From: Hannah Pell

Given how much space junk is in orbit, the need to maintain and monitor cislunar space (the region between the earth and the moon) becomes an increasingly important issue. Doing this effectively may require spacecraft that are available longer than currently, and nuclear reactors can offer a solution.

Recent news of advances in the use of nuclear technology for advanced space travel – including from SpaceNukes’ Demonstration Rocket for Agile Cislunar Operations (DRACO) program – provides an opportunity to review the history of this technology and the origins of nuclear propulsion determine: Project Orion.

The beginnings of nuclear propulsion

At the end of World War II, after experiencing the catastrophic destruction from nuclear weapons, physicists actively sought peaceful uses of such nuclear capabilities. Nuclear power, once considered “too cheap to measure,” is a well-known example of these efforts, but some saw another opportunity: space travel. The Polish mathematician Stanislaw Ulam, who was working on the Manhattan Project, carried out preliminary calculations as early as 1946. More than a decade of work at Los Alamos National Laboratory resulted in a co-authored report from 1955 (and several reports later) entitled “About a Method.” the propulsion of projectiles by external nuclear explosions: Part I. “Ulam’s idea for a spaceship powered by thousands of atomic bombs was taking shape.

Shortly thereafter, Ted Taylor, America’s leading atomic bomb designer at the time (though firmly against nuclear weapons), sold the idea of ​​a nuclear-powered spaceship to General Atomic (jokingly referred to as “Generous Atomics” by some physicists because of its plentiful size) financial resources) and the Orion project began. Taylor knew Ulam from working together in Los Alamos and, in an oral history interview in 1995, described some of their conversations about fissile explosives. Taylor recruited the theoretical physicist and mathematician Freeman Dyson, who effectively joined in to help build Orion’s credibility. “When you were just talking about the project and you said you were going to power a ship with atomic bombs, the immediate reaction was that it was crazy. … You needed people with a solid reputation to stand a chance of getting this approved, ”Dyson explained in the BBC documentary To Mars by A Bomb. Dyson, who dreamed of interstellar travel, performed rigorous calculations that emerged from a proof of concept published in Physics Today that showed that nuclear propulsion was indeed a viable option for inferring the potential radiation exposure per launch. (His son, the science historian George Dyson, wrote 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 manufacture of 2001: A Space Odyssey). Let’s see if we can convince ourselves otherwise. Or just give it a try in the Kerbal Space Program for fun. I’ll wait.

Orion Physics 101 project

Project Orion engineers envisioned design to be fundamentally different from other approaches at the time. Instead of focusing on getting to the bare minimum of what is physically permissible, why not get bigger? “Midrange” Orion would be several thousand tons, about the size of an ocean liner, and would accommodate a crew of 50 people. (The mass of “Super” Orion was estimated to be 8 million tons, the size of a city!) Orion was supposed to be designed for round-trip flights to Mars and even simple trips to Saturn.

Propulsion of an Orion vehicle required the systematic, controlled release of successive nuclear explosions. You can imagine the “nuclear pulse units” being ejected one after the other as if on an assembly line; In fact, the Project Orion scientists consulted the Coca-Cola company, thinking the soft drink company’s machines could easily be scaled to handle the unit, which resembled a beverage can (see image below).

Scheme of an Orion core pulse unit. Image source: NASA.

Scheme of an Orion core pulse unit. Image source: NASA.

You may be asking (rightly): If explosions happened this close to the ship, wouldn’t they cause damage? The Orion design included a 1000-ton steel pusher plate mounted on shock absorbers that smooths acceleration to a human-safe level between 2 and 4g. However, there were two critical problems with the pressure plate: calculations predicted that the plate would ablate (erode) if left unprotected from repeated nuclear exposure, and shock waves from the explosions could cause chipping or breaking off of metal fragments.

Released footage from Project Orion tests. Video Credit: US National Archives.

Secrecy and militarization

The successful launch of Sputnik 1 in 1957 increased competition between the United States and the Soviet Union amid the ongoing space race. This urgency led the federal government to endeavor to find a quick and effective means for space travel. The newly established National Aviation and Space Administration did not support the Orion project due to its structure as a civil space program for reasons of confidentiality.

However, the Air Force agreed to provide funding, but at a different price. “Officially, it had to be justified to budget officers as a military program, so they had to invent fake military requirements for it,” Dyson explained. The Air Force’s involvement in the Orion Project, originally “a translation of a sword into a ploughshare” and inspired by the hope of releasing nuclear technology from its dependence on militarization, may have marked the beginning of its downfall. “Military influences were inevitably at work.”

Eventually, a model car 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 president’s visit would help secure additional funding and political support, but Kennedy felt the last thing the world needed was a nuclear weapons race in space, especially after the Cuban Missile Crisis. In August 1963, the international treaty for a limited nuclear test ban was signed, effectively ending the Orion program.

“Death of a Project”

In 1965 Dyson published an essay in Science entitled “Death of a Project,” in which he attributed the demise of Project Orion to the Department of Defense, the leaders of NASA, proponents of the Nuclear Test Ban Treaty, and the “scientific community at large.” “The story of Orion is significant because it marks the first time in modern history that a major expansion of human technology has been suppressed for political reasons,” he wrote.

Despite the soundness of science, it has been morally difficult for many to leave the Orion project behind. “The idea is not crazy; The idea that we could do it is crazy, ”said physicist and author Arthur C. Clarke of the Orion Project. It is a confluence of narrow-minded secrecy in a context of growing anti-nuclear sentiment that did not find widespread support.

Johndale Solem, the former theoretical physicist from Los Alamos, summarized it briefly: “In general, people shy away from the idea of ​​using nuclear explosives. I do; I shrink from this idea. Because I know we don’t have that kind of world. And I know that having a nuclear weapon in space invites someone to abuse it. ”Indeed, the Orion Project is an important reminder that scientific reasoning by nature is not sufficiently plausible; what can be done cannot be done. Nevertheless, physicists dreamed of expanding the reach of humanity for the cosmos and sought worlds beyond our own, limited and apparently tarnished by destruction. In a way, that feeling still sounds true today.

Artistic conception of a Project Orion spaceship. Photo credit: NASA


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