Titan n-2

by Stephen Baxter

  Discovery coasted, unpowered, on its long trajectory towards the sun. Discovery had left Earth behind, and entered a realm governed only by the simplest of laws, gravity and Newton’s laws, utterly predictable.

  Shadows shifted steadily across the cluttered payload bay as the orbiter went through its slow thermal roll.

  Life in Microgravity:

  Benacerraf had a lot of trouble sleeping.

  When her little alarm watch sounded she was already awake, her eyes crusty and sore. She wriggled out of her sleeping bag; it was a little tight at the neck and she had to squirm.

  Wearing just her underwear, she emerged from her private compartment into the bulk of the hab module.

  Nobody was around. That suited Benacerraf; she liked to have a little time alone, to start the day. Right now, though, according to the schedule, somebody should be using the centrifuge; but she couldn’t feel the characteristic rhythmic judder of that big, heavy arm going through its six-revs-a-minute cycle. She made a mental note; somebody was goofing off.

  The hab module looked clean, intact, its systems humming and whirring. The module was cylindrical, sized to fit into a Shuttle orbiter cargo bay. But inside, the module had a straightforward square cross-section, with flat walls, ceiling and floor, and rounded edges. The color scheme was a cool Earthlike blue, and the lighting was designed to provide plenty of up-down clues. Benacerraf, prone to dizziness and vertigo, appreciated that aspect of the design.

  The gaps between the flat walls and the curved hull housed racks — ORUs, orbital replacement units — which could be folded out and replaced. The design rule was that life support and emergency systems and supplies were housed in the ceiling and floor, and systems the crew would use routinely were located in the walls. And strung out along the length of the hab module were the crew quarters, a health care bay, a galley area, and wardroom and hygiene facilities.

  Briskly, she used the waste management facility. This was a little booth containing a Shuttle-technology commode, with pin-down bars over her thighs, and a unisex urination cup, color-coded for her use. When she closed the switch, fans started up with a rattling whine. Her urine was drawn away by a current of air, for storage and reclamation.

  Benacerraf was proud of the work that had been done on the hab module, under her supervision, at Boeing’s Station assembly facility at Huntsville. They had stripped out the equipment racks, floors and utility systems; they’d taken the thing right down to its structural subassemblies and started again. They even stripped all the paint off, until it looked like it had just come out of the horizontal boring mill. They ran structural tests to check decade-old welds, and pressure and leak tests, and fixed a thousand strain gauges to measure stresses.

  Then there was a whole series of modifications. They had adapted a hab module — intended as part of a frequent-resupply low Earth orbit station — to serve as the core of a many-year deep space mission. They had reconfigured the systems to take power from a couple of reconditioned Topaz fission reactors, for instance. And they had restructured the module to put shielding material around the hull, like water tanks. It was a lot of work; the engineers had to redesign and rebuild on the fly.

  But for Benacerraf it had been a kind of relief, after a decade of frustration. So much fine work had been done on the Station components, only for them to be left standing around in assembly facilities. She had been involved right back when they put together the external structure of the first lab module, back in 1995. Three thousand one hundred inches of weld, all of exceptional quality. You couldn’t buy quality like that. You had to earn it. It was good to see this fine work put to use.

  When she was done she made her way to the personal hygiene station, where she washed her hands, face, armpits and crotch with a sponge. The sponge, and the excess water she shook off, she stored so that her hygiene water could be reclaimed.

  At the little galley, she prepared a quick breakfast: precooked apple sauce, rehydratable granola, beef jerky and breakfast roll; and to drink, chocolate instant breakfast and an orange-grapefruit squash. She had to put the granola bag into a little tray, which slid into a slot in the galley wall to inject the bag with water. She piled the food up on a tray, sticking it down with Velcro pads.

  She ate in a kind of Japanese style, with the food close to her face, and she spooned it into her mouth in smooth, graceful arcs. She worked with care. If she jerked the spoon, the glob of food would just fly off, and end up on her face, in her hair, on the walls. And when she sipped her drink, she took care to blow the excess liquid back into the container, or it would come slithering out of the straw and go floating around the module.

  She didn’t feel hungry, but she made herself finish the food.

  Suppressed appetite was some artifact of microgravity, an illusion. She tried to add salt and pepper to give a little flavor to the meal. But the diluted salt tended to clog the nozzle of its dispenser. Once Angel, frustrated, had squeezed the dispenser so hard it burst, and they spent two days picking salt off the walls of the hab module. And the pepper, in traditional particle form, just floated off around the hab module rather than settle on the food. The crew had anticipated this and had brought along a lot of spices and condiments, like horseradish and soy sauce and Tabasco sauce. But already these were becoming depleted, and they were trying to ration themselves…

  She let herself drift in the air as she ate, her eyes unfocused. She felt herself relax into what the surgeons called the “neutral G” position, with her legs pulled up a little, her shoulders bent into a crouch, and her elbows bent. She was floating like a foetus, in the warm blue womb-like interior of this hab module.

  Right now they were still living off Shuttle-class consumables, but they would be replaced by produce from the CELSS farm as soon as was practicable. Already, their waste was being stored, and would be cycled through the hydroponic farm, so as to close the matter loops of their life support system.

  But they would still have to supplement their diet with stored food — this disgusting beef jerky, for instance — to acquire amino acids and other substances not available from the farm’s vegetables.

  When she was done, she rinsed off her tray in the housekeeping and laundry area. The water she used was sucked away by a vacuum pump, for further recycling.

  It was Benacerraf’s day for fresh clothes. She went to her personal locker in the wardroom area. She pulled out her underwear drawer. The clothing did the usual zero-G jack-in-the-box trick, bursting out of the drawer and into the air around her face. It took her a couple of minutes to stuff it all back in the drawer and strap it down, picking out items to wear today. Then she opened her main clothing drawer and picked out a T-shirt and trousers.

  She went back to her quarters.

  She stripped naked and examined herself briefly, with the help of the little mirror of polished aluminum on the wall. Her face had become puffy, especially around the eyes. The girth of her waist and chest had increased. The blood was pooling in her chest, where it restricted the capacity of her lungs; and in her back, where it was absorbed by the spongy discs between her vertebrae, making them thicker and pushing the vertebrae apart. As a result she was an inch or two taller than she had been on Earth.

  She inspected her legs with some interest. Legs were pretty much useless in space, serving only to bump into obstacles. And after eighty days, her legs — skinny, pale chicken legs, drained of fluid — were covered with bruises and cuts, in various stages of healing. But she was getting better. Actually she rarely moved faster than a couple of feet per second; she found it was more productive, in microgravity, to aim for precision rather than speed.

  She got dressed.

  The clothes were dull: T-shirts, jackets and trousers made of golden-brown Beta-cloth — selected because it was fireproof — with 1970s-style turtle necks and elasticated cuffs. The others griped about the dull, scratchy clothes, but Benacerraf didn’t mind. These designs actually went back to Skylab; the clothes were tough, would s
tand repeated washing, and they were available, just lying around in a store at JSC.

  Getting dressed was always an unexpected struggle. The clothing tended to wriggle away from her. She had to work her stomach muscles to drag her feet up close to her chest to pull on a sock or a shoe, and when she’d finished it always felt as if she had given those muscles a tough workout.

  The gold-brown outfits were fitted with pockets all over, along both sleeves and legs; and in them she stowed everything she was likely to need during the day — flashlight, pad, pencils, Swiss Army knife, scissors. She popped the pockets shut methodically; if she didn’t, the smaller items were likely just to drift out.

  She emerged from her quarters and stuffed her used clothes into the laundry bag.

  Her most important daily task was to check the status of the life support systems. So she made her way to the control panel.

  Every year, a healthy human would consume three times her body mass in food, four times in oxygen, and eight times in drinking water; and would, besides, excrete the same mass in urine, feces, carbon dioxide and water from respiration and perspiration. The only way Discovery could sustain a six-year mission to Titan was by closing as many of its mass loops as possible, to support the slow-burning human metabolisms it shielded, to clean up and feed back waste products.

  In a way, Discovery constituted the ultimate life support technology testbed.

  Benacerraf started with the water management system. Their urine, pretreated with acid, had its water distilled out, reducing the urine to a gooey solid. The water was treated with ozone and charcoal filters before being used again, and anyway went into the hygiene supply first, rather than coming straight back to the drinking water. The still had to be rotated to enable phase separation in microgravity, and the rotation tended to disrupt any experiments requiring stability the crew attempted. And every so often the evaporator had to be evacuated and cleaned out, and the fluids pump replaced. A delightful job. Right now, however, the still seemed to be functioning well.

  Waste water from other sources — hygiene, the laundry and the air condensate — was cleaned up by a series of filters and packed columns of activated charcoal and resin beds. The filter beds had to be replaced periodically. Then there was a biocide injection system, and a series of automated systems that monitored the quality of the water — for acidity, ammonia, organic carbon content, electrical conductivity, microbial concentration, color, odor, foaming, and heavy metal concentrations — before it was returned to its stainless steel tanks…

  She looked over the air management system. The steps here had to mimic some of the processes of life on Earth: carbon dioxide had to be removed and reduced from stale air; oxygen had to be generated, and trace contaminants monitored and removed.

  The carbon dioxide was removed by passing the air over filter beds containing solid amines, steam-heated, A Sabatier reactor combined the extracted carbon dioxide with hydrogen, to produce methane and water. The Sabatier was a nice reliable design which needed hardly any maintenance. Oxygen was produced from the water by electrolysis, a process she remembered from her own high school days, where an electric cell broke up the water molecules into hydrogen and oxygen. The oxygen fed back into the air supply, and the hydrogen was passed back to the Sabatier reactor. The electrolysis technology was so simple and mature that there was hardly anything which could go wrong with it.

  Carbon dioxide in; oxygen out. It was a neat, robust system.

  The trace contaminant control was built into the ventilation. A lot of crap could build up quickly in the closed cycles of the hab module. So there were particulate beds to separate dusts and aerosols, activated charcoal to keep out heavier contaminants, chemi-sorbant beds to remove nitrogen, sulphur compounds, halogens and metal hybrids, and catalytic burners to oxidize anything that couldn’t be absorbed.

  She checked through a few more ancillary systems: composition and pressure control, the heat exchanger slurper that controlled temperature and humidity… The whole system was monitored and controlled in real time by a complex of sensors, including a mass spectrometer and infra-red detectors.

  She checked the SCWO reactor, the supercritical wet oxidation system. The SCWO was a remarkable piece of gear. Inside, slurry was heated to four hundred and eighty degrees Centigrade and two hundred and forty atmospheres, conditions where water went supercritical. It was like liquid steam. If you jetted in oxygen, you could get an open flame, under water. The SCWO would burn anything, any waste they threw into it: crap, urine, food scraps, garbage, mixed up with organic wastes and water. Out came steam, carbon dioxide, and a whole bunch of nitrates — compounds of nitrogen they could use in the farm.

  It looked to Benacerraf as if the temperature control inside the reactor had been a little variable. That was a worry; not everything that happened inside that reactor was well understood. The SCWO was a relatively new technology — the reactor and its backup fitted in Discovery were actually upgrades of breadboard prototypes. There were safety concerns around the high temperatures and pressures in the reactor, and corrosion of the pressure chamber. That corrosion could leak metals into the liquid effluent, which could then end up in the food chain.

  In a way she was relieved to find something wrong. It proved the monitoring systems were working, and that she was maintaining her own attention as she worked through this daily inspection routine. Bill Angel was on SCWO duty this week. Good; Bill was mechanically adept, and might be able to do something with the malfunctioning reactor. She made a note, and moved on to the next system…

  Thus, with this string of clanking and banging mechanical gadgets of varying sophistication and reliability, with a stream of endless small details, the crew of Discovery sustained the stuff of their existence.

  Her last chore, before starting the day proper, was to check the vent grilles, the dark screens that led to the air conditioning system. Not being able to put things down and find them again was the single biggest handicap, as far as she was concerned, about living in microgravity. If you let some small item drift off, you really had no clue as to which direction it might have taken, and you just had to be patient and wait the couple of hours it usually took for items to fetch up against the grille.

  Today she found a syringe, a one-inch bolt, a couple of small bags, a rule, and several scraps of paper. She had a system for this; she saved the stuff that looked useful in one pocket, and the detritus in another.

  She tried to get a little science done.

  There was a telescope mount, equipped with lightweight cameras for observing the sun at a variety of wavelengths: hydrogen alpha emissions from the sun’s surface, ultraviolet and X-ray photography of ionized atoms, solar corona and flare imaging systems. No human crew had ever before ventured so close to the sun, or would again for a hell of a long time.

  But the science was hardly high quality. The equipment in the telescope mount had been improvised from left-over spare parts from unmanned missions, like Soho and Ulysses. And besides, Discovery wasn’t a good science platform. The camera tracking gear had to compensate for the spacecraft’s slow barbecue-mode rotation. And Discovery was just too unstable, with five humans, hundred-and-fifty-pound water sacks, lurching massively around its interior. It was G-jitter, in the jargon, sometimes amounting to five or ten percent of G. Even a cough would exert fifteen or twenty pounds of force, and a squirt on a water spigot would jar the cluster enough to jolt the cross-hairs of a camera from the center of the sun. And of course the use of the centrifuge shook the whole cluster around so much it made any kind of sensible experiment more or less impossible.

  Meanwhile the crew themselves were the subject of endless experimental studies; the bodies of the crew of Discovery would, she knew, write the textbook for the next few decades on the long-term effects of space travel on human physiology. But the studies were distorted by the fact that the crew were doing their utmost, with varying degrees of enthusiasm, to combat the effects of micro-gravity, radiation and the othe
r hazards of the flight. If the studies had been true science, she reflected, you’d have some kind of control: one crew member who didn’t take any exercise or other precautions at all, for instance.

  There were rumors that the Chinese, in the course of their expanding space program, were doing just that. But for Americans, of course, that was just unacceptable.

  The voyage of Discovery was becoming, she thought, a clinching argument against humans in space, for science purposes.

  Anyhow, the truth was that the science stuff had essentially been tacked on to give them all something meaningful to do, while their twenty-six-hundred-day mission wound through its dull course. Nobody on Earth was waiting with bated breath for Discovery’s dazzling streams of data.

  Exercise time.

  She pulled herself through a hatch into the docking node at the aft end of the hab module. Then, another hatch above her head led into the centrifuge cabin. This was a cylinder, only just big enough to hold a single human standing upright, its walls cluttered with equipment and punctured by small round portholes. It was fixed to a robot arm, derived from the Shuttle’s old remote manipulator system.

  When she had sealed up the hatch behind her and given the cabin’s rudimentary systems a check-out, the cabin detached from the docking node and the arm swung it out and away from the body of the orbiter.

  The arm began to pull the cabin through a circle, twenty-five yards in diameter. The cabin creaked, a little ominously, as the arm picked up speed, and she could feel the metallic swaying of the stiff arm as it spun up.

  When it got up to speed the cabin would swing around, like a bucket on a rope, at the best part of six revolutions a minute. That would give her an illusion of gravity, generated by centripetal acceleration, of the best part of a G.

  She peered out the windows.