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 other 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.
Benacerraf was orbiting in a plane a few feet above the orbiter’s payload bay, with its shining insulation blankets, its complex shadows, the empty blackness of space beyond.
As the centrifuge picked up speed, the Universe started to wheel around her, so she closed up the windows, pulling down compact little aluminum blinds. Enclosed, she could feel her feet pressing more firmly against the floor. There were hand-rails here, painted green, and she hung onto them now.
Experimentally, she moved her head, this way and that. Immediately, waves of nausea and giddiness swept over her.
The trouble was, this wasn’t true gravity, but centripetal acceleration induced by the spin. There was also Coriolis force, the sideways push that produced weather patterns on the rotating Earth. It was fine as long as she didn’t move. But if she moved her head in the direction of the spin, Coriolis pushed back with a force of a fifth of a G. And if she moved it in the opposite direction, her head felt lighter by the same amount. If she were to try to climb up, the Coriolis would push her sideways. And so on.