Ark

41

“The leak is here.” Liu Zheng unfolded a big paper schematic, and with a pointing finger showed Matt a feed leading from a secondary coolant reservoir. His hand was gloved; they both wore lightweight NBC suits. He had to shout to make himself heard over the hiss of vapor, the roar of engines as buses and trucks raced around the base of the Ark, the urgent yelling of voices, and an ominous clatter of gunfire. “See? Just above this O-ring.”

“Why can’t the automated systems handle it?”

“They froze,” Liu said. “A multiple failure. Shit happens. Well, that’s why we’re here. The leak has to be fixed; without coolant, if one of those suspension pistons overheats and seizes in flight, the Ark will fall out of the sky. You have your tools?”

Matt hitched a pack on his back.

“OK. Take elevator three.” Liu grinned. “This is your moment, Mr. Weiss.” He stuffed the schematics into Matt’s pack. “Go, go!”

Matt ran to the elevator cage, one of a dozen that allowed access to the Ark for maintenance. He slammed shut the gate and grabbed the dead man’s handle that sent the cage rising up into the shadowed innards of the ship. He rose past the curving flank of one of the crew hulls. A wall of white insulation blanket rushed past his face, pocked with maintenance hatches, safety warnings, valve sockets-and handhelds, labeled with upside-down stencils, for use by spacewalking astronauts in the extraordinary future when this ship would be taken apart at the orbit of Jupiter, and reassembled for interstellar flight. He felt light-headed, unreal. He hadn’t slept much in the last week. Since his liberation from jail a week ago he had dedicated all his time to memorizing every aspect of the systems to which he was going to be assigned. He figured he could catch up on his sleep when he was dead. And with the Ark launch being brought back, he had, of course, suddenly lost twelve hours of his life. Quite a big percentage when you only had a day left anyhow.

He looked up, trying to spot the problematic feed. The Ark’s interior was as brightly lit as the exterior, a mass of gleaming metal, pipes, vast tanks connected by ducts and cabling, all contained within the mighty struts of the frame. He saw cameras swiveling, and, clambering over the wall of one of the big crew hulls, a maintenance robot, a thing like a spider armed with a camera for a head, sucker feet so it could climb vertical walls, and a waldo arm with a Swiss Army knife selection of tools.

Still rising, he looked down the flank of the crew hull, and saw, down below, through gaps in the cluster of tanks and pipes, the impassive bulk of the pusher plate itself. An inverted dish of hardened steel, it was itself a beautiful piece of engineering, forty meters across and just ten centimeters thick. The bombs would be detonated below the plate, a weapon five times the strength of the Hiroshima bomb detonating one every one and one tenth of a second. The bombs would be fired into place by the simplest method imaginable, by shooting them down out of a cannon set square in the middle of the pusher plate. The propellant produced by each pulse unit would bounce off the pusher plate, transferring momentum but evaporating too quickly to damage the plate, which would be further protected by a screen of anti-ablation oil, constantly renewed. The resulting thrust would be soaked up by the shock absorber system, immense pistons that rose up above his head, each with a stroke of eleven meters and with a complex dual action that protected the vulnerable parts of the ship from rebound in case a pulse unit failed.

After studying the technical issues from scratch themselves, the Ark’s designers had reverted to something close to what had become the standard design for much of the duration of the original Cold War Project Orion: a four-thousand-ton brute with that mass split evenly between the pusher plate, the ship’s structure, the bombs, and a full thousand tons of payload. By comparison the Saturn V, the booster that had launched Apollo to the moon driven by chemical energies alone, had weighed in at three thousand tons, of which only forty tonnes was payload. It was hard to grasp the reality, even now. When the ship was in flight this whole space would be the scene of huge engineering activity, with splashes of blinding atomic glare coming from all around the rim of the pusher plate, and those pistons shuddering with each mighty stroke.

Looking up now, Matt could see he was approaching the huge tanks of coolant fluid and ablation oil suspended in their frame, and the complex network of pipes that connected one to the other. That was where his leak was. In flight, an ammonia compound was used to cool the pistons after each stroke. The resulting high-temperature compressed gas was then used to power the pumps that squirted a sheet of anti-ablation oil out over the pusher plate before the next detonation, and to thrust the next pulse unit from the charge magazine. Using the products of one stroke to prepare for the next was pleasing for an engineer, a process that reeked of thermodynamic efficiency. But that complexity led to many failure modes.

The light in his elevator cage died, and the cage jolted to a halt.

“Shit.” Matt squeezed his dead man’s switch, and rattled at the cage door. All power to the cage and the pulleys that had been hauling it had been lost. Matt flicked a microphone at his throat. “Liu, it’s Matt.”

As the link came active, Matt heard Liu Zheng break off another conversation. “Go ahead.”

“I lost power, in number three elevator.”

“Wait… I can see. We lost power all down that side, a generator broke down. Damn.” Liu sounded desperately tense. What they feared above all was multiple failure, one problem compounding another. “You still on that coolant leak? You fixed it yet?”

“Negative.” Matt resisted the urge to snap; of course he hadn’t, in the couple of minutes since he’d left Liu’s side. Liu was juggling a hundred tasks simultaneously, all as urgent as Matt’s; time must be stretching for Liu, in this last hour of his life. “I’m still on my way up.”

“We can’t get power back until-I don’t know. Matt, can you improvise? Yes, Mary, what is it?…”

Matt snapped off the comms link. Improvise. Well, there was no choice, and there were access ladders fixed all over the ship.

He fixed his tool pack on his back, grabbed the manual handle, and hauled the gate open. The nearest ladder was just outside the cage, and there was a rail to which he clipped a safety attachment to his belt. He got hold of the rail, swung out one foot, and reached the nearest rung. He tugged the safety harness to test it. Then he looked up into the cathedral of gleaming metal forms above him, and began to climb.

As he passed, monitor cameras swiveled to track him.