January 14, 2013


Why did it seem more reasonable half a century ago? “Of course we were crazy in a way,” says physicist Freeman Dyson of the Institute for Advanced Study in Princeton. In the late 1950s Dyson worked on Project Orion, which aimed to build a manned spacecraft that could go to Mars and the moons of Saturn. Instead of using nuclear reactors to spew superheated hydrogen, as NERVA did, the Orion spacecraft would have dropped small nuclear bombs out the back every quarter of a second or so and surfed on the fireballs. “It would have been enormously risky,” says Dyson, who planned to go to Saturn himself. “We were prepared for that. The mood then was totally different. The idea of a risk-free adventure just didn’t make sense.” A few years after Orion ended, Dyson outlined in Physics Today how a bomb-powered spacecraft might travel to a star.

These days it’s easier to outline why we’ll never go. Stars are too far away; we don’t have the money. The reasons why we might go anyway are less obvious—but they’re getting stronger. Astronomers have detected planets around many nearby stars; soon they’re bound to find one that’s Earthlike and in the sweet spot for life, and in that instant they’ll create a compelling destination. Our technology too is far more capable than it was in the 1960s; atom bombs aren’t cutting-edge anymore. In his office that morning, Les Johnson handed me what looked like a woven swatch of cobwebs. It was actually a carbon-fiber fabric sample for a giant spaceship sail—one that might carry a probe beyond Pluto on rays of sunlight or laser beams.

Culturally, I’d say our attitudes toward risk are less sane now. But ultimately, not going is probably riskier for the species.

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