Proposed 200-ton test vehicle, 1962: 30 feet in diameter, 0.78-second pulse period, 75-foot separation distance, 1.9-g acceleration, 220-pound charges, yield unknown.
In 1952, at the Nevada Test Site, Ted Taylor added to his already considerable reputation by holding up a small parabolic mirror and lighting a cigarette with an atomic bomb. The fireball was twelve miles away. "I carefully extinguished the cigarette and saved it for a while in my desk drawer at Los Alamos," he says. "Sometime, probably in a state of excitement about some new kind of bomb, I must have smoked it by mistake."[107]
Those who were designing, building, stockpiling, and attempting to understand the effects of nuclear weapons in the 1950s were concerned either with destroying things like cities and hardened missile silos, or with nominally constructive applications like melting oil out of the Alberta tar sands and digging a sea-level Panama Canal. Putting something as expensive as a 4,000-ton spaceship within a few hundred feet of a series of nuclear explosions was going to be a hard sell, even for Ted. Without some material evidence of survivability, even the most enthusiastic officials at the AEC or within the Pentagon would be unlikely to lend support. Fortuitously, evidence was at hand: a series of tests known as "Lew Allen's Balls" (also referred to, according to Burt Freeman, "as Ogle's balls, after Bill Ogle, the great atmospheric test director who was responsible for much progress over many years"). This was the third key ingredient—between the concept of Stan Ulam and the incentive provided by Sputnik—from which Project Orion was being assembled in the back of Ted Taylor's mind.
Lew Allen was an Air Force physicist, born in 1925, who had been assigned to Los Alamos in the early 1950s and rose rapidly through the ranks. He later became Secretary of the Air Force and, after retiring with the rank of 4-star general, director of the Jet Propulsion Laboratory at Caltech. Lew Allen and Ted Taylor became close friends at Los Alamos and among the islands encircling the lagoon at Eniwetok, where they collaborated on a number of tests. After leaving Los Alamos, Lew Allen joined the Office of Special Projects at the Air Force Special Weapons Center at Kirtland Air Force Base in Albuquerque, where he became the first project officer responsible for Orion when the monitoring of ARPA's contract with General Atomic was assigned to AFSWC by the Air Force Research and Development Command in 1958. He was skeptical enough, as an administrator, to be given oversight over the project, and optimistic enough, as a physicist, to recognize the value in giving Orion contractual support. "It was a remarkable period in the Air Force, in which they really encouraged brilliant young technicians to remain technicians and not lose their skills as they advanced in the Air Force," says Bud Pyatt. "I don't think that happens today." As JPL's Voyager 2 space probe headed out toward Neptune and Uranus, after sending back pictures of the moons of Jupiter in 1979 and the moons of Saturn in 1981, there was an old Orion hand—Lew Allen—at the helm.
It was a shortage of tritium that led to "Lew Allen's Balls." In the mid-1950s, as new weapon designs such as Ted's went into production, the AEC began to worry, behind closed doors, that we might not have enough tritium to keep the stockpile up to date. Tritium, an unstable isotope of hydrogen with two extra neutrons in its nucleus, occurs naturally in seawater as one part in 1018 of ordinary hydrogen, produced by collisions with cosmic rays. Since tritium decays 5.5 percent per year, tritium-boosted fission weapons and tritium-initiated thermonuclear warheads have to be periodically replenished and cannot simply be left stockpiled on the shelf. Producing tritium by neutron bombardment in special reactors is expensive and slow. Tritium is also produced during thermonuclear explosions, and that gave Ted an idea. Why not use the neutron flux from a nearby explosion to produce tritium, and then go in and harvest the results?
"Ted was not devoid of wild ideas," Lew Allen explains. "One of the ideas he had when he was at Los Alamos was that one could use a thermonuclear weapon to produce fissionable material, or tritium, by exploding it over a basin which contained raw material that would be transmuted by the neutrons from the bomb. Could you put a covering on the basin in such a way that it wouldn't get torn up by the bomb, because you'd probably want to do more than one bomb? How would material behave in a fireball? So I did a set of experiments aimed at looking at that.
"One of the experiments was to hang some spheres of raw material, surrounded by a fairly thick layer of graphite, from the tower of a bomb, and then see if we could recover the spheres—they were steel spheres with a capsule of material inside—and find out if the material really transmuted, and remained in the matrix. The idea was the carbon would protect the steel spheres, which would go flying away and embed themselves in the sand out in Eniwetok and then we'd recover them. And that worked. I also had some big cylindrical disks of steel with material inside them that we placed at the base of the tower to see how they would survive: three or four feet across and six or eight inches high. That could well be where Ted began thinking about what bombs did to big plates."
The surprise result—and one of the germs of Orion—was that some of the spheres were propelled farther than could be explained by blast effect alone. "We had trouble finding some of those steel spheres," Allen says. "We had thought we could find them using metal detectors. We hadn't realized that the sand at the base of that tower—there had been other shots there before—was littered with pieces of metal, fragments of the tower and what have you, so the metal detector just rang all the time. We ended up taking huge road scrapers and scraping off the top six or eight inches of the sand and just simply following along behind them and uncovering these things." One of the later tests happened to be one of Ted's early boosted designs—a test named "Viper" that was "a big step on the boosting front, a different design of a booster. I probably shouldn't go into that," says Ted.
Proposed
200-ton test vehicle, 1962: 30 feet in diameter,
0.78-second pulse period, 75-foot separation distance, 1.9-g
acceleration,
220-pound charges, yield unknown.
Lew Allen performed a similar series of experiments in Nevada, hanging spheres of material from shot towers in the desert during the Teapot test series in April 1955. "A number of these objects were subsequently recovered and examined," according to Bruno Augenstein at RAND. "From their condition and final landing places, it could be reasonably established that the bodies had been 'propelled' by some mechanism of the nuclear blast."[108] The results, both from Nevada and Eniwetok, attracted notice at RAND and among Edward Teller's group at Livermore who had been looking, independently and in advance of Sputnik, at the possibility of a bomb-propelled, ablation-driven upper stage for thermonuclear ICBMs. At a February 1957 conference, Livermore physicist Tom Wainwright noted that nonmetallic material such as Bakelite suffered markedly less ablation, a phenomenon that became the key to protecting Orion's pusher plate from repeated blasts. "When placed about 100 feet from the center of explosions of 15 to 25 kilotons, plastic specimens suffered very much smaller mass losses," he wrote.[109] Nothing came of the Livermore proposal, which died quietly in the interim between Ulam's 1955 study and the frenzy over Sputnik amid which Project Orion was launched.
After the atmospheric test ban put an end to such experiments. Lew Allen's balls remained among the relics from the era when Orion stood on the verge of advancing to nuclear tests. "They are still there," says Bud Pyatt, who has periodically returned to Eniwetok to study evidence from previous tests. "You can go and see these famous iron balls that, in terms of temperature, were within the 150,000 degrees Kelvin range of the fireball. The phenomena of the self-protection from ablation through the creation of a hot layer that was opaque enough to protect the remainder of the ball from any of the radiation were important observations in terms of could we create a layer or pusher that could exist that close to a nuclear explosion?" Why and how the objects survived so well was not fully understood in 1956, prompting a small group of curious physicists to take advantage of bomb-development and stockpile-reliability tests. "There are still several dozen completely unexplained weapons effects—and all we did was to keep testing the stockpile weapons, without trying to understand them," says Ted. "We knew much more about how to make bombs than about what they did."
According to Ted, it was Lew Allen's experiments that helped convince the skeptics—including himself. "Being able to preserve things that were within twenty feet from the center of the explosion, of tens of kilotons, was a big surprise to a lot of people. That we had those data and had photographs of spheres of metal that had been protected with graphite, showing no sign of any unusual explosion, is what led me to the feasibility of the concept as a whole." As Freeman remembers it, "These experiments helped us to persuade people that the idea of an Orion ship surviving inside a succession of fireballs was not absurd. They showed that solid objects survived much better than most people expected. They were important to us because we could say, 'Look, this piece of plastic lost only X millimeters of its surface sitting inside a fireball for half a second.' That made Orion seem less crazy."
When Lew Allen describes what Ted was thinking about in 1955, it sounds a lot like Orion, upside down: "You carved a big hemispherical basin, somewhere in some remote area, and then you shot relatively clean bombs off at the center of curvature of this thing. Because they were clean and because you designed this basin so that stuff didn't go flying out, you didn't contaminate the air or the surroundings very much at all. You banged off a certain number of these things—I've forgotten how many, about a dozen, say—and then you came back in and mined the products which would be either tritium or lithium 6 and fissionable thorium. The economics were really not unreasonable. It looked like all you needed as a covering was asphalt. The asphalt would ablate and it had enough flexibility that it wouldn't go rippling and tearing off, and the tests in the Pacific showed that the materials would stay in the matrix you prepared. Outside of this little tiny handicap, that one really didn't want to go banging off bombs all over the place, it looked like it would work pretty well. This was just before Sputnik. Ted could well have been thinking about the fact that he was not only flooding the stuff with neutrons, but he was also pushing on it pretty hard."
This scheme was known as BATS—for Bomb Assisted Tritium Supply. Orion was BATS turned right-side up. "Ted was a practical scientist who had participated in the design of some of the key weapons up there at Los Alamos, and was fully accepted in the theoretical community as being a real guy, not an off-the-wall guy," explains Lew Allen. "So, when he came up with these various schemes, I think if anybody else had done it, they would have been cast aside fairly quickly, but when he came up with them, they had a certain aura of plausibility about them just because of Ted."
"When Orion began, shooting bombs off in the atmosphere was really common," Allen continues. "That is, one was doing it all the time, and those of us in the business felt that most of the effects that people were concerned about were significantly exaggerated and that there really wasn't that big a problem. Obviously, the thoughts on that changed. But at least for a while there, the idea was not at all unreasonable. So, in the initial year or so at least, the issues were: Would a thing like this work?' It had so many technical challenges and it scaled up into such a big thing. Could you really make it work? It wasn't until later, when the test-ban treaty began to get signed, that people began to say, 'Hey wait a minute! Suppose this does work, would we really want to start shooting off the bombs?' All of us were skeptical that you would ever actually do this, but felt that it was such an imaginative and exciting idea that it was certainly worthy of the research that had to be done."