“Yes?” said Orphu.
Mahnmut was thinking of the dying power supply, the dwindling reserves of air and water, and the doubtful propulsion system. “Fourth,” he said, “they still don’t know why we’re here.”
Orphu rumbled softly. “I don’t think we do either, old friend.” After a minute of no communication, Orphu said, “Well, you’re right. If they don’t find us in the next few hours, we may have a chance. Or is there any other bad news?”
Mahnmut hesitated. “We have a slight problem with our air supply,” he said at last.
“How serious a problem?”
“We’re not producing any.”
“Well, that is a problem,” said the Ionian. “How much in reserve?”
“About eighty hours. For two of us, that is. Certainly twice that, probably more, if it’s just for me.”
Orphu rumbled slightly over the intercom. “Just for you? Are you planning on stepping on my air hose, old friend? My organic parts need air too, you know.”
For a second Mahnmut couldn’t speak. “I thought . . . you’re a hardvac moravec . . . I mean . . .”
“You’re thinking that I spend long months in space without topping off from the Io tender,” sighed Orphu. “I produce my own oxygen from the internal fuel cells, using the the photovoltaics on my shell to power them.”
Mahnmut felt his pulse slow. Their chances of survival had just gone up if Orphu did not need ship’s air.
“But my shell photovoltaics are blasted to hell,” Orphu said softly, “and the fuel cells haven’t been producing O2 since the attack. I’m surviving on the ship’s supply. I’m sorry, Mahnmut.”
“Look,” Mahnmut said quickly, strongly. “I was planning to keep the air running to both of us anyway. It’s not a problem. I did the numbers—we have about eighty hours at our present consumption rate. And I can lower that. This whole control room and enviro-niche of mine is flooded. I’ll pour it back in and parcel it out. Eighty hours easy, and then we’ll come up for air. Their search should be over by then.”
“Are you sure you can get The Dark Lady out of the mud?” asked Orphu.
“Absolutely positive,” lied Mahnmut, voice firm.
“I vote we lie doggo in the seabed for . . . say . . . three sols, three Martian days, seventy-three hours or so, to see if their chariot search is really called off. Or twelve hours after our last radar contact with them. Whichever comes first. Will that give us enough time to get out of the mud and to the surface, plus leave some oxygen and energy to spare?”
Mahnmut looked at his virtual wall of red alarm and non-function lights. “Seventy-three hours should be plenty of extra time,” he said. “But if they go away sooner than that, we should get to the surface and head for the coast. The Lady can do about twenty knots on the surface with the reactor at this level, so it’ll take the better part of the day and a half to get to land anyway, especially if we’re picky about where to put in.”
“We’ll just have to avoid being picky,” said Orphu. “All right, it looks like the only thing we have to worry about for the next couple of days is boredom. Shall we play poker? Did you bring the virtual cards?”
“Yes,” said Mahnmut, brightening.
“You wouldn’t rob a blind moravec, would you?” said Orphu.
Mahnmut stopped in the process of downloading the green baize card table.
“I’m kidding, for Christ’s sake,” said Orphu. “My visual nodes are gone, but I still have memory and parts of my brain left. Let’s play chess.”
Three sols was 73.8 hours and Mahnmut did not want to stay in the seabed that long. The reactor was losing power faster than he’d estimated—the pumps were draining more energy than he’d planned on—and all the life support was flirting with failure.
During their first sleep period, Mahnmut went on internal power, took pry bars and cutting equipment, and descended the narrow crawlways and corridors to the hold. The interior spaces were flooded, the vertical gangway without power and pitch black. Mahnmut activated his shoulder lamps and swam lower. The water here was much warmer than Europa’s sea. Beams and girders had crumpled, blocking the last ten meters of the approach. Mahnmut cut them away with the torch. He had to check on Orphu’s condition.
Two meters from the airlock to the hold, Mahnmut was stopped cold. The impact had buckled the aft bulkhead, pressing it almost flat against the forward bulkhead. The already narrow corridor had been squashed into a space less than ten centimeters across. Mahnmut could see the hatchway to the hold—closed, dogged, and twisted—but he couldn’t reach it. He would have to cut his way through one or both of the thick pressure bulkheads and then probably use the torch to cut through the hatch itself. It would be a six- or seven-hour job and there was a basic problem—the torch ran on oxygen, just as he and Orphu did. Whatever he gave the torch came out of their air supply.
For several minutes, Mahnmut floated head-down in the darkness, silt floating in front of his lenses in the twin beams from his shoulder lamps. He had to decide now. Once Orphu awoke and realized what he was doing, the Ionian would try to talk him out of it. And logic dictated that he be talked out of it. Even if he got through the bulkheads in six or seven hours, Orphu had been correct—Mahnmut wouldn’t be able to move the huge moravec while they were still embedded in the seabed. Even first aid would be limited to the kits and system inputs that Mahnmut kept onboard for himself—they might not even work with the huge hardvac moravec. If Mahnmut could really get The Dark Lady free of the silt and to the surface, that would be the best time for Mahnmut to get to Orphu—even if he had to cut through the hull bay doors or outer hull. O2 would be plentiful then. And he could remove Orphu if he had to, find a way to lash him to the upper hull, in the sunlight and air.
Mahnmut kicked his way around and swam upward in the tilted and torn corridor, letting himself through the airlock into his personal space again. He stowed the cutting equipment. Later.
He was no sooner in his acceleration couch again when Orphu’s voice came over the comm. “You awake, Mahnmut?”
“Yes.”
“Where are you?”
“At the controls. Where else would I be?”
“Yes,” said Orphu, his deep voice sounding weary and old on the hardline. “But I was dreaming. I thought I felt a vibration. I thought you might be . . . I don’t know.”
“Go back to sleep,” said Mahnmut. Moravecs slept, if only to dream. “I’ll wake you for the buoy check in two hours.”
Mahnmut would deploy the periscope buoy for a few seconds every twelve hours, quickly scan the skies and gentle seas, and reel it back in. Flying machines were still crisscrossing the skies day and night at the end of the first forty-nine hours, but further north, nearer the pole.
Mahnmut was fairly comfortable. His control room and connecting enviro-niche was undamaged, warm, and tilted only slightly bow-down. He could move about if he wished. Several of the other habitable chambers had been flooded—including the science lab and Urtzweil’s former cubby—but although the pumps soon cleared these spaces, Mahnmut didn’t bother flooding them with air. In fact, the first thing he had done after their initial conversation was to hook into his O2 umbilical and drain his enviro-niche and control room. He told himself it was to save the oxygen, but he knew that part of the reason was that he felt guilty being so comfortable in his cozy niches when Orphu was in pain—existential pain at least—and floating in the flooded darkness of the hold. There was nothing Mahnmut could do about that yet—not with three-fourths of the damaged sub embedded in the ocean floor—but he went into the vacuum-filled science lab and cobbled together comm units and other things he’d need if he ever managed to free the Ionian.