Dolf shook his head. "We don't know that. That idea was based strictly on the albedo. Density studies have pretty much debunked that theory. No, I think our best bet is an S-type. Eros has been extensively studied; we'd have a pretty good idea what we're getting."
Abruptly, David smiled. "And we wouldn't have to go as far for it."
Dolf nodded. "That's another factor. There's also the fact that we know it's solid, not just a rockpile held together by a weak gravity."
David slammed his hand on the table, which lifted him several feet into the air. "Okay," he said. "Eros it is. Lets' do it!"
Before David had even drifted within reach of the floor, Dolf was computing orbital changes and delta-Vee requirements
Due to Dolf's careful selection, they would not have to spend extra months in the asteroid belt searching for a prospect. 433 Eros is a near-Earth asteroid, and its orbit does not take it deep into the asteroid belt. Interestingly, Eros had just passed its apahelion, and was already beginning its long orbit inward. They would actually have to chase and catch it.
Dolf computed the delta-vee required to put Carter IV into the proper orbit for interception, and submitted his data to Alcântara for verification. The lightspeed lag was very apparent now, and two-way conversations now required patience.
As their distance from Earth had increased, their communications ability had suffered. First, radio waves travel at the speed of light, and the farther they got from Earth, the more the "lag" between the transmission and receipt of a message. This meant that Frank would say something. His message would take several minutes to reach Man's Hope. By that time, Dolf might have replied to a totally different message, or Frank may have thought of something to add to his original message. Then Dolf would respond to Frank's message. But Frank would have received another message in the interim, and might try to respond to that. The result, of course, was confusion.
A second problem was that as their distance increased; broadcasting to Earth required more and more power. Ron had cobbled together a huge amplifier, but it required much of the capacity of their reactor, and Frank still had to put a signal amplifier into orbit to boost the signal enough for Dolf to reach his audience.
A much more serious problem was the Sun. The Sun is a giant radio transmitter. Man's Hope's antenna was tuned to Earth, of course, and that meant it was pointed directly at the Sun. The solar static had once again increased relative to the power of man's puny transmitters. As they approached the asteroid belt, it was quite difficult to pick the programming out of the pervasive static.
But dolf seemed to have infinite patience. He transmitted and retransmitted his data until he received a faint acknowledgment from Alcântara.
Finally, Alcântara Control agreed with Dolf's figures, and David began triggering the rockets to modify the comet's orbit as necessary.
Though they were calling it such, a comet is not a space ship. It was several hours before their modifications to the comet's orbit became apparent, and three weeks before Dolf could confirm that they were on course to intercept 433 Eros in about a month.
There was much discussion about whether they should free Man's Hope and even the core stage, for safety reasons.
"If something happens, if one of the rocket engines fails, we could end up slamming into Eros much too hard," Yuri said. "If both our ship and the core stage with our long-range engines are buried in the ice, they could be damaged or destroyed. We should dig them out and lift off the comet before the impact."
"But we have stuff spread all over around here," Raoul protested. "We'd have to gather it all up, and move back aboard. That could take a couple of weeks!"
Ron grinned. "You need the exercise anyway, Raoul. Yuri is right. We are in no position to take any chance, when any chance is a life and death chance."
In the end, even Raoul saw the necessity of evacuating their caves and returning to Man's Hope for the interception. The huge, clumsy comet was difficult to maneuver, and there was a good chance that it would actually hit the asteroid, instead of creeping up alongside it as they hoped. The only safe place for the crew would be observing from Man's Hope, preferably with the core stage drifting alongside them.
Dolf had even computed their orbit in such a way that they would approach it from behind, at an angle. If the comet did slam into the asteroid, they could at least hope the impact would actually help knock Eros toward the orbit they wanted it to assume.
In the event, Yuri was piloting Man's Hope, while David remotely controlled the rocket engines mounted on the comet.
433 Eros looked like a huge bean, rotating and spinning rapidly. They spent several days creeping up on it at a relative speed of a few feet per hour, and then a few inches per hour. They had millions of tons of inertia to deal with, in the asteroid as well as the comet.
Due to the irregular shapes of both "vessels," they actually did bump. The comet was rebounded at several feet per second, and Eros' rotation actually slowed slightly. David adjusted the comet's course with the rockets, and soon the two celestial bodies were traveling side by side less than ten meters apart. "Keep an eye on them," Dolf told Yuri. "Both of them do have gravity fields. They're weak ones, of course, but over the course of several days they may be drawn together."
Yuri brought Man's Hope to orbiting Eros while they discussed how to "land" on the rapidly rotating and spinning body.
Finally, they decided to approach it from "behind" in the direction of rotation, on the side away from the comet. They would "land" on the "back side," or trailing side of one end of the asteroid. This would be tricky, due to Eros' rapid rotation and spin. Once tethered to Eros, they would begin the effort to counteract the rotation, using Man's Hope's drive engines, and perhaps two of the rockets still stored in the cargo hold.
They crept up alongside the spinning asteroid, and Yuri used the steering jets to match the asteroid's rotation. Then he very slowly moved the ship "sideways" over the asteroid, until Eros seemed stationary above them. This time David had the honor of being the first man to actually walk on an asteroid – if "walk" was the word. Eros' gravity was much too weak to permit any such movement.
Like Yuri, David solemnly claimed the asteroid in the name of Man's Hope International, and erected one of the small flags.
He tethered Man's Hope to a rocket piton, and the others filed out of the personnel lock with additional tethers. Yuri cautiously rotated the ship so that its engines would be facing forward, in the direction of rotation. The crew secured six tethers with rocket pitons specifically designed to penetrate rock. David inspected the pitons' placement, and then they all returned to the ship. David reassumed command, and slowly opened the throttles of the ship's ion engines. All the tethers tightened, but none pulled loose. David kept opening the throttles until the engines were producing maximum thrust.
It took three weeks, but finally their efforts proved successful. Eros' rotation had been cancelled, and it was "stationary" relative to the Earth, one end of the bean shape now pointing toward home.
Then the real work began. The core stage was brought in and anchored down on the side opposite the depression in the "bean." The depression was actually the site of an ancient impact crater more than five kilometers in diameter.
Then using the rockets installed on it, the comet was very slowly maneuvered into position above the crater, and carefully, slowly, winched toward the asteroid until a gentle bump told them the comet and the asteroid were joined, and were now one celestial body. Yuri spent several days freezing it into position using melt water.
With the comet in position seated in the depression, which was even larger than the comet itself, Eros' shape now resembled a lumpy sausage rather than a bean. The comet had been oriented such that the holes that had been their home and their atmosphere plant were now horizontal to the surface of the asteroid.