Those who have reached a conscious age in the era when there were accidents at the Three Mile Island nuclear power plants or the Chernobyl nuclear power plant are too young to remember the time when "our friend the atom" had to provide such cheap electricity that the consumption would not even be necessary count, and cars that can drive without refueling almost forever.
And, looking at nuclear submarines sailing under the polar ice in the mid-1950s, could anyone have guessed that ships, airplanes, and even atomic-powered cars would be left far behind?
As for aircraft, the study of the possibility of using nuclear energy in aircraft engines began in New York in 1946, later the research was moved to Oak Ridge (Tennessee) to the main center of US nuclear research. As part of the use of nuclear energy for the movement of aircraft, the NEPA (Nuclear Energy for Propulsion of Aircraft) project was launched. During its implementation, a large number of studies of open-cycle nuclear power plants were carried out. The coolant for such installations was air, which was fed through the air intake into the reactor for heating and subsequent discharge through the jet nozzle.
However, on the way to making the dream of using nuclear energy come true, a funny thing happened: the Americans discovered radiation. So, for example, in 1963 the project of the Orion spacecraft was closed, in which it was supposed to use an atomic jet-impulse engine. The main reason for the closure of the project was the entry into force of the Treaty prohibiting the testing of nuclear weapons in the atmosphere, under water and in outer space. And nuclear-powered bombers, which had already begun to make test flights, never took off again after 1961 (the Kennedy administration closed the program), although the Air Force had already begun advertising campaigns among the pilots. The main "target audience" were pilots who were out of childbearing age, which was caused by radioactive radiation from the engine and the state's concern for the gene pool of Americans. In addition, Congress later learned that if such an aircraft crashed, the crash site would become uninhabitable. This also did not benefit the popularity of such technologies.
So, just ten years after the debut of the Atoms for Peace program, the Eisenhower administration was associated not with football-sized strawberries and cheap electricity, but with Godzilla and giant ants that devour people.
Not the least role in this situation was played by the fact that the Soviet Union launched Sputnik-1.
The Americans realized that the Soviet Union is currently the leader in the design and development of missiles, and the missiles themselves can carry not only a satellite, but also an atomic bomb. At the same time, the American military understood that the Soviets could become a leader in the development of anti-missile systems.
To counter this potential threat, it was decided to create atomic cruise missiles or unmanned atomic bombers, which have a long range and are able to overcome enemy air defenses at low altitudes.
Office for Strategic Development in November 1955.asked the Atomic Energy Commission on the feasibility of the concept of an aircraft engine, which was to be used in a ramjet engine of a nuclear power plant.
In 1956, the US Air Force formulated and published requirements for a cruise missile equipped with a nuclear power plant.
The American Air Force, General Electric Company, and later the Livermore Laboratory of the University of California carried out a number of studies that confirmed the possibility of creating a nuclear reactor for use in a jet engine.
The result of these studies was the decision to create a supersonic low-altitude cruise missile SLAM (Supersonic Low-Altitude Missile). The new rocket was supposed to use a nuclear ramjet engine.
The project, the purpose of which was the reactor for these weapons, received the code name "Pluto", which became the designation of the rocket itself.
The project got its name in honor of the ancient Roman ruler of the underworld Pluto. Apparently, this dark character served as the inspiration for the rocket, the size of a locomotive, which was supposed to fly at tree level, dropping hydrogen bombs on cities. The creators of Pluto believed that only one shock wave that occurs behind the rocket is capable of killing people on the ground. Another lethal attribute of the deadly new weapon was radioactive exhaust. As if it was not enough that the unprotected reactor was a source of neutron and gamma radiation, the nuclear engine would eject the remnants of nuclear fuel, contaminating the area in the path of the rocket.
As for the airframe, it was not designed for SLAM. The glider was supposed to provide a speed of Mach 3 at sea level. At the same time, the heating of the skin from friction against the air could be up to 540 degrees Celsius. At that time, little research was done on aerodynamics for such flight modes, but a large number of studies were carried out, including 1600 hours of blowing in wind tunnels. The aerodynamic configuration "duck" was chosen as the optimal one. It was assumed that this particular scheme would provide the required characteristics for the given flight modes. As a result of these blowdowns, the classic air intake with a conical flow device was replaced with a two-dimensional flow inlet device. It performed better over a wider range of yaw and pitch angles, and also made it possible to reduce pressure losses.
We also conducted an extensive materials science research program. The result was a fuselage section made of Rene 41 steel. This steel is a high temperature alloy with a high nickel content. The thickness of the skin was 25 millimeters. The section was tested in an oven to study the effects of high temperatures caused by kinetic heating on the aircraft.
The front sections of the fuselage were supposed to be treated with a thin layer of gold, which was supposed to dissipate heat from the structure heated by radioactive radiation.
In addition, a 1/3 scale model of the rocket's nose, air channel and air intake was built. This model was also thoroughly tested in a wind tunnel.
Created a preliminary design for the location of hardware and equipment, including ammunition, consisting of hydrogen bombs.
Now "Pluto" is an anachronism, a forgotten character from an earlier, but no more innocent era. However, for that time, "Pluto" was the most compellingly attractive among the revolutionary technological innovations. Pluto, like the hydrogen bombs it was supposed to carry, was technologically extremely attractive to many of the engineers and scientists who worked on it.
US Air Force and Atomic Energy Commission January 1, 1957chose Livermore National Laboratory (Berkeley Hills, California) to be in charge of Pluto.
Since Congress recently handed over a joint nuclear-powered rocket project to the National Laboratory in Los Alamos, New Mexico, a rival to Livermore Laboratory, the appointment was good news for the latter.
The Livermore Laboratory, which had a staff of highly qualified engineers and qualified physicists, was chosen because of the importance of this work - there is no reactor, no engine, and no rocket without an engine. In addition, this work was not easy: the design and creation of a nuclear ramjet engine posed a large amount of complex technological problems and tasks.
The principle of operation of a ramjet engine of any type is relatively simple: air enters the air intake of the engine under the pressure of the incoming flow, after which it heats up, causing it to expand, and gases at a high speed are thrown out of the nozzle. Thus, jet thrust is created. However, in "Pluto" the use of a nuclear reactor for heating the air was fundamentally new. The reactor of this rocket, unlike commercial reactors surrounded by hundreds of tons of concrete, had to have a sufficiently compact size and mass in order to lift both itself and the rocket into the air. At the same time, the reactor had to be durable in order to "survive" a flight of several thousand miles to the targets located on the territory of the USSR.
The joint work of the Livermore Laboratory and the Chance-Vout company on the determination of the required reactor parameters resulted in the following characteristics:
Diameter - 1450 mm.
The diameter of the fissile nucleus is 1200 mm.
Length - 1630 mm.
Core length - 1300 mm.
The critical mass of uranium is 59.90 kg.
Specific power - 330 MW / m3.
Power - 600 megawatts.
The average temperature of a fuel cell is 1300 degrees Celsius.
The success of the Pluto project has largely depended on the whole success in materials science and metallurgy. It was necessary to create pneumatic actuators that controlled the reactor, capable of operating in flight, when heated to ultra-high temperatures and when exposed to ionizing radiation. The need to maintain supersonic speed at low altitudes and in various weather conditions meant that the reactor had to withstand conditions under which materials used in conventional rocket or jet engines melt or break down. The designers calculated that the loads expected during low-altitude flight would be five times higher than those applied to the X-15 experimental aircraft equipped with rocket engines, which reached the number M = 6.75 at a significant altitude. Ethan Platt, who worked on Pluto, said that he was "in every sense pretty close to the limit." Blake Myers, head of Livermore's jet propulsion unit, said, "We were constantly fiddling with the dragon's tail."
The Pluto project was to use low-altitude flight tactics. This tactic ensured stealth from the radars of the USSR air defense system.
To achieve the speed at which a ramjet engine would operate, Pluto had to be launched from the ground using a package of conventional rocket boosters. The launch of the nuclear reactor began only after the "Pluto" reached cruising altitude and sufficiently removed from populated areas. The nuclear engine, giving an almost unlimited range, allowed the rocket to fly over the ocean in circles, awaiting the order to switch to supersonic speed to the target in the USSR.
Draft design SLAM
The delivery of a significant number of warheads to different targets remote from each other, when flying at low altitudes, in the terrain enveloping mode, requires the use of a high-precision guidance system. At that time, there were already inertial guidance systems, but they could not be used in the conditions of the hard radiation emitted by the Pluto reactor. But the program to create SLAM was extremely important, and a solution was found. The continuation of work on the Pluto inertial guidance system became possible after the development of gas-dynamic bearings for gyroscopes and the appearance of structural elements that were resistant to strong radiation. However, the accuracy of the inertial system was still not enough to fulfill the assigned tasks, since the guidance error value increased with the increase in the distance of the route. The solution was found in the use of an additional system, which on certain sections of the route would carry out course correction. The image of the route sections had to be stored in the memory of the guidance system. Research funded by Vaught has resulted in a guidance system that is accurate enough for use in SLAM. This system was patented under the name FINGERPRINT, and then renamed TERCOM. TERCOM (Terrain Contour Matching) uses a set of reference maps of the terrain along the route. These maps, presented in the memory of the navigation system, contained elevation data and were detailed enough to be considered unique. The navigation system compares the terrain with the reference chart using downward-looking radar and then corrects the course.
In general, after some modifications, TERCOM would enable SLAM to destroy many remote targets. An extensive testing program for the TERCOM system was also carried out. The flights during the tests were carried out over various types of the earth's surface, in the absence and presence of snow cover. During the tests, the possibility of obtaining the required accuracy was confirmed. In addition, all the navigation equipment that was supposed to be used in the guidance system was tested for resistance to strong radiation exposure.
This guidance system turned out to be so successful that the principles of its operation still remain unchanged and are used in cruise missiles.
The combination of low altitude and high speed was supposed to provide the "Pluto" with the ability to reach and hit targets, while ballistic missiles and bombers could be intercepted on the way to targets.
Another important Pluto quality that engineers often cite was the reliability of the rocket. One of the engineers spoke of Pluto as a bucket of rocks. The reason for this was the simple design and high reliability of the rocket, for which Ted Merkle, the project manager, gave the nickname - "flying crowbar".
Merkle was given the responsibility of building a 500-megawatt reactor that would become the heart of Pluto.
The Chance Vote Company had already been awarded the contract for the airframe, and the Marquardt Corporation was responsible for the ramjet engine, with the exception of the reactor.
It is obvious that along with an increase in the temperature to which air can be heated in the engine channel, the efficiency of a nuclear engine increases. Therefore, when creating the reactor (codenamed "Tory"), Merkle's motto was "hotter is better." However, the problem was that the operating temperature was around 1400 degrees Celsius. At this temperature, the superalloys were heated to such an extent that they lost their strength characteristics. This prompted Merkle to ask the Coors Porcelain Company of Colorado to develop ceramic fuel cells capable of withstanding such high temperatures and ensuring an even temperature distribution throughout the reactor.
Coors is now known for a variety of products because Adolf Kurs once realized that making ceramic-lined vats for breweries would not be the right business to do. And while the porcelain company continued to manufacture porcelain, including 500,000 pencil-shaped fuel cells for the Tory, it all started with Adolf Kurs' slick business.
High-temperature ceramic beryllium oxide was used to manufacture the fuel elements of the reactor. It was mixed with zirconia (stabilizing additive) and uranium dioxide. In the ceramic company of Kursa, the plastic mass was pressed under high pressure and then sintered. As a result, getting fuel elements. The fuel cell is a hexagonal hollow tube about 100 mm long, the outer diameter is 7.6 mm, and the inner diameter is 5.8 mm. These tubes were connected in such a way that the length of the air channel was 1300 mm.
In total, 465 thousand fuel elements were used in the reactor, of which 27 thousand air channels were formed. Such a design of the reactor ensured a uniform temperature distribution in the reactor, which, together with the use of ceramic materials, made it possible to achieve the desired characteristics.
However, the Tory's extremely high operating temperature was only the first of a series of challenges to overcome.
Another problem for the reactor was flying at a speed of M = 3 during precipitation or over the ocean and sea (through salt water vapor). Merkle's engineers used different materials during the experiments, which were supposed to provide protection against corrosion and high temperatures. These materials were supposed to be used for the manufacture of mounting plates installed in the stern of the rocket and in the rear of the reactor, where the temperature reached maximum values.
But only measuring the temperature of these plates was a difficult task, since the sensors designed to measure temperature, from the effects of radiation and the very high temperature of the Tori reactor, caught fire and exploded.
When designing the fastening plates, the temperature tolerances were so close to critical values that only 150 degrees separated the operating temperature of the reactor and the temperature at which the fastening plates would ignite spontaneously.
In fact, there was much unknown in the creation of Pluto that Merkle decided to conduct a static test of a full-scale reactor, which was intended for a ramjet engine. This should have solved all the issues at once. To conduct the tests, the Livermore laboratory decided to build a special facility in the Nevada desert, near the place where the laboratory tested its nuclear weapons. The facility, dubbed "Site 401," erected on eight square miles of Donkey Plain, has surpassed itself in declared value and ambition.
Since after launch the Pluto reactor became extremely radioactive, its delivery to the test site was carried out via a specially built fully automated railway line. On this line, the reactor travels a distance of about two miles, which separates the static test bench and the massive "demolition" building. In the building, the “hot” reactor was dismantled for inspection using remotely controlled equipment. Scientists from Livermore monitored the testing process using a television system that was housed in a tin hangar far from the test bench. Just in case, the hangar was equipped with an anti-radiation shelter with a two-week supply of food and water.
Just to supply the concrete needed to build the walls of the demolition building (six to eight feet thick), the United States government acquired an entire mine.
Millions of pounds of compressed air were stored in pipes used in oil production, a total length of 25 miles. This compressed air was supposed to be used to simulate the conditions in which a ramjet engine finds itself during flight at cruising speed.
To provide high air pressure in the system, the laboratory borrowed giant compressors from a submarine base in Groton, Connecticut.
The test, during which the plant was operating at full power for five minutes, required a ton of air to be driven through steel tanks, which were filled with more than 14 million steel balls, 4 cm in diameter. These tanks were heated to 730 degrees using heating elements. in which oil was burned.
Gradually, the team of Merkle, during the first four years of work, was able to overcome all the obstacles standing in the way of creating "Pluto". After a variety of exotic materials were tested for use as a coating on an electric motor core, the engineers found that exhaust manifold paint did well in this role. It was ordered through an ad found in the Hot Rod car magazine. One of the original rationalization proposals was the use of naphthalene balls to fix the springs during the assembly of the reactor, which after completing their task safely evaporated. This proposal was made by laboratory wizards. Richard Werner, another proactive engineer from the Merkle group, invented a way to determine the temperature of anchor plates. His technique was based on comparing the color of the slabs with a specific color on a scale. The color of the scale corresponded to a certain temperature.
Installed on a railway platform, the Tori-2C is ready for successful testing. May 1964
On May 14, 1961, engineers and scientists in the hangar where the experiment was controlled held their breath - the world's first nuclear ramjet engine mounted on a bright red railway platform announced its birth with a loud roar. Tori-2A was launched for only a few seconds, during which it did not develop its rated power. However, the test was believed to be successful. The most important thing was that the reactor did not ignite, which was highly feared by some representatives of the atomic energy committee. Almost immediately after the tests, Merkle began work on the creation of the second Tory reactor, which was supposed to have more power with less weight.
Work on Tory-2B did not advance beyond the drawing board. Instead, the Livermores immediately built Tory-2C, which broke the silence of the desert three years after testing the first reactor. A week later, the reactor was restarted and operated at full power (513 megawatts) for five minutes. It turned out that the radioactivity of the exhaust is much less than expected. These tests were also attended by Air Force generals and officials from the Atomic Energy Committee.
Tori-2C
Merkle and his co-workers celebrated the success of the test very loudly. That there is only a piano loaded onto the transport platform, which was "borrowed" from the women's hostel, which was located nearby. The whole crowd of celebrants, led by Merkle sitting at the piano, singing obscene songs, rushed to the town of Mercury, where they occupied the nearest bar. The next morning, they all lined up outside the medical tent, where they were given vitamin B12, which was considered an effective hangover cure at the time.
Back in the lab, Merkle focused on creating a lighter, more powerful reactor that would be compact enough for test flights. There have even been discussions of a hypothetical Tory 3 capable of accelerating a rocket to Mach 4.
At this time, the customers from the Pentagon, who financed the "Pluto" project, began to be overcome by doubts. Since the missile was launched from the territory of the United States and flew over the territory of the American allies at low altitude in order to avoid detection by the USSR air defense systems, some military strategists wondered whether the missile would pose a threat to the allies? Even before the Pluto rocket drops bombs on the enemy, it will first stun, crush, and even irradiate allies. (It was expected that from Pluto flying overhead, the noise level on the ground would be about 150 decibels. For comparison, the noise level of the rocket that sent the Americans to the Moon (Saturn V) at full thrust was 200 decibels). Of course, ruptured eardrums would be the least problem if you were under a naked reactor flying over your head that roasted you like a chicken with gamma and neutron radiation.
All this made officials from the Ministry of Defense call the project "too provocative." In their opinion, the presence of such a missile in the United States, which is almost impossible to stop and which can cause damage to the state, which is somewhere between unacceptable and insane, can force the USSR to create a similar weapon.
Outside the laboratory, various questions about whether Pluto was capable of performing the task for which it was designed, and most importantly, whether this task was still relevant, were also raised. Although the creators of the rocket argued that Pluto was inherently also elusive, military analysts expressed bewilderment - how something so noisy, hot, large and radioactive could go unnoticed for the time it takes to complete the task. At the same time, the US Air Force had already begun to deploy Atlas and Titan ballistic missiles, which were capable of reaching targets several hours earlier than the flying reactor, and the USSR anti-missile system, the fear of which was the main impetus for the creation of Pluto., and did not become a hindrance to ballistic missiles, despite successful test interceptions. The critics of the project came up with their own decoding of the SLAM acronym - slow, low, and messy - slow, low and messy. After the successful tests of the Polaris missile, the fleet, which initially showed interest in using missiles for launches from submarines or ships, also began to leave the project. And finally, the terrible cost of each rocket: it was $ 50 million. Suddenly Pluto became a technology that could not be found in applications, a weapon that did not have suitable targets.
However, the final nail in Pluto's coffin was just one question. It is so deceptively simple that one can excuse the Livermore people for deliberately not paying attention to it. “Where to conduct flight tests of the reactor? How to convince people that during the flight the rocket will not lose control and will not fly over Los Angeles or Las Vegas at low altitude? asked Jim Hadley, a physicist at the Livermore Laboratory, who worked to the very end on Project Pluto. Currently, he is engaged in detecting nuclear tests, which are being carried out in other countries, for Unit Z. According to Hadley himself, there were no guarantees that the rocket would not get out of control and turn into a flying Chernobyl.
Several options for solving this problem have been proposed. One of them was the testing of Pluto in the state of Nevada. It was proposed to tie it to a long cable. Another, more realistic solution is to launch Pluto near Wake Island, where the rocket would fly in eights over the United States' portion of the ocean. "Hot" rockets were supposed to be dumped at a depth of 7 kilometers in the ocean. However, even when the Atomic Energy Commission persuaded people to think of radiation as a limitless source of energy, the proposal to dump many radiation-contaminated missiles into the ocean was enough to stop the work.
On July 1, 1964, seven years and six months after the start of work, the Pluto project was closed by the Atomic Energy Commission and the Air Force. At a country club near Livermore, Merkle hosted a "Last Supper" for those working on the project. Souvenirs were distributed there - bottles of mineral water "Pluto" and SLAM tie clips. The total cost of the project was $ 260 million (in prices of that time). At the height of Project Pluto's heyday, about 350 people worked on it in the laboratory, and about 100 more worked in Nevada at Object 401.
Even though Pluto never flew into the air, exotic materials developed for a nuclear ramjet engine are now being used in ceramic elements of turbines, as well as in reactors used in spacecraft.
Physicist Harry Reynolds, who was also involved in the Tory-2C project, is currently working at Rockwell Corporation on a strategic defense initiative.
Some of the Livermores continue to feel nostalgic for Pluto. These six years were the best time of his life, according to William Moran, who oversaw the production of fuel cells for the Tory reactor. Chuck Barnett, who led the tests, summed up the atmosphere in the laboratory and said: “I was young. We had a lot of money. It was very exciting."
Every few years, Hadley said, a new Air Force lieutenant colonel discovers Pluto. After that, he calls the laboratory to find out the further fate of the nuclear ramjet. The enthusiasm of the lieutenant colonels disappears immediately after Hadley talks about the problems with radiation and flight tests. Nobody called Hadley more than once.
If someone wants to bring "Pluto" back to life, then perhaps he will be able to find a few recruits in Livermore. However, there won't be many of them. The idea of what could have become a hell of an insane weapon is best left behind.
SLAM missile specifications:
Diameter - 1500 mm.
Length - 20,000 mm.
Weight - 20 tons.
The radius of action is not limited (theoretically).
The speed at sea level is Mach 3.
Armament - 16 thermonuclear bombs (power of each 1 megaton).
The engine is a nuclear reactor (power 600 megawatts).
Guidance system - inertial + TERCOM.
The maximum sheathing temperature is 540 degrees Celsius.
Airframe material - high temperature, stainless steel Rene 41.
Sheathing thickness - 4 - 10 mm.
