Titan. Stephen Baxter

      She had a couple of hours before the flight back to Houston. She could afford to indulge Rosenberg a little more.

      It would be a thought experiment. It might make a neat little paper for the Journal of Spacecraft and Rockets. Or maybe one of the sci-fi magazines.

      She sat down and started to go through Rosenberg’s back-of-the-envelope numbers more carefully, trying to find the mistake that had to be in there, the hole that would make the whole thing fall apart, the reason why it was impossible to send people to Titan.

      

      Nicola Mott did not want to go home.

      She and Siobhan Libet, her sole crewmate on Station, had spent the last day packing the Soyuz reentry module as best they could with results from their work – biological and medical samples, data cassettes and diskettes, film cartridges, notebooks and softscreens. Then Libet dimmed the floods in the Service Module, the Station’s main component, and pulled out her sleeping bag.

      But Mott didn’t want to sleep. She wanted to spin out these last few hours as much as she could.

      So, alone, she made her way through the open hatch and down to the end of the FGB module, the Russian-built energy block docked on the end of the Service Module.

      She stared out the window at the shining, wrinkled surface of the Pacific.

      The shadows of the light, high clouds on the water grew longer, and the Station passed abruptly into night. She huddled by the window, curling up into a foetal ball. She could see the lights of a ship, crawling across the skin of the darkened ocean.

      She – Nicola Mott, English-born astronaut – might be the last Westerner ever to see such sights, she thought.

      She was too young to remember Apollo, barely old enough to remember Skylab and ASTP. She’d been eleven, in the middle of an English spring, when Columbia made her maiden flight, and it had been a hell of a thrill. But after a while she started to wonder why these beautiful spaceships kept on flying up to orbit and coming back down without ever going anywhere.

      And when she’d come to understand that, she started to realize that she’d been born at the wrong time: born too late to witness, still less participate in, Apollo; born too early, probably, to witness whatever came next.

      Still, she’d decided to make her own way. She’d moved to America and worked through a short career at McDonnell Douglas, where she’d worked on the design and construction of a component of Station called the Integrated Truss Segment So, a piece that now looked as if it would never be shipped out of the McDonnell plant at Huntingdon Beach. She’d enjoyed her time at Huntingdon, looking back; the Balsa Avenue assembly area had the air of an ordinary industrial plant, no fancy NASA-style airlocks or clean rooms …

      Anyhow, then she’d transferred to NASA. She’d worked as a payload controller in Mission Control, and then, at her third attempt, made it into the Astronaut Office. She’d paid her dues as an ascan, and finally been attached to a Shuttle flight – STS – 141, Atlantis – and come flying up here, to Station, for a six-month vigil.

      It turned out to be a question of just surviving in this shack of a Service Module, boring a hole in the sky for month after month. Russian and American crews, brought up by Shuttle, had been rotating up here on six-month shifts, struggling to do some real research in these primitive conditions, their main purpose to keep this rump of the Station alive with basic maintenance and housekeeping.

      Even so, at first she’d been thrilled just to be in space, all these years after those Illinois dreams. And as her relationship with Siobhan Libet had matured, the experience had come to seem magical.

      Then, after a few weeks of circling the Earth, she’d got oddly frustrated. She got bored with the stodgy Russian food and with the daily regime of exercise and dull maintenance. The Station blocks were so small compared to the huge spaces out there; it seemed absurd to be so confined, to huddle up against the warm skin of Earth like this.

      Damn it, she wanted to go somewhere. Such as Titan, where those hairies at JPL thought they’d found life signs … But nobody was offering a ride.

      It wasn’t really the great tragic downfall in human destiny that was bothering her, she admitted. It was her own screwed-up career.

      Mott was thirty-four years old, and she wasn’t given to morbid late-night thoughts like these. She started to feel cold, and, suddenly, terribly lonely. Staying up all night no longer seemed such a great idea.

      She pulled herself back through to the Service Module.

      The interior of Station was cramped and crowded. The walls were lined with instrument panels, wall mounts for air-scrubbing lithium chlorate canisters, other equipment. These two modules had been serving alone as the core of the Space Station for too many years now, and as parts had worn out replacements had been flown up and crudely bolted in place, and new experiments had been brought up here and fixed to whatever wall space was available. As a result the clutter was prodigious; cables and pipes and lagged ducts trailed everywhere, and there was a sour smell, the stink of people locked up in a small space for too long.

      She pressurized the water tank, and fired the spigot. A globe of water came shimmering through the air towards her face, the lights of the module sharply reflected in its meniscus. She opened her mouth and let the water drift in; when she closed her mouth around the globule it was as if the water exploded over her palate, crisp and cold.

      If she couldn’t get back into space, she’d never in her life be able to take a drink like that again, she thought. Returning to Earth was going to be like a little death.

      

      Her sleeping compartment was a space like a broom cupboard, with its own window, cluttered with bits of gear and clothing. Her sleeping bag was fixed straight up and down against the wall of the module, and she had to crane her neck to see out of her window, at the slice of Earth which drifted past there. With the Earthlight, and the subdued floods of the compartment, the Service Module was pretty bright, and the pumps and ventilation fans kept up a continual rattle. It was like being in the guts of some huge machine.

      She pulled herself deeper into her sleeping bag, which soon became warm enough for her to be able to forget the endless vacuum a few inches away from her face, beyond the module’s cladded hull.

      After an unmeasured time, she felt a hand stroking her back. She turned in her bag. Siobhan, naked, her hair floating around her face in a big burst of colour, was silhouetted against the cabin lights.

      Mott smiled and reached out. She brushed Libet’s hair back, revealing her fine, high brow. ‘You look like Barbarella,’ she said.

      ‘In your dreams. Are you going to let me in?’

      The sleeping bags were too small for two people. But they’d found a way of zipping their two bags together. It was cold, the opening at the top liable to let in draughts, but their bodies would soon build up a layer of warm air around them.

      ‘Anyhow,’ Mott said, ‘I thought you wanted to sleep.’

      ‘I did. I do. But I guess I can spend the rest of my life asleep. Down there, at the bottom of the gravity well. This seems too good an opportunity to pass up. The last time anyone will be having sex in space, for a long, long time …’

      Mott clung to Libet.

      Libet stroked her back. ‘Who was the first, do you think? The first orgasm in space.’

      Mott snorted. ‘Yuri Gagarin, probably. Or one of those Mercury assholes fulfilling a bet. Maybe even old Al Shepard managed it.’

      ‘Oh, come on. He only had fifteen minutes. Even Big Al couldn’t have done it in that time. Anyway, those Mercury suits were hard to open up.’

      ‘Fifteen minutes. Well, we haven’t got much longer.’

      Libet’s hand, warm now, moved over Mott’s stomach. ‘From first to last.’

      ‘From first to last,’ Mott