Untethered

Chapter 1: Bright Side Pass

The sunrise came every ninety-two minutes up here, and it never got old.

Tamsin Anderson floated at the end of the station's port truss, her boots locked into a foot restraint, her gloved hands resting on the thermal blanket she'd just finished replacing. Below her—though "below" was a negotiable concept—Earth's terminator line slid across the Indian Ocean, a razor-sharp boundary between cobalt blue and the amber glow of a sun that was always either rising or setting. The station's solar arrays caught the light and blazed gold, eight enormous wings stretching out from the central truss like the skeleton of some impossible bird.

"ICS, Houston. Tamsin, how's the blanket looking?"

Reggie Lund's voice was warm molasses in her earpiece. She'd known Reggie for eleven years—he'd been her CAPCOM on her first mission, back when she was a green mission specialist who couldn't stop grinning inside her helmet. Now she was a veteran flight engineer on her third long-duration rotation, and Reggie was lead flight director, and neither of them had lost the easy rhythm they'd built across a decade of shared orbits.

"Blanket's nominal, Houston. Good adhesion on all four corners. I'm going to take a few photos for the thermal team and then head to the next worksite."

"Copy that. You're about twelve minutes ahead of the timeline, so no rush."

"No rush," Tamsin repeated, and allowed herself a moment.

She tilted her helmet back and looked along the length of the International Cooperative Station. It was enormous—a hundred and ten meters of pressurized modules, trusses, radiator panels, and docking ports assembled over twenty years by a dozen nations. The ICS had succeeded the old ISS after the original station was deorbited in 2031, and it was bigger, more capable, and more international than its predecessor. The Americans and Europeans had built the core modules. The Japanese had contributed the research laboratory. The Canadians had built the new robotic arm. Even the Chinese had a module now—the Harmony Node, docked to the station's nadir port—a symbol of a diplomatic thaw that had seemed impossible a decade ago.

Home. For the past four months, this had been home.

Jude Korhonen's voice crackled over the intercom. "Tamsin, you daydreaming out there?"

She smiled. Jude was inside—specifically, he was in the European laboratory module, running a materials science experiment that involved heating titanium samples to absurd temperatures and then cooling them in microgravity. He was Finnish-Canadian, tall and angular, with a dry wit that could sneak up on you like a cat. They'd trained together for two years before this mission, and he was the best crewmate she'd ever had.

"Just admiring the view," she said. "You should try it sometime."

"I can see the view from in here. Through a window. Where there's air."

"Overrated."

"Air is overrated?"

"Windows are overrated. The real thing is better."

She heard him chuckle. "I'll take your word for it. I'm about to start the next melt cycle. Should be done by the time you finish the antenna repair."

"Copy. I'll check in when I'm at the S-band array."

Tamsin released her feet from the restraint and clipped her safety tether to the next anchor point on the truss. Movement in a spacesuit was deliberate, methodical—you always maintained at least one point of attachment to the station, and you always, always knew where your tether was. The suit itself was a marvel of engineering, a hundred and twenty kilograms of layered Kevlar, Mylar, and neoprene that kept her alive in a vacuum, but it was also clumsy and exhausting to work in. Every motion required effort. Every task took three times as long as it would have in a shirtsleeve environment.

She made her way along the truss, hand over hand, moving toward the S-band antenna array that was her next worksite. The antenna had been intermittently dropping its link to the Tracking and Data Relay Satellite network, and the comm team suspected a loose connector. Simple fix—if she could reach it. The array was mounted on a boom that extended out from the starboard truss, and getting to it required traversing a section of the station's exterior that had no handrails. She'd have to free-float on her tether for about four meters, then grab the boom's base and pull herself in.

Routine. She'd done harder things in the Neutral Buoyancy Lab back in Houston.

The sun was fully up now, and the station was bathed in hard, shadowless light. She could see the curvature of Earth in her peripheral vision—the impossibly thin blue line of the atmosphere, the swirl of a cyclone over the Bay of Bengal, the brown and green patchwork of Southeast Asia sliding past below.

"Houston, Tamsin. I'm at the S-band array worksite. Going to unclip and free-float to the boom."

"Copy, Tamsin. We've got good telemetry on your suit. You're go for traverse."

She unclipped her tether from the truss anchor, attached it to a slide wire that ran along the boom's base, and pushed off gently. Four meters of open space. She drifted across it, feeling the familiar lurch of her inner ear as her body tried to reconcile the absence of gravity with the visual evidence of a planet rotating beneath her feet. Then her gloves found the boom, and she pulled herself in, locked her boots into another restraint, and began working on the antenna connector.

The connector was corroded—micrometeorite impacts had degraded the thermal coating around it, allowing atomic oxygen to eat at the metal. She cleaned it with a wire brush from her tool caddy, applied a fresh coat of sealant, and tested the connection.

"Houston, Tamsin. S-band connector is cleaned and resealed. Can you check the link?"

A pause. Then Reggie: "We're seeing solid signal on TDRS-West. Looks like that did it. Nice work."

"Easy day."

"Don't jinx it," Jude said from inside.

Tamsin laughed. She was about to reply when something caught her eye—a flash of light, sharp and brief, high above the station's orbital plane. She tilted her helmet up. Another flash. Then another. A rapid sequence of bright points, like a string of firecrackers going off in silence.

"Houston, Tamsin. I'm seeing some kind of... light show above us. Looks like it's in a higher orbit. Multiple flashes."

Silence on the loop. Then Reggie's voice, and it had changed. The warmth was gone. He sounded clipped, precise—the voice he used during sims when something had gone wrong.

"Tamsin, Houston. Stand by."

She waited. The flashes continued—dozens of them now, spreading across a wide arc of sky. They were beautiful in a way that made her uneasy, like watching lightning in a clear sky.

"Tamsin, Houston." Reggie again. "We're getting reports of a collision event in the seven-hundred-kilometer band. A defunct weather satellite impacted a communications constellation. We're tracking multiple debris objects. Repeat, multiple debris objects. We're assessing the situation."

Tamsin felt something cold settle in her chest. She knew what a collision event meant in a crowded orbital environment. She'd studied Kessler syndrome in training—the theoretical cascade where one collision generates debris that causes more collisions, which generates more debris, in an exponential chain reaction that could render an entire orbital band unusable.

Theoretical. Until now.

"Houston, what's the threat assessment for our altitude?"

"We're working it. Stand by."

The flashes were multiplying. She could see them spreading now—not just above the station but laterally, across the sky, as if someone were scattering diamonds across black velvet. Each flash was a collision. Each collision was creating hundreds or thousands of new fragments. And those fragments were hitting other objects, which were creating more fragments.

She did the math in her head. The station orbited at four hundred and twenty kilometers. The initial collision was at seven hundred. But debris from a high-energy impact didn't stay in one orbit—it spread out, some pieces going higher, some going lower, depending on the geometry of the collision. Lower-altitude debris would reach the station's orbital band in—

"Tamsin, Houston. Emergency. We are declaring a debris emergency. You need to get inside immediately. Repeat, get inside immediately. We are tracking a debris field descending through your orbital altitude. Time to first possible impact: eleven minutes."

Eleven minutes.

She was outside, on the end of a boom, four meters from the nearest truss handrail, and the airlock was forty meters from there.

"Copy, Houston. I'm moving."

She unclipped from the boom restraint, grabbed the slide wire, and pulled herself back toward the truss. Her heart was hammering, but her hands were steady. Eleven minutes. She could make it in eleven minutes. She'd done emergency ingress drills in six.

But the drills were in the pool, where you could push off the bottom and the water slowed you down in a forgiving way. Out here, every movement had to be controlled. Push too hard and you'd overshoot your handhold. Miss a tether point and you'd drift.

"Jude, you copy?" she called.

"I copy. I heard. I'm closing hatches and getting to the core module."

"Good. I'm on my way in."

She reached the truss and began moving hand over hand toward the airlock, clipping and unclipping her tether at each anchor point. The station's exterior was a maze of handrails, equipment racks, and cable bundles, and she knew every centimeter of it—she'd memorized the layout during hundreds of hours of training. Left hand, right hand. Clip, unclip. Move.

"Tamsin, Houston. Update. The cascade is accelerating. We're now tracking over twelve thousand new objects in the four-hundred-to-eight-hundred-kilometer band. Time to first possible impact at your altitude: eight minutes."

Eight minutes. She'd lost three minutes already.

She moved faster, sacrificing caution for speed. Her breath was loud in her helmet, fogging the visor at the edges. The airlock was ahead—she could see it, the white cylinder of the Quest module, its outer hatch open and waiting.

"Tamsin, Houston. Six minutes."

She was at the base of the truss now, where it connected to the station's central module stack. Twenty meters to the airlock. She unclipped her tether and pushed off, sailing along the station's hull in a controlled drift, reaching for handrails as they passed.

The first impact came with no warning.

There was no sound—sound doesn't travel in vacuum—but she felt it. A vibration through the station's structure, transmitted through the handrail she was gripping. Then she saw it: a spray of debris erupting from the station's starboard solar array, silent and violent, pieces of photovoltaic cell and aluminum framework spinning away into space like shrapnel from a grenade.

"Houston, we're hit! Starboard array is hit!"

"Copy, Tamsin. We see it. Keep moving."

Another impact. This one was closer—she saw the flash as something small and fast punched through a radiator panel ten meters to her left. The panel began venting coolant, a white plume of ammonia crystals spraying into the void.

"Tamsin, four minutes. Get inside now."

She was close. Fifteen meters. Ten. She could see the airlock hatch, the white interior, the handrails inside. She reached for the last external handhold—

The station lurched.

It was a sensation she'd never felt before—a sudden, violent translation, as if the entire four-hundred-ton structure had been shoved sideways by a giant hand. She lost her grip. Her fingers slipped off the handrail, and she tumbled backward, spinning slowly, her tether pulling taut—

The tether snapped.

She felt it go. A sharp jerk, then nothing. She was drifting away from the station, rotating slowly, watching the hull recede. Two meters. Three. Five.

"No," she whispered. "No, no, no."

She activated her SAFER unit—the Simplified Aid for EVA Rescue, a small jetpack built into the back of her suit. It fired a burst of nitrogen gas, killing her rotation and pushing her back toward the station. She reached for the handrail—

The station broke apart.

It happened in sections, like a building collapsing floor by floor. The central truss buckled as something—a piece of debris the size of a baseball, moving at seven kilometers per second—punched through it. The solar arrays on the port side folded and shattered. The Japanese laboratory module crumpled inward. The European lab—where Jude had been working—

"JUDE!"

—was struck by a piece of the truss and torn from its docking port. She watched it tumble away, venting atmosphere in a white plume, spinning end over end.

More impacts. The station was being shredded by a hailstorm of orbital debris, each piece carrying the kinetic energy of a bomb. She watched in horror as the habitat she'd called home for four months was reduced to a spreading cloud of wreckage.

The SAFER unit pushed her toward the station, but there was nothing left to grab. The section of hull she'd been heading for was gone. She fired the jets again, trying to match the tumble of the nearest intact piece of structure, but her propellant was limited—the SAFER was designed for short-range rescue, not sustained maneuvering.

She was drifting. Away from the station. Away from everything.

"Houston, Tamsin." Her voice was steady. She was amazed by that. "The station is destroyed. I am untethered. My SAFER has approximately—" she checked the readout on her wrist display— "sixty percent propellant remaining. Suit oxygen is at five hours fifty-two minutes. I have lost visual contact with Jude. Please advise."

Static. Then Reggie's voice, and she could hear the strain in it, the effort it took to keep it professional.

"Tamsin, Houston copies all. We are... we are assessing. Stand by."

She hung in space, alone, watching the debris field expand around her. Pieces of the station glittered in the sunlight—fragments of solar panel, shreds of thermal blanket, a laptop computer tumbling end over end, its screen still glowing blue. Below her, Earth turned, serene and indifferent.

She was four hundred and twenty kilometers above the Pacific Ocean, moving at twenty-eight thousand kilometers per hour, and she had less than six hours to live.

Unless she did something about it.