Nuclear rocket engine – the path to the heart of the Burevestnik
The Tory II Nuclear Jet Engine – A True Horseman of the Apocalypse
Every engine is different
Physicists from Los Alamos National Laboratory can rightfully be considered the pioneers of nuclear-powered interplanetary travel. Although nuclear propulsion systems never reached space, the idea was first proposed during the famous Manhattan Project. A trio of scientists—Stanislaw Ulam, Frederick Reines, and Frederick de Hoffman—proposed two nuclear propulsion concepts. In the first, nuclear fuel acts as a heat source for the working fluid (such as hydrogen); in the second, a nuclear explosion provides momentum for the spacecraft.
Frederick Reines and Stanislaw Ulam were among the authors of the idea of a nuclear engine.
Physicists have seriously proposed launching interplanetary expeditions by detonating nuclear weapons behind them. Theoretically, it seems flawless; fortunately, no one has yet tried it in practice. But there have been attempts. The newest story engineering points to the American Project Orion, which can also be called an explosive aircraft.
The concept was absurdly simple: hydrogen bomb explosions ejected from the spacecraft vaporized disks ejected behind the bombs. The expanding plasma imparted momentum to the spacecraft. The craft was capable of traversing the vastness of space at speeds two to three times greater than conventional ones. It was planned to use up to 800 miniature hydrogen bombs for a single round-trip to the planet. It's unknown where Project Orion would have ultimately flown, but in 1963, the Americans and Russians signed the Nuclear Test Ban Treaty. weapons in the atmosphere, in outer space, and underwater. Nuclear pulse engines were finished.
The Orion spacecraft, powered by a nuclear pulse engine. NASA drawing from 1999.
Orion Spacecraft - Key Components
The idea of using nuclear fuel as a heat source in jet engines seems quite sound. More precisely, uranium or plutonium aren't the only fuel in this case. The second component is hydrogen, pumped through the reactor's hot zone (approximately 3000 degrees Celsius), instantly expanding and exiting the engine nozzle. No chemical reaction occurs at this point—the hydrogen simply heats up and, escaping from the reactor's working zone, creates powerful thrust. According to the law of conservation of energy, the jet stream and the ship receive equal but opposite impulses.
Hydrogen is the lightest gas. When heated, its molecules fly faster than all other gases. The faster the exhaust, the more efficient the engine. This is called specific impulse, and nuclear engines have it twice as high as the best chemical propulsion systems – 850-900 seconds versus 450 seconds for kerosene and hydrogen-oxygen engines. A gas-phase reactor in which fissile uranium is heated to a plasma state is completely out of science fiction. Temperatures here reach 6000 degrees Celsius, and the impulse is immediately 2000 seconds, which is 4-5 times higher than that of traditional engines. The only remaining task is to find materials with the appropriate heat resistance and learn how to handle uranium in plasma.
Demonstration Rocket for Agile Cislunar Operations (DRACO) – a nuclear-powered spacecraft
It's clear from the operating diagram that no one would install such propulsion systems on intercontinental airliners under terrestrial conditions. When fissile uranium and hydrogen are in the same bottle, expect big trouble. Sooner or later. But for space, the system is quite feasible. In 2027, the Americans intend to test the Demonstration Rocket for Agile Cislunar Operations (DRACO). Rocket "for flexible circumlunar operations." If everything works out, the first nuclear-powered spacecraft will appear in space. Under Trump, the chances of realizing this project in metal have diminished—funding was significantly cut next year. They cite the effectiveness of Elon Musk's Starship project. Last year, Russia announced the development of the nuclear tug "Zeus," which former Roscosmos head Borisov predicted would be launched in the 2030s or 2040s.
Straight-through and turbojet
Our focus isn't on DRACO or even Zeus, but on the nuclear air-breathing engine installed under the hood of the Burevestnik. Strictly speaking, the Russian missile isn't the first to try out such a powerplant—we've simply perfected it. The Americans were the first with their Pluto project. This was a heavy cruise missile with a real nuclear reactor on board—the US spent about two billion dollars in today's dollars on this entire endeavor.
The development of a nuclear rocket engine began in 1957 and was very relevant for its time. At that time, the Soviet Union already had a quite adequate Defense, which did not guarantee unimpeded passage of American bombers to strategic targets. Intercontinental ballistic missiles were still in development, and a backup plan was needed in case of failure.
The result was a 27-ton cruise missile with a Tory-II reactor on board. Its design revealed that the craft had been designed by adventurers. The missile was intended to fly at two to three times the speed of sound at an altitude of a few dozen meters—the resulting shock wave would shatter windows and destroy lightweight structures. Upon reaching cruising speed, air was forced directly through the red-hot ceramic fuel rods made of uranium oxide, the reactor's hot zone. The temperature rose to several thousand degrees, and the jet thrust accelerated the gigantic missile to three times the speed of sound.
The apocalypse machine, armed with 16 nuclear warheads, poisoned everything it passed over with radioactive emissions from its nozzle. Perhaps, in a World War III scenario where everything is reduced to dust, this isn't particularly critical, but the Americans were still cautious.
Aerodynamic performance testing of the supersonic low-altitude missile (SLAM) powered by a nuclear ramjet engine developed under Project Pluto
But it wasn't just environmental concerns that drove the development – by the early 60s, intercontinental ballistic missiles appeared more promising. The Americans weren't alone in their pursuit of a nuclear cruise missile. In the USSR, several similar projects (known designations include "Tema 31," RD-0411, and others) were being developed in parallel at the Voronezh Chemical Automation Design Bureau and the Research Institute 1 (now the Fakel Design Bureau). The goal was to create a subsonic cruise missile flying at extremely low altitudes (50-100 m), with a range of over 10 km, capable of maneuvering and evading enemy air defense systems. The warhead was a nuclear one with a yield of up to 1 megaton.
The rocket was intended to be launched from land-based launchers or submarines. Ground-based rig tests of air-cooled reactors were achieved, but a flight prototype never materialized. "Topic 31" was closed in 1964, but work on two nuclear jet engines—the RD-0410 (small) and RD-0411 (large)—had already begun in 1965. These engines could be considered "environmentally friendly"—the reactor's heat was transferred to hydrogen, which heated and expanded, imparting momentum to the engine. Their specific impulse was 910 seconds, twice that of kerosene- and oxygen-fueled rocket engines. The engines were dual-purpose—for interplanetary missions and for installation on heavy cruise missiles. After several rig tests, work was curtailed in the 80s. The Americans had completed their Project Pluto experiments at roughly the same level of readiness a couple of decades earlier.
It's safe to say that the Tema-31 and RD-0411 were the forerunners of the modern Russian nuclear-powered rocket, the Burevestnik. Apparently, Russian engineers managed to solve a number of complex problems. The first was the creation of a compact fast-neutron nuclear reactor with a power output of several hundred megawatts. The second was the development of a high-temperature alloy for a heat exchanger operating at 2000-3000 degrees Celsius. It must resist oxidation and melting for several weeks or even months—the Burevestnik is a long-lasting product.
The Russian rocket uses atmospheric air as its propellant, which contains oxygen—a fairly strong oxidizer. There is no direct contact between the air and the fuel elements in the reactor's hot zone. The air is heated through a heat exchanger, the design of which is worthy of being the century's greatest mystery. The third challenge is that all rocket components and assemblies must be extremely reliable and robust.
Unlike the Burevestnik, conventional missiles operate for a few dozen minutes at best. Moreover, the payload of a nuclear cruise missile doesn't allow for a positive outcome in the event of an emergency. However, in the event of actual combat use, the term "emergency" would have a completely different connotation.
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