I don’t know how old I was when I first heard about Orion, the “spaceship propelled by atomic bombs.” I was probably in my mid-teens. I do remember thinking, “What a cool idea!” I wanted to know all about it. Unfortunately, there wasn’t all that much publicly available information about Orion back then. The concept was something of a legend in science fiction circles.
By the late ’70s and early ’80s, I finally began to learn more. Jerry Pournelle wrote about Orion a bit in some of his science columns for Galaxy, and a picture of a conceptual Orion-style spaceship appeared in an installment of Carl Sagan’s popular Cosmos PBS series. I eventually tracked down Freeman Dyson’s article in Science, “Death of a Project,” and entirely via serendipity I came across Kenneth Brower’s The Starship and the Canoe, a biographical book about Freeman Dyson and his relationship with his son George.
Later came science fiction novels with nuclear-bomb-propelled spacecraft as keys to the plot. Orion Shall Rise, by Poul Anderson comes to mind. And the aliens in Niven and Pournelle’s Footfall are defeated when a crash program by the humans produces an Orion spaceship loaded for bear and ready for battle that proves too formidable for them.
Though the project may have died as Freeman Dyson detailed in his piece, the idea survives, and the concept has perhaps more power now than ever to capture the imagination and hold it. And my children, should their imaginations demand it, won’t have the trouble I had in learning about Orion. For in a fit piece of historical irony, George Dyson, son of Freeman and the “canoe” portion of Brower’s book, has written the definitive (unclassified) account of Project Orion.
Project Orion: The True Story of the Atomic Spaceship (Henry Holt and Co., 2002. ISBN 0-8050-7284-5) is a remarkably interesting book, and not just because of the spaceship. It offers a look into an alternate universe where physicists and engineers were allowed to work essentially unfettered by the demands of bureaucrats and paperwork. It is a world where an idea could go from the chalkboard to full-scale testing in the south Pacific within the same calendar year. Indeed, General Atomic, where most of the work on Orion was done, seems to have been as Heinleinesque a haven for can-do scientists as has ever existed on this Earth.
For those (no doubt few) of you who have no idea, or perhaps only a hazy idea, of what Orion was all about, picture this: A spaceship, about 200 feet tall, 30 or so feet wide at the base (which consists of a thick metal plate), standing out in the hot desert sun. The weight of this ship is 4000 tons, 25% of which is payload, 25% of which is that pusher plate on the bottom, and the rest of which is ship and nuclear bombs. Connecting the base plate to the upper part of the ship are six tall shock absorbers.
The clock counts down and at T minus zero we have blast off—and in this case, we really do mean blast off, as the first bomb detonates underneath the plate. Of course, the common understanding of nuclear bombs is that they are good for nothing except blowing things to smithereens, so what a surprise it is to see the spaceship begin to rise into the sky, rather than disappearing in a mushroom cloud. The first blast is followed less than a second later by another, and then another, and another. Blast follows blast follows blast, the potency of the blasts slowly increasing from shot to shot, until the last blast putting our Orion ship into orbit is, at five kilotons, perhaps ten times more powerful than the one that got her started.
To a generation for which World War II exists only in books, movies, and a father’s memories, and for which the mushroom cloud will forever be vilified as “the destroyer of worlds,” it may seem inconceivable that a spaceship like Orion can exist at all. How can anything withstand the blast of a nuclear bomb? Indeed, even during its heyday, at a time when H-bombs were routinely air, land, and sea-tested, the Orion concept was considered outlandish at best, and more often than not, self-evidently suicidal. As Freeman Dyson recognized, “If you do not think about it carefully, it looks obvious that you can’t do it.” (p. 66)
But when you do think about it carefully . . .
It helps to know what made Ted Taylor, the driving force behind Orion, come to believe his spaceship might work in the first place, and this is described by George Dyson in a chapter entitled “Lew Allen’s Balls.” It is the case that during some nuclear tests, iron and steel balls containing some “test material” were suspended near the towers that held the test bomb. The spheres were coated with graphite, and it was hoped they would survive the blast enough, even after having been hurled a considerable distance, to be recoverable, thus protecting the “test material” for examination. Though some of these spheres had literally been within 20 feet of the center of a tens-of-kilotons nuclear explosion, surprisingly they often showed no evidence of it. The heat and radiation from the bomb would cause the graphite coating to ablate, and this would protect the spheres. So Taylor reasoned that if a coated sphere could survive the blast, so could a coated pusher plate.
It also helps to know that Ted Taylor was the Beethoven of nuclear bomb design. He knew how to make atomic bombs that required less than a kilogram of plutonium. Furthermore, he knew how to make shaped nuclear explosions, which greatly enhanced the per-pulse efficiency of each charge. So the image that no doubt comes to most people’s minds of some kind of big water-tower-looking thing atop a Hiroshima-esque mushroom cloud is a false one. It would have looked much more like a Saturn V launch with the bright exhaust at the tail strobing at about one hertz.
(The astute reader has perhaps already noticed in the preceding paragraph two clues as to why many of the official reports written for the Orion project remain classified more than 40 years later. Details as to just how little plutonium you really need to build a nuclear bomb are details best kept under wraps. Secrets about how to get most of the destructive energy in your nuclear weapon to go just one way are secrets best held close to the vest. During many of the interviews Dyson conducted with former Orion project workers, they would interrupt themselves to say, “But I can’t talk about that,” or words to that effect.)
An early version of the “baseline” 4,000-ton Orion vehicle pictured the use of 800 bombs to reach a 300-mile orbit. The first bombs would only yield about .15 kilotons, and it would take until about bomb number 100 before you got to the “standard” charge of 5 kilotons each. You can use smaller bombs in the atmosphere because the surrounding air allows for tighter coupling of the charge energy to the plate.
That’s a lot of bombs. One big fear with building Orion was just this: What do you do if one of your bombs doesn’t go off? Scarier than that was the fear that only the high explosive surrounding the core might go off, and not the nuclear explosion itself. Then you’d have a load of high-velocity shrapnel slamming into your pusher plate. Ted Taylor said their solution was to “make damn sure they all go off.” (P.91)
Another big fear is radiation. It’s obvious that if the pusher plate didn’t also protect the crew from the radiation of the bombs, the entire Orion propulsion idea, at least for manned spaceships, would have been a non-starter. That leaves us with the problem of fallout from the bombs as the ship leaves the surface of the Earth.
Orion was conceived in an era when above-ground nuclear tests were commonplace. A flight or two of a full-scale Orion space vehicle would have only added a percent or two of additional fallout into the background that was already there by virtue of weapons testing. Nevertheless, as the problem of fallout and nuclear testing in general began to weigh more and more heavily on the politicians during the late ’50s and early ’60s, it soon became clear that Orion might never be allowed to lift off from Earth. So greater effort was put into designing smaller Orion ships that could be launched in pieces via chemical rockets for assembly in space. Given this possibility, even Wernher von Braun became an enthusiastic supporter of Orion.
Unfortunately, the book brings to light here one caveat about fallout that was certainly new to me. As it turns out, simply not using the bombs until the ship is in orbit will not prevent the fallout from reaching the Earth’s surface. The bomb material is ionized by the explosion and the cloud of charged particles (many of them radioactive nuclei) gets trapped by the Earth’s magnetic field. So if fallout is a big concern, then the Orion ship must either be boosted outside the Earth’s magnetosphere prior to using the drive (and if we can do that, do we still need Orion?), or we need to use cleaner bombs.
It’s been 40 years since the program officially closed up shop. Right up to the end, Ted Taylor was still trying to save it. He found solid support from one Lt. Col. John R. Burke (well known at the time from other nuclear-powered projects). In January of 1965, Burke argued in favor of preserving Orion with these words, and they remain true today: “ORION is not just another advanced propulsion system. Practically every DOD/Air Force and NASA evaluation over the past 3 years has concluded that ORION provides the only capability for missions well beyond those achievable with chemical or nuclear rocket propulsion. The results point to a technique of rapidly traversing interplanetary distances substantially superior to any other method known today. . . .” (p. 267)
If there are some methods “unknown” to most of us but perhaps mastered in a black-budget bunker, then we may never need Orion to own the Solar System. For myself, I have never been turned off by the idea of using nuclear bombs to propel a spacecraft, not even if one launches from the ground. Hell, the twenty-first century contains so many other ways to kill you that I wouldn’t care if the background radiation levels went up a bit just so long as it meant I had a fighting chance of leaving the Earth altogether in a decade or two.
And NASA appears to be getting on board again to some extent. On page 292 Dyson relates, “NASA is dusting off the old idea, both as a prospect for future interplanetary missions and as a near-term contingency plan for asteroid and comet defense. The Nuclear Pulse Propulsion of Orion times has been renamed ‘External Pulsed Plasma Propulsion’—removing most references to ‘nuclear’ and all references to ‘bombs.’”
A “rose by any other name,” I guess.
