"Pizza." Dan declared, as if that somehow followed from Garvin's question. "When I get back home, it's pizza. And not just any pizza, Chicago pizza."
"Yeah," said Garvin, "there's a pretty good pizzeria where I..."
"No, No." Dan interrupted. "There's pizza, which is ok, but then there's Chicago pizza. They're completely different. A slice of stuffed spinach, and a slice with sausage, onion, and mushroom. Heaven!"
"All right - knock it off. You're just driving yourselves crazy." Nancy felt a little dizzy as she ate her morning bar. It felt like the blood was being sucked out of her brain, and she voiced her concerns. "Listen, I'm a little worried about the high gravity. We shouldn't stay here more than a week, two at the most, so we need to be productive. At the same time, we can't work as many hours as we did yesterday. That's too much. I suggest we work, physically, for a couple hours in the morning, rest for an hour, eat lunch, and work a couple more hours in the afternoon. The rest of the day will have to be spent sitting or lying down."
"How do you think the Arcots did it, month after month?" Garvin asked.
"The gravity is a bit higher on Arcot," Dan began, "and they're shorter, and their physiology is a bit different. For one thing, their heart is higher up in their chest, just below the neck. Getting blood up to the brain isn't such a big deal."
"What's on the agenda today?" asked Garvin.
"There's a couple more rooms down the hall, and I'm sure there's a way out of these living quarters and into the rest of the probe. We're just going to explore, and see what we can find. Dan, will you wear the cam today? The elastic band is killing my head."
"Sure." He strapped it on, and the camera, in the middle of his forehead, reminded Nancy of the Arcot's third eye. She looked away out of reflex, then shook it off.
They walked to the end of the now familiar hall, past the laundry room and past the kitchen, and opened a door onto a huge room, as large as the living quarters they left behind. Most of the room was filled with a glass tank, from floor to ceiling, enclosing a volume comparable to an olympic swimming pool. The tank was virtually empty, except for an inch of clear liquid at the bottom. Garvin approached the glass and tapped gently. He looked straight ahead, from one side of the tank to the other, then he looked at an angle, trying to get some information from the refracted image. Much of this took place at a subconscious level. He didn't even realize he was turning his head this way and that. Finally his brain teased out the configuration that would be confirmed later by his instruments.
"Nancy, there are two walls, an outer wall and an inner wall. The outer wall," he tapped again, "isn't nearly thick enough to hold the pressure of all that liquid, when the tank is full; but the inner wall is. If you've ever been to Sea World, you've seen those glass walls that stand up to tons of water, separating you from the fish. Those walls are at least two inches thick. The inner wall is at least that thick, and I assume this tank was full when the probe left Arcot."
"Why two walls?" asked Nancy.
"The obvious reason is to keep air away from the inner wall. But why would they want to do that?" Garvin was thinking out loud. He looked at the liquid in the bottom of the tank and noticed that it rested on a glass floor floating just above the floor of the room. "Captain, it's a giant dewar."
"Dewar?"
"Invented by Sir James Dewar in the 19th century. It's a double pane thermos for holding ultra cold liquids. Usually the glass walls are separated by a vacuum, so heat cannot enter the system and boil the contents away. I think that's a cryogenic liquid in there." He pointed to the bottom of the tank. "It would probably boil away with the heat of your hand, giving you frostbite in the process."
"All right, the vacuum prevents conduction, but what about radiation? Why doesn't my body heat enter the system and boil the liquid away? It would be like one of us standing next to an oven."
"I'm sure some of the ambient heat flows through the glass walls and into the tank. Every cryogenic system, no matter how well insulated, requires active cooling. There's a refrigerator around here somewhere. also, the glass may be designed to transmit visible light and block infrared. That would help."
"Can you determine the composition of that liquid?"
"Yes, but I'll need your help. I need a continuous white spectrum, and those fluorescent lights won't cut it." He handed Nancy a flashlight with a narrow beam. "Walk around to the far side of the tank and shine this beam towards me. I'll analyze it with the high precision spectrometer."
It took a couple minutes for Nancy to circumnavigate the large tank. Finally she stood directly opposite him, almost 100 feet away. Dan stood to the side, his head-cam relaying the images back to Earth. Instead of trying to project his voice all the way around the tank, Garvin opted for the communicator on his wrist.
"Ok Nancy, point the beam straight at me." The narrow beam passed through four layers of glass, and a thin vapor of the unidentified liquid inside, losing key frequencies along the way. Garvin pointed the parabolic end of his spectrometer at Nancy, hoping to capture the beam, while excluding the fluorescent light that was bouncing all over the room. He turned the unit this way and that, trying to get a good lock.
"I can kill the lights if that would help." Dan offered, pointing to the panel on the wall.
"No," said Dan, "I got it." He got down on the floor and spoke into his communicator. "Ok Nancy, try to send the beam straight through the liquid on the bottom. See if you can pass through the liquid, and not the glass floor below. Straight across to me." Fortunately Nancy was a trained sharpshooter, and her aim was true. Garvin had two measurements, one through liquid and one through a near vacuum. Both passed through four glass walls, so that factor would subtract away. What remained was the liquid itself. He almost recognized the pattern by eye, but he compared it to the library, just to make sure. "It's liquid nitrogen, ultra pure. I'm missing some of the wave lengths that were taken out by the glass, but I can tell it's liquid nitrogen. And based on the spread of the wave lengths absorbed, I'd say it's about 60 degrees above absolute zero. That's almost 20 degrees below the boiling point - a safe operating temperature."
Nancy was surprised. "That's not a fuel, or an oxidizer. I expected liquid oxygen, or a light hydrocarbon, or liquid hydrogen. That has been the mainstay since the earliest rockets."
"Right. That's what I expected too. But for some reason the Arcots are carrying tons and tons and tons of liquid nitrogen."
"Garvin, didn't you say the air around us is 85% nitrogen?" Dan asked.
"What was that?" Nancy couldn't make out the question around the corner.
"Dan asked if the air around us isn't mostly nitrogen. It is, and the Arcots could turn it into a liquid any time they wanted. So Dan is right; there's no need for a giant tank filled with liquid nitrogen."
"Unless..." Nancy's voice trailed off.
"Unless what?"
"Hold on, I'll come back around. These communicators are pretty good, but I'd rather talk in person." Nancy walked around the left side of the tank and joined her companions.
"All right, you're on to something."
"It's liquid antinitrogen. And the inner wall is antiglass. Everything on the inside of that vacuum," she pointed to the gap between the two glass walls, "is antimatter."
"Of course. This supplies all the energy for the probe. The antinitrogen in the tank combines with the nitrogen in the air to make pure energy."
"The antimatter could combine with any form of matter, could it not?" asked Dan.
"Sure, but nitrogen is optimal. If you merge an atom of antinitrogen with an atom of oxygen, for example, you have a proton, a neutron, and an electron left over. And with all that energy, the extra subatomic particles are probably racing off at high speed. Thus, intense radiation, that will be hard to contain. You really don't want leftovers. Somewhere in this room, or in an adjacent room, there has to be a cryogenic separator that pulls pure nitrogen out of the air. This mixes with the antinitrogen in the tank to create pure energy. If you like, you can think of the antinitrogen in the tank as fuel, and the nitrogen in the air as oxidizer." He chuckled at the thought. Nitrogen, an extremely inert gas, is playing the roll usually reserved for oxygen in the galaxy's most energetic chemical reaction.
"Garvin," Nancy mused, "what would happen if I pulled out my gun and shot through this glass wall?"
"The outer wall would shatter, but the inner wall would hold. That would delay your death by a quarter second or so. The air would rush in to the gap, and as soon as the air touches the antimatter in the inner glass wall, that is, the antiwall, the resulting explosion would make our atomic weapons look pretty tame. So I suggest you don't do it."
"Ok," Nancy smiled, "I won't. But Garvin, what keeps the inner wall away from the outer wall? You can't suspend that much weight with magnets."
"No - and these materials aren't magnetic in any case." He got down on the floor and looked between the two layers. "Most of the support has to be at the bottom, to hold the weight of a full tank." He used a laser site to measure imperfections in the antifloor. After thousands of years, the glass, albeit thick, would have bent slightly in response to the forces acting on it. "There are supports between the floor and the antifloor, forming a grid, with a spacing of about eight feet." He moved a little to his right. "I'm looking at one of the supports right now. The upper floor warps downward slightly, in all directions, from this point. But I can't see a thing. The support, whatever it is, is completely invisible."
Dan was confused, and rightly so. "A physical support couldn't be made of matter, or antimatter, or it would react to one of the two floors. What's left?"
Garvin sat up and straightened his back. "I don't know. Dark matter perhaps. It would be invisible to us. Maybe they know how to manipulate small amounts of dark matter. I'm sorry, I really don't know. It's beyond anything we understand."
"Well, they're still constrained by the laws of physics."
"Yes they are. I guess we can take some solace in that. And if you think about it, the laws of physics that you already know force a design much like this if you want to send a probe across the galaxy in a relatively short time. You have to use antimatter; nothing else will do." Garvin made some quick estimates in his head. "Captain, I wonder if there are other tanks like this one. I mean, it takes a lot of energy to accelerate this much mass to 80% of c. One tank may not be enough."
"I agree," said Nancy, "but for a different reason. I don't believe in luck. We chose one hatch out of four, at random, and we happened to stumble upon the one and only fuel tank? I don't think so. I think each hatch opens on an identical complex, complete with living quarters, a fuel tank, and a generator, which powers a master grid. And there may be other generators as well." She paused for a moment and returned to an earlier topic. "When I asked you about shooting the glass wall, I wasn't engaged in a suicidal fantasy. Suppose we find all of these power stations, and attach conventional explosives to each one. We set the explosives to go off in three days, at precisely the same time. Then we get the hell out of here. The probe literally blows itself up."
"For starters, you only need to blow this tank. The explosion will definitely blow all the others, wherever they are in the probe. But that won't help. It would have helped a year ago, when the probe was moving into position. But it's coasting now. We could shut down everything, by turning off the power or by vaporizing the entire superstructure, and the neutron star at the center will still slam into Earth in two and a half years. The rock is already thrown, already on course, and that's the problem. That's why NASA wants us to take over this ship and put it on a new heading. I think we better keep everything intact."
"Right. Let's see if we can find the actual generator." Instead of taking the short way around, as Nancy had done earlier, they took the long way around, walking the length of the tank towards the far end. As she slowly traversed the distance, almost 200 feet, Nancy tried to comprehend the scope of the Arcots' technology. So far, the combined efforts of the most powerful labs on Earth had produced a thimble of antihydrogen; yet the Arcots could produce antinitrogen, and probably other anticompounds, at will, and in bulk. Furthermore, these substances could then be utilized as a practical, portable energy source. She could only look at the tank and marvel.
As they rounded the corner they discovered three large machines, interconnected by pipes, cables, and wires. The first was a tall white cylinder, looking something like a hot water heater. It had fans near the floor and ceiling, and a thin insulated pipe leading to the next machine in the sequence. "I think this is the nitrogen separator." Garvin surmised. "Air is drawn in here, at the bottom. Somehow the nitrogen is extracted. We would use cryogenics, but they may have a better system. In any case, the oxygen and trace gases are vented out the top, and the liquid nitrogen flows through this thin, insulated pipe into the next machine."
"And that machine would be?" asked Nancy, with a pretty good idea of the answer.
"I assume it's the generator." They followed the pipe to a large black sphere, almost nine feet across. At the top of the sphere the metal fanned out once again, looking a bit like a hyperboloid. It spread out to a larger radius than the sphere below, then blended into the ceiling. Dan started to walk around the generator, as he had done with the nitrogen separator, sharing his vision with the folks back on Earth. He was about to pass between the generator and the antimatter tank when Garvin stopped him.
"Wait! If that's what I think it is, and if you step on it, and if you break it, the game is over." He was pointing to a thin glass tube that ran along the floor from the tank to the base of the generator. Dan got down on the floor so that he, and NASA, could see it. It was a double glass tube, with an outer wall and an inner wall. The inner wall held a clear liquid, which flowed, imperceptably, from the tank to the generator. "It's the fuel line." Dan summarized. "And no, I wouldn't want to break it. That would definitely put a damper on our day. Thank you."
"You'd think the all-knowing Arcots would run their fuel lines under the floor." muttered Nancy. "Talk about a hypergolic situation. Better watch your feet from now on."
"Somewhere in this generator," Garvin pointed to the black sphere, "nitrogen meets antinitrogen in a perfect annihilation, and the resulting energy is converted into electricity."
"But the conversion isn't perfect." remarked Nancy as she looked towards the ceiling. "All that metal carries waste heat away, probably up to the shell. We saw how it conducts heat; it's the perfect heat sink and radiator."
"Yes, that makes sense." Garvin touched the metal gingerly, then placed his hand on the smooth surface. "When the engines are running, calling for terawatts of power, I'll bet this thing gets red hot." He turned towards the giant antimatter tank behind him. "Look at the silver coating that covers this part of the glass. It reflects the radiant heat and protects the ultra cold liquid inside."
"And that last device?" Nancy inquired. It looked like a metal gray box, about chest high. A cable ran into it from the generator, and a dozen cables went out the other side and into the wall and floor.
"I'd say it was a power conditioning unit. It cranks out 181 volts for residential areas, and higher voltages for the long distance grid." He made a few measurements in and around the device, and then stepped back. "The electric fields are over 1,000 volts per meter in some places. Best to stay away from this thing."
"Yes," agreed Nancy, "but we may not have that luxury." She spoke into her communicator. "Houston, you've seen the images, and you've heard our conversations. If we wanted to shut the power off, completely, without triggering an antimatter explosion, how would we do it? I'm not saying we're going to, I don't even know why we'd want to, but I've always found that power is everything; so we may want to control it, or shut it down." She turned back to Dan. "Get some close images of all this equipment, and then let's get out of here. I'm getting dizzy, and hungry."
Dan took a close look at everything for the benefit of NASA, whereupon they returned to their bedroom, ate a couple of bars, and gratefully assumed a prone position. Nancy retrieved the air mattress from the supply room, inflated it with the touch of a button, gathered a couple of pillows from the adjacent bedrooms, and created a makeshift bed on the floor between Dan and Garvin. She didn't want to be alone right now, and if her companions didn't mind, she might not want to be alone tonight either. Too many dreams. Besides, she finally had a bed that was long enough to accommodate her head and feet simultaneously.
"Gentlemen, we have another message from Houston." Dan started to sit up. "No no, lay back down. I'll turn it up. If there's anything on the screen you need to see, I'll poke you. I think you know what Julie looks like by now, so just relax and give your backs a rest." She slid the volume up to 6 and pressed play.
"Hey hey!" Julie began. "Looks like you made it into the probe. just press a button and walk right in." Julie was smiling again, and her green eyes sparkled, as though there was hope for her planet after all. "We appreciate the continuous feed from the head-cam. Makes us feel like we're right there with you. I can see you moving your supplies into the entryway right now. It reminds me of squirrels stashing nuts for the winter. Nobody knows what you're going to find when you venture inside, but you're the best team Earth has to offer. We have every confidence in you. Well - that's all we have for now. Once again, congratulations on an easy entry. Take care. Over and out."
"Nans, can you pull up some music from the ship's library through that communicator? This place is as silent as a tomb, and it gives me the creeps."
"Please." seconded Dan. "And believe me, you don't want to hear Arcotian music, although I could probably call some up through this panel on the wall."
"That won't be necessary." chuckled Nancy. She stepped through several menus as though she were back in the lounge on her ship, in front of the big screen. "What'll it be?"
"Why don't you call up Mozart's piano concertos." suggested Garvin. "Start with number 15 and just let them play through."
"Fair enough." 17 was Nancy's favorite, but it would come around soon enough. By that time, however, she was fast asleep, along with her crewmates. They had planned to rest for an hour, but their diurnal cycle was gradually being reprogrammed by the higher gravity. One could only work for a few hours at a time. Then, since you had to rest anyways, you may as well sleep. Their "day" would shrink to 16 hours, 10 working and 6 sleeping.
Nancy woke up once during their abbreviated night. She went to the bathroom, and collected a couple more pillows from down the hall. The air mattress wasn't as comfortable as the bed, but she liked having a place for her feet. She wondered if she could put two beds together, end to end, but the bedrooms were too small. She would have to sleep out in the hall, with the lights overhead, and that was not at all appealing. So she arranged her mattress and pillows, and went back to sleep, without disturbing either of her roommates.