Interstellar Flight: A Progress Report

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


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.

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.

Those pursuing the idea of interstellar flight remain undaunted. “We have to keep pushing,” says Richard Obousy, an organizer of the Starship Congress and a director of Icarus Interstellar, the conference’s host organization. “It’s a long, hard road, but what humanity is capable of on long time scales is tremendous.”

The long-road, long-time-scale theme is a common one. It’s reflected in the title of the group that won this field’s equivalent of the lottery: a half-million-dollar grant from DARPA. The 100 Year Starship (100YSS) organization, which was created after a 2011 agency-sponsored conference, is charged with developing the infrastructure needed to make it possible to launch a crew-carrying starship within the next century.

“Our task is to push radical leaps in technology design,” says 100YSS director Mae Jemison, a physician and former space shuttle astronaut who once guest-starred on “Star Trek: The Next Generation.” “I’m sure that we can create the capabilities. That’s a rather radical and bold thing to say. But I always think about putting a human on the moon.... When President Kennedy proposed landing a person on the moon in 1961, we had barely gotten someone off on a suborbital flight.”

The group’s early focus has been less about leaps in technology than about the mundane tasks of running an organization: raising money, arranging conferences, setting up a research institute. Much of the emphasis so far has been on education, public outreach, and linking starship research to problems on Earth. That has led to some of the more technology-oriented folks in the interstellar community feeling mildly resentful. Icarus, an original partner in the DARPA grant, dropped out “to pursue our own way,” Obousy says.

Yet Jemison, who operates 100YSS from a small suite of offices in Houston’s eclectic Montrose neighborhood, says the challenges of building a starship go far beyond just designing the hardware. “Everything that we need to know to have a successful human trip beyond our solar system are the very same things that we need to know to survive as a species on this planet,” she says. “If we look around us, we’re already on a starship.”


If our goal is to escape this particular starship and head for a similar one orbiting another star, we’ll need some kind of advanced propulsion. The topic brings out, depending on your perspective, radical dreamers—or just radicals. Starship Congress offered ideas for fission-fragment rockets, inertial containment fusion power, magnetic sails, and FTL (faster-than-light) warp drives, among others. Some concepts, like gigantic solar sails, are allowed by the laws of physics, but require engineering well beyond today’s capabilities. Others, like matter-antimatter engines and warp bubbles, draw oohs from the faithful but mild snickers from the more skeptical, who say the plans require too many leaps of faith.

“If you really want to get something done, science fiction won’t get it built,” says attendee Philip Lubin, a professor of physics at the University of California at Santa Barbara. “In some of the presentations, it was ‘A miracle is required here, a miracle is required here, a miracle is required here.’ But there was no acknowledgment of that.” Lubin acted as conference contrarian, frequently asking presenters pointed questions about their proposed technologies. But he also offered up his own sci-fi-sounding project: a planetary defense system that could double as a solar sail’s power source, using beamed energy to propel an unmanned probe to the stars.

The system would collect sunlight with miles-wide solar arrays in Earth orbit and convert it to a beam of energy, similar to a giant laser. Lubin says that over a year, such a beam could completely vaporize a threatening asteroid a third of a mile (1,760 feet) wide at a range of one astronomical unit—the distance from Earth to the sun (93 million miles)—and deflect much larger ones. “It wouldn’t require any miracles, just a lot of hard work,” he says. Such a system could start on a much smaller scale—big enough to zap space debris, perhaps—then be expanded as engineering and funding allow.

If used to propel starships, the energy beam could boost probes to substantial speeds, Lubin says. A 100-kilogram (220-pound) probe with a 100-foot reflector to catch the beam could reach Mars in three days; with a much larger reflector, such a probe could hit three percent of lightspeed—up to 20 million mph—by the time it reached the edge of the solar system in less than a month.

Such a probe might not survive all the way to another star, and even if it did, communications would be a major challenge. But some suggest that the first destination for an interstellar probe need not be a star. A journey into interstellar space might do just fine, providing a technology shakedown and an incremental step toward the stars, just as the suborbital Mercury flights of Alan Shepard and Gus Grissom were the first steps toward Neil Armstrong’s “giant leap” onto the moon. NASA’s Les Johnson thinks that missions to distances of 250 to 1,000 astronomical units (two to eight times Voyager 1’s current distance) could be ready for launch within a few decades.

For most interstellar mission planners, the ultimate goal is to send people blasting across the cosmos in big honkin’ spaceships. Few expect that to happen for at least a century, leaving scientists and engineers plenty of time to work out strategies. Meanwhile, others are already considering what may be the most important element of star travel: the people who will make that long—and presumably one-way—journey.

Sheryl Bishop, a social psychologist at the University of Texas Medical Branch, has studied mountain climbers, cavers, teams that have wintered over in Antarctica, and others to understand the motivations and behaviors of those who operate in extreme environments. In 2005, she even participated in a simulated Mars expedition in the Utah desert, spending two weeks with an all-woman crew.

That work brought her to the attention of Danish filmmaker Michael Madsen, who is producing a documentary titled Odyssey about how we might select the crew for a “worldship”—a miles-long craft that would carry hundreds or thousands on a generations-long star trek.

“The limitless expectations we have on Earth don’t apply” to such a journey, Bishop says. “Columbus didn’t have to worry about breathing—he wasn’t going to suffocate if something went wrong with the ship. With a worldship, you’re through with everybody on Earth, and everybody on Earth is through with you. So what kind of person is both willing to go and sane enough to select? They’d have no family ties, they wouldn’t miss the skies and seas. After a while you start thinking, ‘Oh my God—I’m defining a sociopath.’ ”

Such is the state of interstellar-flight planning, circa 2013—separating the committed from those who perhaps should be committed, the visionaries from the daydreamers, the difficult from the impossible. Even the experts can’t always tell the difference, so they keep studying, keep advocating, keep pushing toward the stars.

Damond Benningfield is a freelance science writer and audio producer in Austin, Texas.

NASA’s Les Johnson (holding an ultralight aerogel) says he once had “the coolest job title in NASA: manager of the interstellar propulsion research project.” Now almost all planning for starflight is left to private organizations. Courtesy Les Johnson
Testing a 65-foot solar sail at NASA’s Glenn Research Center in 2005. A larger version called Sunjammer, with four times the area, is scheduled to be tested in space in 2015. In order to reach the nearest star within a millennium, a solar sail would have to be as big as the state of Alabama. NASA MSFC

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