will support complex ecosystems of microbes, plants and animal life. Rather than building homes on top of the soil, humans will live within, carving out rooms in a network of connected burrows.

"We need to think how we might live in space long term," said Rachel Armstrong, lead researcher on Project Persephone at of Greenwich University. "So far, our approach to space has been very top-down. We take a vessel, put an environment in it, and off we go. For generational starships we need a different approach."

Armstrong, a doctor-turned-architect, hopes to develop synthetic soils that are optimised to support life and recycle waste. Electronic circuits sowed throughout the soil could monitor biochemical activity and use organic signals to communicate with plants and microbes to reshape the ecosystem as it evolves. The goal is to make the spaceship self-sufficient, life-supporting and self-fuelling, perhaps by mining asteroids or scavenging materials from space junk.

"By asking these questions the project is challenging the industrial view of sustainability. It's all very fine to conserve energy and be considerate about polluting the environment, but is that actually sustainable? We want to build sustainable environments that promote life," Armstrong said.


"There's an urgency to this and the urgency is our own sustainable practices. I don't see my generation as being the ones that solve the starship [question]. It may be my grandchildren's generation that makes something qualitatively different from people who have only known an industrial era."

The lessons learned from the project will have a more earthly impact long before any cosmic Noah's Ark has been built, by improving the sustainability of homes and cities, the researchers believe.

Project Persephone has no central funding, but the team's studies are supported by individual grants secured by the researchers. The project is part of an international non-profit foundation called Icarus Interstellar, which is dedicated to starship research and development.

Designing a self-sufficient, closed environment is a daunting task. In the 1990s, US "crews" tried twice to grow all their food and recycle waste and water at Biosphere 2 in Arizona. The missions faced a number of problems, including almost continuous hunger, falling oxygen levels, an explosion of cockroaches and ants, and a water filtration system clogged with dead fish.

Armstrong concedes that humans might not turn out to be the best lifeforms to save when the end of Earth is nigh. "We might decide that a giant microbial culture is all that the starship can support. We might have to have the humility to accept we're not the most likely to survive," she said.

There are other challenges beyond generating enough food, water and air for a trip with no certain end. The spaceship will need to simulate gravity if humans and other life are to survive the voyage. And then there is the need for a radical and revolutionary propulsion system to blast the ship into space. These problems are the focus of other Icarus Interstellar projects.

Though closer to the realm of science fiction than science fact, Icarus Interstellar are not the only ones with an eye on interstellar travel. In 2012, the US launched the 100 Year Starship, an ambitious project funded by Nasa and the government's Defence Advanced Research Projects Agency (Darpa), to explore technologies needed to make interstellar space travel a reality a century from now.

Richard Brown, director of the Centre for Future Air-Space Transport Technology at Strathclyde University, who is not involved in Persephone or the 100 Year Starship, said the projects could stimulate useful discussions. "The more people are interested in these things, the more debate there is, and the more consideration we'll have of what humankind's future might be," he said.

One of the greatest hurdles facing space exploration today is the cost of reaching Earth's orbit. To explore beyond the solar system, spacecraft might in future be built at orbiting manufacturing facilities. "Once you are in Earth's orbit, you have solved half of the problem," Brown said.


Steve Fuller, a sociologist at Warwick University who works on Persephone, said the project was one of several that takes seriously the idea that humanity may face a global catastrophe in the not too distant future. "The project is trying to put in some safeguards so that humanity can survive somewhere else.

"This is a different kind of spaceship from the ones we are used to. It isn't necessarily designed to come back to Earth. We're talking about a spaceship that a new generation of people would be born on. There might be people who live their entire lives in this place," he said.

The project's researchers have not nailed down the precise global catastrophes that might warrant the launch of a giant spaceship to save life as we know it. But beyond who decides when to abandon Earth, is the thorny question of who would get a seat on board. Armstrong said a ball-shaped spaceship 15km across might support 50 to 500 people, a tiny fraction of the Earth's 7 billion-strong population.

"Who are you going to take? They are going to look for diversity, and high-end skilled people," said Fuller. "You're not going to take people who lack skills. You're not going to take homeless people, though that's not official policy."

Faced with the prospect of living out their years in a mud burrow with no one but scientists and engineers for company, some may prefer to take their chances on Earth.

"Some people will say we wouldn't be in this situation if it wasn't for science and technology and these clever clogs who gave us the industrial revolution and nuclear power, let them go and find their own planet," said Fuller.