Nebula (15 page)

“That’s right. I did a full range of tests on that sentry. We could take it here with almost no extra work. Good idea.”

“There’s only one hitch,” Doug said. “One of the sentry’s arms and a part of its outer shell that includes the hatch to the electronics chamber were damaged in the crash, so we had to replace them with things that we made to fit. But they’re not the same type of composite, and the arm looks different, so the aliens would see that the sentry had been tampered with. We’ll need to fix that.”

“Can you make something that would look right?” Brad asked.

“Sure, we could do that, but I’m not sure how long it would take. But wait a second. Let me check something.” Doug then went to his toolbox and took out some tools that fit the fasteners that the aliens used. He then removed the sentry’s outer panel that contained the hatch and measured it carefully. Then he measured one of the arms, and he looked at some diagrams in the notebook that he had taken with him from the lab. “I have the drawings for the sentry on Earth, and the measurements look the same. We should be able to take the pieces that we need from this sentry and use them on the other one. The sizes seem the same, and they may be interchangeable parts. The joints and actuators in the arms also look identical. Maybe the electronics and computer are the only differences. I think it should work. We’ll need to remove the connector on the inside of the hatch here and replace it with the one that’s on our sentry, but that shouldn’t be a problem if Judith can make all the electrical connections.”

“That should be easy,” Judith said. “If you can get me a hatch with the right connectors on its inner surface and make sure that they plug into the robot’s ports, it should be easy.”

Brad looked very relieved. “How long will all this take?”

“I can be done in about three or four days,” Doug answered. “It just depends on how much unexpected trouble we find when we start.” The “unexpected trouble” comment wasn’t lost on any of them after what had just happened, but things were looking up.

“My work will be easier,” Judith added. “I’ll only need to check that all the electrical connections are right. A couple of hours should be sufficient. We shouldn’t encounter any more unexpected problems in my area. I’ve had enough of that already.”

Brad patted both of them on the back. “Good. Let’s get this big boy onto the ship and take him back to Earth.”

They didn’t want to activate the sentry since they couldn’t be absolutely certain of what would happen when it left Mars and arrived on Earth. Before the unexpected model differences, they would have been much less cautious since they were confident that they understood everything about the robots down to the smallest detail. They’d worked with the ones on Earth for many years and had made every sort of measurement that they could think of. They still had confidence that they could activate the sentry and the other robots, at least to move them out of the base under their own power, but now they weren’t inclined to take any more chances, even very small ones. So they moved the sentry into one of the ships like any other large piece of equipment and secured it in the cargo area with straps and clamps. They moved the other three back to where they had been in the area outside the aliens’ base.

*

The flight back to Earth was the usual quick trip with nothing out of the ordinary as far as the ship and its maneuvers were concerned. But they all felt the “eerie presence” of the alien sentry with unknown “thoughts” and behaviors standing silently in the cargo area. The fact that it was deactivated gave them confidence that it wouldn’t burst out and attack them, but it was still different from the other robots, and they didn’t really know the full extent of the difference. That made a routine trip a bit more nerve-wracking than it should have been.

They went directly to Nebula Two, where all the development and production facilities were. Harry had been there three times before, mainly to look around and meet people, but he was always impressed by how large it was compared to Prime and Ops and how large some of the work rooms were. Doug’s laboratory was in one of the smaller rooms. The larger ones were where big things like the spacecraft were built. Robots required much less space, but the fabrication machinery and test equipment were just as impressive as the ones in the bigger rooms.

When they entered Doug’s laboratory, they saw that the sentry robot had already been moved from Ops and stood near one of the work benches. Harry had never paid much attention to details of its construction, but now he could see where the outer panel and arm were different from the rest of the panels and arms on the sentry. The aliens would definitely notice that.

A few minutes later, the other sentry was brought into the room and placed near its almost-twin. Harry had an amusing image of Tweedledee and Tweedledum standing over there and grinned for the first time since they discovered the problem on Mars. But these weren’t those two bizarre characters. They were potentially deadly enemies, built by a race of aliens who were about to use machines like them in a war of extermination against the human race. The grin faded.

“Let’s get to it,” Doug said to one of his assistants as he started to undo the panel on the sentry that they just brought from Mars. “Let’s do the panels first since that may be the most difficult part. The arms are so identical that I doubt that it will take us any more than a couple of hours to make the switch. But the panels may require more work. We need to make sure that the electrical connectors mate properly with the ones in our new sentry, and that may require some fabrication. I’ll work on this one since it may be a bit different from what we’re familiar with. You take the panel and arm off the other one.”

The panels were easily removed from both sentries and they were laid out and clamped securely in a metal frame on a large work bench. Doug and his assistant then made numerous measurements with what appeared to be a laser scanner that rode over the frame. They also made manual measurements with a standard micrometer and a large precision caliper. The scanner recorded its data automatically into a computer at the side of the work bench. The manual measurements were entered by the assistant.

When he was satisfied that they had all the data they needed, Doug went over to the computer and began to sort and merge data until he had very precise comparisons of the two panels and hatches, including the locations, sizes, and shapes of the connectors on the inside surfaces of the hatches. He was so preoccupied with his work that he was completely oblivious to the rest of the team who had gathered around him and were watching over his shoulder. They had no idea what they were supposed to see in the displays that Doug created, but they stared nonetheless as if this were the most interesting thing that they’d ever seen.

“Good news,” Doug suddenly exclaimed as he jumped off his lab stool and backed away from the work bench. “The physical dimensions are identical, as I hoped. The main chore now is to modify the hatch to take the connector that our sentry needs. Then we should be able to make our sentry look as good as new from the outside. The inner surface will need to be machined a bit to handle differences in the connectors, but I can cover all of that with the composite material that we’ve been working with. Our material looks exactly like the aliens’. If they don’t do any detailed analysis, they’ll never see what we did. I should be able to complete this by tomorrow afternoon.”

“What about the arm?” Brad asked.

“My part of it will be easy. Like I said, all the physical details seem to be identical. We’ll need to do some precision measurements, but that won’t take long, and it looks like it’s just going to be a simple swap. I won’t need to do any machining or cover any changes like with the hatch. But Judith will need to look at the electrical connections and check the arm control processes, especially any of the control loop constants or any of the tactile sensor characteristics that may be different with the newer model.”

“I’ll start on that while you work on the hatch,” Judith replied.
“We can check the control processes in both of them and do a comparison. If there are any differences, Ludmila and I can work on the necessary changes. I expect that we should be able to finish in a couple of days at most, unless the models are a lot more different than they seem to be. Leave the arms in place for now so that we can exercise them and collect our data.”

Doug hadn’t thought about having to leave the arms in place for Judith and Ludmila. He’d been focused only on the mechanical issues, and now he was concerned that this could delay his work. “When will you be done with your data collection? I’d like to remove and exchange the arms since we really don’t know if I’m right about the interchangeability. I’d like to verify that as soon as possible.”

“We won’t need too long. Then you can remove the arms. It shouldn’t delay the project since we’ll still need a day or two to work on the electronics and software mods. You should be done before us.”

“OK, let’s hope that we don’t run into any more surprises.”

“Well, I guess that you know what to do and have it all planned,” Brad said as the discussion came to a close. “We’ll leave you alone for a couple of days so you can work without any interference, but let us know if you run into any problems.” With that, they decided to call it a day.

“Anyone for pizza?” Nigel asked. “I’m hungry, and I hear that the mess hall is serving its special New York style pizza today. They have that Mediterranean salad with the feta cheese, and they have the garlic bread too. I’m hungry enough to eat one of those robots.” The affirmative response was unanimous, and off they headed for the feast. “I hear that they have that great imported Belgian beer too,” Nigel concluded as they walked out and turned off the lights. It was a long day, and it had its problems, but things were looking up.

*

No plan survives contact with the enemy. That’s a basic principle of warfare. But plans often begin to unravel even before first contact on the battlefield, usually due to wrong assumptions or unknown factors. Some unknowns may be recognized as uncertainties in the assumptions and can be considered in the planning. But others may be overlooked entirely until the time comes when they arise unexpectedly. Such would be the case for Nebula as contact with the aliens drew near.

The problem began at about the time that the exploratory team that headed toward Earth sent its message telling the fleet that they were going further than originally planned so they could look more closely at an interesting star system, one that might have a suitable planet. The fleet had started to move at about 80% of the speed of light toward the next destination, allowing the returning explorers to rejoin them before accelerating to high relativistic speed. The message arrived about thirty years later, since it had to catch up with them as they moved away. Even at that speed, the distance grew rapidly.

The fleet normally would have continued to move at low speed, waiting for a second message from the team on Earth and allowing more time for the other teams to catch up. This was their usual procedure, and it was what Nebula assumed they would continue to do. But instead the aliens made an unusual decision to stop at that point and wait for the next report about the interesting star system. They sent a self-sufficient group of ten ships along the preplanned course to rendezvous with the other returning explorers and await orders to keep moving toward the next destination or to reverse course and head back toward the interesting star system. The remainder of the fleet stopped in place to wait for the message that they hoped would bring good news. That way they could travel back to their new home more quickly and begin to resettle their population after so many years as homeless nomads.

Several messages between the fleet and the exploratory team crossed in space during this time. The first reply from the fleet arrived on Earth long after the exploratory team had perished, so it was never received and there was no record of it. The second message from the exploratory team, the one that told the fleet that Earth was an ideal home world, was sent about a year before their accident, and it arrived at the fleet about fifteen years after the first one, many years after the crashes in the United States, Russia, and the United Kingdom. The fleet immediately sent a reply to the exploratory team on Earth, telling them that they would return at high speed, but since that message was never received, it was never recorded.

Nebula’s plan was flawed from the start, based on a wrong assumption of the enemy’s intended actions and the overall time-distance factors that would determine when the enemy would arrive. The planners had no idea that the arrival would be much sooner than they had expected.

Nebula also mistakenly assumed that the fleet was aware that their team on Earth was preparing material for a biological attack and that this would be the optimum approach to eliminate the human race without causing much damage to the planet and its ecosystem. A third message to the fleet was sent shortly before the crash in Roswell and contained this information, so it was only natural to assume that the fleet received it and would proceed accordingly. But since the fleet was already traveling toward Earth at very high relativistic speed when the message reached them, they were unable to receive it. Relativistic Doppler shift could be managed at lower speeds, but at 99.999% of light speed, the receivers couldn’t lock onto the signals, so they never learned of the biological weapons that were being prepared, and they had no information on the bases that were being built by the robots on Mars and Titan to support the attack. As a result, Nebula’s assumption that the aliens would know about the biological warfare preparations was no longer such a safe one.