Chronicles of The Hardships of Komachi in The Sengoku Era

Early July, 1572.

The encirclement led by Honganji Temple and Takeda was nearing completion, but there was no sense of tension specific to wartime in the Oda territory that was supposed to be surrounded. Reports from the spies of Honganji Temple who were hiding in the Oda territory revealed that the Oda family was unaware of Takeda’s betrayal and were not aware that the encirclement was closing in. Kennyo and his close aides smirked upon hearing this report. Shimotsuma Rairen, who would later be called the “Commander-in-Chief of Osaka,” muttered “We won” as soon as he heard the report.

“It is impossible for the weak Oda to defeat the Takeda, who has made a name for themselves throughout the land. Last time, the fool from Asakura hindered us and allowed Oda to escape, but this time it is the undefeated Takeda. There is no chance of failure.”

This perception was not only held by Honganji Temple, but also by the countrymen and the shogun Yoshiaki, who advocated against the Oda. In fact, Takeda had never been invaded by other countries for over thirty years, and on the contrary, they attacked other countries and achieved victory, or at worst, a draw. On the other hand, the Oda troops, known for their weak soldiers, were considered inferior to the Kai soldiers that Takeda had, to the point where one Kai soldier was worth five Oda soldiers.

“Let’s leave it to Takeda this time. It is not wise for us to interfere and disrupt Takeda’s pace. We will respond to Takeda’s request and focus on coordinating the daimyos and behind-the-scenes work.”

“Yes!”

Upon receiving Kennyo’s instructions, his close aides began to work on their respective tasks. They had only one thing on their minds: how they would navigate their way once Takeda unified the land, and they didn’t even consider the possibility of unforeseen circumstances. However, they were being careless. Even if they were weak soldiers, there was a saying that “a cornered rat will bite the cat,” meaning that even the prey could bare its fangs and cut the predator’s throat.

There was another miscalculation. The Oda soldiers were by no means weak soldiers. They may have been in the past, but now it was definitely different. Originally, Owari had fertile land, making it easy to obtain daily provisions. On the other hand, in Kai, which had steep mountainous areas, a certain level of ability was required to make a living. In other words, they were trained through the survival competition, and their basic strength was different. This difference in individual soldier’s abilities due to this fact was one of the reasons for the evaluation of weak soldiers in Owari and the strong Takeda. However, this only applied when comparing non-combatants and comparing them to the emergency reserve forces.

Even ordinary people can acquire physical abilities comparable to athletes through training. However, in the Sengoku period, where farmers were conscripted and turned into Ashigaru (light foot soldiers), the idea of training them was almost non-existent. Only a limited number of candidates for soldiers, such as close subordinates or relatives of vassals, received combat training. Nobunaga broke this common sense. Backed by abundant financial resources, he separated the military from the farmers and established a standing army. And Shizuko took it a step further. In order to reduce the attrition rate of new soldiers, she proposed the establishment of large-scale soldier training facilities and thorough training for new recruits. As a result, the weak soldiers who were mocked as Owari soldiers underwent a transformation. The rigorous basic training became feared among the new recruits as “one week of Buddha, three months of Shura, six months of hell, and three months of longing for death.”

However, those who passed through Shizuko’s soldier training facilities could enjoy benefits that corresponded to their harsh experiences. First, those who completed the training would not have trouble finding a position. The warlords who would become their employers knew how rigorous the training was. Some even sent their own sons to the training facilities, leaving behind their close relatives.

The second benefit was that as long as they could engage in basic conversation and had not committed any crimes, their social status would not be questioned. In an era where primogeniture was the norm, anyone other than the eldest son who would inherit the family estate was treated unfavorably. As a reserve in case something happened to the eldest son, they would be kept in a room in the family’s house, known as “room-dweller.” They were treated like lodgers, constantly watching the family head’s mood, and were not allowed to establish their own households or marry. Even if the eldest son succeeded to the family estate, the room-dweller would not change. They would continue to be supported by the new family head while living a life prepared for the worst-case scenario.

Therefore, many disliked the life of being kept like pets and chose to work as servants or become adopted children. Having one reserve was enough, and the third son and beyond couldn’t even become “room-dwellers.” However, being in the position of the eldest son came with responsibilities. In exchange for receiving all the inheritance from their parents, they had the responsibility of earning a living for their own family as well as supporting their siblings, finding employment or adoptive families for their siblings, and providing dowries for their sisters’ marriages.

In a global context, Japan was relatively better off due to the options of adoption and servitude. In the world, especially in Europe, the idea of working as a servant or being adopted was only found in certain parts of Germany, and in general, the family head would either keep them as pets or give them a small amount of money and exile them. As a result, family disputes were more likely to occur, and there were even cases where the death of the family head was not mourned but celebrated. However, those who inherited the wealth still had the same responsibility towards their siblings as in Japan. There were other paths such as becoming a clergyman or serving as a knight to the king, but privileges were monopolized by the powerful, and the extent of one’s own family’s abilities had a significant impact.

Returning to the story, the last advantage is that food and lodging are guaranteed during the training period. Even if they are deemed unsuitable as soldiers and drop out, there is a period of observation before a decision is made. During that time, they can enjoy three meals a day and a warm place to sleep. However, the training imposed is so intense that it is not worth it to volunteer just for the sake of food and lodging.

While Honganji Temple, Asakura, and Asai were plotting against the Oda, Shogun Yoshiaki was also scheming in the shadows. Although their relationship was not harmonious, they maintained a friendly appearance with Nobunaga on the surface while preparing for a confrontation in secret. Two years had passed since the collapse of the first Oda encirclement in 1570, and the second Oda encirclement was steadily and quietly closing in on Nobunaga.

In late June, Shizuko headed towards the Chita Peninsula for the trial run of the screw ship. Although there were no problems in the Nagara River due to the trial run, the screw ship was designed with the intention of operating in the open sea. Therefore, it made more sense to conduct the trial run at sea. On the other hand, there was no need to insist on a screw ship in rivers, and the current traditional Japanese boats were sufficient.

“Then, please start.”

Shizuko, who was given full authority for inspection by Nobunaga, gave the signal to start the trial run. Two types of screw ships were prepared for this trial run: single-seater and two-seater. As the name suggests, the single-seater is operated by one crew member who handles everything. It is like a modern motorboat with the steering mechanism and the screw integrated, and the steering and output adjustment must be done by one person. The two-seater has separate devices, with one person steering and the other adjusting the output, and they cooperate with each other to operate the ship. The reason for not having more than three crew members is that the devices are simple, and non-specialized crew members would only get in the way. Moreover, the training required for piloting is strict, so there is no surplus personnel to spare.

The basic structure of the ship is the same for both types. It is a mechanism that transmits the rotation of the external combustion engine, the Stirling engine, to the screw through a crank mechanism. The difference between the types lies in the engine output. Although it requires a dedicated operator, the device can be enlarged, resulting in a significant increase in output. Despite the common systems and parts, the development period was prolonged due to the gearbox and torque converter. In order to operate the screw ship efficiently, it is necessary to dynamically and quickly change the rotation speed and torque of the screw. To achieve this, a gearbox and torque converter, which are transmission mechanisms, were required.

It is a general rule for all vehicles that even if the speed is slow, a strong force (torque) is required to transition from a stopped state to the initial motion. On the other hand, when the speed is high, if the rotation speed is low, it becomes a resistance, so there is a need to rotate at a high speed even with a small force. A gearbox is necessary to switch between these states, and a torque converter is desired to smoothly perform the switching.

However, the development of the torque converter was extremely difficult, and the prospects for its development are still uncertain. Therefore, the gear shifting is operated using a clutch system. Since there is no hydraulic power-assist mechanism, shifting gears requires physical strength, and specialized personnel are required.

“Let’s start with the Type I.”

Due to the long names of the types, Shizuko assigned the development code names as Type I for the single-seater and Type II for the two-seater. These names were adopted as the official names.

“Type I, begin the test!”

An Ashigaru light foot soldier, who was in charge of giving the signal, beat the drum. In response, the Type I ship started to move slowly. Although they had studied and trained with simulators, it was their first time touching an actual ship, so their movements were awkward. Some struggled with gear changes and had barely moved from the starting position. However, as time passed, they began to accelerate.

“Next, start the Type II.”

“Type II, begin the test!”

When the Type I ships reached cruising speed, it was time for the two-seater Type II to undergo the trial. Thanks to having a dedicated operator, the speed increased smoothly.

“Is everything going smoothly?”

Both the Type I and Type II ships were conducting the trial successfully. Shizuko was optimistic that they could be put into actual combat soon. However, they were about to fall into the pitfalls that often accompany technical trials.

“Hmm? A warning signal? Did something happen?”,When the test was about halfway through, an alarm suddenly sounded, indicating an anomaly. A messenger quickly arrived and reported the reason for the anomaly to Shizuko. It was a reason that neither Shizuko nor the Kuki Navy, who were involved in the development, had anticipated.

“Did it experience an engine stall?”

“Yes. The engine suddenly stopped while operating at high speed. The technicians are currently identifying the cause.”

Both the I-type and Ro-type experienced a malfunction that caused the engine to stall during the high-speed rotation test. And it wasn’t just once or twice, but it happened repeatedly. Shizuko understood that this was an abnormal situation.

(Engine stalls? Was there a flaw in the gearbox? No, that can’t be right. I checked the gearbox design drawings, and there didn’t seem to be any abnormal mechanisms that even an amateur like me could notice. Besides, it operates fine at low speeds, so I don’t think it’s a problem caused by the difference in gear ratios.)

The developers were currently disassembling one of the gearboxes for investigation, and the results would determine the course of action. If there were any issues with the gearbox, they didn’t know how long it would take to make the necessary modifications. Tension filled the air. Everyone was silently waiting for the report, although they didn’t say it out loud. It was only an hour later that the heavy atmosphere dissipated.

“So, it was due to insufficient rotation speed causing the engine stall?”

Shizuko felt relieved after hearing the report. The reason for the repeated engine stalls was that the deformation of the screw propeller was larger than expected, increasing water resistance and causing a torque shortage at high speeds, resulting in a decrease in rotation speed and the inability to maintain the specified rotation speed. They disassembled the gearbox to investigate if there were any other causes, but there were no faulty parts in any of the components, and there were no problems with the connections.

They immediately conducted interviews. Shizuko and the others finished the interviews shortly before sunset and decided to discuss the future course of action the next day. The following day, after reviewing the interview results, they would discuss the next steps.

“With this test, we have demonstrated the usefulness of the screw ship. Both the I-type and Ro-type have exceeded the speeds achievable with oars, even though we have only conducted tests at low speeds. The issues that occurred during high-speed rotation can be resolved by adjusting the gear ratio to provide a wider torque range. Therefore, we conclude that the screw ship has entered the practical stage.”

Shizuko declared to the gathered team. Based on the interviews and the investigation report on the mechanism, they concluded that the deformation of the screw propeller could only be resolved by changing the material, but using metal would make it heavy and difficult to process. Since there were no issues with the gearbox structure, they decided to solve the problem by inserting an intermediate-speed gear between the low-speed and high-speed gears. The team was relieved to know that there were no major flaws in the mechanism itself. The screw propeller was an essential mechanism for venturing into the open sea, and therefore, there were high expectations from Nobunaga. After years of development and testing, everyone was anxious about the consequences if the results were embarrassing.

After that, they excluded all the test items during high-speed rotation and resumed testing only at low speeds. Although there were minor issues and mistakes due to the inexperience of the personnel, there were no fatal problems. Shizuko compiled the test results into a report to be submitted to Nobunaga. Just like a business report, she included the conclusion at the beginning.

“In the current river transport, there are few advantages. However, for large-scale transportation with a small number of personnel and achieving high-speed transport at sea, the engine-driven screw ship is the superior choice.” This was the conclusion they reached. Although the oar-propelled ship was more efficient for small-scale operations in rivers, it quickly became inefficient when it came to larger ships and reaching a certain speed. On the other hand, the screw propeller could cover a wide range of vessels, from leisure boats to transport tankers, using the same principle of propelling through water displacement.

“In river transport, there are few advantages at the moment. However, by achieving large-scale and high-speed transport in maritime shipping, significant profits can be obtained…”

Shizuko included the answers to the questions that Nobunaga would likely have in the test report as much as possible. Whenever he had any doubts, he would bombard them with questions like a storm. It was physically and mentally exhausting, so the report to Nobunaga was often avoided. Some technicians had tried submitting their own reports, but they were returned with a pile of questions and a demand for answers, and since then, it had become an unwritten rule that Shizuko would write the reports. That’s why the technicians didn’t hold Shizuko in high regard. One technician said that answering Nobunaga’s questions wasn’t as simple as just providing an answer; they had to build a convincing theory to satisfy him. Even if someone had mastered the technology perfectly, being able to explain it in a way that others could understand required a different talent.

“Hmm, I feel like I’m becoming a middle manager or something. Maybe it’s just my imagination.”

Shizuko finished writing the thick report and placed it in a wooden document case for transport. The assistants would take care of the rest, delivering it to Nobunaga. After handing the document case to Shou and requesting him to send it to Nobunaga, Shizuko stretched her body to relax.

“Phew, next is the confirmation of the improved Stirling engine and blast furnace. Ashimitsu-san has been preparing various things over there, so I can relax until the test day.”

“If you have the time, please handle these documents.”

As Aya placed her hand on Shizuko’s shoulder and stood beside her, she handed her a mountain of documents.

The operation of a blast furnace involves two stages: “ironmaking” to produce pig iron and “steelmaking” to refine the pig iron into steel. “Ironmaking” is the process of melting iron ore by alternately charging coke and iron ore into a tall and narrow furnace called a blast furnace.

The coke charged into the blast furnace burns due to the hot air blown in from the lower part of the furnace. Some blast furnaces also use fine powdered coal as a reducing agent. The burned coke generates carbon monoxide and hydrogen, which become the reducing gas that melts the iron ore and removes (reduces) impurities contained in the iron ore. In other words, coke has two roles: creating the temperature to melt the iron ore inside the furnace and acting as a reducing agent to remove impurities from the iron ore.

The molten iron, from which impurities have been removed by the reducing gas, flows down to the bottom of the furnace by gravity. It then comes into contact with the coke burning in the lower part of the furnace, and the coke reacts with the carbon generated during combustion, resulting in iron containing a few percent of carbon accumulating in the hearth at the bottom of the furnace. At the same time, impurities contained in the iron ore accumulate as a layer on top of the molten iron. This layer is called slag and is discharged from the blast furnace as a byproduct of ironmaking. Slag is reused in the steelmaking process.

The prototype of the blast furnace, which can perform the entire process from removing impurities to melting in one go, was developed in the 14th to 15th centuries in the Rhine River tributaries in Germany. In the early days, waterwheels were used to operate the bellows and increase the air supply, and charcoal was used as the heat source and reducing agent. It wasn’t until the early 18th century that coke began to be used as fuel. Before that, a significant amount of wood was cut down, leading to the destruction of forests. Although there were other reasons such as land reclamation, it is said that iron production by blast furnaces accelerated the depletion of forests in Europe.

It has been about three hundred years since the birth of the modern blast furnace, but it still maintains its superiority over modern chemical plants due to its ability to remove impurities with simple equipment while performing the smelting process at once. Additionally, blast furnaces have a longer lifespan compared to other chemical plants. Despite being exposed to high temperatures 24 hours a day, the furnace can continue operating by simply replacing the bricks inside the furnace every ten years or so. In a blast furnace that operates continuously, 24 hours a day, 365 days a year, a long lifespan is an essential requirement. In the case of other chemical plants, if there is damage, it may require rebuilding, so blast furnaces have an advantage in this aspect as well.

“I’m quite worried.”

Shizuko expressed her worries openly, feeling a heavy burden in her chest. The test of the blast furnace would not be conducted all at once but would consist of several individual tests followed by the final integrated test. Today was the test day for the important equipment in the blast furnace, the blower, and the Stirling engine that powered it. Although they had allowed some margin in the schedule, if any issues arose during the test, it would delay the subsequent test dates, including the critical integrated test of the blast furnace. Any delay in the schedule would affect the entire project, so Shizuko didn’t have much peace of mind compared to before.

“If the commander is worried, it makes the subordinates uneasy. Stay calm and composed.”

Ashimitsu reprimanded Shizuko, who was restless. Unlike her, he maintained his usual calm and composed expression. Although no one could tell what he was thinking, at least Ashimitsu seemed more composed.

“Anyway, did the sintering test finish over there?”

“…That doesn’t concern me. Besides, we start with crushing the iron ore, so it will be a while before we get the results.”

Iron ore comes in various sizes, and if it is directly loaded into the blast furnace, it can cause blockages. To prevent this, the iron ore is first crushed into powder, mixed with powdered coke, and about ten percent of limestone, and then baked to give it a uniform shape. This process is called sintering. The same applies to coal coke and bio-coke; they are also prepared in a similar way. Only after completing these preparations can the iron ore and coke be charged into the furnace.

“I’d like to conduct the verification test of the value of using bio-coke as soon as possible.”,Although it does not serve as a reducing agent, there is an advantage in raising the temperature inside the furnace higher than with coal coke alone and shortening the time for melting due to the combustion effect of the pyrolysis gas. However, it can only be determined through repeated demonstration tests how much it can be replaced. Fortunately, it is not particularly difficult to manufacture experimental blast furnaces unlike in modern times.

“That’s not all. With bio-coke, it can also be used as a heat source for Stirling engines. Although it may not be as high-quality as the German-made ones that can generate 1 kW of electricity with air as the working gas.”

“Considering the abundance of helium gas, I think it’s quite impressive that Germany uses air.”

“In return, we are spared the trouble of generating helium gas here.”

Stirling engines with a maximum output of 1 kW are beginning to be practicalized with air as the working gas. Of course, it is not possible to achieve the exact same performance as the specifications, and the output will decrease to some extent. The reason why engines designed about two hundred years ago are attracting attention, especially in military submarines, is because they are quieter than diesel engines and nuclear reactors, and can be operated using the waste heat generated by them. In fact, the modern Japanese Soryu-class submarines are equipped with Stirling engines called AIP (Air-Independent Propulsion) engines. However, the reason why Stirling engines were installed on Soryu-class submarines was because there were no efficient fuel cells and no good storage methods for hydrogen, so the installation of fuel cells was postponed in consideration of any accidents.

“Once the blast furnace is completed, we can finally start steel production. Industrial products require steel that is harder than iron, so it’s tough. Also, the initial production of parts is done manually… using a hobbing machine.”

A hobbing machine is a type of gear cutting machine used for cutting gears. Gear cutting is the process of cutting teeth into a gear blank (also known as a gear blank) using a special cutting tool called a hob. Although gears have been important parts for a long time, industrial production using hobbing machines became possible in the late 19th century. Until then, gear manufacturing was done manually.

“It’s currently done manually. If you need a large quantity of gears with uniform sizes, a hobbing machine is necessary.”

“Gears are important parts. Although we have succeeded in making brass-cutting hobs with iron hobs, we still need iron gears. Wooden gears… seem to be cut with a thread saw rather than a hobbing machine.”

It is possible to manufacture brass gears using iron hobs, but steel hobs are required for iron gears. Wood has different strength characteristics, so it is better to cut them with a thread saw rather than using a hobbing machine.

“There is a lot of manual work now, so it was quite a burden during mass production of gearboxes. Well, once the blast furnace is completed, if they can make steel hobs just like the iron ones, it will be easier. So, it’s still relatively easy.”

(The initial manual work is the most difficult… well, as long as Shizuko doesn’t have a hard time)

Pioneers always struggle in any industry. However, a hobbing machine is an essential machine tool if one aims to mass-produce gears. It greatly improves efficiency compared to craftsmen making gears one by one manually.

“It’s more troublesome to standardize specifications for machine tools than to manufacture them. Well, it’s about time to start preparing the Stirling engine, isn’t it?”

Shizuko cleared her throat and forcefully changed the subject, pushing away the unpleasant memories of standardizing and specifying hobbing machines from her mind. She went to confirm the results with various people, and reported back to Shizuko without needing to be told. She felt fortunate to have excellent subordinates, but she tightened her face.

“Alright. Let’s move when it’s time.”

Four and a half quarters later, Shizuko and the others moved to the test site. By that time, Keiji and Saizo, who had gone somewhere, had returned. Shizuko accepted Nagayoshi’s explanation that his clothes were slightly stained with blood from the sumo wrestling, and didn’t ask any further. In reality, he had found undercover agents hiding here and there and interrogated them while practicing on sandbags.

When they arrived at the test site, the Stirling engine cylinder was already being heated. The Stirling engine to be used in the test this time was a 2-piston engine. The main components were two pistons, heating and cooling sections connected to each piston, and a regenerator that temporarily stored the working fluid. The working fluid is also known as the working gas. In an external combustion engine, it is necessary to convert the heat energy obtained from an external source into mechanical energy, and the substance used for this conversion is called the working fluid. In the case of a Stirling engine, the basic working fluid is atmospheric air, and when it becomes high-performance, compressed helium gas or hydrogen gas is used.

This time, instead of helium gas or hydrogen gas, an air gas Stirling engine was used. The operation begins with the heated air in the heating section moving the piston and cylinder on the high-temperature side of the crank mechanism, and then the high-temperature air moves to the cooling section, moving the piston and cylinder on the cooling side. The working fluid then undergoes repeated heating and cooling, converting the reciprocating motion of the pistons on both the high-temperature and cooling sides into rotary motion through the connecting rod.

The rotary motion of the crank is transmitted to the gearbox through the output shaft. The gearbox is used to either decrease speed and increase torque or increase speed and decrease torque, depending on the application. In this case, a high-speed, low-torque gearbox is required for the blower. The combination of gears in the gearbox is set for the blower, and finally, the rotational motion is transmitted to the impeller through the output shaft of the gearbox to send hot air into the blast furnace.

The hot blast furnace, which can be achieved by deploying such a large-scale facility, is a facility that is installed alongside the blast furnace. The hot blast furnace increases the temperature inside the blast furnace, dramatically increasing the amount of iron produced. It is ideal to have a higher temperature for the blast, but it is not possible to blow hot air exceeding a thousand degrees like in modern times. However, even with that limitation, it can produce several tons of iron per day, which is an extraordinary production capacity in the Sengoku period.

The blast furnace has a disadvantage of not being able to use sand iron. This is because when titanium contained in sand iron burns inside the blast furnace, it becomes titanium oxide, which hinders the flow of molten iron. Therefore, only iron ore with a low titanium content can be used in the blast furnace. However, iron ore production in Japan is limited, and it has to rely on overseas producing countries. The closest producing country is China, but Chinese iron ore has a low iron content, making it cost-ineffective. Therefore, iron ore is imported from multiple countries such as India, Vietnam, and Thailand. The reason why iron ore and coal were able to be imported to Japan during the Sengoku period was because the Jesuits, who had a significant influence in Nanban trade, had the rights. Of course, it required a corresponding amount of silver bars.

“A considerable amount of silver was spent. Well, if the blast furnace is successful, they will also benefit from it, so it’s an investment.”

Although the Jesuits may seem unrelated to business at first glance, they are actually profiting from the Nanban trade. The trade routes between India, Southeast Asian countries, Europe, and Japan are controlled by the Jesuits and the Catholic Church behind them. Therefore, every time a ship goes on a trade route, merchants have to pay them money. It can be called a donation in a positive light, or a prepayment fee in a negative light for using the trade routes. Furthermore, they had certain privileges in ports scattered throughout Asia and in Macau, which had the largest slave market in the Asian region. So, the more Shizuko engaged in Nanban trade, the more opportunities the Jesuits had to collect donations from merchants. They gladly made investments to promote trade. In fact, as Shizuko increased the export goods, the trade increased, and as a result, the Jesuits’ finances improved significantly.

“But more importantly, the Stirling engine is about to start.”

“Oops, can’t lose focus now. Let’s concentrate on the present.”

Shizuko, who returned from the depths of her thoughts at Ashimitsu’s reminder, forcefully pushed away any unnecessary distractions from her mind. She watched the craftsmen with her hand on her chin. Slightly pressured, the craftsmen were discussing something in low voices while turning the handle. And after about thirty turns of the handle, the Stirling engine finally started.

“Wow!”

Nagayoshi exclaimed in admiration. Keiji and Saizo didn’t raise their voices, but they were captivated by the Stirling engine. After a while, when the output reached the required level, the blower started through the gearbox. The initially gentle breeze quickly became powerful enough to blow away the dust on the ground. Although the actual test of sending hot air was scheduled for another day, Shizuko was confident that there would be no major problems based on the current situation. And her confidence was justified. The test of the hot blast furnace, which aimed to increase the temperature inside the blast furnace, was successfully completed without any major issues until the final test.

The test runs related to the blast furnace went smoothly without any major problems. Although there were some minor issues that caused the test schedule to be delayed by a few days, it was within the range that could be recovered. Compared to the troubles with the screw ship, the test of the blast furnace, which seemed to have no significant problems, was completed until the final test. Shizuko congratulated the people involved, held a grand celebration, and submitted all the reports to Nobunaga. She was enjoying a brief moment of rest.,”Whew, I thought it would be a disaster for a moment.”

“You did well, Shizuko.”

Ashimitsu praised Shizuko, who was resting on her desk, exhausted. After the test of the blast furnace, there was nothing in particular to do until Kimyomaru (Oda Nobutada)’s first battle ceremony. He was undergoing strict training from his grandfather, so he was not present at the moment, but rumors had it that he was becoming quite skilled. Shizuko wished him success as the legitimate son of the Oda family in her heart.

“Ashimitsu, thank you for helping me with various things when I couldn’t handle them.”

Shizuko also expressed her gratitude to Ashimitsu.

“Don’t worry about it. I’m doing it because I like it.”

He had a nonchalant attitude, but a small smile appeared on his face. Shizuko, who lay on the desk again, rolled her head and thought about the future of the blast furnace.

After ironmaking, the next step would be steelmaking, but Shizuko had a reason why she couldn’t do it. The converter, which is used for steelmaking, had the same dilemma as the refractory bricks. In other words, steel is needed to make the converter for making steel. More precisely, the pillars that support the converter and the crossbars that move it need to be made of steel, or else they would not have enough strength and would crack.

Because of this dilemma, Shizuko had to come up with a solution. The iron produced in the blast furnace would be molded and hammered like a Japanese sword to transform it into steel containing the necessary amount of carbon. However, the molten iron could not be molded as it is. It contains impurities such as phosphorus and sulfur, which would make the resulting steel brittle. To prevent this, a process called pretreatment of the molten iron is necessary. In simple terms, it is the process of removing impurities contained in the molten iron. Basically, three steps are taken: deoxidation, desphosphorization, and desulfurization. The materials used for this are lime, iron oxide, and fluorite. These are added to the molten iron and stirred. At this time, no oxygen is supplied. If oxygen is supplied, the molten iron will become hot, and as a result, the desphosphorization reaction will become slower. Lime and iron oxide are easily obtained, and there is no difficulty in obtaining fluorite in Japan (such as at the Hiraiwa Mine in Gifu Prefecture).

The iron that has undergone pretreatment of the molten iron is refined into steel using the techniques of Japanese swordmaking. Only then can the converter be built, and mass production of steel can finally be achieved. If a higher quality steel is desired, a secondary refining process called adjustment of the concentration of components in the steel is necessary after refining in the converter. Secondary refining is the final process of steelmaking and is a crucial process that determines the quality of the steel. In modern times, the four processes of refining in the blast furnace, pretreatment of the molten iron, refining in the converter, and secondary refining have become the standard processes for producing high-quality steel.

“So we refine the iron produced in the blast furnace and make steel, huh?”

The test of the blast furnace was successfully completed. Although a considerable amount of slag was produced, it was impossible to reduce the slag from the beginning. The important thing was that iron was melted without any problems and refined into steel, even though it was not in the converter. The slag produced by the blast furnace and the coke furnace, which replaced coal with coke, were also reused as byproducts. Especially in the coke furnace, various byproducts could be obtained. Since discharging the combustion exhaust gas directly would cause pollution, the emitted gas needed to be refined into clean exhaust gas.

The structure of the coke furnace is basically a furnace with a combustion chamber and a carbonization chamber made of brick walls arranged alternately. The heat in the combustion chamber vaporizes the coal in the carbonization chamber. The resulting coke is cooled to be usable in the blast furnace due to its high temperature. Water is not used for cooling because it would lower the quality, so it is cooled using an inert gas (such as nitrogen) in a dry fire extinguishing facility. The high-temperature gas generated during this process can be used to generate steam by turning a turbine for power generation.

When coal is vaporized, the volatile components turn into gas and are released. Since the gas contains harmful substances such as crude oil, sulfuric acid, and ammonia, it is dangerous to release it directly. First, the high-temperature gas is cooled with ammonia water. Dilute ammonia water is the most effective for efficiently removing hydrogen sulfide and chlorine gas from the coke oven gas. Then, the remaining gas is refined into tar, crude oil, sulfuric acid, and ammonia, and the remaining gas is reused as fuel for the coke furnace. It is also possible to produce ammonium sulfate (also known as sulfur ammonium) as a nitrogen fertilizer using sulfuric acid and ammonia, or to produce ammonium nitrate (also known as nitro ammonium) using them as materials.

Ammonium sulfate is important as a fertilizer, but ammonium nitrate has various uses in addition to being a fertilizer. When ammonium nitrate is mixed with water, it undergoes an endothermic reaction, so if impure ammonium nitrate and water are mixed and frozen, portable cold packs can be made. However, if ammonium nitrate is mishandled, it can explode and cause significant damage to the surroundings. Therefore, Shizuko decided to limit the handling of ammonium nitrate to using it only as a portable cold pack by intentionally reducing its purity.

“The results look good. With this, can we make the pillars for the converter in about six months?”

“Well, who knows. Even if it works well with a small amount, there are often cases where it fails when it comes to mass production.”

“Well, we’ll gradually increase the production volume and make sure there are no problems.”

The test of the blast furnace was a success. But this was not the end. It was just the beginning. Technology advances every day. The quality of iron in the current blast furnace is low. It will take decades, and possibly over a hundred years, to produce high-quality iron and steel through careful research. As the quality of iron and steel improves, wooden ships will eventually be replaced by iron ones. With iron, even larger ships can be built, and logistics will change significantly. However, high-quality steel also enables the production of powerful cannons. Furthermore, the technology of the blast furnace and converter can be applied to the production of explosives. But technology is just a tool, and whether it is used for the sake of peace or becomes a dangerous element in human history depends on the intentions of those who use it.

An example would be the Haber-Bosch process. Until the birth of the Haber-Bosch process, humanity had been plagued by poverty due to the “Malthusian limit” (the idea that if population growth is not restrained to match the productivity of land, the resources for sustaining life will inevitably be insufficient). However, with the advent of the Haber-Bosch process, the synthesis of ammonia became possible, leading to the creation of many chemical fertilizers and a significant increase in the yield of crops and other resources. This allowed humanity to surpass the “Malthusian limit” for the first time in history, and the population increased dramatically. It is said that if the synthesis of ammonia through the Haber-Bosch process were to become impossible in modern times, approximately three billion people would die of starvation.

The Haber-Bosch process, which greatly contributed to the prosperity of humanity, also made it possible to mass-produce nitric acid, which is a raw material for explosives. In modern times, the industrial production method called the “Ostwald process” is used, and ammonia plays an important role in it. In the Ostwald process, ammonia is mixed with a mixture of oxygen and a small amount of rhodium, one of the impurities contained in platinum and platinum ore, and heated using a catalyst. As a result, nitric oxide is generated, which then combines with the oxygen in the air to form nitrogen dioxide. This nitrogen dioxide is reacted with hot water to produce nitric acid and nitric oxide. The nitric oxide generated in the final step is reused and becomes nitrogen dioxide again, which then reacts with nitric acid to produce nitric oxide.

In this way, with the Ostwald process, ammonia, air (pure oxygen increases the production volume), and hot water can be used to produce explosives. Since sulfuric acid can be mass-produced within the country without being affected by the situation in other countries, wars that used to end when resources ran out have become prolonged. For this reason, the Haber-Bosch process came to be described as “producing fertilizer from the air in peacetime and producing gunpowder in wartime.”

“For now, it’s natural to improve the quality, and then we can test it in private use for a while before considering military use.”

Ashimitsu nodded in agreement with Shizuko’s words, as if saying there was no problem with that.