Pierre was puzzled. "I don't see how you can do that. Even if you could shrink it so the surface density equals that of a neutron star, the equation of state is unstable and it will collapse into a miniature black hole."

"We are aware of that," said Plasma-Sheath. "By injecting only one type of monopole into the deorbiter ma.s.s, we can increase the center density by the formation of monopolium, but the monopolium atoms will have a tendency to repel each other since they will have the same magnetic charge. It is hoped that in this way we can keep the shrinking of the deorbiter under control and keep it from collapsing into a black hole."

"Sounds risky to me," said Pierre. "Are you sure of your calculations?"

"No," replied Plasma-Sheath. "But it is a risk that we must take."

Suddenly another cheela appeared on the screen. Pierre recognized the two-star cl.u.s.ters on the hide of Admiral Steel-Slicer, leader of the s.p.a.ce cheela.

"That is not what concerns us," he said. "We not only want to use the deorbiter ma.s.s as a base to build our gravity catapult, but to deliver the catapult to the surface of Egg. We will have to divert it from its normal orbit."

"That's all right," said Pierre. "All we need is its gavitational field, and it makes no difference if it is a degenerate asteroid, a miniature neutron star, or a black hole. The external gravity field is the same. Just make sure you put it back in its elliptical orbit when you are through so we can use it to get back up to St. George. You aren't going to be using it for too long, are you? We only have supplies for a few weeks since this mission was designed for eight days."

"That is the problem." Steel-Slicer was now alone on the screen. "It is possible that the compensator ma.s.s will be destroyed in the process of placing the gravity catapult on Egg."

Pierre paused for a few seconds in shock, then quickly realized that he was wasting the equivalent of weeks of time of the cheela whose blinking image indicated he was checking in at the console every fifth of a second.

"Without the deorbiter ma.s.s, we would be stuck here.... What are the odds?"

"We are constantly trying to find another way of doing it," Steel-Slicer replied, "but right now the odds are 12 to 1."

"Well," said Pierre. "That's not bad."

"There is an 11 in 12 chance that the deorbiter ma.s.s will be tidally disintegrated while delivering the gravity catapult to the surface of Egg and only a one-twelfth chance it will survive. It all depends upon how the orbital and tidal dynamics couple into the interior vibrational modes of the deorbiter ma.s.s during the actual transit."

Pierre paused a few seconds again, but this time his brain was not worrying about the cheela.

"There is Oscar, the other large asteroid ma.s.s that was used to put the deorbiter ma.s.s into its elliptical orbit. Couldn't you use that?"

"With our limited resources, we do not have the power to alter the celestial laws for large, low-density ma.s.ses," said Steel-Slicer. "That asteroid is well on its way out of the Dragon's Egg system. The best we could do is bring it back in about six months. That is equivalent to eternity for us."

"Hmmm." Pierre considered the options, then said, "I think I'd better talk with Commander Swenson and the rest of the crew."

They gathered in the viewport lounge to discuss the question. Doctor Wong blackened the viewport in the floor as they entered. No one objected. It would be hard enough to make a decision without having the bright yellow image of Sol flickering through the port.

"Commander Swenson says the decision is up to us," Pierre replied. "Her only conditions were that there be a secret ballot and that the decision to let the cheela use Otis be unanimous."

"It would be a lot easier to say 'Yes' if the chances were better," Jean said. "Eight percent is not very good odds."

"Eight and a third percent," corrected Seiko. "We must also remember the number of intelligent beings involved. By putting our five lives at risk, we prevent the demise of an entire intelligent civilization."

"I just don't like the way we have to go," said Abdul. "Starving to death is not my idea of fun. I'd rather go quickly."

Cesar spoke up. "I would like to remind everyone that just over three hours ago, all of us would have experienced a quick death if it had not been for the efforts of the two cheela, Admiral Steel-Slicer and Engineer Cliff-Web, who now ask for our help."

Pierre waited for more discussion. There was none, so he pa.s.sed out blank sheets of paper.

"Write 'Yes' if you agree to let the cheela use Otis, and 'No' if you think the risk is too high." Then Pierre collected the ballots and went through them quickly.

"There are four 'Yes' votes and one 'No.' I will inform Admiral Steel-Slicer that they will have to find another way of getting down to Egg. Then I will program the herder rockets to change Otis's...o...b..t so we can go home."

"Just a minute," Abdul spoke up. "I change my mind. Switch my vote to a 'Yes.' It wasn't the fault of the cheela that Amalita was taken away and it's stupid to be mad at a neutron star. It doesn't care."

10:25:02 GMT TUESDAY 21 JUNE2050.

Steel-Slicer and a newly rejuvenated Cliff-Web watched from a scout ship as the cargo ship brought the first batch of north monopoles from the distant monopole factory and dumped them into the human deorbiter ma.s.s. The monopoles scattered into a diffuse cloud from their mutual repulsion as they were released from the hold of the cargo ship. The cloud was sucked up by the gravity field from the deorbiter ma.s.s and disap- peared beneath the fuzzy surface of the kilometer-sized ball. Later they would have to shoot the monopoles into the magnetized ball with an electromagnetic accelerator.

"One," said Cliff-Web. "And an infinity more to go." He sucked on a chewy red ball from one of the new food machines.

"It's going to be a long, dull job," Steel-Slicer said. "Forty generations of ferrying monopoles over the same dull stretch of s.p.a.ce between the factory and the deorbiter ma.s.s. The situation is ripe for boredom, mistakes, and even mutiny. I want plenty of history in the creche-cla.s.ses, lots of time off from the ferrying job at entertainment centers, and the best and newest of the food machineson the ferry ships."

They watched the second ship dump its cargo of north monopoles.

"Let's go over to the refurbishment facilities at West Pole s.p.a.ce Station," said Cliff-Web. "I want to see how they are coming on the conversion of the Abdul from an exploration ship to a cargo ship."

20:55:45 GMT TUESDAY 21 JUNE2050.

It was many greats later when Steel-Slicer and Cliff-Web visited Otis again. Having recently undergone his 34th rejuvenation, Steel-Slicer was now young looking, while Cliff-Web and the scoutship were old and tired. The black hole at the center of the scout ship was now noticeably less ma.s.sive, as its rest ma.s.s had been used up to operate the inertial drives for the past 1300 greats. They watched as a cargo ship unloaded the last of the north monopoles in the holding tank of a long electromagnetic gun. A stream of high-speed monopoles shot from the tube and penetrated deep into the now solid crust of the deorbiter ma.s.s. In the center, the monopoles were held by the strong gravity forces of the ten-meter-diameter ball despite the magnetic repulsion from the rest of the monopoles in the ultra-dense core.

As the last of the stream spluttered out, a continuous combination of'trumming and dancing for joy rose throughout the communications links. It grew in volume as the image of the last of the monopole stream spread through the s.p.a.ce around Egg at a slow crawl of the speed of light.

"We're done!" Cliff-Web's aged tread was trying to keep up with the victory'trumming of his engineers.

"That's one giant ripple for cheela-kind," said Steel-Slicer calmly, knowing that they still had much to do.

"We'll let it cool down for eight to twelve greats, then we can take the next tread-ripple on our long journey home."

"My new cla.s.s of gravitational engineers will be ready. Will you have a good gravity-well pilot to take us down?" Cliff-Web asked. "Even though the surface gravity and escape velocity of Otis are only a small fraction of that of Egg, it will be a tricky landing for someone used to flying around in s.p.a.ce."

"My next cla.s.s of pilots are already training on the ring ma.s.ses around the human s.p.a.cecraft Dragon Slayer," said Steel-Slicer. "In about two greats they will transition to simulated landings 50 meters up from Otis. You'll get the best one from that group, and he or she will be allowed to choose a new name.

Everyone in the cla.s.s agrees that the name they want is 'Otis-Elevator.' "

Landing

21:00:10 GMT TUESDAY 21 JUNE2050.

"Everyone out of the southern hemisphere," Captain Otis-Elevator said into his tread amplifier. The command rippled out from the control deck at the "north pole" of the large cargo hauler and echoed back and forth through the hull underneath the deserted cargo holds on the bottom of the spherical ship. The warning was unnecessary. They were rapidly approaching the surface of Otis, and from the southern hemisphere it looked as if the planetoid were falling directly down upon them.

The inertia drive humming vigorously, the mighty cargo ship approached the planetoid. Otis-Elevator hovered at a point fifty meters from Otis while they watched the asteroid slowly turn. The attraction from Otis was now stronger than the attraction from the black hole in the middle of the cargo ship.

"Feels good being under a little gravity once again," said Cliff-Web.

"I wouldn't know; I've always lived in s.p.a.ce." Otis-Elevator slowly descended in a vertical trajectory. As they drew closer, the gravity became stronger and began to approach the gravity on Egg. Choruses of groans could be heard through the deck.

"I can't hold my eyes up," said Otis-Elevator.

Cliff-Web looked at the pilot, who was struggling to keep his eyes elevated in the strong gravity field.

The eye-stubs were thin, and wavered as they attempted to balance the heavy eyeball on top of them.

Cliff-Web's eye-stubs had automat- ically thickened into the proper exponential shape. They ached slightly from generations of little use, but at least the automatic balance reflexes kept the eyes steady.

"I didn't realize that you might not be able to function in high gravity," said Cliff-Web. "Shall I take over the controls?"

"No, I can handle it, but I'm going to have to switch to tread-screen control." He pulled his eyes in under his eyeflaps and concentrated on the taste image on the deck beneath his tread.

They dropped quickly down the last few meters, then, very slowly, Otis-Elevator put the cargo ship down on the crust. The hemispherical top flattened noticeably as Otis pulled hard at the black hole at the center of the cargo ship. Squeals and pops could be heard through the deck plates. The stabilizing fields that held the black hole at the center of the s.p.a.cecraft finally reached their limit and the black hole fell through the bottom of the hull into the center of Otis where it evaporated. The hull rebounded a little, then stabilized.

Cliff-Web had thought they could begin work as soon as they landed, but it took a dozen turns and a lot of food to build up the s.p.a.ce-bred cheela to the point where they could function in the strong gravity field. Cliff-Web had returned to normal rapidly and had taken a prospecting trip out on the ten-meter ball while the others were building up their strength.

"The portable a.n.a.lyzer says that the crust has a high percentage of high-strength metals," he said upon returning. "The volcanic regions where we inserted the monopoles have ejecta containing some of the rarer neutron-rich isotopes that we might need for alloying, but other than that, the composition of the crust is pretty much the same everywhere. Let's set up the power generators and start the ma.s.s separators and foundries going."

Within half a great, the ma.s.s separators were pouring out powdered raw materials that were turned into working stock by the foundries. The first structure they constructed was a simple s.p.a.ce fountain. It only had one stream of rings and only went up 50 meters to a crude top platform, but it sufficed as a landing dock for other s.p.a.cecraft in the fleet. Soon, most of the s.p.a.ce cheela were on Otis, working to make the gravity ma- chines that would enable them to return from their enforced exile from Egg.

Their next task was the construction of a large gravity catapult capable of accelerating the lander at many times Egg gravity so it would reach the escape velocity of Egg after less than 10 centimeters of travel.

Unlike the ancient gravity catapults now lying dormant on Egg, which had only to toss small s.p.a.cecraft into the sky, this gravity catapult had to be big enough to toss a miniature copy of itself to those speeds. It took nearly four greats of turns to fabricate the twenty-centimeter ring with its meters and meters of high-strength tubing full of ultra-dense liquid and the battery of pumps to accelerate the fluid to high velocities rapidly. The uniformity of the resulting gravitational repeller field was important.

"Run it up again," Cliff-Web ordered. He was monitoring the display of the array of gravity sensors spread across the center of the gravity catapult ring. The ring was large in diameter, but small in thickness. Cliff-Web had pushed every rule of gravitational engineering to make it. It only had to work once, but if it worked, it was worth it. The tests they were doing now were at fractions of its operational power levels. That would do-until the final blink when full power was applied. The machine hummed, and the sensors displayed a contour map of gravitational force levels.

"There is only a difference of a billion gravities across the central centimeter portion," Engineer Push-Pull announced. "Surely the lander can handle that."

Cliff-Web looked carefully at the contours, made minor adjustments to some trim loops and closed down the display.

"The launch ring is ready. Next is the lander," he said. "We have pa.s.sed apoapsis, so we have only four greats of turns to build it."

"It will be ready long before that," said Push-Pull.

"I'm sure," said Cliff-Web. "But there is someone else we must consult with before it is properly delivered." He reset his tread screen, treaded a brief formal message, then left without waiting for a reply.

The reply would come later, much later.

21:02:03 GMT TUESDAY 21 JUNE2050.

The call that Pierre had been dreading came. "Request asteroid O-l be reprogrammed to arrive at s.p.a.ce- time point given by following coordinates," said the image of Cliff-Web. There followed anx,y,z,q,f,l ,t listing of coordinates in the Dragon's Egg s.p.a.ce-time system. The requested orbit went far down in the gravity well of Egg so that the ten percent time rate and frame drag difference between deep s.p.a.ce and the surface of the neutron star was significant.

Cliff-Web was not used to talking to humans. He forgot to always a.s.sume the same position each time he checked in at the screen for a reply, so his image flickered every fifth of a second.

Pierre hesitated. The image flickered.

The real decision had been made long ago. Pierre touched the screen in front of him, and the coordinates were transferred to the herder rockets that kept Otis on its desired path. Pierre then pushed theexecute square on his touch screen. The engines on the herder rockets flared. Within seconds Otis was on a new trajectory that would take it within a few meters of the surface of Dragon's Egg.

21:02:20 GMT TU6SDAY 21 JUNE2050.

Push-Pull looked up from his testing apparatus to stare out at the herder rockets that swarmed around Otis. "There seems to be some activity in the large human s.p.a.cecraft surrounding us."

"I noticed," said Cliff-Web. "What is the status of the high flow-rate tubes?"

"They pa.s.sed flow tests at twice design pressures, and failed just above that," said Push-Pull.

"Good, but too good. Reduce their thickness by a half-dozeth and test them again. I want this machine light enough to jump itself 40 meters off Egg."

The construction of the four-centimeter-diameter self-levitating gravity lander took significantly less time than the larger machine. They were finished with nearly a great of turns left before Otis reached periapsis.

Steel-Slicer came to see the completed lander. It was a torus sitting inside a larger torus.

"What's its name?" Steel-Slicer asked.

"It's just the lander," Cliff-Web replied with obvious annoy- ance. "It doesn't have a name except Egg Surface Descent Craft, if you want to be formal."

"All ships have to have a name," said Steel-Slicer. "Since it flies above the surface of Egg it should have the name of some flying animal."

"Thereare no flying animals on Egg." Cliff-Web was even more annoyed.

"There are flying animals on the human planet Earth," Push-Pull interjected. "One of them is the eagle."

"Eagle it shall be." Steel-Slicer declared.

"If you say so," said Cliff-Web.

"Is there anything else we should do?"

"I would do some thinking," said Cliff-Web. "Once we have landed on Egg, there is no way to get off again until we have rebuilt civilization. We are ma.s.s limited and must only take the things we will need. If we forget to take something, there is no going back. Tell me. What is the minimum list of skilled technologists and equipment you need to rebuild a civilization?"