The vibration sensor on cargo hold bulkhead 3 went off. On the bridge, Taeho checked the monitor. The vibration frequency of bulkhead 3 had drifted outside the normal range. 38 hertz. 4 hertz off the hull's resonant frequency. Taeho set down his coffee and switched on the hold's surveillance camera. The screen was dark. Either dust had settled on the lens, or the lights inside the hold were off. Taeho pressed the lighting switch remotely. Nothing came on. He pressed it twice more. No response. Taeho rose slowly from his chair.
The freighter Geongon was on its way back to Earth from the asteroid 2187-Eris. The cargo loaded at the asteroid mining base was 84 tons of Erisite—a nickel-iron asteroid mineral laced with a trace of amorphous metal. Delivery contracts were in place with 3 of Earth's aerospace alloy manufacturers. The contract came to 240 billion won. It was the Geongon's 14th round trip, and the last voyage on which Taeho would ride as cargo officer. 23 days remained until Earth. The name 'Geongon' was etched into the outer hull. The crew numbered 3.
Taeho came down from the bridge and walked the cargo hold corridor. From the floor of the passage, the vibration rose up through the soles of his feet. The 38-hertz tremor traveled along his bones to his knees. He stopped before bulkhead 3. He laid a hand against its surface. It was warm. A cargo hold bulkhead should sit near minus 120 degrees, the same as the hull's exterior. He could touch it bare-handed without frostbite. Taeho stripped off his glove and pressed his bare hand to the bulkhead. The metal surface was not smooth. There were fine protrusions. It was rough, like sandpaper. He rubbed it with his fingers. The protrusions seemed to be growing out of the bulkhead's surface. Taeho pulled his hand away and switched on his headlamp. The light played across the surface. The bulkhead's original color was gray. It was different now. Black striations had bled across the gray. The striations were spreading along the bulkhead's weld seams. They were darkest where the weld seams ran thickest.
Taeho stood in the corridor and opened the intercom.
“Seyeong, are you in the engine room?”
Three seconds later, a reply.
“Yeah. What is it?”
“Come down to bulkhead 3 and take a look. There's something wrong with the surface.”
Five minutes later Seyeong appeared at the end of the corridor, work-suit sleeves rolled up. She stood before the bulkhead, shone her headlamp on it, and looked at the black striations. She scraped at them with a finger. They didn't scrape off. Her nail slid across.
“This isn't the coating peeling,” Seyeong said. “The surface itself has changed.”
Seyeong drew a portable hardness gauge from her pocket and pressed it to the bulkhead. A number came up. Her eyes widened.
“The bulkhead's hardness is 1.7 times the design spec.”
Together, Taeho and Seyeong opened up the interior of bulkhead 3. They loosened the bolts and pulled off the inspection panel. The inside came into view. Taeho's hands stopped. Something had grown in the gap between the inner face of the bulkhead and the outer wall of the cargo container. A black crystalline structure. It stretched out in a form that bridged the metal of the bulkhead and the metal of the container. The surface of the crystal was smooth. Held to the light, it threw back a faint iridescence. Taeho brought a finger to the crystal. Its surface was not cold. It was lukewarm.
“Did the Erisite get out of the container?” Taeho asked. Seyeong shook her head.
“The container's sealed. This grew from outside. Out of the bulkhead's metal.”
Seyeong pointed to the base of the crystal. It rose up out of the bulkhead's surface. There was no boundary between the metal surface and the crystal. The metal was turning into crystal. No border—one side slowly melting into the other.
Seyeong went back to the engine room and ran a compositional analysis. Twenty minutes later the results came up on the bridge monitor. Taeho and Minji looked at the screen. The crystal's main constituent was a nickel-iron alloy. The same material as the bulkhead. But the crystal lattice was structured differently. The bulkhead's nickel-iron was face-centered cubic. The crystal's nickel-iron held a lattice arrangement never observed on Earth. The amorphous metal had rearranged the crystal structure of the nickel-iron. The trace of amorphous metal in the Erisite was making contact with the bulkhead's metal through the container, and rewriting the bulkhead's atomic arrangement.
“If the hardness is up 1.7 times,” Minji said from the pilot's seat, “then the hull's gotten stronger, right? That's not a bad thing, is it?”
Taeho looked at Minji.
“The problem is the direction. If it's bulkhead 3 now, next is bulkhead 2, and after that bulkhead 1. You know what's past bulkhead 1?”
Minji fell silent. Past bulkhead 1 was the engine room. The engine room's bulkhead was built to work through repeated thermal expansion and contraction. If the bulkhead's hardness climbed, the thermal expansion would be constrained, and the pressure in the engine's combustion chamber would have nowhere to disperse. Once the pressure crossed the threshold, the engine would stop.
Taeho asked Seyeong,
“What's the rate of fusion?”
Seyeong answered over the intercom from the engine room.
“I measured the converted area on bulkhead 3. At the inspection 8 hours ago there was none. Right now 14 percent of bulkhead 3's surface area has converted. About 1.7 percent an hour.”
Taeho did the math. Roughly 50 hours until bulkhead 3 fully converted. Add bulkhead 2 and that came to 100 hours. Bulkhead 1 after that. Around 170 hours to reach the engine bulkhead. 7 days. 23 days until Earth. If the engine stopped, they would not make it there on day 23. They would drift on inertia. Adrift on the edge of the solar system with no thrust. Until a rescue ship came.
Taeho sent his report from the bridge to Earth Control. The comm lag was 18 minutes each way.
"Taeho, cargo chief of the Geongon. Metallic conversion of Erisite composition detected at bulkhead 3 in the hold. Spreading at 1.7 percent per hour. Estimated to reach the engine bulkhead in 7 days. Requesting response instructions."
36 minutes later, Control's reply came.
"Geongon, this is Control. Jettison cargo only as a last resort. Contract penalty is 120 billion won. Cargo preservation takes priority. Devise your own means to suppress the conversion rate."
Taeho switched off the comm panel and sank into the chair. A penalty of 120 billion won. Three years of the Geongon's operating revenue. Taeho was captain and cargo chief both. Primary responsibility for any cargo loss was his. Seyeong came up the engine-room ladder.
"A way to suppress it?"
Seyeong asked, reading Taeho's face. Taeho slowly shook his head.
"We could try packing insulation between the bulkhead and the cargo, but the parts where conversion's already started can't be reversed."
Seyeong thought a moment, then said,
"Temperature. Atomic migration in amorphous metal is sensitive to temperature. Lower the bulkhead's temperature and the spread rate could drop."
Taeho looked at her.
"How?"
"We reroute the coolant from the cooling system over toward bulkhead 3. The catch is the engine room loses 30 percent of its cooling capacity."
Cut engine-room cooling and engine efficiency falls. Thrust drops, arrival is delayed. Taeho asked,
"How much later do we arrive?"
Seyeong ran the numbers.
"23 days becomes 31. Eight days added."
Taeho looked at Minji.
"Food?"
Minji checked the stores.
"25 days' worth. Cut the rations and it's 30. 31 isn't enough."
Taeho leaned back against the seat. He could hear air pushing out of the ceiling vent. Taeho closed his eyes. Three seconds later he opened them.
Taeho decided on the reroute. In the engine room Seyeong switched the coolant piping valve over by hand. Bulkhead 3's temperature began to fall. From 8 degrees to minus 30. Twelve hours later he measured bulkhead 3's conversion rate again. It had dropped from 1.7 percent per hour to 0.8. Less than half. Taeho looked at the number and let out a breath. But it hadn't stopped. Only slowed. At 0.8 percent, full conversion of bulkhead 3 was 107 hours off. About 350 hours to reach the engine bulkhead. 14 days. Arrival was set for day 31. Just barely enough.
On the third day, Taeho went to inspect bulkhead 3. Walking the corridor, he felt the vibration underfoot had changed. What had been 38 hertz had come down to 34. The gap with the hull's resonance frequency was closing. Once the natural frequencies of the bulkhead and the hull begin to match, resonance sets in. And once resonance starts, fatigue builds up in the hull's structure. Taeho stood in front of bulkhead 3 and shone his headlamp. Black striations had spread across the whole bulkhead. Not just the weld seams — the entire face of the bulkhead had gone black. The nodules on the surface had grown larger. And they had arranged themselves into a regular pattern. A honeycomb. The pattern nature uses to distribute stress most efficiently had etched itself into the metal, unbidden.
Taeho opened the inspection panel. The crystal structure inside had expanded since three days ago. The crystals bridging the bulkhead and the container now stretched all the way to the metal of the corridor floor. The floor Taeho was standing on. The vibration rising through his feet sharpened. It was being carried straight through the crystals. Taeho knelt and looked at the floor. A fine black line had appeared along the edge of the floor's metal panel. The conversion had crossed the bulkhead and moved into the floor.
He called Seyeong.
"It's spread from bulkhead 3 into the floor. What about bulkhead 2?"
Seyeong's voice came back.
"Checked it. It's started on bulkhead 2 too. Discoloration at the weld seam."
Taeho's mouth hardened. The cooling had slowed the rate, but as the contact surface widened, the overall pace was actually picking up. The wider the contact surface, the more points where conversion ran at once. Slowing it down had, in effect, bought the spread time to widen its reach.
Taeho went back to the bridge. He called Seyeong and Minji. The three of them gathered there. Taeho threw the bulkhead status up on the screen. He laid out where they stood.
"We reach the engine bulkhead not in 14 days but within 10. 28 days left to arrival. If the engine stops, we drift. A rescue ship takes 40 days minimum."
Minji asked,
"40 days, and the food—"
"Won't hold out."
Taeho said. The bridge went silent. Just the three of them breathing, and the vent.
Seyeong spoke up.
"What if we dump the cargo."
Taeho looked at her.
"Release the cargo and the cause of the conversion is gone, so it stops, right. The parts already converted can't be reversed, but we can keep it from reaching the engine bulkhead."
Taeho slowly shook his head.
"Bulkhead 3 has already converted. We'd have to cut through the hold's outer wall to jettison it, and cutting a converted wall opens cracks. With ordinary nickel-iron the cut comes out clean, but with that rearranged crystal structure the stress under the blade is unpredictable. It could start a decompression."
Seyeong looked at him.
"And if we don't cut?"
"There's a way — loosen the outer-wall bolts and detach the whole panel. But if the bolts have converted, they won't come loose."
Taeho went out to check the bolts on the outer wall of Cargo Hold 3. He put on an EVA suit and passed through the airlock to the exterior of the hull. The outer wall of the Geongon spread out under the beam of his headlamp. Twenty-four bolts on the outer-wall panel of Cargo Hold 3. Taeho fitted the power wrench to the first bolt. He turned it. It didn't move. He cranked the torque to maximum. The bolt didn't budge. The converted metal had fused bolt and frame into one. Taeho tried all 24 bolts, one by one. From 1 through 18, nothing moved. Number 19 turned. That part hadn't converted yet. Number 20 turned too. Number 21 wouldn't. Number 22, it turned. Number 23, nothing. Number 24, it turned. Only 6 of the 24 would come loose. The other 18 had become one body with the hull.
Taeho came back through the airlock and stripped off the suit. His hands were shaking. The fingers inside the gloves were cold. He climbed up to the bridge and told Seyeong.
"18 of the 24 bolts are seized. The panel won't detach."
Seyeong was silent a moment, then spoke.
"That leaves only cutting."
Taeho looked at her.
"If we cut, decompression starts."
"We isolate the decompression zone to Cargo Hold 3. Close the airtight doors on both sides of Bulkhead 3, decompress only the hold, and the rest of the hull holds."
Taeho thought it over. It was possible. Write off Cargo Hold 3, vent its cargo into space. But there was a problem.
"Bulkhead 3 has already converted. If the airtight door's sealing touches the converted metal, I don't know whether the seal will hold."
Seyeong thought for a moment.
"We have to check it directly."
Taeho and Seyeong inspected the airtight door of Bulkhead 3. They examined the sealing along the door frame. The seal's rubber packing was pressed against the converted metal. The rubber was discolored. Black metal was bleeding into it. Seyeong measured the rubber's hardness. Higher than normal. The rubber was losing its elasticity.
"The seal is hardening," Seyeong said. "If we cut now, the seal might still hold. But given time, it could harden completely, and then the airtight door itself might not close."
Taeho asked, "How long do we have?"
Seyeong looked at the spread of discoloration along the seal.
"12 hours. 18 at the most."
Taeho went back to the bridge. He sat down in the chair. He laid both hands on his knees. His hands were shaking. He had to decide within 12 hours. Vent the cargo and 84 tons of Erisite were gone. Contract penalty: 120 billion won. The company could go under. Don't vent it, and in 10 days the engine stops and they drift for 40 days. There wasn't enough food.
He reported to Control again.
"Geongon, Taeho. No alternative but to vent the cargo. Panel detachment impossible due to seized outer-wall bolts. Cutting will cause decompression, but isolation possible via Bulkhead 3 airtight door. Seal hardening in progress, remaining time within 12 hours. After 12 hours, even venting becomes impossible. Requesting a decision."
The reply came 36 minutes later.
"Geongon, Control. Cargo venting not approved. Contractual obligation to fulfill. Devise additional measures to suppress the conversion rate. Upon conversion reaching the engine bulkhead, execute emergency shutdown and await rescue."
Taeho stared at the screen. Await rescue. It meant let the engine stop and drift for 40 days. It meant hold out 40 days on 30 days' worth of food. Taeho switched off the comms panel.
From the pilot's seat, Minji spoke.
"Taeho. 12 hours."
Taeho looked at her. Her face was half-lit by the glow of the instrument panel.
"Control said no."
Minji looked back at him.
"Is Control here?"
The bridge went quiet. Seyeong heard it over the engine-room comms. She said nothing.
Taeho rose slowly from the chair. He walked down the passage and stood before Bulkhead 3. He laid a hand on the bulkhead. Lukewarm. He could feel the honeycomb pattern of the crystal structure under his palm. A regular, precise, beautiful structure. If this material reached Earth, it could change the aerospace industry. But this material was feeding on the Geongon to grow. Taeho took his hand away.
Taeho put the EVA suit back on. He took the plasma cutter and went to the airlock. From the engine room, Seyeong closed the airtight door of Bulkhead 3. The sound of the door closing rang down the passage. The dull sound of metal meeting rubber. Seyeong spoke over the comms.
"Seal confirmed. Sealing pressure within normal range. For now, it holds."
Taeho checked the cutter inside the airlock. On the bridge, Minji was preparing the cargo-hold decompression procedure.
"Taeho, if you vent without Control's approval, it's on you."
Minji said it. Taeho pressed the airlock's comms panel.
"I know."
The airlock's outer hatch opened. Taeho moved along the outer hull toward the No. 3 cargo hold. The sound of the magnetic boots clamping onto the hull and the safety line sliding along the rail rang inside his helmet. He came to a stop before the outer wall of the No. 3 hold. He switched on the plasma cutter. A blue flame bloomed in the vacuum. Taeho settled on his cut line. A path that skirted the 18 bolts still fast and, taking the 6 loosened bolts as its markers, sliced away part of the panel. The cut would cover 40 percent of the whole panel. Of the 84 tons of Erisite, roughly 34 would go out through this hole. The other 50 would stay in the container. This wasn't a full jettison. It was cutting down the cause of the conversion. Taeho touched the cutter to the metal. The flame bit into it. The converted metal parted. Sparks leapt from the cut. It was unlike ordinary nickel-iron. The sparks burned white, not red. The sound of the metal being severed carried through his suit. A high, needle-sharp vibration. A sound you could only bear with your teeth clenched. As the cut advanced, fine cracks opened along the panel's edge. The cracks spread along the cut line. Just as he'd predicted. Taeho picked up the pace.
The cut was done. Taeho's arm was trembling. The residual heat of the plasma cutter came through his glove. Forty percent of the panel had broken away from the hull. Taeho hung from the rail and watched. Part of the container was pushed out into space through the hole. Chunks of Erisite scattered into the black. In the beam of his headlamp the shards of Erisite glittered. A flash of rainbow, then gone into the dark. It was 240 billion won of light. 34 tons of Erisite had come away from the Geongon. Air was leaking from the cut. As the hold's residual air bled out into space, ice crystals formed. Fine particles of ice scattered around the cut. The ice glittered in the headlamp's beam. Ice clung to Taeho's visor. He wiped it away with his glove.
Taeho returned to the airlock. He took off the suit. His hands were shaking. He failed three times to get the gloves off. There was no strength in his fingers. On the fourth try they came free. He went up to the bridge. Minji was watching the decompression data.
"No. 3 hold decompression complete. Pressure-seal door holding. Pressure normal in the rest of the hull."
Seyeong's voice came up from the engine room.
"Reading the No. 3 bulkhead temperature. Conversion rate down to 0.3 percent per hour. The contact surface's shrunk."
Taeho took in the number. 0.3 percent. Down from the 0.8 percent before. As the amount of Erisite dropped, so had the material driving the conversion.
Taeho sent his report to Control.
"Geongon, Taeho. Partial cut of the No. 3 hold outer wall. 34 tons of Erisite jettisoned. Remaining cargo 50 tons. Conversion rate down to 0.3 percent per hour. Recalculating estimated time to reach the engine bulkhead. Hull pressure holding."
Thirty-six minutes until Control answered. Taeho didn't wait for the answer. He sat down in the chair and looked at the panel. Fuel remaining, oxygen remaining, food stores. The numbers stood listed across the screen. Taeho lifted his eyes from the panel's numbers and looked out the bridge window. Behind the Geongon, shards of Erisite lay scattered. The glittering points were growing smaller and smaller. Starlight showed between the points. Taeho turned his eyes from the window. Seyeong's voice came through again.
"The No. 2 bulkhead conversion rate's dropped too. 0.4 percent."
Taeho nodded. He was sitting alone on the bridge. No one saw it, but he nodded. A vibration came up from beneath his feet. 36 hertz. Still climbing toward the resonant frequency. The hull was trembling. Taeho sat in the chair, feeling the vibration through the soles of his feet. Control still hadn't answered.
