Siheyuan (traditional courtyard house): Starting with the Korean War, returning home to take charge

The day Ma Yuejin returned from Xishan, He Yuzhu was waiting for him in the office. When he pushed the door open, He Yuzhu noticed he had lost weight, his cheekbones were prominent, and his eye sockets were sunken, but his eyes were still bright. He Yuzhu pushed the stack of documents over; they were wrapped in kraft paper, with the words "Thrust of 300 tons" written on them in pen. Ma Yuejin untied the rope, opened to the first page, looked at it for a few seconds, and then looked up.

"Dean, three hundred tons? Our largest one is only one hundred and twenty."

He Yuzhu didn't reply. Ma Yuejin lowered his head and continued flipping through the documents, his finger pausing on the combustion chamber blueprints before turning to the page on the turbopump, where he studied it for a long time. He closed the document, took out a cigarette from his pocket, lit it, and took a deep drag.

"It's possible. But this isn't something you can just draw and use. You have to light it again and again, and explode it again and again. I'm afraid it's..." He didn't finish his sentence, flicking off the ash from his cigarette.

He Yuzhu looked at him. "What are you afraid of?"

Ma Yuejin stubbed out his cigarette. "I'm afraid if I explode too much, I'll blow away all my confidence."

He Yuzhu stood up and walked to the window. "It's blown up, so be it. Pick it up and get back to work."

Ma Yuejin didn't say anything more, picked up the stack of documents, turned and left. He Yuzhu stood by the window, watching his figure disappear at the end of the corridor. One of the corridor lights was broken, and the green light from the emergency exit illuminated him, flickering on and off.

He Yuzhu visits the test bench in the mountains of Huairou every few weeks. The first time he went, Ma Yuejin was squatting next to the engine tightening screws. His work clothes were covered in engine oil, and there was a black mark on his face. When he saw He Yuzhu, he stood up, wiped his face with his sleeve, and the black mark actually disappeared.

"Dean, the fuel pump is installed. During the test run, the bearing overheated. I changed the material, but it still overheats. I suspect it might be a lubrication issue."

He Yuzhu squatted down and looked at the fuel pump. Its casing was made of shiny aluminum alloy, standing out starkly against the surrounding old equipment. He reached out and touched it; it was cold. "You handle the lubrication. The bearing temperature can't exceed 120 degrees Celsius."

Ma Yuejin nodded, then squatted down again to continue tightening the screws.

The second time he went, there was a charred crater on the test bench. Ma Yuejin squatted by the crater, clutching a piece of shard in his hand, its edges curled up and blackened. Several people stood nearby, none of them saying a word.

"There's a hole burned in the combustion chamber." Ma Yuejin handed the fragments to He Yuzhu. "It burned for ten seconds, the wall temperature exceeded the limit, and it started burning from the inside out. The cooling channel design is flawed, the flow is uneven."

He Yuzhu took the fragment and examined it against the light. Molten metal flowed down, solidifying into tiny beads embedded in the fracture surface. He handed the fragment back to Ma Yuejin. "Modify the cooling channel. Increase the flow rate and velocity, let the fuel carry away the heat."

Ma Yuejin responded and stood up. His legs were numb from squatting, and he swayed slightly. A young worker next to him helped him up. He pushed the man's hand away, walked to the test bench, picked up the blueprints, and looked at the charred crater.

On the third visit, He Yuzhu waited for a long time in the office. Ma Yuejin ran over from the test bench, a large, shiny blister on his lip, wincing in pain as he spoke.

"Dean, the cooling channel has been modified. This time it burned for a minute without burning through, but the thrust is insufficient. The design is for 300 tons, but the actual measurement is 240 tons. That's a difference of 60 tons."

He Yuzhu asked him to bring out the blueprints for the injection machine. The blueprints were spread out on the table, covered with over a thousand tiny holes, densely packed together. He Yuzhu ran his finger along the holes, pausing for a moment.

"Enlarge the fuel orifice, keep the oxidizer orifice unchanged. Adjust the ratio to give more fuel. Improve atomization, and combustion efficiency will increase."

Ma Yuejin looked down at the blueprints, then looked up at He Yuzhu. "How much should we adjust?"

"Adjust it by 10% first. Let's try it and see."

Ma Yuejin took the blueprints and ran away.

On the fourth visit, it was still dark. When He Yuzhu arrived at the test stand, Ma Yuejin was standing under the launch pad, looking up. The rocket wasn't large, smaller than a real launch vehicle; it was a scaled-down demonstrator. It was entirely white, gleaming dimly in the morning light. The blister on Ma Yuejin's lip hadn't healed, and two smaller ones had appeared beside it. There were dark circles under his eyes, as if he hadn't slept for days.

"Dean, this time we've modified the injector, changed the turbopump bearings, and increased the combustion chamber wall thickness by another five millimeters." He paused, his voice lowering. "Will it work?"

He Yuzhu didn't answer. He walked to the control room door, glanced back at Ma Yuejin, and said, "Order."

The control room was crowded with seven or eight people, all staring at the screen. Ma Yuejin stood in front of the console, his fingers pressed on the ignition button, his knuckles white. He took a deep breath and pressed the button.

The engine ignited. Orange flames shot from the nozzles, billowing thick smoke that enveloped the entire test stand. The thrust curve on the screen surged upwards—one hundred tons, two hundred tons, two hundred and fifty tons, two hundred and eighty tons, three hundred tons. It stabilized. He Yuzhu stared at that line, his palms sweating. Ten seconds, twenty seconds, thirty seconds, one minute. The thrust curve remained at three hundred tons, unmoved.

Ma Yuejin turned around, looked at He Yuzhu, his lips trembling, unable to utter a word.

He Yuzhu didn't look at him, continuing to stare at the screen. Two minutes, three minutes, four minutes. The engine was still running, the flames were still shooting, the data was still fluctuating. No one spoke in the control room, only the hum of the machines.

Five minutes were up. Ma Yuejin pressed the stop button. The flames went out, the thick smoke slowly dissipated, leaving only charred marks and still-smoking debris on the test stand. The engine hadn't exploded.

Ma Yuejin slowly squatted down, covering his face with his hands. His shoulders were sobbing, but he didn't make a sound. The people in the control room stood there; some bowed their heads, some turned away, and some wiped their eyes with the back of their hands. He Yuzhu walked over, stood beside Ma Yuejin, and placed his hand on his shoulder. After a long while, Ma Yuejin raised his head, his face covered in tears. He wiped his face with his sleeve, stood up, and walked to the observation platform, looking at the still-smoking rocket. The sun rose behind the mountain ridge, shining on the test stand, gilding the charred marks with a layer of gold.

"Dean, it really worked this time. Three hundred tons of thrust, and it held steady for five minutes. That's enough." His voice was hoarse, like sandpaper rubbing against sheet metal.

He Yuzhu nodded. "That's enough. Go back and rest. The blisters on your lips should have gone down by now."

Ma Yuejin touched his lips, wincing in pain. "It's alright. It was worth it."

On the way back to Beijing, He Yuzhu leaned against the car window, watching the mountains recede into the distance. The driver remained silent, and so did he. He remembered Ma Yuejin squatting on the ground crying, the blisters on his lips, and how much weight he had lost. He remembered He Nianhua waiting for him at the door the last time, holding up the tank made from a bullet casing and calling out "Dad." That was several months ago.

He closed his eyes, and the mountain breeze blew in through the cracks in the window, cool and refreshing.

That evening, He Yuzhu sat in his office and took the list out of his drawer. Turning to the page about "rockets," after the words "high thrust," he added a line: "Engine test successful, thrust 300 tons, stable for five minutes." After finishing, he put the list back and locked the drawer. He stood up, walked to the window, and looked at the moon outside. On the windowsill was a note, drawn by He Nianhua during his last visit. It depicted a person and a kite, the lines crooked and uneven, the person's arms longer than their body. He picked up the note, looked at it for a long time, folded it, and put it in his pocket.

He turned off the light and walked out of the office. The corridor was dark, except for the emergency exit light, which glowed green. He walked to the door of the records room and paused. The door was closed and securely locked. The key felt heavy in his pocket. He continued walking and pushed open the door. A cool breeze blew in. He took a deep breath and headed home.