Aftermath

14

When would the orbiters leave the space station to make their reentry?

Where would they land?

Who would be on each one?

Zoe Nash had taken total responsibility for those three decisions. “I’ll tell you, when, and where, and who.”

Zoe was confident, if not casual, and for that Celine was profoundly grateful. Thinking about the situation as she made her way through the silent interior of ISS-2, she knew she would have agonized endlessly and never been able to come up with answers. She was a natural procrastinator, able to see a hundred roads to failure.

How much preparation was enough? To Celine, two days was a ridiculously short time. On the other hand, you could check instruments and programs forever and still miss something. How did you divide the group in two? It was absolutely necessary, but how did you decide the mix of skills to place on each orbiter? The whole point of the Mars expedition crew was that it worked best as a single integrated unit.

Fortunately, Celine had a practical task to occupy her mind. She had been told to search the derelict for a dozen of a particular type of bonding clamp, needed in the orbiters, and she had located a whole cabinet of them in the central supply room of ISS-2. Now she was heading back through the desolate corridors. The previous two days had not hardened her to the sight of the frozen corpses, but she knew where they were and she had learned not to look at them.

At the open airlock she paused. In front of her, framed against the backdrop of a sunlit Earth, hung the Schiaparelli. It had been home for so long, the very idea of leaving it was frightening. To leave it in one of those - she glanced to her right, at the tiny, vulnerable orbiters — was doubly daunting. The interiors, even with the padded seats pulled out, were impossibly small. They were definitely one-person ships.

If everything went well, Lewis and Clark — Reza Armani’s off-the-cuff names for the twin orbiters had stuck — would return to a torn and battered planet, whose peculiar cloud patterns and high dust clouds were evidence of the physical trauma that the world had suffered. What would the crew find when they landed? The radio signals remained sparse and weak, with some countries and continents totally silent. The Schiaparelli had sent calls for help and information on all frequencies. It had received not a word or a beep in reply.

Celine floated her way across to Clark, the nearer orbiter. She confirmed that the clamps were the right size and style to attach the hammocks to the walls, and performed the simple installation. The hammocks were tough, made of Mars tent materials that by good fortune had neither been landed on Mars nor discarded before the return trip. Without seats, hammocks would be the crew’s only cushion against the high accelerations of reentry.

Celine tested that the bonds would hold for body loads up to thirty gees. Beyond that, humans would not survive even if the clamps could. She moved across to Lewis and performed the same task of installation. Then she headed to the home ship — home, at least, for another few hours — and passed through the Schiaparelli’s airlock. She removed her suit, rubbed her itching eyes, and floated on to the main cabin.

The other crew members were already there. Zoe gave Celine an inquiring glance, and she nodded.

“I found them. They fit.”

“Good. Jenny?”

Jenny Kopal was crouched over a diagnostic pad. She shrugged. “I can only debug to a point using simulated inputs. According to every test routine that I have, the chips we put into the orbiters from this ship will perform identically to the dead ones they replaced. I loaded them all from the general program library for single-stage orbiters. But you know what they say. No matter how much testing you do, every program always has one bug left in it.”

“Let’s hope it’s a bug we don’t encounter before we’re down on Earth.” Zoe leaned back. “Alta?”

“I don’t know.” Alta paused and thought for thirty seconds. “I guess the orbiters are as ready as they’ll ever be. I’m still worried about center-of-mass changes because of the unusual loading. But I think any one of us could fly one.”

“Coming from a pessimist like you, I take that as a rave report. All right.” Zoe leaned back. “It’s showtime again, folks. And here is the plan. Lewis will perform reentry first. As you know, it can only hold three people. Those three are going to be Zoe Nash, Ludwig Holter, and Alta Mclntosh-Mohammad. I will pilot Lewis. Then, unless someone wants to stay up here and wait for the next shuttle up from Earth” — Zoe smiled at her joke, but no one else did — “Clark will take Reza Armani, Jenny Kopal, Celine Tanaka, and Wilmer Oldfield. Reza will pilot Clark.

“Lewis will send telemetry back here all the time during reentry, except when it goes through the period of radio blackout. I believe the increased mass load on the second reentry will be more than compensated for by the opportunity to fine-tune Clark’s control parameters using the data from Lewis. Any questions so far?”

There was silence. It was obvious to Celine, as it must be to all of the others, that Zoe had included factors other than mass balance in deciding the complement of the two crews. She had placed the people pairs, Jenny/Reza, Alta/Ludwig, and Celine/Wilmer, on the same orbiter as each other. To some, that might suggest sentiment on Zoe’s part. To a worrywart like Celine, it said that the reentry dangers were more than Zoe was willing to admit. She was offering them a chance to die as the couples that they had become.

“Now there is the question of where,” Zoe went on. “Where should we aim to land? I think we can make one decision very easily: we avoid the Southern Hemisphere. We’ve picked up hardly a radio signal from there. Also, if we are off in our final along-track position, the Southern Hemisphere offers a higher chance of landing in water. The orbiters are not designed for an ocean splashdown, and even if they were I don’t feel like a thousand-mile swim.

“The majority of the radio signals we have received come from North America, with considerably more from the northern states than the southern, and more from the east than the west. So north is good, and east is good. We are in a low inclination orbit, so a very high latitude touchdown is not possible. I think we can reach forty degrees north, and I propose that we try to do so. I will aim to make Lewis’s landing close to the fortieth parallel, near the eastern seaboard but at least a hundred miles from the Atlantic Ocean. Normally the orbiters can land on a dime, but we need a margin of error. I will not try to specify a final landing location now, because we have not been able to obtain a clear picture of surface conditions. We’ll see what we have available when we get there. An airport would be nice, but any decent highway will do at a pinch. Naturally, once Lewis is down we’ll send a message telling Clark what to aim for or what to avoid. We’ve been over all this before, in smaller groups. But does anybody have a question or a comment?”

She waited a few moments, and went on: “Then the only remaining question is, when?

“We will do one final start-to-finish checkout of everything, which ought to take no more than a few hours. After that, Lewis will take the next available reentry window. The main requirements are that we have a daytime landing — it’s currently night in North America — and that Lewis has line-of-sight communications with those of you who are still here on the Schiaparelli. That means there has to be some orbit matching, but Jenny already did those calculations. Once Lewis is down, we can decide the schedule for Clark based on our experience. Any other questions?”

“I have been thinking.”

To Celine’s surprise, the speaker was Wilmer. He almost never contributed to group meetings. Quite often, he didn’t seem to be listening. But he was. He would go away, brood over what he had heard, and return to offer crucial suggestions or devastating criticisms.

Celine decided that Wilmer understood, better than she had, the nature of this particular meeting. There would be no chance for later discussions. This was it, the final meeting of the Mars expedition until they were all once more on Earth.

“All right, Wilmer,” Zoe said. “What’s your worry?”

He put his hand up to scratch the top of his bald head — a habit that looked ludicrous and that Celine had not been able to change. It gave him a permanent and ugly red patch. “This is a suggestion, not a worry. You speak of a line-of-sight requirement for communications, and I assume that you mean radio signals. But I think we should also track the descent of the Lewis visually, using the biggest scope on the Schiaparelli.”

“What would be the point of that?”

“Suppose that you encounter trouble during that period of reentry when ionization around the orbiter prevents the transmission of radio signals. Visual observation might then offer the only evidence of the nature of the difficulty.”

“We don’t anticipate trouble.” Zoe glanced around the rest of the group, who were showing uneasiness in various ways at the implications of Wilmer’s suggestion. “I guess we all like to think positive. But Wilmer is right. If anything were to go wrong with Lewis, the rest of you will need to learn all you can from our difficulties before Clark makes its own return from orbit. Celine, please make sure that the big scope is set up for continuous visual coverage of the reentry of Lewis.

“Anything else? No?” Zoe went on casually, as though orbital reentry to a radically changed Earth in an untested ship was the most routine operation imaginable. “Let’s get to it, then. I’m fond of the Schiaparelli, and it’s been good to us. But I’m a little bit itchy to get home.”

“Day” and “night” on the Schiaparelli violated human nature and common sense. The Mars ship was locked into the same orbit as ISS-2, and every ninety minutes brought a new dawn and a new sunset. It took five of those “days,” almost eight hours, before the motion of Earth and ship were synchronized, and Zoe was able to say from the controls of Lewis, “We have thrust. See you all down there.”

Celine and the other three were in the control room of the Schiaparelli, where they could receive radio inputs from Lewis and visual images from the biggest of the onboard scopes. She looked at Jenny, Reza, and Wilmer and felt a strange uneasiness. Zoe, Ludwig, and Alta had not always been in the same cabin with her on the Schiaparelli; for much of the time on the return journey, they had all hidden themselves away from each other. But in a sense the other six had been “there,” all the time. They had formed a unit, working together in the greatest feat of human exploration ever undertaken.

Now they were split, and even when they came together again on Earth it would not be the same. Something had been lost in that moment of Lewis’s departure. Celine hated the feeling of loneliness.

At the moment the orbiter was still close to them, and they did not need a scope to see the blue-white flare of its nuclear rocket. But Lewis dropped away steadily, losing altitude and velocity, and as the minutes passed the ship as seen without the scope dwindled to a fiery spark. It was beginning the long arc down to the atmosphere of the Earth.

“Everything is nominal.” Zoe’s voice was clear over the telemetry. “The control routines are behaving exactly as we hoped and expected. You will lose radio contact with us in eight minutes.”

Even when ionization induced a temporary radio silence, the image of the orbiter would still be picked up by the big onboard telescope and displayed on the control-room screen. Celine looked, and saw that Lewis had already switched off its engine and turned for the nose-first reentry. The image of the orbiter was tiny but quite clear. She even imagined she could make out the dots of people’s heads in the cabin’s transparent viewport.

She glanced at the display showing elapsed time. Only nine minutes since first thrust. It felt much longer.

“Looking good.” Zoe sounded a fraction fainter, but maybe that was Celine’s imagination. “We are losing altitude as planned and are already experiencing atmospheric drag. We project loss of radio contact in five minutes and seventeen seconds, eight seconds ahead of schedule. Report back receipt of this signal.”

Celine did so, automatically. The Earth below was invisible. It was still night there, though in another nine minutes Celine would look down onto a sunlit United States. Lewis was heading for a single-step reentry. There would be no “bounce” aerobraking as they had used it on Mars, skimming into the upper atmosphere and out again several times, like a pebble skipped across the surface of a lake and shedding velocity on each transit. The Earth orbiters and landers all accomplished reentry in a single pass. Aerodynamic and thermal forces were much greater that way, but the ships were designed to take it.

“The hull indicates an increase over predicted temperature,” Zoe said. Her voice was overlaid with the faintest hiss and crackle. “Parameters are still within the predicted range. Ionization is beginning, somewhat ahead of schedule. We expect radio blackout in two minutes and eleven seconds, seventeen seconds ahead of schedule. Report back receipt of this signal.”

Celine glanced at the other three in the control room. Jenny was serious, following the flight parameters coming over the telemetry and nodding approval. Reza was smiling, moving his hands as though he were flying the Lewis himself. Wilmer alone seemed worried, his hand to his chin and his heavy brow furrowed.

“Hull temperature is rising more rapidly.” The distortion in Zoe’s voice was greater. “It is a good deal more than predicted. I have to lessen the angle of attack and I project a change in downrange landing distance. I am taking manual control of orbiter attitude. We expect radio blackout in fifty seconds.”

More than a minute ahead of schedule. Much too soon.

“Refer to visuals,” Jenny said softly. Celine looked at the display from the big scope and saw on it a bright arrow trail. The Lewis was the silver tip at the head of the arrow.

Celine gave one rapid glance at the unmagnified display. The tiny mote of the Lewis, a hundred and more miles beneath the Schiaparelli, was not visible. She said urgently, “Lewis, we are losing radio contact. Report if you are hearing us.”

The radio signal telemetry sounded in her ears as a loud hiss of static, within which every trace of Zoe’s voice had been lost. The control board provided the real-time power spectrum of the telemetry, and it was pure white noise.

“They are entering the period of maximum drag and maximum ionization,” Celine said — an unnecessary comment for the others in the control room, who knew it as well as she did, but needed for a full record of events. “This has occurred sixty-six seconds ahead of prediction. Radio contact has been lost.”

The display from the big scope also showed the nominal flight trajectory for the Lewis as it had been calculated ahead of time. The two curves, computed orange and observed yellow, were diverging. Celine could see the separation increasing as she watched. The real ship was falling far behind its simulated twin.

“The atmospheric drag force is way high,” Wilmer said suddenly. “The reentry angle must be too steep. It’s as though they made an attitude correction the wrong way.”

It was useless to ask how he knew — he had his own inexplicable way of making estimates. It was also pointless. The big scope was still providing its display. As Wilmer was speaking, the silver arrow tip brightened.

“Black body equivalent temperature of Lewis’s hull, forty-two hundred degrees,” Jenny said. She was reading the output of the Schiaparelli’s bolometer. “That exceeds predicted maximum by six hundred degrees.”

Still well within tolerances. The exotic materials of the orbiter’s hull were rated up to fifty-four hundred degrees. But a normal reentry never came close to that. And Celine did not need the bolometric output to tell her that the temperature of Lewis’s hull was still increasing. The silver arrowhead had become a blaze of blue. Telemetry was a roar of static in her ears.

“Go up,” Reza said urgently. He was working imaginary controls, pulling back on them. “Forget the one-shot reentry. Go higher, take another shot later.”

Radio silence was two-way. There was no chance that Zoe Nash could hear him. Frictional heating surrounded the racing orbiter with a blaze of ionized gases.

“Black body equivalent temperature of Lewis’s hull, six thousand degrees.” Jenny’s voice was a dead whisper. Then, with urgency, “Cool down. You can’t take that for long.”

She was right. As she spoke, the blazing arrow tip vanished. It was replaced by a puff of white, round and delicate as a cotton ball.

Celine did not cry out. She leaned forward and covered her face with her hands. That innocuous cottony cloud was an incandescent rage of flaming gas. In its heart were Zoe Nash, Ludwig Holter, and Alta Mclntosh-Mohammad, reduced to their component atoms in Lewis’s fiery explosion.

They would be carried away by the pendent winds, blown and dispersed by the restless violence of the atmosphere. If the three crew reached a single final landing place, no one would ever know it.

The control room was silent except for Reza’s harsh breathing. Celine rocked backward and forward, unable to weep or to make any sound. All she could think was that Zoe, supercapable and superconfident Zoe, had been wrong.

Zoe would not be down on Earth in two days. Zoe would not be there ever.