Atomic warfare, nuclear doctrine, mutually assured destruction, a dead man's switch, Star Wars, these all are punchlines which highlight the crux of the era we now know as the Cold War.  Both of the world's greatest superpowers clashed with one another in a different war that was fought with science and technological advancement.  It was a war of the minds, imaginations, and dreams.  However, it would be foolish to think that only the sane amongst those imaginations and dreams were the ones to make it to the drawing board.  In some cases, this meant that nightmares would become reality.  No one can explain such the realization of such horrors better than the people who were suffocating by being alive during thirteen days in October of 1962.  Even though these were some of the most tense days in the common era, with being one of the closest moments to a nuclear holocaust, they are not the pinnacle of what truly devilish design arose from the Cold War.  That had started in 1957, and would continue until President Lyndon Johnson entered office in 1963.  Even so, the thought of such a weapon entered the defense community - a harrowing tale ensues as we examine Project Pluto; "the Devil's dirty secret."

The Military Doctrine of the 1950s

After the successful deployment of the atomic bomb in Japan in 1945, the doctrine of the U.S. military forces adapted to include atomic weapon systems in their plans and practices.  The Truman Doctrine, the foreign policy which highlighted the need for communist containment, added the dimension of defense into American military policy as well.  As such, many military weapon systems were deployed for defensive purposes as well.  This included atomic weapon systems and later nuclear devices.  The first short and medium range devices for use as atomic defensive weapons were the Honest John and Little John rocket systems.

Pictured right: The MGR-1 Honest John 762 mm rocket system, the first of its kind.

The concept was to deploy the weapon systems in areas at risk for Soviet invasion.  Should the Soviets break through, these weapons would be used to contain the Soviet forces behind a wall of radiation.  Likewise, fallout shielded infantry and cavalry could then be deployed to fight off the invaders.  By the mid 1950's, the U.S. Army maintained most of these weapon systems, including the two John systems, and the M65 280 mm Atomic Cannon.  Subsequent field artillery systems were designed with the requirement that they fire an atomic shell.  This included the retrofitted M101, the M114, and M115.  But still, a natural deterrent would be one that could strike with little notice, have a one up against the enemy, and do so with speed while remaining virtually invisible.

Pictured right: Atomic Annie is another example of front-line atomic weapon deployment systems.


Applications of Nuclear Devices & Power

As early as the 1940s, it was already apparent that nuclear power was capable of more than just sheer destructive force.  It was also capable of providing a means of clean and sustainable energy if stabilized.  This signified the beginning of research for nuclear power plants, both on a small and a massive scale.  The modern design for nuclear power plants comes from this era.  In addition, all branches of military were looking for ways to harness this power within dynamic weapon systems, such as aircraft carriers, submarines, ships, planes, and even tanks.  If an engine had previously functioned using fossil fuel, the military wanted to know if it was possible to transition it to nuclear power.  The issue with any nuclear reactor was stability, however.  Turbulence and weight posed a problem in larger aircraft, such as the NB-36.  However, smaller designs were still considered plausible.

Pictured left: The NB-36 was a proposed nuclear powered bomber that never advanced beyond the prototype phase.

Unconventional Propulsion

By the end of World War I, alternative propulsion systems were in the process of examination.  The first *jet design (not to be confused with rocket designs) was conceived in the seventeenth century.  It was not until 1906, however, that the first of these was designed; the pulsejet.  By the time World War II had ended, however, the highest performing engine was arguably the ramjet.  The ramjet, however, required a booster phase for the engine to function properly.  When boosted to its minimal operating speed of Mach 3, it was capable of achieving speeds that achieved hypersonic thresholds of Mach 5.  Some were designed to perform as high as Mach 7.  By 1950, the most successful deployment of a ramjet engine remained the German Luftwaffe's Komet aircraft, even with a loss that exceeded 75%.

Pictured right: Profile design of the proposed SLAM concept.

Pictured above: Artists impression of the SLAM - the Flying Crowbar.

The Birth of SLAM

The Supersonic Low-Altitude Missile (SLAM) design was conceived by the demand of the United States Air Force's (USAF) demand for a cruise missile weapon system capable of utilizing both nuclear power and ramjet technology to deliver a payload over enemy territory.  The order was made on 1 January 1957 for feasibility studies to begin, and research to be funded with the intent to procure materiel and produce such a weapon.  The cruise missile would ensure a relatively cheap means to deploy weapons to virtually anywhere in the world with little to no notice, and it would be able to be launched and guided at an elevation that would make it virtually invisible to radar.

The missile was designed to launch Multiple Independently Targeted Vehicle warheads (MIRV), enabling the missile to strike multiple targets at the same time.  However, the problem was still the need for the ramjet.  Testing at Jackass Flatts provided some limited success, with ramjet deployments lasting anywhere between sixteen seconds and five minutes.  Reducing a nuclear reactor to the size that was required was a challenge, especially considering the power required by the drivetrain from the powerplant.  The short-lived testing of the nuclear powered ramjets suggested that the project would have taken much longer to reach production, however, the Pentagon cancelled the project in 1964 prior to the completion of testing.  They cited the reason as the weapon was "too provocative", especially in light of events in Cuba.  But what exactly made the SLAM so provocative?

The Capabilities of a Flying Crowbar

A weapon of brutality, that's what earned SLAM and Project Pluto it's modern moniker of the Flying Crowbar.

The weapon was designed with various states of deployment means, however, it's specifications, design, and the time which it was conceived point to a heinous and ethical concern.  Let's first talk about the weapon's intent.

It's nuclear powerplant meant that it was capable of flying virtually without any range restrictions.  That is, the weapon could stay in a state of perpetual flight after it was launched as long as the reactor or payload did not explode or shut down.  In a state of heightened tensions, this weapon could be launched and left in a state of flight, say over an ocean, ready to strike at the behest of its operator.  Due to the nature of its powerplant and its payload, however, the only way for it to land again - even if there was no need for it to strike - would result in massive nuclear fallout and destruction.

It's nuclear powerplant also was not just a powerplant.  The use of a nuclear reactor meant that it was capable of melting down and going critical.  While in critical mass, the missile would be able to continue its flight, as the reactor would not simply cease to power the powertrain.  Meanwhile, the only means of exit of waste and radiation would be through the exhaust of the missile, falling over whatever areas the missile was traversing.  In theory, the weapon would be able to jettison it's payload and force a critical mass, thereby causing nuclear explosions but spreading fallout radiation to virtually anywhere.

The multiple payload system ensured that multiple targets could be struck with the weapon.  Some designs included that up to ten separate MIRV warheads be deployed.  By this time, thermonuclear devices had been employed, and multiple Intercontinental Ballistic Missiles (ICBM) had been designed as well.  The largest test carried out by the Americans at the time was roughly 15 MT, totally an output of over 150 MT of explosives, three times that of the Russian Tsar Bomba.

Pictured above: Cross-section of SLAM's multi-warhead design

A Condition of the Heart

While SLAM would undoubtedly be a game changer in the Cold War era, it was felt that it was too much of a game changer.  Multiple other means of atomic and nuclear deployment were readily available, including the fresh B-52 Stratofortress.  The weapon presented a moral and ethical dilemma to those who were examining it in the Department of Defense.  Tensions of the Cuban Missile Crisis had brought a stark realization of the dangers of an atomic battle.  The weapon was conceivably capable of destroying all life on Earth on it's own.  In addition, the risk of it's malfunction en route to its target presented difficulties that the military was unable to reconcile.

Later ICBM designs also were deploying MIRV concepts in large quantities.  These concepts proved to be just as destructive as the SLAM payload concept, without the risk of runaway vehicles and the chance of single-impact strikes.  It did not require the eventual critical mass of a weapons system or long-term nuclear fallout risk.  Long-range, deep-penetration bombers were also being deployed, such as the B-58 Hustler which reduced the risk for out-of-control deployment.

Pictured left: Artists romanticized concept of SLAM, the system could still fly after deploying it's nuclear payload.


The technology and dangers of SLAM have not totally been removed, despite the projects cancellation and termination in the 1960s.  SLAM's concept of MIRV deployment continued in many weapon systems and continues with most cruise missile and ballistic missile designs.  Further, nuclear reactors were eventually incorporated into larger naval vessels, such as destroyers and aircraft carriers.  Perhaps most significantly, however, is that recently the notion of a nuclear powered missile has returned.  The Russian SSC-X-9 Skyfall missile was announced by Vladimir Putin in March of 2018, with a reported failed launch in 2019.  It remains unclear, however, what exactly is the tactical use for such a weapon with unlimited range and what potential payload may be on board.  However, the original risk of Pluto seems to have been curbed for now, but for how long - only time will tell.

Further Reading (Inconclusive)

Gaddis, John Lewis.  The Cold War: A New History. Penguin Publishing, New York. 2005.

Publications for this system are available in limited quantities from the Defense Technology Information Center (DTIC).

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