"No, sir."

"Okay. Well, I'm off. See you in three weeks."

Kapoor glanced up. "You're going on vacation?"

"Theoretically, yes. Practically, it'll be one week of rest and two of speeches on Earth and Luna."

"It will be a nice change for you, anyway."

"Yes." Talking to Kapoor always depressed Carter a little. Something about the Indian's att.i.tude seemed to indicate disapproval, although it was nothing you could put your finger on. As near as Carter could remember, Kapoor's geniality had evaporated during the a.s.sembly's debates on a name for the project. It had come within a hair of being called Shiva, after the destroyer/regenerator of Hinduism, and Carter strongly suspected that Kapoor had considered even the suggestion to be sacrilegious. "Well, take care of the project, Kapoor," he said, a bit lamely, and left the room.

It could have been worse, Carter thought, walking down the hall. The a.s.sembly had also considered the name Lucifer.

As things turned out, Carter was not away from Firefly for three weeks. He was gone for exactly fifty-eight hours, and the ship that returned him to the station was a big Patrol craft that made the trip in record time. No one aboard would tell him what was going on, but the message was painfully clear.

Something was terribly wrong at Firefly.

The entire senior staff was a.s.sembled in the conference room when Carter arrived and slid into his usual chair. Nodding to the group, he turned to the Deputy Director and asked, "What's happened, Paul?"

Dr. Paul Rurik looked like he was next in line for a oneway tumbril ride. "We may have a runaway on our hands, Ray."

Carter felt his hands tightening into fists under the table. "Fill me in."

Rurik touched a switch and a set of graphs appeared on one of the displays.

"During last night's Owl shift Firefly's temperature started to rise. When we tried to restabilize this morning we discovered we couldn't do so. We tried everything we could think of and then sent the Patrol to get you.""Who was the operator last night?"

"I was, Doctor," a young man spoke up, a slight quaver in his voice.

"It wasn't Galton's fault," Rurik said. "The temperatures were within the allowable range we've calculated."

Carter nodded heavily. An operator couldn't be expected to notice that the rate of temperature increase was not following the theoretical curve. Only one of the scientists like Rurik or himself would have had the necessary knowledge.

Rurik went on, "I suspect Firefly drifted a little out of place, causing one or more of the neutron beams to miss it"

"No." Carter pointed to a display. "If that had happened you'd have gotten a big energy jump in the heat exchanger directly across from the beam that's missing. Instead, that extra neutron flux is spread out over several exchangers; furthermore, it's happening for all three beams. The beams aren't missing-they're being deflected."

"How?"

Carter looked toward the voice in surprise. "What are you doing here, Senator?"

"I was still here at Firefly when the crisis occurred," Chou said. "It is my right to be kept informed. How are the neutrons being deflected, Doctor?"

"Firefly emits particles in a thermal spectrum," Carter explained. "That means there are some at every speed from zero to near lightspeed. The ones that are moving slowly tend to stay near the black hole, forming a sort of cloud around it, and it's this cloud that's deflecting the beams."

"Surely they can't change the beam directions very much," Chou argued.

"They don't have to," Rurik put in. "Firefly is much smaller than the neutrons themselves. But, Ray, we took that effect into account when we set our temperature limits."

"I know. All I can think of is that our subatomic particle theory must be wrong somehow. If there are some particles coming out of Firefly that we haven't taken into account, all of our temperature curve calculations will be off."

"h.e.l.l cubed," Rurik muttered under his breath. "I'll get the theory people on this right away. Maybe with the extra particle emission data Firefly's giving them they can figure out where we're going wrong."

"For the moment, that won't help us," Carter said. "What we have to do is get more ma.s.s into Firefly, and that as soon as possible. The hotter it gets, the denser that particle cloud becomes. Not much, since most of the particles emitted have high kinetic energies, but even a slight increase in the number of low-energy particles just makes things worse. What have we got that we can throw at the black hole?"

"We have a spare DeVega accelerator," Rossetti volunteered, "but I don't think that'll help any."

"Why not?" Senator Chou asked. "That would give you an extra neutron beam."

For an instant Carter had an overpowering urge to tell the Senator to shut up.

None of them had the time to explain things to a layman. "DeVega dipole accelerators require very tricky and sensitive electromagnetic fields to function.

On a ring the diameter of the accelerator platform we can place only three DeVegas, s.p.a.ced one hundred twenty degrees apart. Any closer and their fields would interfere with each other."

"What about putting the extra accelerator farther out from the center?" Chou persisted.

"At the distance we'd need the beam would spread out too much to be useful.

And before you ask, directly above and below Firefly are the charged plates that hold it in place, so we can't run a neutron beam through there. Paul, can we increase present flux any?"

"No way. We're already running them ten percent above spec maximum, though I don't know how long they can hold that. We may in fact have stopped the runaway-the temperature is changing so slowly now we can't tell if it's going up or down."

"Let's a.s.sume it's still going up," Carter said. "Anything else we can use?"

"We've got a few X-ray lasers," someone said. "They could be set up to fire at Firefly."

"I've already checked that," Rossetti said. "It won't give a significant ma.s.s increment, and might add an extra scattering component to the neutron beams."

"Sir?" Galton spoke up hesitantly. "I may have an idea."

"Spit it out, son," Rurik said brusquely. "This is no time to be shy."

Carter winced at the tone as Galton blushed slightly. The young man's reticence was clearly not shyness, but instead the result of guilt feelings over his part in this mess. Rurik had never been good at understanding human emotion, though. He had declared that the fault was not Galton's and, for him, that ended the subject. It would never occur to him that Galton might still be upset.

"Sir, the DeVegas will accelerate any neutral particle that has a reasonable dipole moment. If we used, say, iron atoms instead of neutrons, we might be able to reverse the runaway."

Rurik nodded slowly. "That might just work, Galton. You'll probably get fewer hits on Firefly because of heightened beam self-interference diffusion, but the ones that go in are fifty-six times more ma.s.sive. And they'll be deflected less by that particle cloud around Firefly." He looked at Carter inquiringly.

"It's worth a try," Carter agreed. "Anyone know how long it would take to switch beam materials?"

"I checked, sir," Galton said. "The beam would only have to be off for ten minutes. And there's enough spare iron around for about ten hours of operation."

"If we can't reverse the runaway in that time we'll have to try something else, anyway." But to have the beams off for even ten minutes might prove disastrous.

Carter weighed the options briefly, painfully aware of the need for speed. "All right. Galton, get the DeVega crews together and brief them. We'll switch just one accelerator for now-make it Beta. If it helps, we'll do the other two a little later.

Paul, I suggest you get the control room people ready for the switchover. The rest of you go to your Emergency posts-I want to be ready if any problems crop up.

Get to it."

There was a mad scramble for the door, but as Carter turned to leave he found his way barred by Senator Chou. "Dr. Carter, a word with you, please."

"I'll be up in a minute," Carter called to Rurik over Chou's shoulder. Rurik nodded and glided from the room, not bothering to use his Velcro shoes. "What is it, Senator?" Carter said when the others had gone. "Make it fast, please. I'm in a hurry."

"What are our chances of stopping it, do you think?"

"Is that what you wanted? I have no idea. You'll just have to wait until the rest of us know."

"I can't wait for certainties-probabilities must do for now. I have a duty to the people of Earth. If anything goes wrong here we will have to begin taking steps to protect them, and the sooner we start the fewer will have to die."

Carter looked at Chou with new insight. For the past several months he had seen the Senator as simply an opponent, a cardboard cutout violently and irrationally opposed to the Firefly Project. Now, suddenly, Carter saw him as a human being. "You really care about Earth, don't you?" he said softly.

"It's my profession to care, Doctor. You may recall that I wanted the black hole placed a good distance further from Earth, where it would have been less of a danger to both the planet and the s.p.a.ce Colonies. I am not anti-technology, despite your side's efforts to paint me so, but I wished for a larger safety factor."

"Senator, there wasn't a decent safety factor available. If we can't stop the runaway, Earth has had it no matter where Firefly is."

"I don't understand."

Carter took a deep breath. "If we can't stabilize Firefly's temperature, it will keep getting hotter and hotter. The hotter it gets, the faster it radiates its ma.s.s as energy until it basically explodes. According to current theory, in the last tenth second of its existence it will radiate with one percent of the sun's total power output."

Chou's eyes were very wide. "Good Lord! And you allowed this-this nova to be placed in Earth orbit? You must be insane!"

"Senator, if Firefly lets go anywhere in the solar system Earth is finished. The sun will go crazy with all that extra radiation hitting it. If the extra solar heat doesn't sterilize the inner system, the extra radiation will. But we had no real choice in the matter. I don't think more than a handful of people realize this, but if we had just ignored the black hole from the very beginning the same thing probably would have happened. Firefly was already too close to blowing. We didn't deliberately put Earth in danger, Senator; we were trying very hard to save it. And we still are. Excuse me, but I have to get to the control room."

It was an hour later before Carter was satisfied that the DeVega accelerator crews had the technique down well enough to be able to switch beam materials in the shortest possible time. The Project's chief design engineer, Felix Mahler, floated by Carter's shoulder as the control-room personnel waited for word that the changeover had been completed.

"Santos and Trumbell are the best techs I've got," Mahler said into the brittle silence as the minutes ticked by. "If anyone can get the DeVegas going in ten minutes it's them. Matter of fact, Ray, I'll bet you they'll do it in nine."

The speaker crackled. "Beta station; Santos. We're ready here."

Rossetti, at the control board, didn't wait for Carter's nod. "Firing," he said.

"Eight and a half," Mahler muttered to no one in particular. "They're better than I thought."

Carter smiled slightly, but it was an automatic response. His full attention was on the meters that gave Firefly's luminosity and temperature, both of which had been running. The indicators jumped wildly, as always happened when a new beam was brought to strength, and Carter's heart rate jerked in sympathetic response.

"Beam's steadying down," Rossetti muttered.

"How's it look?""It's hard to say, Doc. We're getting extra power just from the gravitational energy effects-since the iron atoms are heavier than neutrons-and that's fouling all our calibrations." Rossetti stared hard at the temperature indicator. "If Firefly's cooling down I can't tell from this. Not yet, anyway."

"We could shift the feed on the other DeVegas," Mahler suggested. "That would make any temperature change more visible."

"I'd rather not risk shutting off the neutron beams for the time that would take," Carter said. "Not until we're sure it'll do us any good. Let's give this an hour or so and see what happens."

The results after two hours were very clear. Firefly's temperature was still increasing.

"d.a.m.n!" Carter muttered through clenched teeth. "It's got to work. Galton's numbers prove that. What's going wrong?"

He threw a glance around the room, a glare br.i.m.m.i.n.g with frustration that most of the others seemed to interpret as fury. "I've looked over Galton's work, Ray," Rurik spoke up with some hesitation. "I can only think of one effect that hasn't been taken into account."

"Well?"

"We're dealing with iron atoms here, much larger than neutrons, and with electron clouds at-relatively-great distances. As the atoms approach Firefly, the first things to be swallowed will be an electron or two, which will leave the atom with a net positive charge. Since the black hole is also positive, the atom-the ion, now-will be deflected slightly before the nucleus gets to Firefly."

"And some of the shots that would otherwise have hit don't make it in," Carter growled. "Makes sense. Unfortunately. Is it worth switching the other two beams, do you think?"

"I doubt it. We'd gain a little, maybe, but most of that would be offset by the losses while the DeVegas are being altered."

"Doc, would it help to run the beams faster?" Rossetti asked. "If the time interval between ionization and contact was smaller, the atoms wouldn't be deflected as far."

Carter looked at Mahler and raised his eyebrows. "Possible?"

"Sorry. These DeVegas were specially designed to deliver high-particle currents, and for technical reasons we can't boost the velocities any higher than they are now."There was a moment of silence. Then Kapoor's soft voice broke into the others' thoughts. "Dr. Carter, are you going to switch back to a neutron beam?"

"Why? The iron atoms aren't doing any worse than the neutrons are and we'd just lose ten more minutes of beam during switchover."

"It seemed to me, sir, that if the black hole is absorbing one or two electrons from even those atoms which are deflected-"

Kapoor never got to finish his sentence. "My G.o.d!" Rurik exploded. "He's right, Ray. We've got to change that beam, fast."

"Right." Carter had caught Kapoor's drift at the same time Rurik had, and his heart was pounding violently in his ears. "Felix, get your men on that beam, now."

Mahler was already talking urgently into his intercom.

"I don't understand, Dr. Carter," Senator Chou murmured from his left.

Carter turned to face him. "The only thing that keeps Firefly in place is the electric field from the main plates, and for that to work Firefly has to have a heavy positive charge. Each extra electron that goes in cancels one of those charges. If the charge goes down to zero, we'll have no way of holding Firefly in the neutron beams."

"You couldn't recapture it?"

"Not in time. Possibly not at all."

Mahler looked up. "Okay, Ray, Beta's down again. Santos and Trumbell will have it running with neutrons in a few minutes."

"And I've just talked to the control room," Rossetti added. "Firefly's still holding positive charge, well within safety limits."

Rurik leaned back in his chair. "We were lucky," he muttered to no one in particular.

"Yes," Carter agreed. He took a deep breath and let it out slowly before continuing. "Gentlemen, we still have a crisis on our hands. We have got to find a way to get more ma.s.s into Firefly. Suggestions?"

There was a long silence. "I don't suppose it would help to enclose Firefly in degenerate matter of some kind," Rossetti said hesitantly.

Rurik shook his head. "We'd need better than neutron star density to make any headway-and even if we could make material like that we'd never get it near Firefly. The thing's just too hot."

Mahler looked up from a tablet he'd been writing on. "Whatever we're going to do, we have to do it fast," he announced quietly. "At the current rate of temperature increase, Firefly's radiation pressure will soon match the driving force behind the neutron beams. When that happens the DeVegas are, for all practical purposes, useless."

Carter had to force the words out. "How long?"