Mars Crossing

by Geoffrey Landis

  As it happened, although the Mirusha was at a nearly identical altitude, it had an orbital plane tilted in a different orientation. The laws of orbital mechanics mandated that there is no easy way to change orbital planes. To get to the Mirusha from the international space station required so great an orbital plane change that the easiest way to do it would actually be to return to the Earth and take off again into the new orbit.

  So when the news came through the grapevine that the two Russian cosmonauts in the Mirusha were in trouble, that the station was leaking and the Russians had blown up two launch vehicles trying to rescue them, John Radkowski nearly ignored the news. They would be rescued, or not rescued, but the situation, he figured, had nothing to do with the American space station, or with him.

  5

  DESCENT

  They lowered the rockhopper slowly, with Ryan watching the cables to make sure that they didn't snag or rub. The cliff was smooth and almost vertical. Even in his Mars suit, Ryan Martin was sweating. Lowering the rover was exacting work, and he was terrified that a frayed cable would let the rover slip, or a miscalculation might let it swing into the rock face.

  It took them over an hour to lower the rockhopper two hundred meters to the top of the scree. As soon as they had all six wheels resting on the talus slope, to Ryan's relief, Commander Radkowski called a break.

  Ryan took a deep breath, and then lay flat back on the ground, face upward. It was a relief to stare into the blank flatness of the sky and not worry about a rope snagging and the rover tumbling down the cliff.

  After a brief rest, it was time for the crew to begin descending. The rockhopper was still precariously balanced on the talus slope below, with the taut cable holding it from sliding down the slope. "I can tie off the cable to the rockhopper, to free up the winch to start lowering the crew," Ryan said.

  Radkowski shook his head. "Tie it off," he said, "but we can't leave the winch behind up here. We'll rappel down."

  Radkowski got into the harness first and clipped the rappelling brake into it. He checked, double-checked, and triple-checked the harness and the connections, then checked the anchors.

  "Those anchors held fine when we lowered down a two-ton rockhopper," Ryan said. "I think it will hold you."

  "I'm checking it anyway," Radkowski said. He leaned back, pulled at the superfiber with his full weight. The anchor, unsurprisingly, held up. He clipped a second line to his harness. "On belay," he said.

  Ryan moved to the deployment spool. "On belay," he replied. He turned and said, "Trevor, watch me on this, you may need to know."

  "I have done rappelling before, you know," Trevor said, his voice dripping sarcasm. "I don't think you can teach me anything. It's easy." "Good," Ryan said. "Have yon used bare superfiber?" Trevor shrugged, a gesture all but invisible under the suit unless you knew what to look for. "I don't see how it makes any difference."

  Superfiber ropes were used for rock climbing on Earth, but almost always the superfiber itself was covered in an external woven sheath. The outer coating gave the climbers something to see, and made it less dangerous to handle. "Watch me anyway," Ryan said. "You can let me know if I do anything wrong."

  "I'm heading down," Radkowski said. He stood at the edge of the cliff, looked back over his shoulder, and then leaned back over the edge, holding on to the rappel brake with one hand, leaning back farther and farther until he was almost horizontal, and then he matter-of-factly began to walk smoothly backward down the cliff.

  6

  DUMPING GARBAGE

  Each day that he was space station commander, at the end of his shift Radkowski would float through the space station, checking all the seals, verifying that the safety equipment was accessible and that none of the pressure hatches were blocked by cables or equipment. He came across Ryan Martin in the electronics laboratory module. He was working on an electrical breadboard that was connected to a microwave antenna pressed hard against the small external porthole. From the look of it, Ryan had built it himself.

  "A C-band transmitter?" Radkowski said. "You have a frequency-control permit for that?"

  "Nah," Ryan said. "Nobody uses those old low-frequency microwave bands but the Russians; a permit would be nothing but paperwork. Anyway, it's a low-power rig, not good for much but orbit-to-orbit."

  Radkowski liked the young astronaut, but it bothered him when he dismissed management directives so quickly. Who knew what experiments the science crew might be running that could be ruined by unregulated electromagnetic interference? Well, for that matter, Ryan Martin probably did know—he kept up with all the work that the scientists were doing, and seemed to always know what experiment runs were being scheduled when.

  Ryan looked at his calculator. "They should be over the horizon any second now." He powered up his homemade transmitter. "Mirusha, this is Space Station. Mirusha, Space Station. Are you there?"

  "Da, Mirusha here." A heavily accented voice. "This is Martin?"

  "Yes, Martin here. How are you holding out down there, buddies?"

  "Holding out not so good."

  "Any chance of rescue?"

  There was a long pause. "We think not."

  "Can you use your return capsule?"

  "No."

  The Mirusha had an ancient Soyuz module attached. The Soyuz spacecraft was, according to the design specifications, the lifeboat that the crew was to use to return to Earth in the event of a failure. But the Soyuz had been designed for only one year in orbit.

  "We have been using it for junk storage," the Russian said. "We have been removing out the junk and try to power up the systems. No is working." Long pause. "Is designed for one year in orbit. Is now twelfth year. Nothing works. Is junk."

  "Better than suffocating."

  "No," the Russian replied. The signal was beginning to acquire static. "Cannot undock, my friend. Is welded to Mirusha. Not even big hammer can work to undock."

  "Signal's breaking up, buddies," Ryan said. "I'd better sign off. Hang in there, buddies."

  "Da," the Russian replied. "We will hang here. Where else we hang, no?"

  And then there was nothing but static.

  "Passed over the horizon," Ryan said. "If we had a joint data-relay agreement, I could relay communications, but as it is, that's it for today."

  Radkowski hadn't realized how bad the Russian's situation was. But there was nothing they could do about it, he knew. The Russians would have to solve their own problems. "You talk to them every day?" he asked. It was an odd hobby, talking to the other space station over what was, essentially, an amateur radio link, but there were no regulations against it.

  "When there's a line-of-sight window," Ryan said. "I like Russians. They're the friendliest people in the world. And their space station may be small and cramped and low-budget, but it's still a space station, and it's great that they've managed to keep it going, with a budget of old paperclips and broken rubber bands."

  He paused for a moment, and then added, "If nobody else is going to do it, I will."

  "You will what?" Radkowski asked "Why, I'll save them."

  Radkowski chuckled. "Right," he said. "You do that."

  Garbage is a big deal on a space station.

  Garbage accumulates. Food containers and byproducts, used and reused pieces of paper, human waste, broken equipment, worn-out underwear, used chemicals, filled barf-bags, shaving bags, and vacuum-cleaner bags, sanitary napkins, used-up sponges, biological sample containers, dead petri dish cultures, used personal hygiene supplies, wastewater too contaminated to recycle—garbage accumulates. With every docking of a logistics transfer vehicle, more material is brought up to the space station, and all of it, eventually, becomes garbage.

  Some of it can be returned to Earth with the shuttles. But more refuse and wastewater is generated on the space station than can be returned to Earth in the empty space in a personnel transfer module.

  Garbage can't be just thrown overboard; garbage tossed out a hatch would accumulate in the sam
e orbit as the station, turning into lethal debris at the orbital velocity of 17,000 miles per hour. Not even the wastewater can be vented; one of the benefits of the station is to use the high-vacuum environment of space, and a wastewater dump would contaminate the environment near the station, destroying its usefulness.

  Instead, garbage is lowered on a string.

  The principle is simple. A month's load of garbage is placed into a plastic disposal bag, which is attached to one end of a spool of thin super-fiber. The garbage load is dropped out the nadir hatch and nudged infinitesimally backward in orbit. A satellite in its own right, but tethered to the spacecraft by the superfiber cable, the garbage-satellite drops into a lower, and hence faster orbit. It moves ahead of the station and unwinds the superfiber behind it. A brake on the superfiber reel pulls back on the garbage, and the more the garbage is pulled backward, the lower the orbit it drops into. At its full extension of twenty kilometers, the garbage satellite hangs directly below the space station. Now the superfiber cable is pulling straight outward on the garbage. And then the cable is cut.

  When the cable is cut, the garbage satellite drops into an orbit lower yet. The orbit, in fact, has a perigee which is lower than the space station's orbit by exactly seven times the length of the tether. Left to itself, the garbage would diverge from the space station by a hundred and forty kilometers. But an orbit a hundred and forty kilometers below the space station skims through the Earth's atmosphere. Anything in such an orbit will burn up.

  And so, in the form of a briefly flaring meteor, the garbage is returned to the Earth it came from. It was a far more efficient way to deorbit garbage than using a rocket; no fuel is needed, and the superfiber tether was a low-technology system no more complicated than a fishing reel.

  John Radkowski was in command of the station and had just finished running a garbage dump. It was one of the more interesting duties, actually; if performed incorrectly, the superfiber cable could snag or could go into an oscillation such as the "skip-rope" mode or, in the worst-case scenario, the brakes could fail and the tether deploy too quickly, rubber-band itself back into the station, and hit any of a million possible damage points with a two-ton wrecking ball of garbage.

  When he had completed the garbage dump and returned to the lounge area, he found Ryan Martin and several others already there, engaged in an animated discussion.

  "Hi, Ryan," he said.

  "Radkowski," Ryan said. He was wearing a T-shirt that read: HIGH ENERGY PHYSICISTS HAVE A STRANGE CHARM. He floated with the tip of one foot hooked under a loop to keep him from drifting away. He was oriented sideways to Radkowski's local vertical; it didn't seem to bother him, although Radkowski still had trouble adapting to it. "What do you think?"

  "About what?"

  "The rescue, of course."

  Radkowski blinked. "I'm sorry. I don't know what you're talking about."

  "The Russians, man," Ryan said. "The cosmonauts. We're going to rescue them."

  Radkowski shrugged. "No, of course not," he said.

  Ryan Martin shook his head. His body rotated in counterpoint, and the foot he had hooked under a restraint loop popped loose. He started drifting. "If we don't rescue them, it's damn certain that nobody else will," he said. "They're leaking. They've got five, maybe six days. Who's going to rescue them that fast? Not the Russians—that last blast tore the hell out of their pad; it will take them six months to get back operational. Not the U.S.— we have only four shuttles; two of them are up here with us, and we can't get them down and then back up again that fast. The other two are in for refurbishment; they're going nowhere. Not the Brazilians—they can't hit that orbit from their launch site. So, if we don't save them, then who will?"

  "Don't be ignorant," Radkowski said. "Can't get there from here. They're in a completely different orbital plane."

  Ryan smiled. "The crew return vehicle can do it."

  Radkowski shook his head so vigorously that he had to hold on to a loop to keep from moving. "Not enough delta-vee for a plane change. Not by half."

  Ryan Martin nodded. "Nope. So we have to be clever. We have to be very, very clever."

  Ryan Martin, as it turned out, was clever.

  The crew return vehicle was a tiny, four-person lifting body. It had been designed to be an ambulance, an emergency way to land an injured astronaut fast. It had a rocket engine for the deorbit, but not enough fuel to make the plane change needed to get into the Russian orbit. Plane change maneuvers need a tremendous amount of fuel; even if every drop of rocket fuel in the space station could be used, it would not be enough to get the little vehicle into the right orbital plane.

  Ryan's plan was to use the tether. The tether was used to drop garbage downward, but there was no reason it couldn't equally well be used to sling the crew return vehicle outward. He calculated that four hundred kilometers of tether, twenty times the amount used for a garbage dump, would toss the little lifting body into an orbit with an apogee of five thousand kilometers above the Earth. "That's into the Van Allen radiation belts," he said, "but I'll only be there for less than an hour, no big exposure concern there." At the apogee of the orbit, he would fire the crew return vehicle's little rocket perpendicular to the direction of the orbit, as well as two solid propellant STAR booster rockets stolen from the perigee kick motors of satellites being repaired on the station. The trick, as he pointed out, would be to gain altitude before trying to do the plane change. The farther away from the Earth, the easier it is to make a plane change, and the added five thousand kilometers that the tether boost could give him would make an enormous difference.

  Radkowski closed his eyes, trying to picture the situation. He wasn't good at doing math in his head. Five thousand kilometers, that was, what, three thousand miles. Slightly less than one Earth radius. "It's still not enough," he said.

  "Right," Ryan said. "Not enough. Yet. Okay, here's what happens next. The return vehicle is screaming in from five thousand kilometers, see. It has a lot of excess kinetic energy to dissipate. So what happens? Here's what happens. Highly elliptical orbit. I dip into the atmosphere. But, here's the trick. I don't just use the atmosphere to brake. The return vehicle has lift, right? It's a lifting body. So I point it sideways. Roll the beggar over ninety degrees, use the lift as a vector. I can take my excess delta-vee, and I can turn it into plane-change vector. Two passes through the atmosphere, I've got the orbit circularized, and as a free bonus, I get my plane change. Piece of cake."

  "Shit," Radkowski said. "Does that really work?"

  Ryan had been spinning lazily end over end as he talked. As he finished talking, his head was in the middle of the lounge, his feet next to the computer console. He reached out with one foot and tapped the keyboard. The screen lit up. Ryan smiled. "Believe it," he said. "I've got it all worked out in computer simulation."

  Radkowski nodded. What Ryan was looking for, he realized, was not for somebody to check his work—it was obvious that he had complete confidence in that. So what was he asking about? "You're requesting for permission to use the CRV?"

  Ryan Martin shook his head. "Radkowski, I'm not asking your permission. I'm going, whether you agree or not."

  "You take that CRV without permission," Radkowski said, "and they'll kick your ass so far out of the astronaut corps that you won't need a booster to get into orbit."

  "Maybe they will." He shrugged. "Nevertheless, permission or no permission, I'm not going to leave them to die."

  "Okay," Radkowski said. "We'll do it."

  Ryan reached out a hand to stop his slow spin and looked up at Radkowski in surprise.

  "Just one minor detail," Radkowski said.

  Ryan smiled. "Name it."

  "This mission you're proposing is dangerous as hell, more than likely it's not going to work, and even if it does work, it may already be too late to rescue the Russians. Half-baked, untested, dashed-together schemes like this are a formula for killing pilots. There's no chance I'm going to let you do it."

 
"It's not dangerous," Ryan said. "I know I'm low on pilot-in-command hours, but the computer will be doing the flying. If it looks like I can't make the rendezvous, the computer will tell me, and I will abort to Earth."

  "No, you won't. You'd only end up killing yourself, and I'm not about to allow you do that," Radkowski said. "I'm going to fly it myself."

  7

  DESCENDING

  Rappelling down is the part of a climb that most rock climbers like least. To Trevor, however, rappelling was the best part. It gave all of the giddy thrill of hanging on a rope over immense heights, with far less work than actually climbing. He had rappelled long before he had ever climbed, driving with his older brother to the top of canyons in Arizona and rappelling down the cliffs. So he knew about rappelling.

  Nevertheless, he watched Ryan as he fed rope out. The superfiber was different. The fiber itself was coated with a monolayer of fluropolymer that gave it an incredibly low friction; this meant that the fiber was less likely to snag on protrusions or be sawed through by a sharp corner, but also meant that only the specially designed braking mechanisms worked well on it.

  The commander was smooth and matter-of-fact about belaying down. Trevor had always descended a cliff in bounces, pushing off and dropping, letting the cable swing him back into the cliff like a pendulum. It was more fun that way. The commander, though, methodically paid out line through the braking fixture, and walked step by step backward, his eyes fixed on the rock at his feet.