As Richard Rhodes points out in this article, Robert H. Goddard’s attempt to produce a workable rocket propelled by a series of controlled explosions failed and he went on to devise the liquid-fuel system that became the basis for most of his subsequent work.

Yet the concept of a “machine-gun” rocket did not die with Goddard in 1945. In the academic year of 1958-59 the physicist Freeman Dyson became involved with Theodore B. Taylor and other scientists on Project Orion at Point Loma, California, aimed at developing a spaceship powered by small, controlled nuclear explosions. Dyson telk the story in his recent memoir, Disturbing the Universe:

“We intended to build a spaceship that would be simple, rugged, and capable of carrying large payloads cheaply all over the solar system. Our slogan for the project was ‘Saturn by 1970.’ … For Ted and me, the words … were not just an idle boast. We really believed we could do it if we were given the chance. We took turns looking at Jupiter and Saturn through a little telescope that Ted kept in his garden. In our imagination, we were zooming under the arch of Saturn’s rings to make the last braking maneuver before landing on the satellite Enceladus. …

“The most beautiful part of the project was the flight-testing. We built model ships that propelled themselves with chemical high-explosive charges rather than with nuclear bombs. One of our team was Jerry Asti, a Czech refugee scientist who was an artist with high explosives. He knew how to build complicated high-explosive devices with elaborate fusing and timing systems, and they almost always worked. …

“I often wondered what the Saturday-afternoon sailors thought when they saw some weird-looking object rise briefly from the test stand and blow itself into a thousand pieces. … I still keep in my desk drawer a bag of aluminum splinters that I collected after one of our flight tests. The last and most successful of our tests took place on November 12,1959. This was a few weeks after I had left the project and returned to my respectable scientific work in Princeton. Dr. Brian Dunne … reported the event to me by letter: ‘Wish you could have been with us to enjoy the Point Loma festivities last Saturday. The Hot Rod flew and flew and flew! We don’t know how high yet. Ted, who was up on the side of the mountain, guessed about 100 meters by eyeball triangulation. Six charges went off with unprecedented roar and precision. … The chute popped exactly on the summit and floated down unscathed right in front of the blockhouse. … We are planning a champagne party for Wednesday.’

“So ended the second romantic age of space travel. In the summer of 1959, the decision was made not to use nuclear propulsion for the