In the decades since Project Pluto’s cancellation, the Russians have taken the core idea as their own—and unlike the Americans, do not appear concerned about the ethical quandaries it presents.
In the heat of the Cold War, the United States dreamed up some of the most audacious and terrifying weapon concepts imaginable. Among these was Project Pluto, a program to develop a nuclear-powered cruise missile capable of unlimited range and devastating effect. Known as the Supersonic Low Altitude Missile (SLAM), this nuclear ramjet-driven behemoth represented both a high point in US nuclear weapons design—as well as a sad example of how dangerous the Cold War was becoming.
America never went forward with this project. Interestingly, it was the Russians, decades later, long after the Cold War had ended with a victory for the United States, who created their own nuclear-powered cruise missile, the so-called “Burevestnik”—which today now threatens Ukraine and Europe.
How did this happen? And why did the United States abandon this mega project?
What to Know About “Project Pluto”
Project Pluto officially launched on January 1, 1957, as a joint effort between the United States Air Force (USAF) and the Atomic Energy Commission (AEC). Tasked with studying nuclear reactor applications for ramjet engines, the project was led by Lawrence Radiation Laboratory (now Lawrence Livermore National Laboratory) under Theodore Charles Merkle.
The concept built on earlier ideas from the National Advisory Committee for Aeronautics in 1954-55, amid broader Air Force explorations of nuclear propulsion for aircraft and missiles.
The goal was simple: create a cruise missile that could evade defenses by flying low and fast, powered indefinitely by a nuclear reactor. This SLAM missile could carry multiple nuclear warheads, too—in essence offering a recallable alternative to intercontinental ballistic missiles (ICBMs). Development soon shifted to Nevada’s Jackass Flats test site, where facilities included a remote-controlled railroad for handling components. By 1963, the project had cost $260 million (or about $2 billion today).
At the heart of Project Pluto was the nuclear ramjet engine, a design that superheated incoming air with a fission reactor instead of chemical fuel. Air entered at supersonic speeds, passed over the unshielded reactor core, expanded from the intense heat (up to 2,500 degrees Fahrenheit), and was expelled as thrust. The reactor, codenamed “Tory,” used ceramic fuel elements from Coors Porcelain Company and highly enriched uranium oxide and beryllium oxide for moderation. Its initial version produced 46 megawatts of power, while the later Tory II-C reached 513 MW, simulating around 35,000 pounds of thrust.
The SLAM missile would launch from the ground via rocket boosters, then engage the reactor for Mach 3+ at altitudes as low as 150 meters (492 feet). Guidance relied on inertial navigation and terrain-comparison radar, enabling accuracy within dozens of feet over a theoretical range of 113,000 miles—allowing it to circle the globe many times. The missile could even loiter for months, dropping up to 16 hydrogen bombs before self-destructing with its own thermonuclear warhead. In essence, the US Air Force built the Russian Burevestnik missile—70 years before the Russians did.
Nuclear-Powered Missiles Are Literally Radioactive
Project Pluto had one major drawback: its radioactive exhaust. While nuclear-powered submarines and aircraft carriers have contained reactors that prevent the release of radiation, the missile lacked any such safeguards. As it flew, its unshielded reactor would blast out a trail of deadly radiation over the path it crossed.
Of course, one might argue that in the event of a nuclear war, exposing the public to radiation was inevitable in any case. But even without a warhead, the SLAM was unquestionably an indiscriminate “weapon of mass destruction”—spewing lethally toxic clouds over allies and neutrals on its way to the USSR. In fact, due to contamination fears, no flight test was ever conducted. No safe overland path existed, and ocean disposal of spent reactors was deemed unacceptable amid growing environmental awareness.
So, despite its technical successes, Project Pluto was scrapped on July 1, 1964. Advancements in ICBMs, like the Minuteman, offered faster, cheaper alternatives without the vulnerabilities of low-altitude flight (and the obvious side effects). Budget cuts slashed funding from $8 million, reflecting shifting priorities. Geopolitical risks, including provoking the USSR, along with ethical concerns over indiscriminate destruction, sealed the project’s fate.
In the decades since Project Pluto’s cancellation, the Russians have taken the core idea as their own. The Kremlin has tested the Burevestnik missile several times in remote regions of the country—even though it has not solved the radioactive exhaust problem. Indeed, the missile has been nicknamed the “Flying Chernobyl,” and has already been involved in several radiation accidents—including one that killed a handful of Russian civilians.
However, unlike the Americans, the Russians do not appear concerned about the ethical quandaries or geopolitical risks the missile presents. If anything, Moscow seems enticed by the ethical and geopolitical problems associated with this system.
Nevertheless, as hypersonic and drone technologies advance, a nuclear-powered SLAM seems somewhat ridiculous. Even though the Americans long abandoned their Project Pluto, today, the Russians have their own—and they are disinclined to abandon it as readily as the Americans did.
About the Author: Brandon J. Weichert
Brandon J. Weichert is a senior national security editor at The National Interest. He is also a contributor at Popular Mechanics, and has consulted regularly with various government institutions and private organizations on geopolitical issues. Weichert’s writings have appeared in multiple publications, including The Washington Times, National Review, The American Spectator, MSN, The Asia Times, and countless others. His books include Winning Space: How America Remains a Superpower, Biohacked: China’s Race to Control Life, and The Shadow War: Iran’s Quest for Supremacy. His newest book, A Disaster of Our Own Making: How the West Lost Ukraine is available for purchase wherever books are sold. He can be followed via Twitter @WeTheBrandon.
Image: Wikimedia Commons.
