The alarm in Cargo Bay 3 went off just after the shift change. The first thing Hyerin saw was the numbers trembling on the oxygen monitoring console. The tank pressure gauge was falling from 2.3 atmospheres to 1.8. The rate of the drop wasn't steady. Hyerin pushed aside the mug she'd set on the console, rose from her chair, and ran down the corridor. The slap of her slippers against the steel floor echoed all the way to the far end. The hull's total oxygen was managed by the liter. An error of even 0.1 liter, once it accumulated, could change everything on the return trajectory.
When she opened the hatch to Cargo Bay 3, the cold struck her in the face. Frost formed on her eyelashes instantly. White crystals clung in layers to the outer wall of the Zeronium coolant tank, and through the frost she could see a thin crack. Fourteen centimeters long. At the crack's end, liquid oxygen was vaporizing like mist and leaking out. The mist spread along the floor and wrapped around her ankles. Hyerin pulled an emergency sealing patch from the wall's emergency box and pressed it over the crack. It took 8 seconds for the patch to adhere to the outer wall. The rate of vaporization dropped, but it didn't stop completely. With her bare fingertips she pressed down the edges of the patch, sealing it flush. The cold of the metal surface bit into her fingers as if burning them. Five seconds later the patch was fully sealed. She lifted her hand and curled her fingers, then straightened them. The feeling in the tips of her thumb, index, and middle fingers was gone. The skin had turned white.
Interior tank temperature: minus 187 degrees. Zeronium's deactivation threshold: minus 170 degrees. There was still some margin, but the problem was the amount of coolant oxygen that had just leaked out. Hyerin opened the cargo bay console and calculated the loss. About 4 minutes from the moment the alarm sounded until the seal. In that time roughly 23 liters of liquid oxygen had escaped. Hyerin checked the figure again. Her fingers on the calculator stopped. Twenty-three liters. In her mind the number turned into the shape of a person. One person's breath, enough to last until return. Hyerin licked her dry lips.
There was a bloodstain on the floor. Only then did Hyerin notice the person collapsed in the corner of the cargo bay. It was Semin. He'd been doing a routine inspection when the alarm went off. It looked as though the burst of cold from the ruptured crack had thrown his body against a fastening bolt. Hyerin picked up the intercom handset.
"Medical. Injured crew in Cargo Bay 3."
When she reached the bridge, Gijun was standing at the navigation console. He seemed to have already checked the alarm log. Before Hyerin could give him the number, he spoke first.
"Loss."
"23 liters. Seal complete. No further leakage."
Gijun tapped the console screen with a finger. Navigation data came up. 138 hours to return. Orbit change impossible. The remaining fuel was allocated precisely for deceleration.
"Total oxygen remaining in the hull."
"580 liters left for breathing. From now on, 5 people breathing for 138 hours needs 579.6 liters, so in theory the margin is 0.4 liter."
"And the coolant."
"Separate tank. It was 340 liters, now 317 after the leak. The minimum needed for cooling is 318 liters."
Hyerin stopped.
"We're 1 liter short. To make it up we'd have to take from the breathing supply, and then the breathing margin goes to minus 0.6 liter."
"Minus 0.6, meaning."
"Meaning for the last 43 minutes, all five of us can't breathe. Calculated out. Or… if one person gives up 22 hours' worth of oxygen, everyone lives and the cooling holds."
Gijun lifted his hand from the console. The air coming from the ventilation duct in the bridge ceiling stirred his hair faintly.
"All hands to the bridge. Fifteen minutes."
Yura came up from the medical bay. She was peeling off gloves marked with bloodstains.
"How's Semin."
"Two ribs gone, and his right lung's collapsed."
Yura crumpled the bloody gloves into her pocket.
"Must've hit that fastening bolt dead-on. The lung isn't doing its job."
"Oxygen consumption."
Yura looked at Hyerin. She shut her mouth for a moment, then answered.
"In that state he needs at least 1.2 liters an hour. That's 1.4 times normal respiration. And you want to cut his supply from here? Then even the good lung goes."
Hyerin ran the numbers again. If Semin's oxygen use ran 0.36 liter above normal, the extra consumption over 138 hours came to about 50 liters. The breathing margin was already negative.
"Artificial hibernation."
"We don't have the equipment. This ship is a freighter."
Yura's tone was flat. Like a closed door.
Hyerin pulled up the medical bay monitor. Semin lay on the bed. An oxygen mask covered half his face, fogged on the inside. With each breath the mask swelled, then shrank. The intervals were uneven.
Fifteen minutes later four people had gathered on the bridge. Semin couldn't come. Hyerin put the numbers up on the console screen.
"Breathing oxygen: 580 liters. Five people, 138 hours. Including the increase in Semin's consumption, total need is 629 liters. Shortfall: 49 liters. At the same time, cooling is 1 liter short."
Donghyeok listened with his arms crossed, leaning against the wall.
"Can't we borrow from the coolant tank?"
"Coolant remaining: 317 liters. Minimum needed: 318 liters. There's nothing to borrow."
"So in the end we're short on both. And you can't just make oxygen out of nothing. What are we supposed to do?"
Gijun spoke without rising.
"Lay out the options."
"One: shut down Zeronium cooling. Deactivation within 72 hours. Impact on three continents' power grids. The breathing shortfall of 49 liters stays as is, so everyone breathes on reduced supply. Two: stop one person's breathing. That frees up their 116 liters for 138 hours, which covers both the breathing shortfall and the cooling top-up."
Donghyeok pushed his back off the wall. "So there it is. Either someone dies, or Earth goes dark."
"Not dark—grid collapse." Gijun corrected him. "Three quantum-resonance plants, all fueled by Zeronium, with a six-month reserve. If this cargo doesn't make it, three continents go out in six months. 4.2 billion people."
The bridge went quiet. Only the hiss of air through the vents. Hyerin found herself suddenly aware of the sound of her own breathing. She'd never imagined she'd end up pricing out what a breath in, a breath out, was worth.
Still in her chair, Hyerin looked at the console screen again. 629 liters. 580 liters. The gap between the two numbers was 49 liters. 49 liters was what one person breathed in and out over 58 hours. Two days and 10 hours. Hyerin pulled an emergency ration bar from the drawer beneath the console and bit off a piece. It had no taste. Her throat tightened and it was hard to swallow. She drank some water. The water was recycled. Everything aboard was in circulation. Everything except the oxygen.
Donghyeok caught Hyerin in the corridor, at the junction where the passage toward the engine room met the one toward the cargo hold. "You said it was one or the other. Is that really all there is?"
"That's what I'm about to check."
"Check what."
"Whether there's a gap in the spec."
Donghyeok leaned his back against the junction wall and unfolded his arms, letting his hands fall to his sides against his thighs. "Semin's the bunk right next to mine. His snoring's got to be a good 3 decibels. I sleep with earplugs every night." He paused. The corridor's guide light lit the underside of his jaw. "You can't just erase that snoring to make some number come out right. Can you?"
Hyerin didn't answer, and walked on toward the cargo hold. Donghyeok's footsteps faded off the other way. Passing the engine room, she glanced inside. Donghyeok was perched on top of a pipeline, tapping at a tablet, a piping schematic spread across its screen. He seemed to be studying how to reroute the carbon-dioxide removal line into the cooling tank. When Hyerin stopped at the hatch, he looked up. "I was thinking, what if we divert part of the CO2 output to cooling. Purity's the problem, though."
"Zeronium cooling has to use pure oxygen only. If CO2 gets mixed in, a carbonate film forms on the tank's inner wall."
Donghyeok set the tablet down on his knee. "Then look for something else. I'll look too."
Hyerin nodded and moved off toward the cargo hold.
Cargo hold 3. Seal patch intact. Frost had settled evenly over the tank's surface again. Hyerin switched on the cargo-manifest terminal mounted on the wall beside the tank. Zeronium Transport Specification. A document she'd read three times before departure. Maintain cooling temperature below -190 degrees. Deactivation within 72 hours if breached.
This time she was looking for something else. Page 121 of the 142-page technical appendix. "Zeronium Crystal Structure Phase-Transition Chart." Hyerin's finger stopped on the screen.
Below -190 degrees: alpha crystal. Quantum-resonance efficiency 100 percent. Between -170 and -190 degrees: beta crystal. Quantum-resonance efficiency 78 percent. Above -170 degrees: non-crystalline. Inactive.
Beta crystal. 78 percent. The "deactivation" in the body of the spec applied only above -170 degrees. Between -170 and -190 the crystal structure changed, but the quantum resonance itself was still possible. Whether someone had deliberately ignored this range, or whether whoever wrote the spec had decided that anything short of 100 percent was meaningless, she couldn't tell. Hyerin checked the appendix's list of references. The phase-transition chart was sourced to a 2068 paper from the European Crystallography Society. The body of the spec had been written in 2071. A three-year gap. Whether the person who wrote the body had simply failed to reflect the appendix's data, or had left it out on purpose, couldn't be settled from the spec alone. -175 degrees. Zeronium doesn't die. Its efficiency only drops. With the finger that had been trembling over the screen, Hyerin pressed down hard on that line. The data seemed to give off a faint light.
She recalculated the cooling oxygen consumption. Holding -190 degrees took 2.3 liters per hour. Lowering it to -175 took 1.4 liters per hour. Over 138 hours the difference came to 124 liters. It covered the 50-liter breathing shortfall and still left 74 to spare.
Hyerin captured the terminal screen. Three frostbitten fingers trembled over the display.
When she got back to the bridge, Gijun was sitting alone. Hyerin held out the terminal screen. "Page 121 of the spec. Quantum resonance is possible even in the beta-crystal state. 78 percent efficiency."
Gijun looked at the screen. It took him 30 seconds to read. "That's a transport-spec violation."
"It's data that's in the spec."
"It's the appendix, not the body. The transport contract specifies holding at -190 degrees."
"But the plants still run, don't they? Isn't that better than them shutting down?"
"And if headquarters turns it down? You think there'll be a way to cool it back down on Earth? Where's the guarantee you can turn beta back into alpha?"
Hyerin shut her mouth. The appendix said nothing about re-transition. "There isn't one."
"It's an irreversible choice. All three plants lose 22 percent of their output. If it holds for more than six months, hospitals, water-treatment plants, food stores shut down in that order. Estimated population affected: 80 million to 120 million."
A chill spread across Hyerin's back. She sat down in her chair.
"There's one more thing."
Gijun turned his head.
"The chart in the appendix assumes pure Zeronium. Our cargo is 2071-Tethys ore, with an impurity content of 3.2 percent. If the titanium oxide stabilizes the crystal lattice, the efficiency could run higher than 78 even in the beta state. If I run a resonance test on a 1-gram sample, we'll have results in 4 hours."
Gijun rose from his chair. He stopped in front of the comms panel. Transmission to Earth was 4 hours one way.
"When the test results come in, send them to headquarters. Keep the coolant at minus 190 until approval comes back. As of now, everyone cuts their breathing volume by 20 percent. 0.67 liters an hour."
"What about Semin? With his lung collapsed—"
"Check the minimum sustaining level with Yura."
Hyerin left the bridge. The corridor lighting had switched to emergency mode, leaving only the guide lamps along the floor lit.
From cargo hold 3 she extracted 1.2 grams of the Zeronium sample. She placed it in a small vacuum chamber and set the temperature to minus 175. The chamber's cooling module hummed to life with a low sound. Four hours. Hyerin sat on the floor beside the chamber. She leaned her back against the outer wall of the tank. The cold seeped through her whole back. The bloodstain from where Semin had fallen was still there. Someone had tried to wipe it, but it had dried brown in the grooves between the bolt threads.
Yura came down into the cargo hold. She had a heating pad in her hand.
"Let me see your hands."
Hyerin held out her hands. Three frostbitten fingers were swollen and red. Yura wrapped the pad around them. Warmth began to circulate back into her fingertips. It stung.
"Semin?"
"I've capped his oxygen at 0.95 liters. Captain's orders. Blood oxygen saturation is 89 percent. Below 90 is the danger zone."
Yura sat down on the floor. Beside Hyerin. The chamber's whirring drifted between them. Hyerin peeled off the heating pad and tried bending her fingers. Her middle finger followed half a beat late.
"Look, Hyerin. If everyone drops their oxygen 20 percent and holds out for 138 hours, by the last day we'll all be limp as corpses. Who's going to run the deceleration burn then?"
"There's an automatic sequence."
"And if the automatic sequence fails?"
The chamber's temperature gauge held steady at minus 175.2, not wavering. Hyerin bit the inside of her lip. The taste of iron spread across the lining of her mouth.
Yura said as she got to her feet.
"The frostbitten fingers—I need to check them again in 12 hours. If the blood doesn't circulate, the tissue could go necrotic."
"Understood."
Yura climbed the ladder. Hyerin was left alone. The chamber's whirring bounced off the metal walls of the hold and echoed. Beside Semin's bloodstain lay the wrapper Yura had left behind from the heating pad. Hyerin picked it up and put it in her pocket.
3 hours and 47 minutes later, the results came out of the chamber. Hyerin read the screen. She read it, and read it again.
2071-Tethys ore Zeronium. Minus 175. Beta crystal state. Quantum resonance efficiency 91 percent.
Not 78, but 91. The titanium oxide in the impurities had stabilized the lattice structure. Hyerin saved the results and ran up to the bridge.
Gijun checked the results. His expression didn't change.
"Transmit them to headquarters."
"If I transmit, it's 8 hours until we hear back. In that time Semin will—"
"Transmit them."
Hyerin sent the data. The signal flew off toward Earth. 4 hours one way. Review. Reply. 8 hours total.
Hyerin opened the medical bay monitor. Semin's blood oxygen saturation was dropping from 88 to 87 percent. The interval at which his breath fogged the inside of the mask was slowing.
Hyerin went down to cargo hold 3. She opened the cooling system's control panel. She changed the target temperature from minus 190 to minus 175. She rested her finger over the confirm button. A warning window appeared. 'Transport specification breach. Do you wish to continue?' Hyerin pressed confirm.
As the cooling module's output dropped, its sound shifted. The high hum fell an octave. The frost on the tank's surface began to melt from the edges. Droplets ran down the surface of the tank. The oxygen it saved began flowing back into the breathing lines. On the monitor, the pressure in the breathing tank rose slowly.
She went to the medical bay. She returned Semin's oxygen supply to 1.2 liters an hour, back to its original level. The fog inside his mask settled into an even rhythm again. Semin's chest rose a little deeper, then fell.
Gijun came down into the cargo hold 20 minutes later. He saw the droplets beaded on the tank's surface where the frost had been, and looked at Hyerin.
"You changed it without approval."
That was what Gijun said. A statement, not a question.
"Yes."
"Why."
"Semin's oxygen saturation dropped to 87 percent. If we wait 8 hours, he could suffer irreversible brain damage."
Gijun stood beside the tank. A droplet running down the tank's surface fell to the floor beside his boot with a drip.
"And if headquarters rejects it."
"At 91 percent efficiency, there's no problem running the power plants. The power reduction would be around 9 percent."
"Calculating that is headquarters' job, not ours."
Hyerin didn't answer. Gijun turned and walked toward the hatch. He put a hand on the ladder and stopped. With his back to her, he said.
"Log it as my order. That the captain changed the coolant temperature, under his own authority. Based on the test results. Not the oxygen manager acting alone—it was the captain's command. Amend it to read that way."
Gijun climbed the ladder. The sound of his boots on the metal rungs faded upward. Alone now in the cargo hold, Hyerin opened the log on the control panel. 'Coolant temperature changed — executed by: oxygen manager Hyerin.' She edited the executor field. 'Captain Gijun.' She pressed save.
The incoming-message alert on the comms panel sounded 7 hours and 38 minutes later. Sooner than expected. Hyerin went up to the bridge. Gijun was already opening the message. Yura and Donghyeok stood behind him too. The screen's blue light lit the four faces.
'Coolant temperature change denied. Comply with transport specifications. Restore minus 190 degrees immediately. Failure to comply will result in removal of the captain and termination of all crew contracts.'
Gijun closed the screen. No one spoke. Only the hiss of the ventilation duct moved through the bridge. Donghyeok was the first to speak.
"Bastards."
Yura grabbed his arm, but he didn't shake her off. Gijun looked for a moment down the corridor toward the medical bay. The direction of Semin's bed. Then he turned back to the comms panel.
"We're not restoring it."
Hyerin raised her head. There was no expression on Gijun's face. But she could see his right hand, inside his pocket, clenched tight around the fabric of his uniform. The outline of the tendons showed faintly through the cloth.
Gijun began typing in the response field. Over his shoulder, Hyerin read the words appearing on the screen. 'Review of experimental data confirms beta crystal efficiency at 91 percent. To protect the lives of the crew, the coolant temperature change will be maintained. All responsibility rests with the captain.'
Gijun pressed the send button. A short, high electronic tone sounded. The message flew off toward space. Gijun left the bridge. The sound of his boots faded down the corridor.
Hyerin was left alone. Stillness settled over the bridge. There was only the low noise of the ventilation duct and the faint tremble of a relay somewhere inside the control panel. Hyerin lifted her left hand. The tips of the three frostbitten fingers were still red and swollen. Slowly she lowered it, laying her fingers against the cold metal surface of the navigation console. Through skin gone dull to sensation, the hull's minute vibration reached her, faint and distant. On the screen, the number glowing green for total oxygen no longer wavered.
