Flight Engineer Koslov went through his system checks. He had been a structural engineer on Earth, helping firms construct bridges and tunnels that could transport heavy machinery – but in the rush to flee the oncoming gamma ray burst, he had been pressed into a crash course in spacecraft. Koslov didn’t know enough to design a spacecraft himself, but he knew enough to be able to help maintain one that was already built, and in the years since launch he had a lot of time to read up on details that the training course hadn’t covered. Koslov longed for the day that he would have his feet on land again and maybe even apply his training to bridges once more. But for now, it was spacecraft maintenance.
Koslov had been tracking an issue for some time, and now it was unmistakable – something was off with the gravity ballast. This ship, constructed in orbit, maintained artificial gravity by housing its crew compartments in the “rim” of a giant spinning ring – more of a hollow cylinder, really – which constantly spun around the long “spine” that carried the primary engines, their requisite fuel and reaction mass, and the reactors that kept things powered.
Rotational gravity was the easiest way to maintain gravity on a large ship and greatly mitigated the negative effects that weightlessness would otherwise bring the crew. However, there was one critical challenge – the great cylinder’s mass had to be balanced around the spine of the ship as it spun. Without this, the stress on the ship’s frame would eventually compromise its structural integrity.
In principle, the mass had already been balanced during the ship’s design, but people and equipment moving around the vessel could throw this off. Something as simple as a shipment of raw materials from storage to auxiliary fabrication or a large group of personnel gathering on one side of the ship could in principle unbalance the ring ever so slightly, and in time this could prove to be a real problem. To mitigate this, the gravity ring used ballast tanks and a network of pumps that transferred water from one part of the ring to another in the proportions needed to keep mass equal on each side.
However, it seemed the ballast corrections had slowed, and the ring mass was beginning to skew. Worse, even when the mass was notionally even, the ballast was actually unbalancing it somewhat by taking too long to return to normal. Koslov’s tests had finally pinpointed the issue – a set of valves on the third deck.
“Koslov to Engineering. I’ve isolated the problem but we will need to take the ballast system offline for repairs. This is high priority – the structural damage sustained by these failures is slight but cumulative, and we don’t know how many more problems like this we may have before arrival.”
“Affirmative.” came the curt voice of Chief Engineer Perez. “Prep your tools for repair, we derotate in fifteen.”
A klaxon rang out, sudden and harsh, followed by the incongruously calm and genderless voice the ship’s computer used for announcements:
Ring derotation in fifteen minutes...
Ring derotation in fifteen minutes...
Secure all loose equipment.
Say again: Ring derotation in fifteen minutes...
Ring derotation in fifteen minutes...
Secure all loose equipment.
Koslov knew some of the crew would be cursing Engineering for the disruption to their schedules, but he admired the Chief Engineer for her dedication to duty. Making people lock up loose equipment might be irksome, but it was saving the ship precious structural integrity in the long run. He turned to the rapid metallics fabricator and got it printing a new set of valves while he got his tools together. The best he could do for the complainers was to work efficiently, so that the disruption was as brief as possible.
Space travel was a game of mass. Precious mass could not be spared to pressurize and provide life support for the entire ship – so while the crew compartments were pressurized and had breathable air, many of the ship’s essential systems – solar panels, engines, and so on – were in unpressurized sections with no life support, and some areas were completely open to space. The ballast system was (thankfully, Koslov thought) a rare exception, accessible from within the ship – and without requiring any form of depressurization!
Koslov entered the ballast access compartment as the final derotation alarms were sounding.
Warning: Derotation imminent!
Warning: Derotation imminent!
Secure all loose equipment!
Sixty, fifty-nine, fifty-eight...
He clipped his belt line to the eye-hook next to the ballast access panel, lashed his toolkit and the container of freshly-printed valves to a nearby handhold, tied his shoulder-length hair back into a bun, double-checked the charge on his magnetic boots, and waited.
In space, micro-thrusters on the exterior of the great cylinder flared into life, slowing and then stopping its rotation. The vast ship continued its travel, of course – halting the cylinder rotation did not affect its primary trajectory – but with the cylinder halting its rotation, the environment within would become quite different.
Inside, the gravity seemed to lessen and then abate completely. Koslov, a few strands of ungathered hair now floating around his head, began his work. The system had been designed more or less efficiently for maintenance in zero gravity  – humanity had not been a true spacefaring civilization prior to this effort, but there were still many lessons it had learned about zero-gravity engineering from the limited inter-system travel to the now-abandoned Moon and Mars colonies.
Koslov wondered again if there had been any holdouts who refused to leave the colonies, and if so what had happened to them – the Moon would almost certainly have been hit by the gamma-ray burst, but it was possible that Mars would miss the worst of it. Then again, those colonies hadn’t been self-sufficient, and without the supply ships from Earth, it didn’t seem likely any holdouts would be holding out for very long. On the other hand, maybe with most people evacuated a few diehards would be able to make supplies stretch much longer than they had before?
He banished the idle thought and returned to his task. There would be time for speculation when he wasn’t holding up the system. Koslov unscrewed the panel, taking care to catch each screw on the magnetic panel on the inside of his wrist – it wouldn’t do to have something like that go floating off into the compartment. Valves AB23 through 27 were the ones he was after in this section, then he’d have to go up a deck to replace another set.
Koslov breathed a sigh of relief as the panel opened and he saw the valves were clearly marked and positioned so that he wouldn’t have to dig around to find them. Zero gravity aside, this was a lot easier to work with than some of the things Koslov had seen on job sites on Earth! These ships were some of the best engineering Koslov had ever seen, at least in their original designs – once you got away from the core systems, though, some of the things that had been added in the final scramble were among the most extreme jury-rigged, last-minute fixes Koslov had heard about. Luckily, the ballast system was relatively core and free from such time pressures, and the engineer was able to replace the offending valves quickly and efficiently.
Task complete and panel back in place, Koslov pulled himself up the handholds toward the next deck. All this trouble for a few simple valves, he thought. It was, however, understandable – even a small issue like this could be a matter of life and death, if left for long. The closest equivalent to a spaceship Old Earth had to offer was probably a submarine, and Koslov had learned as a young engineer about a submarine back in the Second World War that had been sunk as a result of someone operating a toilet valve incorrectly. It had sounded like a joke at the time, but now Koslov knew things like that could be deadly serious – and worse still because, unlike the crew of that doomed submarine, there would be no rescuers waiting to pick Koslov and his fellow passengers up if this ship went down. Koslov set up at the next panel and got to work. Soon enough he was done.
Warning: Rotation burn imminent!
Warning: Rotation burn imminent!
Secure all loose equipment!
Sixty, fifty-nine, fifty-eight...
With the repairs complete, micro-thrusters flared back into life and the gravity ring once again began to turn, rotating calmly as the vast ship sped silently through the black emptiness of space.