Seveneves - Страница 98

As they had done with Ymir, they mined ice from the interior volume of Endurance, leaving the outer “walnut shell” as a structural support and as a first line of defense against bolides. But as J.B.F. and other Dump and Run partisans had never tired of pointing out, such a heavy craft lacked maneuverability. When a big rock was seen far enough in advance, they could use her engines to make small course changes that would have large outcomes by the time the rock came close. Doing so was the full-time occupation of most of Endurance’s complement, which worked at it three shifts a day. But below a certain threshold they could not see rocks soon enough, or maneuver out of their way quickly enough, and then they just had to hope that the bolide would strike Amalthea. Most did, but some hit the icy lower slopes, and of those, some struck with enough power to penetrate and kill.

Suicide took about one in ten over the course of the three-year journey. Sometimes this was for traditional reasons. After a great burst of creative activity during the weeks when Endurance was being designed and crafted, Rhys fell into a black depression and took his own life a month into the voyage. In other cases a spacewalker agreed to go on what was clearly a suicide mission, or a patient suffering from cancer decided to end her life rather than create a drain on limited resources of food, air, and medical supplies. And there was quite a bit of cancer, for Dinah’s prediction on the day of the Break had been borne out. In spite of all precautions, particles of fallout made their way into the air and the food chain and lodged in lungs and guts. Even without this, the environment of space, with its ambient radiation, lack of exercise, poor diet, and exposure to various chemicals, tended to jack up the cancer rate. Endurance’s medical facilities were not up to the job of detecting and treating cancer in the way people had been used to on Earth.

Periodic crises in the supplies of food and air, caused by blights in the greenhouses or breakdowns in equipment, took away people whose strength had been sapped to begin with. The journey entailed thousands of traversals of the Van Allen radiation belts. Rather than passing through these but one or two times, as might have been the case in a more traditional space voyage, they had to do it twice on each orbit; and during the first year they were, for all practical purposes, never out of them. They sheltered as much as they could in shielded parts of the ship. But no shelter was perfect. Some of the crew were obliged by duty or by happenstance to remain in exposed locations. And the mere fact of being crammed together in a confined space for a significant fraction of the time was a drag on health.

The gender ratio began to skew even more toward females. The General Population, whose Break-surviving members had made up roughly a quarter of Endurance’s original complement, had been predominantly male. This was a simple consequence of the fact that they had been drawn from traditionally male-dominated professions such as the military, the astronaut corps, and science and engineering. The other three-quarters had been Arkies. The original Arkie population had been 75 percent female and 25 percent male. The ones who had elected to stay with Endurance at the time of the Break were more strongly skewed toward women.

The men tended to be older — in many cases two or even three times the age of the Arkies. Compared to the Arkies, who had mostly been sent up at the last minute, they tended to have been in space, and subject to its health effects, for much longer. They had been picked for brains, not for physical fitness. At least at the beginning, while the Arkies were still learning the ropes, they tended to draw the most hazardous duty, such as space walks. And men simply were not as well suited to life in space. They were more biologically vulnerable to radiation. They needed more air and more food. And, whether it was the result of cultural upbringing or genetic programming, they simply were not cut out psychologically for the idea that they were going to spend the rest of their lives in crowded indoor spaces. Many of them felt an urge to go outside and get away from people that manifested itself as a tendency to volunteer for more space walks. People who went on space walks were much more likely to die of radiation exposure, bolide strikes, equipment malfunction, misadventure, or contamination by reactor fallout.

As well, there was an understanding, widely shared but rarely spoken of, that men were not the scarce resource. Women — to be specific, healthy, functional wombs — were. Acting on that belief, or perhaps just electing a more socially constructive form of suicide, men continued volunteering for hazard duty, instinctively herding the women toward the protected interior spaces of the ship; and when the women objected to it, as some did, they were apt to be shut down by the simple, hard-to-argue-with assertion that their lives and health had to be preserved at all costs.

Communication with the Swarm was sporadic and tended to come in bursts, when the Swarm needed something. The groups had separated under conditions that would have been deemed a state of war had the Break not happened in the midst of a catastrophe more deadly than anything that one side could have inflicted upon the other with force of arms. Neither side was likely to begin trusting the other anytime soon. Free, Internet-style communication between them was forbidden on both sides, since it could have been used for purposes that were mischievous or worse. The channel between Swarm and Endurance was more akin to a hotline linking two Cold War capitals. It went unused for months at a time. This was not so much a matter of the two sides snubbing each other as it was that they were both fully occupied trying to stay alive. Ivy and J.B.F. were like the captains of two damaged ships, many miles apart in stormy seas, with other things on their minds. When the channel was used, it was to negotiate terms of exchanges between the two groups. Neither side was of a mind to share much information about its status. But much could be inferred from the things that the Swarm urgently asked for: mostly propellant, but also the sort of medicine used to treat radiation sickness, blight-resistant strains of food crops, nutrients, spare parts for CO scrubbers and for the Stirling engines that supplied power to arklets. In exchange they offered mostly food, which was the only thing they could make that Endurance didn’t already have.

Eleven weeks following the Break, a solar flare had occurred, followed by an event known as a coronal mass ejection: a vast release of charged particles hurled out from the sun into the solar system. With its array of sensors, some of which were always pointed toward the sun for just this reason, Endurance had seen the storm coming and had sent a warning message to the Swarm. In those days Endurance had been well inside the protection of the Earth’s magnetosphere. That plus the shielding provided by iron and ice had enabled her crew to ride out the storm with little exposure to its radiation. They had no way of knowing, though, whether the Swarm had even received or understood the warning. The danger of coronal mass ejections had been well understood by the Arkitects, who had provided “storm shelters” in each arklet: sleeping bags, in effect, made so that water could be pumped into the space between their inner and outer walls, surrounding the occupant with molecules that were good at absorbing high-energy protons. The arklets were also stocked with doses of a drug called amifostine, which protected DNA from damage produced by the free radicals generated in the body by radiation exposure. The scheme was a good one provided the Arkies had at least half an hour’s advance warning and enough water in their arklets’ tanks to fill up all the shelters. They practiced it every so often, as sailors would perform lifeboat drills. But there was a lot that could go wrong, and it seemed unlikely that all eight hundred Arkies had made it through the storm unscathed.

In the ensuing three years there had been ten more coronal mass ejections big enough to worry about. Endurance had transmitted a warning to the Swarm in each of those cases but never received an acknowledgment.

It was worrisome that the Swarm always seemed to want more water. Since the water of an arklet’s ecosystem was recycled, the only way the arklet could lose it was by expending it as propellant: splitting it into hydrogen and oxygen and feeding it to a thruster. All the arklets in a swarm would have to do this from time to time, simply in order to remain in formation. That was true even if they never dodged a rock and never changed their orbit around the Earth. But it seemed that they had changed their orbit on several occasions, making it higher and more circular to keep it clear of the Van Allen belts. Presumably they had their reasons for doing so. But if they ran so low on water that they couldn’t fill their storm shelters when needed, they were open to a disaster that might kill most or all of them at a stroke. Ivy could only assume that they were still reasonable people and that if things got that bad, they would call for help. In the meantime, she tried to guard against the seductive idea that Endurance had all the water it could ever need. There weren’t going to be any more Ymir expeditions. The water they carried with them might be all that the human race had to live on for hundreds of years.

She had already made up her mind what she would say if J.B.F. ever contacted her with an urgent demand for storm shelter water: nothing doing, come to us, rejoin the crew of Endurance and take shelter here. She wondered, sometimes, if J.B.F. had anticipated that Ivy would make such a demand, and just how far she was willing to go to avoid such an unconditional surrender.