The period of his career that Dyson remembers most happily, the endeavor during which he believes he learned the most, began the year after Sputnik. In 1958, he took a leave of absence from the Institute for Advanced Study and moved to La Jolla, California, where he joined Project Orion, a group of 40 scientists and engineers working to build a spacecraft powered by nuclear bombs. The Orion men believed that rocketry was hopeless as a means of settling the universe. Only nuclear power had sufficient bang to propel the requisite payloads into space. The team called the concept “nuclear-pulse propulsion.” From a hole at the center of a massive “pusher plate” at the bottom of the craft, atom bombs would be dropped at intervals and detonated. The shock wave and debris from each blast would strike the pusher plate, driving the ship heavenward on a succession of blinding fireballs. Shock absorbers the size of grain silos would cushion the cabin and crew, smoothing out the cataclysmic bumpiness of the ride.

To the layperson, this seems exactly the sort of contraption that Wile E. Coyote, in his efforts to overtake Road Runner, habitually straps on before self-immolation. But the layperson is wrong, apparently. Specialists in the effects of nuclear explosions saw no reason Orion would not work. The Advanced Research Projects Agency, the precursor to NASA, underwrote the project, then NASA took it on, and nuclear-pulse propulsion briefly held its own against the chemical rockets of Wernher von Braun. Dyson and his colleagues did not want to delegate; they intended to go bombing into space themselves. Their schedule had them landing on Mars by 1965 and Saturn by 1970.

The Volkswagen camper in which I was driving Freeman through the forest was a ’69, assembled the same year the Orion ship was supposed to thunder silently through space toward its 1970 rendezvous with Saturn. Like all VW minibuses of that vintage, mine was underpowered and prone to overheating. It was primitive transportation—internal combustion, just 57 horsepower—yet it got us down the road. Now and again, I checked the speedometer. We were averaging about 50 miles per hour, well under the 22 million mph that Freeman had hoped to coax from an interstellar spacecraft, but safe under the conditions. To the tinny pocketa pocketa of the four cylinders, I steered beneath the narrow swath of stars bounded by the crowns of conifers on either side.

The détente between the Dysons, father and son, was something I had helped mediate. This drive through the forest to unite them had the look of family counseling, but in fact it was fieldwork. I was gathering notes for my book The Starship and the Canoe, an account of the two men, their two vessels, and their two diverging views of the future.

Occasionally I stole a sideways glance at Freeman, who rode shotgun, very erect in the seat, staring in his unblinking way at the pavement ahead. It did not escape me that the black macadam in my headlights covered a road on Vancouver Island, British Columbia, Canada, Planet Earth. This was not extraterrestrial basalt on the dark side of Saturn’s moon Iapetus, which Freeman had especially wanted to visit, curious about why one side is black and the other white. This was not some haul road on Mimas, the innermost of the major moons of Saturn, a cratered satellite of water-ice just 115,000 miles from the planetary surface and favored by Freeman both as a place to provision and for its spectacular view of Saturn filling most of the sky. Back in 1958, Freeman had calculated the velocity increments required to deposit the Orion ship on various inner moons of Saturn and Jupiter, laying out the data in tables—but all for naught, in the end. The Limited Test Ban Treaty of 1963, with its prohibition of nuclear explosions in the atmosphere and outer space, killed Project Orion. President Kennedy’s signature effectively condemned Freeman to spend the rest of his life on this planet.