Walking Around Hiroshima: How an American Limousine Vanished
No, not completely evaporated, but enough to give rise to one curious scientific phenomenon.
It all began in 2019 when Italian geologist Mario Vannier was digging through the sands of Hiroshima Bay, searching for tiny glass spheres typically formed from molten sand in a nuclear explosion. His interest lay in the fact that his colleague at the University of Florence, Luca Bindi, while studying trinitite—glass spheres formed during the explosion of the Trinity nuclear device on July 16, 1945—discovered that it contained an alloy of silicon, calcium, and copper.
Further, fans of studying the geological impact of nuclear explosions must have come to the conclusion that in Hiroshima, unlike in the New Mexico desert, there were more metals in the blast zone, therefore, the same glass balls should also contain interesting alloys.
Some time spent scooping up sand from the bottom of Hiroshima Bay, washing it, and classifying it yielded the result of hiroshimaite—glass beads formed by the nuclear explosion over Hiroshima. It wasn't easy, and the haul was small, just a few dozen beads, of which 34 samples were selected for detailed analysis.
Alloy of evaporated metals
One of the spheres, just 10 micrometers (0,01 mm) in diameter, yielded a phenomenal result. It contained an intermetallic crystal containing six metals: iron, chromium, nickel, manganese, molybdenum, and aluminum.
Multicomponent alloys have been studied since the mid-1980s, and some of them have unique properties. For example, an alloy of chromium, cobalt, and nickel was found to be extremely stable at very low temperatures and retained its rigidity even in liquid hydrogen.
Other Hiroshimaite samples were found to contain alloys of silicon, calcium, aluminum, iron, and chromium, indicating the formation conditions of these alloys: instantaneous heating to temperatures above 1800 degrees Celsius, evaporation, and subsequent condensation from the vapor as the zone of extreme heating rapidly cooled. According to available data, the temperature of the Hiroshima explosion's fireball reached 7700 degrees Celsius, and at the epicenter, surface temperatures reached 3000-4000 degrees Celsius.
Silicon, calcium, and aluminum are, of course, found in concrete, which at 1200 degrees Celsius turns into a liquid glass-like substance, and at 2500 degrees Celsius, its elemental substances begin to boil away. But minerals with this composition are also found in basalt, gabbro, and some varieties of granite.
The iron in such alloys is a product of steel evaporation. Of course, the very phrase "steel evaporation" sounds somewhat improbable. However, the thermal power of the Hiroshima explosion is estimated at 75 terajoules. This is enough to vaporize 879 tons of steel in 0,1 seconds. This energy was dissipated in all directions, and only a small portion of the heat flux reached the ground. Less than 0,0001% of the total thermal energy of the explosion was deposited per square meter at the epicenter, where the radiation fell strictly vertically. But even this 4 megajoules is enough to vaporize 494 grams of steel in 0,1 seconds. If the part is sufficiently massive, it will first heat up, then melt on the surface, and from this melt, evaporation will occur. This is several tens of grams of iron vapor.
Similar conditions persisted at some distance from the epicenter, but the heat flow there was also lower, and consequently, evaporation was also lower—grams, perhaps milligrams. However, even such minute quantities are sufficient for the nuclear explosive fusion of a multicomponent alloy followed by the formation of an intermetallic crystal. The weight of the sphere in which the six-component alloy was found is negligible—0,000000000524 grams—and the metal content is even less.
Evaporation of car paint
Now the interesting question is: what could have evaporated to form such alloys? This something stood on the streets of Hiroshima near the epicenter, with its surfaces exposed to the light beam directed downward. Only then could the necessary conditions for the evaporation of metals have been created.
The fact is that the alloy of iron and chromium—the components of chromium steel—already raises questions. Nowadays, chromium steel is often used for external metal structures due to its corrosion resistance. But during the war, chromium was in short supply in Japan, so chromium steel was used for critical items like armor. tanks, gun barrels, parts aviation engines and so on.
In principle, the source of such an alloy could have been an anti-aircraft gun. However, according to available data, in August 1945, the positions of the 135th anti-aircraft artillery The regiment and the 22nd separate anti-aircraft division, which had 70-mm anti-aircraft guns type 88, were located on the hills around the city: Mount Futaba in the north, the hill of Eba Park in the southwest, the Mukainada area in the east - the hills behind which was the Toyo Kogyo plant, the islands of Ninoshima and Mukai-Ujina. That is, a ring Defense around the city. They didn't fire because of the all-clear signal.
Private First Class Toshio Nakamura, a soldier with the 135th Anti-Aircraft Artillery Regiment, was at the Mukainada position that morning, approximately 4 kilometers from the epicenter; his crew was cleaning their guns. He described the ground shifting beneath his feet, absolute silence, and unbearable heat that caused the skin on his hands to turn red and blister (second-degree burns).
Therefore, there were most likely no weapons in central Hiroshima at the time of the explosion. The chrome steel could have been part of the structure of a building belonging to a wealthy company or corporation, which was built before the war and could well have been equipped with expensive materials.
But molybdenum and aluminum, made from a six-component alloy, are a mystery. Molybdenum is still rare; the closest thing to a common everyday object made from molybdenum is the wire that supports the tungsten filament in an incandescent light bulb. Aluminum is plentiful now, but back then, it wasn't lying around on the streets of Japan. Yet something containing these elements was standing on a street in Hiroshima, roughly where the fireball erupted.
Only one theory came to mind: the source of the materials for this strange, nuclear-synthesized alloy could have been an American luxury car.
So, about the materials.
Iron - thin sheet metal rolled products of 0,9–1,2 mm, from which car body parts were stamped.
Manganese – 0,3–0,6% manganese was added to thin sheet metal to reduce brittleness; manganese dioxide was also used as a pigment in black, brown, and chestnut paints for premium automobiles.
Chrome and nickel - stainless steel for radiator masks, headlight housings, wheel caps, and also for electroplating chrome parts (first a layer of copper, then a layer of nickel, and then a layer of chrome on top).
Aluminum - decorative elements (emblems, nameplates, mascots), door handles and radiator grille trims, which were partially chromed.
Molybdenum - in most premium cars, it was used only in high-strength steels used to make bolts and bumper brackets, and was also contained in pigments of premium automotive enamels.
There were only a few car brands that could have produced such a composition of components. Among them were the Cord 812 roadster, the Packard Twelve, the Chrysler DeSoto (the car that Toyo Kogyo founder Jujiro Matsuda was driving on the day of the explosion), as well as the Ford Deluxe and Lincoln Zephyr.
However, the Cord 812 is preferable because it stood out from other American premium cars in that its metallic paint, which covered the front apron, front and rear fenders, and trunk lid, contained both aluminum powder and lead molybdate as pigments. It was, in fact, the only car of its time that had all six alloy components on the exterior, specifically the top surface.
First, the nitrocellulose lacquer underwent instant pyrolysis. Then, at 500-800 degrees Celsius, the paint pigments—lead sulfate, chromate, and molybdate—decomposed into lead and molybdenum oxides, and the molybdenum oxide immediately began to sublimate, turning into vapor. The body steel and aluminum particles from the metallic lacquer were completely exposed. Then, as the temperature rose above 3000 degrees Celsius, the metals began to boil, forming a cloud of hot plasma.
Then the temperature began to drop, the main components of the alloy began to cool and condense, and the aluminum in the vapor phase reacted with them, forming intermetallic bonds that formed a crystal. The lead was isolated; firstly, it was still in vapor form when the crystal formed; secondly, lead does not mix and does not form intermetallic bonds with iron and chromium.
Who could have been the owner?
It is worth adding that in Hiroshima in August 1945, only a very few people, literally 5-8 people closely connected with the army, could own such an expensive American limousine as the Cord 812 and Chrysler DeSoto, and even drive it in conditions of severe gasoline shortages and a ban on the use of private cars. fleet or the military-industrial complex.
The restrictions were very strict. In August 1941, gasoline was banned from private cars, and in January 1942, the sale, registration, and movement of cars were prohibited; cars were confiscated from owners in exchange for war bonds. In 1943, campaigns were launched to confiscate tires and inner tubes, then batteries, then non-ferrous metals, and finally whatever remained. Therefore, in 1945, the following were allowed to drive their own cars in Japan: the Emperor and members of his family, ministers and senior dignitaries, army and navy commanders, and the heads of major military concerns, such as Toyo Kogyo. Military-industrial concerns were provided with gasoline and lubricants for in-plant transport, for testing purposes, and for the vehicles of the director, chief engineer, and military liaison officers.
Therefore, number one on the list of possible owners of the American limousine vaporized in the nuclear blast is the deceased son of Toyo Kogyo director Shojiro Matsuda. He could have owned such a car, could have driven it, and since his father's factory was one of the main arsenals of the Japanese army, no one in Hiroshima would have dared to object. It is known that on the morning of the explosion, Shojiro was in the company's office, in the central district of the city, 260 meters from the epicenter, where he shared the same fate as all the office employees.
There's also an additional factor. Both the elder Matsuda and his heirs were deeply interested in automotive matters, and after the war, they created the powerful Mazda company. While they didn't produce cars during the war, they did research new designs. The Cord 812 featured a number of original and advanced features; in Japan, it was being studied by several companies simultaneously. Therefore, Matsuda could have purchased a limousine like the one his eldest son used to study its design and operating characteristics.
Of course, there are other possible explanations, both for the cars and their owners. But the list is very short, and there are various circumstances that reduce the likelihood. For example, Field Marshal Shunroku Hata could have had a requisitioned Packard Super Eight. But it is known that Hata was near his car near the train station (1,8 km from the epicenter) at the time of the explosion. Furthermore, requisitioned cars were repainted in protective colors, often over the original paint, using oil-rosin-based varnishes with a generous addition of talc, using iron oxide hydrate, manganese dioxide, and chromium oxide as pigments. So, this is not our case. Other possible owners have similar circumstances.
All this isn't just idle curiosity. This discovery in a fine grain of hiroshimaite demonstrates that it's possible to create such multicomponent alloys, as technology allows for very high temperatures that vaporize even highly refractory metals. And these alloys may have some special properties.
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