“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.