Nilis wasn’t intimidated. “Oh, have you? Or are you looking out for yourself, Commander? Seeking whatever advantage you can gain from the project, while always keeping your backside covered, in the grand Navy tradition!”
Torec saw Darc’s hands close on the arms of his chair, his knuckles whiten.
To her relief, before they came to blows, there was a soft chime, and a small Virtual window opened up before her. It revealed a shining sphere. She gaped.
“I have a visitor,” she said.
When Darc saw the Ghost’s image, he snarled, “Send it away. I won’t have that monstrosity in a Naval facility.”
Enough, Torec thought. “It’s my visitor,” she said. “Not yours, sir, with respect.”
Darc shot her a glance, but he knew she was right; by ancient Navy tradition sick bay patients had a few temporary privileges. But he waved a hand at the Virtual of the test run, dispersing it — as if, Torec thought, the Silver Ghosts assigned to the project hadn’t seen the whole thing live and firsthand anyhow.
The Ghost’s bulk was barely able to pass through the door. It hovered beside Torec’s bed, massive, drifting slightly, the glaring lamps of the room casting highlights from its hide.
She shivered, as if the Ghost’s immense mass was sucking the warmth out of the air. She pulled her med-cloak a little higher, and the semisentient wrap snuggled more tightly into place. A Silver Ghost, a bedside visitor in a Navy hospital, come to see her…
Nilis’s characteristic curiosity cut in. He stood before the Ghost, hands on hips, rheumy eyes alive with interest. “So,” said Nilis. He held out a liver-spotted hand, as if to stroke the Ghost’s surface; but he thought better of it and pulled back, curling his fingers. “Which one are you?”
“I am the one you call the Ambassador to the Heat Sink.” The Ghost’s chill contralto voice seemed heavily artificial in this small sick-bay room. “We met on Pluto.”
“Of course we did. I should have guessed it was you. But how would I know if you were lying, if you’re a different Ghost entirely? Hah!”
The Ghost didn’t respond. Darc, still as a statue, was almost as unreadable.
Nilis went on, “And what are you doing here?”
“It’s come to see me, Commissary,” Torec said gently.
Nilis made a mock bow.
Torec plucked up her courage and faced the Ghost. She could see herself in its hide, a distorted image of a head and shoulders, clutching her med-blanket. “Maybe that’s what’s so scary about you,” she said aloud.
The Ghost said, “I do not understand.”
“That every time I look at a Ghost, I see myself.”
The Ghost rolled slowly, slight imperfections on its surface marking its movements. “Identity is a complex concept which does not translate well across cultures.”
Torec said, “Why have you come to see me, Sink Ambassador?”
“Because your project is failing,” it said.
Nilis nodded. “Yes, yes. We are battling the instability of your gravastar shield, it can’t be denied.”
Darc snorted. “And it’s a fundamental flaw. The spherically symmetric solution of the equations — a complete gravastar, a shell surrounding a ball-shaped pocket universe — would be stable. Your half- and-half solution, a spherical cap preceding a pocket universe that matches to ours asymptotically, is analytically complete, but is not stable.” He gave a thin-lipped grin. “Oh, don’t look so shocked, Commissary. Even Navy grunts know a little math. The problem is simple: instability. You have your pilot balancing a ten-meter pole on the palm of her hand; she can run as fast as she likes, but sooner or later she will fall.”
The Ghost said, “But we have a solution.”
Nilis and Darc both turned to face the Ghost, startled.
Torec smiled. “So that’s why you’ve come. You weren’t concerned about my health at all.”
The Ghost seemed to think that over. “No offense.”
Nilis gaped. “Did a Silver Ghost just make a joke?”
Darc said sternly, “You say you have a solution. Describe it.”
The Ambassador rolled, and Virtual images scrolled in the air. Torec recognized a map of the phase space of a system. It was a schematic diagram of the possible states of the gravastar shield. It looked like a slice of a rolling landscape, with valleys, peaks, and plains, and it was marked with contours that showed regions of chaos and stability, attractors and poles.
“The trick,” said the Ghost, “is to use the instability, not to fight it. You are trying to emulate the stability of the strongest attractor, which is the spherically symmetric solution here.” A point on the map winked red. “So you allow the shield to form at low velocities, or even when the projector is stationary. You find an equilibrium, but it is not stable. Then when you try to fly, the smallest instability disrupts the solution. Your running child trips on a pebble, Commander, and the pole is dropped.”
Nilis laughed out loud. “You have spent a long time studying human idioms.”
“We have little else to do,” the Ghost said.
“So,” Darc growled, “what do you suggest instead?”
“It would be better to operate the projector when it is being carried at close to lightspeed.”
Nilis frowned. He walked up to the image and poked his finger into its shining innards. “But that would bring us up to this region.” It was the complex border between order and chaos. “The shield would be no more than meta-stable.”
“But solutions in this part of the phase space, on the edge of chaos, would be responsive to small adjustments.”
“Ah.” Nilis nodded. “Which would make the shield more manageable, because it would respond more sensitively; we could control out the instabilities before a catastrophic disruption.”
Darc was visibly unhappy. “How rapidly would we have to react?” He brought up a Virtual of his own, ran some quick calculations. “There,” he said in triumph. “Look at that! Your meta-stable shield will flap like a sheet in a breeze. There’s no way we could react quickly enough to respond to it.”
“Of course you could,” the Ambassador said. “You have arbitrarily high processing speeds available on your ship. Your CTC-processor technology—”
Darc shot to his feet and stalked up to the Ghost, fists clenched. “Is that the game? How do you even know about that? If you think I am going to let you anywhere near the CTC system—”
Nilis said, “Commander, please. We’re simply discussing possibilities.”
Darc remained standing, glaring at the Ghost. “Why are you doing this? Humans destroyed your kind. Why would you help your conquerors?”
“Curiosity,” the Ghost said.
“And nothing else?” Darc asked heavily.
“Nothing. You recreated us at a whim. You could destroy us as easily. We have no hope.”
Darc’s eyes narrowed with suspicion, but he stayed silent.
Nilis was still thinking over the idea. “This would actually simplify the overall design, of course… You don’t seem happy, Ensign.”
Torec said, “I’m a pilot, sir. No pilot likes giving up control.”
“Hmm. I can sympathize with that. And of course this sort of active-control system isn’t without risks. You would go into battle behind an intrinsically unstable system. If the CTC failed, you would die immediately.”
“But we all die one day, Commissary.”
He embarrassed her by allowing his eyes to fill up. “Lethe, this laconic courage — I’m sorry! I can’t get used to it.”
The Ghost said, “You have one more test ship.”
“One more chance,” Nilis said. “The modifications would be straightforward.” He stared at Darc.
Darc held his stubborn stance for a moment, then seemed to give in. “All right. Lethe take this whole plagued project! But what are we to do for a crew?”