Be worried. Be very worried.

The new era of 21st century missile design could lead to developments even scarier than the Cold War

An accident on August 8 at the Nyonoksa missile testing range in Arkhangelsk Oblast (district), Russia, has focused attention on the more terrifying aspects of modern weapons development. The Russian atomic energy commission, Rosatom, announced something went wrong during a test of a nuclear-powered liquid-fuelled jet propulsion system on August 8. At least five technicians died at the offshore site. Radioactivity spiked to 16 times the normal levels locally, and there were evacuations. This is actually not particularly dangerous — Chernobyl hit 7,000 times normal. 

Nuclear-powered flight was first researched in the 1950s with both the US and the USSR seeing this as an obvious pathway to weapons development during the Cold War. But both sides had shelved the research by the early 1960s. The engineering problems in developing a nuclear powered flyer were very serious. 

Designing reactors for nuclear-powered ships and power plants generating electricity are both relatively easy, even if the early designs turned out flawed in the light of power plant disasters at Chernobyl, Three Mile Island, Fukushima, and the demise of the Kursk nuclear submarine. But any flight propulsion system needs a good power-to-weight ratio with high power and low weight. 

One of the issues with nuclear power plants is that they are heavy. A lot of shielding is also required if there is human cargo due to the potentially lethal radiation. There are also issues with massive heat generation. 

By the 1960s, both the US and the Soviet Union had the engineering skills to produce jet engines with far better power to weight ratios than nuclear plants. Conventional rockets also delivered much better power to weight ratios. 

In March 2018, Russian President Vladimir Putin announced that Russia was designing, or had designed, several new weapons including a nuclear-powered cruise missile and a nuclear-powered torpedo. In an unusual populist move, Russians were asked to vote online on names for these weapons. The missile was named Burevestnik (petrel, a seabird) while the torpedo was called Poseidon (the Greek god of the sea). The Nato codebook refers to the Burevestnik as the Skyfall. 

In February 2019, it was announced that the miniaturised power plant designed for the Burevestnik had been successfully tested. Cruise missiles are designed to fly very close to the ground to evade radar detection. Since it cruises at low speeds, it doesn’t even require much power and hence, the nuclear engine can be very small. 

One advantage of using a nuclear power plant is that it doesn’t require refuelling for very long periods. A nuclear-powered missile with a few kilograms of fuel could have effectively unlimited range, and stay up in the air for years at a time. Using a smart on-board computer, it could also be programmed to change trajectory randomly making it near impossible to detect, or intercept. 

The actual design of the propulsion system is classified. It’s likely, going by the 1950s experiments that any engine would be started by conventional means before switching over to nuclear. The missile could use nuclear power in several ways. One is to convert heat from radioactive decay directly into electricity — this is the method used in Nasa’s Curiosity Rover. Another way is to use radioactive heat to ignite conventional liquid fuel rockets with fuels like liquid hydrogen. 

The most likely design however, would be some sort of nuclear-powered ramjet. A ramjet is like a turbocharger — it only operates in a vehicle that’s already moving at high speeds. Air is drawn in at high speed, compressed in a chamber of the engine, and heated up. The hot air tries to expand and it’s forced out, creating a thrust. Using radioactive heat to heat the air, a nuclear ramjet could fly for years in theory. It could, again in theory, hit insane speeds such as Mach 10 or more. 

The engineering problems are as follows. The heat generated by nuclear processes is tremendous and it’s hard to put together a lightweight material that can withstand those temperatures. Due to weight constraints, radioactive shielding is also difficult. The exhaust will be radioactive, contaminating the flight path. So, once it’s up, a nuclear-powered missile is bound to cause some radioactive contamination, even without warheads. 

The research into this stopped for these very good reasons. Even Cold War hawks baulked at the thought of unleashing missiles with radioactive exhausts. The research has started up again with Putin explicitly stating that Russia needs weapons that can evade anti-missile shields. New materials and AI can overcome some engineering constraints but those cannot eliminate radioactive exhaust. The new era of the 21st century missile design could lead to even scarier developments than the Cold War.