Both concepts are insane, that is the nature of nuclear weapons, but an “autonomous” launcher is a bit LESS insane than the second coming of Project Pluto: (aka “The Flying Crowbar”)

How the mainstream media reported an August 8 accident at a top-secret missile test facility in northern Russia should serve as a cautionary tale regarding the dangers of rushed judgments via institutional bias.

In the days following the initial report of the accident, the media exploded with speculation over both the nature of the device being tested at the Nenoksa State Central Marine Test Site and the Russian government’s muted response. Typical of the hysteria was the analysis of Jeffrey Lewis, director of the East Asia Nonproliferation Program for the James Martin Center for Nonproliferation Studies and editor of the blog “Arms Control Wonk.”

Lewis and his collaborators penned a breathless article for Foreign Policy that asked, “What Really Happened?” According to Lewis, the answer was clear: “The reference to radiation was striking—tests of missile engines don’t involve radiation. Well, with one exception: Last year, Russia announced it had tested a cruise missile powered by a nuclear reactor. It calls this missile the 9M730 Burevestnik. NATO calls it the SSC-X-9 Skyfall.”

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They’re all wrong. Here’s the real story of what actually happened at Nenoksa.

Liquid-fuel ballistic missiles are tricky things. Most Russian liquid-fueled missiles make use of hypergolic fuels, consisting of a fuel (in most cases asymmetrical dimethylhydrazine, or heptyl) and an oxidizer (nitrogen tetroxide), which, when combined, spontaneously combust. For this to happen efficiently, the fuel and oxidizer need to be maintained at “room temperature,” generally accepted as around 70 degrees Fahrenheit. For missiles stored in launch silos, or in launch canisters aboard submarines, temperature control is regulated by systems powered by the host—either a generator, if in a silo, or the submarine’s own power supply, if in a canister.

Likewise, the various valves, switches, and other components critical to the successful operation of a liquid-fuel ballistic missile, including onboard electronics and guidance and control systems, must be maintained in an equilibrium, or steady state, until launch. The electrical power required to accomplish this is not considerable, but it must be constant. Loss of power will disrupt the equilibrium of the missile system, detrimentally impacting its transient response at time of launch and leading to failure.

Russia has long been pursuing so-called “autonomous” weapons that can be decoupled from conventional means of delivery—a missile silo or a submarine—and instead installed in canisters that protect them from the environment. They would then be deployed on the floor of the ocean, lying in wait until remotely activated. One of the major obstacles confronting the Russians is the need for system equilibrium, including the onboard communications equipment, prior to activation. The power supply for any system must be constant, reliable, and capable of operating for extended periods of time without the prospect of fuel replenishment.

The solution for this power supply problem is found in so-called “nuclear batteries,” or radioisotope thermoelectric generators (RTG). An RTG generates electricity using thermocouples that convert the heat released by the decay of radioactive material. RTGs have long been used in support of operations in space. The Russians have long used them to provide power to remote unmanned facilities in the arctic and in mountainous terrain. Cesium-137, a byproduct of the fission of U-235, is considered an ideal radioisotope for military application RTGs.

On August 8, a joint team from the Ministry of Defense and the All-Russian Research Institute of Experimental Physics, subordinated to the State Atomic Energy Corporation (ROSATOM), conducted a test of a liquid-fueled rocket engine, in which electric power from Cesium-137 “nuclear batteries” maintained its equilibrium state. The test was conducted at the Nenoksa State Central Marine Test Site (GTsMP), a secret Russian naval facility known as Military Unit 09703. It took place in the waters of the White Sea, off the coast of the Nenoksa facility, onboard a pair of pontoon platforms.

The test had been in the making for approximately a year. What exactly was being tested and why remain a secret, but the evaluation went on for approximately an hour. It did not involve the actual firing of the engine, but rather the non-destructive testing of the RTG power supply to the engine.

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When the actual testing finished, something went very wrong. According to a sailor from the nearby Severdvinsk naval base, the hypergolic fuels contained in the liquid engine (their presence suggests that temperature control was one of the functions being tested) somehow combined. This created an explosion that destroyed the liquid engine, sending an unknown amount of fuel and oxidizer into the water. At least one, and perhaps more, of the Cesium-137 RTGs burst open, contaminating equipment and personnel alike.

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The Russian Meteorological Service (Roshydromet) operates what’s known as the Automatic Radiation Monitoring System (ASKRO) in the city of Severdvinsk. ASKRO detected two “surges” in radiation, one involving Gamma particles, the other Beta particles. This is a pattern consistent with the characteristics of Cesium-137, which releases Gamma rays as it decays, creating Barium-137m, which is a Beta generator. The initial detection was reported on the Roshydromet website, though it was subsequently taken offline.

This makes a lot more sense than a nuclear ramjet, if just because you could test it without the certainty of a radiological incident.

Also, this sort of weapon fits right into Russian, and Soviet, doctrine.