Interstellar Flight: A Progress Report

When it comes to star travel, some people won’t take no for an answer

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Like many boys growing up in 1950s England, Gerald Webb dreamed of the stars. He followed the exploits of the British Buck Rogers—Dan Dare, “pilot of the future”—and was thrilled by the launch of Sputnik in October 1957. Unlike most boys, Webb followed his dream. He joined the British Interplanetary Society at age 16, earned a degree in physics, and was helping to build payloads for sounding rockets when the society asked for volunteers for a new project: designing an interstellar probe. The team met every few weeks at a pub, The Rising Sun, and in 1978 produced the world’s first detailed plan for a starship: Daedalus, a 60,000-ton agglomeration of spheres, disks, and cones with an engine nozzle big enough to cover Trafalgar Square.

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After that, Webb lost touch with the stars for a while. He stayed in the space business, becoming an aerospace consultant and helping to start a company that brokered satellite launches on Russian boosters, but the scope of his work was limited to Earth orbit.

On an unusually mild afternoon last August in Dallas, though, the stars once again feel within his grasp. Webb has joined about 200 other attendees at Starship Congress, a conference dedicated to promoting interstellar travel. The discussions range from solar sails to distributed databases, warp bubbles to game theory, exoplanets to international monetary policy. Session chairs periodically call on Webb, a sort of minor rock star among the interstellar crowd, for comments or to lead off the questioning.

While the speakers in the hotel meeting room talk about future searches for extraterrestrial intelligence, Webb, taking a break from the presentations, sits just outside, fidgeting with piles of brochures on a display table. Starship posters line the wall behind him, while another table offers colorful postcards promoting “Sunny Gliese 581e: Only 22 Light Years.”

“There hasn’t been a lot of progress in the field—all the problems we talked about are still being discussed,” Webb says. “I’m not disappointed in the lack of progress though. Things have started to get better—the necessary conditions for a starship are being laid. It’s reached the point where I think it’s inevitable. It will happen.”

Most of the other conference attendees likely would agree. A surge in interest in the last few years, driven largely by the discovery of hundreds of planets in other star systems and a bit of money from DARPA—the Defense Advanced Research Projects Agency—has led to the creation of several star-travel advocacy groups trying to fan enthusiasm through conferences; Starship Congress is one of several in 2013 alone. “There are some serious scientists and engineers looking at this because they’re dedicated to the idea of interstellar travel,” says Les Johnson, a physicist, science fiction writer and editor, and deputy manager of the Advanced Concepts Office at NASA’s Marshall Space Flight Center in Alabama. “It’s not some hobbyists in their garage. There’s no serious funding, but…a lot of us continue to meet, gather, publish, and work on this stuff in our free time.”

At the turn of the century, Johnson led a project that was one of the first to actually pay researchers to study the idea of interstellar travel, and one of the first drivers (along with a similar effort at another NASA center) of the current increase in interest. He was managing NASA’s efforts to link spacecraft with tethers when the agency began looking for a “stretch” goal: evaluating whether it was possible to send probes or people to other stars. “I was the new guy in the group, and it sounded exciting, so I raised my hand and said ‘I’ll do it!’ ” Johnson recalls. “For about two years, I had the coolest job title in NASA: manager of the interstellar propulsion research project.”

Johnson’s team determined that the most practical path to the stars was via solar sails, which required fewer scientific breakthroughs than fusion-powered nuclear engines or exotic propulsion methods like warp drive. Ultra-thin sails would use the faint but constant pressure of sunlight or high-powered lasers to propel them to a few percent of the speed of light. (NASA plans to launch a 124-foot solar sail, called Sunjammer after a sail in an Arthur C. Clarke novel, in 2015, although it will stay well within the bounds of the solar system.) “Sailships are the only way we know to get to velocities that are anywhere close to the speed of light,” Gregory Benford, another physicist/sci-fi author, tells the Starship Congress attendees.

Yet even with this relatively reasonable-sounding technology, the problems are so vast that we won’t be sailing to the stars anytime soon. Johnson says that to propel a craft to Alpha Centauri, the nearest star system, a solar sail would have to be as big as the state of Alabama, and would need a millennium to travel the 4.3-light-year distance. Change the power source from solar radiation to terawatt-scale lasers and you could cut the travel time to a century. The big drawback? Such a system would require power “equivalent to the total output of humanity today,” Johnson says.

And that neatly encapsulates the challenge of traveling to the stars. Even if the science allows it, the engineering demands are monumental, the energy requirements stupendous, the distances unfathomable, the time scales...well, pick your own adjective.
To understand the scale of the problem, consider that the most distant spacecraft yet launched, Voyager 1, recently exited the solar system—35 years after it left Earth. At that rate, if the probe were headed toward Alpha Centauri (it’s not), it would not arrive for another 75,000 years.

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