The moon landings reinvigorated interest in manned space travel. In the 1970s, the British Interplanetary Society led a five-year study called Project Daedalus, named for the mythological figure who crafted wings to fly. The group looked at building a nuclear-fusion powered starship to travel some six light years away to Barnard's Star, a star reasonably close to Earth which was then thought to have orbiting planets.
Interest also grew in novel propulsion methods, driven in part by the idea that conventional rocket technology was just too slow to mount even a one-way trip to our closest stellar neighbour, Alpha Centauri. Some estimates suggested it would take at least 80,000 years to travel the four light-years there, requiring multi-generation spaceflight and fuel demands that do not bear thinking about.
Hence, interest grew in technologies such as solar sails, blown along by streams of light particles. In the 1980s, physicist Robert L Forward even proposed a solar sail driven by a giant laser, which would push a spaceship at close to the speed of light (although some consider even that technology too slow for interstellar exploration).
Writing about those ideas is one thing, but building them is another, says Mark Lewis, a professor of aerospace engineering at the University of Maryland and a former US Air Force chief scientist. The laser-powered light sail, for example, would require planet-sized optics as big as Jupiter. “One can write the equations to demonstrate how it would be done, but the resources needed to actually build it would be enormous,” he says. “We know how to build them, but that doesn’t mean we could.”
Nearly three decades later, Forward’s laser-powered light sail – as well as other ideas for interstellar travel – are still popular among space enthusiasts and science fiction writers, but they have gained little traction by way of funding or serious progress. In the 1990s Nasa briefly supported the Breakthrough Propulsion Physics programme, which funded scientific research in areas such as rocketless space drives and faster-than-light travel. However, that program lost its funding in 2002.
Advancing these ideas, say experts, would require decades of research and billions of dollars, something that a government, particularly in a time of austerity, is unlikely to do. “Right now the established aerospace community is reaching a stagnation point; it is trying to finish what was started in ‘60s, rather than adapt,” said Mark Millis, a former Nasa scientist who headed the Breakthrough Propulsion Physics programme.
Millis, who left Nasa in 2010, now dedicates his time to the Tau Zero Foundation, an Ohio-based nonprofit he started to help further interstellar travel. “I tried to keep doing cool, futuristic stuff, but it’s just not going to happen in government,” he said of his decision to leave Nasa. “I realized I’m going to have to go independent.”
Ironically, that same thinking is what motivated Darpa and Nasa to start the 100YSS. Neyland, the Darpa official, says the idea for the project came out of a meeting he had with the head of Nasa’s Ames Research Center, Pete Worden, who has a reputation as an out-of-the-box thinker willing to take risks.
“What we realised right off was that if you look at history, any major exploration, like crossing the oceans, crossing the continents, building telescopes for looking into space, those things have always been done outside of government circles,” said Neyland last year. “They’ve been funded by patrons or non-government organisations.”
Their idea was to do for interstellar travel what the Medici court did for Galileo: provide long-term funding to encourage scientific breakthroughs.