Buzz Blog | PhysicalCentral


By: Hannah Pell

Considering how much space waste is in orbit, the need to maintain and monitor cislunar space (the region between the Earth and the Moon) is becoming an increasingly important issue. To do so effectively may require spacecraft capable of propelling longer than those currently available, and nuclear reactors may offer a solution.

Recent news progress using nuclear technology to propel extended spaceflight – from the Rocket for Agile Demonstration Program Cislunar Operations (DRACO), SpaceNukes, among others – is an opportunity to reexamine the history of this technology and identify the origins of the nuclear propulsion: the Orion project.

The beginnings of nuclear propulsion

At the end of World War II, after witnessing the possible catastrophic destruction of nuclear weapons, physicists actively sought peaceful applications of these nuclear capabilities. Nuclear power, once considered “too cheap to measure,” is a well-known example of such efforts, but some saw it as another opportunity: space travel. Polish mathematician Stanislaw Oulam, who worked on the Manhattan Project, began preliminary calculations as early as 1946. Over a decade of work at Los The Alamos National Laboratory resulted in a report co-authored in 1955 (and several reports thereafter) titled “On a Method of Propelling Projectiles Using External Nuclear Explosions: Part I.Ulam’s idea of ​​a spacecraft propelled by thousands of nuclear bombs was taking shape.

Soon after, Ted Taylor, America’s leading atomic bomb designer at the time (though fiercely opposed to nuclear weapons), sold the idea of ​​a nuclear-powered spacecraft to General Atomic (also jokingly referred to as “Generous Atomics” by some physicists because of their vast financial resources), and the Orion project has started. Taylor knew Ulam through collaborative work at Los Alamos and described some of their conversations about fissile explosives in a 1995 oral history interview. Taylor recruited theoretical physicist and mathematician Freeman Dyson, who effectively joined him to bolster Orion’s credibility. “If you just talked about the project, said that you were going to propel a ship with nuclear bombs, the immediate reaction was that it was crazy. … They needed people with a solid reputation to have a chance to get it approved, ”Dyson explained in the BBC documentary. Towards Mars by A Bomb. Dyson, who dreamed of interstellar travel, handled rigorous calculations, proof of concept published in Physics Today showing that nuclear propulsion was indeed a viable option for deriving potential levels of radiation exposure per launch. (His son, science historian George Dyson, is the author of a detailed account of the Orion project).

What kind of science fiction is this? (In fact, Stanley Kubrick considered using nuclear propulsion technology in the making of 2001: A Space Odyssey). Let’s see if we can convince ourselves otherwise. Or, for fun, just go try Kerbal Space Program. I’ll wait.

Orion Physics 101 Project

The engineers of the Orion project saw its design in a fundamentally different way from other approaches of the time; rather than focusing on the minimum of what was physically permissible, why not take it a step further? The “mid-range” Orion would weigh several thousand tons, approximately the size of an ocean liner, and could hold a crew of 50 people. (The mass of the “Super” Orion was estimated at 8 million tonnes, the size of a city!) Orion would be designed for round trips to Mars, and even one-way trips to Saturn.

The propulsion of an Orion vehicle required the systematic and controlled triggering of successive nuclear explosions. You can imagine the “nuclear pulse units” being ejected one by one like on an assembly line; in fact, Project Orion scientists consulted with the Coca-Cola Company, believing that the soft drink company’s machines could be easily scaled to handle the unit, which resembled a soda can (pictured) below).

Diagram of an Orion nuclear pulse unit. Image credit: NASA.

Diagram of an Orion nuclear pulse unit. Image credit: NASA.

You might be wondering (quite reasonably): if explosions happened so close to the ship, wouldn’t they cause damage? The Orion design incorporated a 1,000-ton steel thrust plate mounted on dampers smoothing acceleration to levels humans could withstand, between 2 and 4g. However, there were two critical issues with the thrust plate: Calculations predicted that the plate would deteriorate (erode) if it was not shielded from repeated nuclear exposure, and that the shock waves from the explosions could. cause splinters or splinters of metal.

Declassified images of Project Orion tests. Video credit: United States National Archives.

Secrecy and militarization

The successful launch of Sputnik 1 in 1957 further magnified the competition between the United States and the Soviet Union amid the ongoing space race. This emergency meant that the federal government was eager to find a fast and efficient way to travel to space. The new National Aeronautics and Space Administration did not support Project Orion due to privacy concerns due to its structure as a civilian space program.

The Air Force, however, agreed to help fund it, but with another price. “Officially, this had to be justified to budget officials as a military program, so they had to invent bogus military requirements for it,” Dyson explained. The Air Force’s involvement in Project Orion, initially “a translation of a sword into a plowshare” and inspired by the hope of disentangling nuclear technology from its reliance on militarization, may have marked the beginning of its fall. “Military influences were inevitably at work there. ”

Eventually, a car-sized model of the Orion spacecraft was built, and then-President John F. Kennedy visited the California site to see it in person. Managers had hoped the presidential visit would help garner additional funding and political support, but Kennedy felt the last thing the world needed was a nuclear arms race in space, especially after the Missile Crisis in Cuba. In August 1963, the International Limited Nuclear-Test-Ban Treaty was signed, thus ending the Orion program.

“Death of a project”

In 1965, Dyson published an essay in Science titled “Death of a project“, attributing the demise of Project Orion to the Department of Defense, NASA executives, supporters of the nuclear test ban treaty and” the scientific community at large. “” Orion’s story matters because this is the first time in modern history that a major expansion of human technology has been suppressed for political reasons, ”he wrote.

Despite the strength of the science, Project Orion was morally difficult for many to support. “The idea is not crazy; the idea that we can do that is crazy, ”physicist and author Arthur C. Clarke said of Project Orion. It’s a confluence of closed secrecy against a backdrop of growing anti-nuclear sentiment that hasn’t exactly garnered broad support.

Johndale Solem, the former theoretical physicist from Los Alamos, offered a succinct summary: “In general, people shy away from the idea of ​​using nuclear explosives. I do; I recoil from this notion. Because I know we don’t have that kind of world. And I know that having nukes in space invites someone to abuse them. Indeed, Project Orion is an important reminder that scientific justifications may not inherently prove sufficient plausibility; what can be done may not be done. Nonetheless, physicists dreamed of extending humanity’s reach into the cosmos and sought out worlds beyond our own, limited and seemingly darkened by destruction. In a few ways, that feeling still rings true today.

Artist’s conception of a spacecraft from the Orion project. Image credit: NASA

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