Unlight

  “Design docs?” Larry looked down and sighed. “We don’t have any.”

  “What?”

  Larry looked troubled and guilty. “Unfortunately, I didn’t ever get to designing and installing a diesel-based backup heating system.”

  “But that’s crazy!” Jessica stared at Larry. “You never created a backup? Why the hell not?”

  Larry flinched from her accusing glance. “It was partly lack of time and partly overconfidence. I simply stocked up with fuel and figured I’d worry about it later. I’m sorry, Jessica.”

  She was immediately contrite. “Sorry, I didn’t mean to yell at you.” She hugged him, somewhat awkwardly, and held him close for a few seconds. “You did everything for us. I’ve no business finding fault.”

  “It’s okay. Don’t give it a thought.”

  “You’re not mad?”

  “Only at myself.”

  “Stop that. Don’t start blaming yourself again. Look how much trouble we had last time!”

  Larry blushed, remembering the “therapy” he had undergone. “I won’t, I promise.”

  “Good, let’s go ahead and build the backup.”

  “Sounds good. But as we were talking I realized there are two big catches we need to address.”

  “There always are! What’s number one?”

  “Diesel exhaust. What do we do with it? We’ve been rather spoilt by the geothermal well. All that clean heat! All we had to deal with was a bit of hydrogen sulfide, some carbon dioxide, and steam. But with a fossil fuel …”

  “We’ll get emissions—shedloads of it.”

  “Yes. I think about three kilos of carbon dioxide per kilo of diesel.”

  “Hold on, let me check.” Jessica queried the computer database and found the answer. “You’re close. It’s 3.16 kilos of CO2, and about half as much steam.”

  “And that’s a lot. The steam will condense, and we can collect it and even drink it, but the carbon dioxide …”

  “… will suffocate us.”

  “Yes.”

  “Couldn’t we use some of the energy to turn it back into carbon and oxygen?” Jessica asked.

  “Unfortunately, no.”

  “Why not?”

  “Thermodynamics.”

  “I don’t get it.”

  “Can I get into lecture mode for a second?”

  “Isn’t that your normal mode?”

  Larry grinned despite his tension. “When you burn diesel, the carbon in it burns into carbon dioxide, giving off energy in the process. To reverse that process, or any exothermic reaction, you’ll need to supply at least as much energy as is produced. That’s the theory. In practice you need much more energy to split open a CO2 molecule than the energy that came from burning that atom of carbon.”

  “Bummer.” Jessica was quiet for a few seconds and then had a thought. “Wait a minute. Doesn’t diesel have hydrogen as well as carbon? Couldn’t we use energy from burning the hydrogen portion to pay for carbon dioxide reversal?”

  “Hmm, that’s a thought.” Larry chewed on a pencil for a few seconds and then shook his head. “But if I remember right, only a third of the energy from diesel combustion comes from the hydrogen component. So you’ll still be in the red.”

  “What about chlorella? Couldn’t we set up a hundred more panels of it to soak up the extra carbon?”

  Larry nodded appreciatively. “That’s another idea. But again, I don’t think it’s practical.”

  “Thermodynamics again?”

  “Indirectly. Let me go into lecture mode again. Plants and algae and cyanobacteria do fix carbon, using it to grow. And they do it very efficiently. But you need to consider two things. Firstly, they’re biological organisms and can’t grow very fast. Secondly, they’ll need loads of sunlight. So, more chlorella will certainly help, but we’ll never grow enough to keep up with combustion.”

  “Silly me. If it was that easy, global warming would’ve solved itself.”

  “Exactly. Let’s say we use a hundred kilos of diesel every day. That means a daily output of three hundred kilos of carbon dioxide. Fully grown chlorella can fix up to half a kilo of carbon per square meter per day. So we’ll need about six hundred square meters of it for our needs.”

  Jessica snorted. “Good luck finding the space for that. Not to mention the six hundred solar lamps and six thousand watts of electricity.”

  “Right. Also, the chlorella won’t soak up other pollutants in the diesel exhaust such as nitrogen oxides and sulfur dioxide. And though diesel emits less carbon monoxide than gasoline, given enough time even that will accumulate to toxic levels.”

  “Okay, Mr. Engineer, you’ve made your point! So we have to vent the exhaust out.”

  “Right. And lose most of the heat in doing so.”

  Jessica groaned. “It’s hopeless. No wonder they call it exhaust.”

  “You should leave the bad jokes to your elders,” Larry chuckled.

  “Now a different question. How did you plan to get heat from Entry to Central?”

  Larry grimaced. “That’s what I should’ve worked out before dragging you all here. But I think we could modify the piping system we have now. Hot fluid will go from Entry to Central, transfer heat, and then return to the heat source in Entry. Continuously.”

  “A closed thermal circuit between Entry and Central?”

  “Exactly, once we close all the other domes.”

  Jessica flipped through a sheaf of papers and picked out one that had a diagram of the piping system. She studied it for a while and then looked up. “What if we dumped the fluid and ran the exhaust through the pipes?”

  “Say that again?”

  Jessica repeated her idea, and Larry sprang up in excitement. “Now that’s an idea that might work! It would certainly transfer heat very effectively from Entry to Central.” Then his face clouded. “But the capacity of the pipes is limited. In a few hours they’ll be at full pressure and won’t take any more exhaust. What happens then?”

  “Then we vent out the cold exhaust and put more hot fumes in.”

  “Hmm.” Larry’s brows creased in though for a few moments and then his face lit up. “You know what? I think we finally have a plan. It’ll need a huge amount of re-engineering, we’ll need to change the piping and install new vents, but I think it might actually work.”

  Jessica beamed with pleasure. She was no longer tormented by conflicting feelings when praised. Though for old times’ sake she would deflect a compliment with an ironic quip, it was now more out of modesty than perverse sentiment.

  “It will work if a hundred things don’t fail,” she said.

  “No, we can make it work. There’s one more catch, however.”

  Jessica groaned. “God! Just when I thought I’d saved us all from eternal cold. I should’ve known it was too good to be true.”

  “Your idea is brilliant. We just need to consider one more thing.”

  “Okay, let me guess. Engineering issues are often symmetric. First was exhaust, so second has do with intake, right?”

  “Right again! It’s the second problem with burning fossil fuels—it not only produces carbon dioxide, it also uses up oxygen. So to run the generators, we’ll have to install vents to draw in cold air from the outside. Nothing fancy with valves and gauges, just a crude arrangement of piping. But the air outside, at minus 127 degrees, will have to be pre-heated to plus 50 degrees, the flash point of diesel. In this case, what will the net energy output be?”

  Jessica made a face. “Much lower, I’ll bet.”

  “I think so, too. Could you work out some answers? And estimate how much energy we would need to heat the two domes?”

  “Will do, Chief.”

  Jessica went to work that afternoon and remained busy with her calculations for several days. She used a blend of mathematical calculations and computer modeling to arrive at the answers. A few days later she shared her results with Larry.

  “Good news and bad news,” she said. “The good
news is we need to preheat air only to minus 30 degrees, not plus 50.”

  “Good news, indeed! How did you reckon that?”

  “The air can be colder, because the diesel itself will be inside the dome and relatively warm.”

  “Well done, Jessica! You’re smarter than you look.” Larry tried to dodge a well-aimed pencil. “And how long will the diesel last?”

  “That’s the bad news.” Jessica retrieved her pencil. “The efficiency of the system is only about thirty percent. The main problem is the cost of preheating, as you feared. We can reduce it somewhat by capturing heat in the spent exhaust, but that won’t be enough. Preheating will need a lot more energy. Between that and various losses, barely a third of the energy from diesel will be available for our use. If we assume we need the heat from a hundred kilos of fuel per day, we’ll actually have to burn close to 350 kilos. Which means …”

  Larry finished her sentence: “… we only have a year’s worth of fuel.”

  They gazed at each other for a while in silence.

  “Should we break it to the others?” Jessica said eventually.

  “What do you suggest?”

  “Let’s wait. Tell them the good news that we have a diesel backup plan.”

  “And if they ask how long it’ll last?”

  “Tell them it’s hard to estimate.”

  “Will they believe that?”

  “Sure they will.”

  Larry looked at her thoughtfully for a moment and nodded. “I agree. A white lie is the best policy for now. No sense in causing premature alarm.”

  “And the well might stabilize.”

  “Yes, let’s hope we never have to use the diesel option.”

  “Amen.”

  CHAPTER TWENTY-SIX

  Diesel

  As if to allay their concerns, the well remained true for a while. The spare energy from it went to the Entry dome where Larry and Jessica spent several hours each day on their diesel project. After some puzzlement, the others accepted this effort as a prudent backup measure. Only Larry and Jessica knew the true situation; the others’ anxiety was allayed by the well’s seemingly stable energy output.

  Work in Entry posed a new set of challenges for Jessica.

  Her earlier stint at Air had exposed her to a mechanical system far more complex than anything she had seen before. Though she would never have admitted it, Jessica, like her sister in Eco, was terrified by the burden of the responsibilities on her young shoulders. At least Anna had some leeway; if she botched up and lost her plants, she could plant some more. The loss would be only temporary. With her, on the other hand, the stakes were higher. Air and heat being vital for survival, any slipup in her work—an over-tightened valve, an incorrect pressure setting, an accidental reversal of electrical polarities—could have lethal consequences. Although Larry assured her that the system had many checks and safety mechanisms that made it resilient to human error, Jessica was engineer enough to know that the blunders you don’t plan for are the ones that will get you. Many historical engineering failures attested to this. The Challenger space shuttle debacle, for instance; as Richard Feynman famously demonstrated, it all came down to a rubber seal that failed because of the unexpectedly cold weather on launch day. Then there was NASA’s 125 million–dollar Mars orbiter that broke apart before it could start its mission because the agency’s contractor mistakenly used imperial instead of metric units. Not to mention innumerable other exhibits in the engineering Hall of Shame—Exxon Valdez, Deepwater Horizon, Columbia—that showed how simple, preventable flaws could have lethal consequences. When even seasoned pros made such Titanic blunders, how could a novice like Jessica avoid them? On top of these fears, in the past she’d had other struggles, such as adapting to life inside the Shell and learning to work with Larry.

  Now, in Year Seven, the situation was different. She had matured into a skilled engineer, confident in her ability to handle any situation that arose with her machinery. She was also confident that any error that occurred wouldn’t be due to her incompetence. And she now got along with Larry like a house on fire. He let her make all the major design decisions, content to play a supporting role. Her theoretical knowledge of air flow, heat transfer, and fluid dynamics now exceeded his. On practical matters he still held the edge thanks to his two decades of experience in getting systems to work. Even here, though, she was no laggard. Her apprenticeship in the Air dome had paid off, and she was as dexterous with drills, saws, and other tools as any skilled craftsman. Larry was only too happy to acknowledge her abilities. In their early days she had been turned off by what she considered his arrogance; now she was touched by his humility. For a self-made billionaire, he was amazingly free of ego. And now he actually “got” her jokes and occasionally even made a neat jest of his own. She grew extremely fond of him and would have indignantly denied ever disliking him. Together they made a fabulous team, she thought. If anyone could get the diesel backup to work, it would be the two of them.

  On the flip side, however, she had even more responsibility than before, and the work of creating a new system was far trickier than her previous task of maintaining an existing one. The Entry dome, previously left cold, now got some heat from Geo. But not much could be spared for them, so they had to work in below-freezing conditions most of the time. Drilling holes for the new intake and exhaust vents, though tedious, was not too complicated. But the moment they broke through the dome’s outer shell, an intense blast of glacial air from the outside struck them like a body blow. Hands would freeze and lungs would burn before they could put a temporary plug in the vent. Compounding her physical misery was the constant reminder of the ghastly world outside. Under normal conditions, she, like the rest of the family, could afford to insulate her mind from it. Now that cold dark reality was inescapable. Back with the others at the end of a grueling day’s work, however, she couldn’t talk too much about that for fear of alarming the others.

  If the extreme conditions made work unpleasant, they also spurred Larry and Jessica to work harder and faster. By mid-October of Year Seven, the two had finished the initial construction and were ready for a test run.

  Testing the system offered its own challenges. All heat to Central would need to be shut off for a day or two to get rid of the residual effects of the well, and the heat would remain off for a few more days until the trial run was completed. This meant relocating everyone to Eco during that period. The conditions there, already crowded, got even more cramped. There was barely any place for them to sit, let alone sleep, and the uncarpeted floor was colder than ice. But no one uttered even a murmur of protest. By now, their cohesiveness as a team was absolute. Larry was moved to tears by their instant cooperation and cheerful stoicism. On Nicole’s suggestion, she, along with Anna and Elizabeth, donned spacesuits and went to the closed domes to salvage any bits of carpet or other floor covering they could find. Back in Eco, they toiled for several hours to move the plants around and set up a viable living and sleeping space. When Larry and Jessica returned each day after their testing, half-frozen and shivering, noses running, hands stuffed into armpits, they had a nice, snug spot to relax in.

  “I can’t thank you enough,” Larry said the first evening.

  “Thanks a million …” Jessica began at the same instant.

  “Shut up you two and snuggle up, or I’ll get cross,” Anna cut in. “Nobody is allowed to say ‘thanks’ here.”

  Larry and Jessica had to make scores of modifications and adjustments to their system. The number and configuration of pipes, the gas pressure through them, the rate of fuel combustion—all that took several trial-and-error cycles before the system would work. Then more iterations to optimize it. But by the fifth day of testing, the Central dome had begun to warm again, and by the seventh it was nearly as warm as it had been before.

  “Success,” said Jessica.

  That evening they celebrated with another bottle of champagne that Larry produced from his mystery location. He gave Jes
sica the credit for the success, a compliment she accepted with modesty. She has acquired grace, Elizabeth thought with a smile.

  Their test completed, they shut down the diesel system and switched the Geo heating back on at Central. Life resumed its normal course. The well remained stable. Their makeshift kitchen in Eco ran smoothly. They resumed their routine activities: games, classes, films. To compensate for the loss of their gym, they danced for an hour or two every day. Larry, as the only man, was in demand. He divided his attentions between the two girls and could never decide who was the better dancer—Anna, light and swift, was a delight to twirl around, while Jessica, slightly heavier and slower, nonetheless had a languid grace that was equally pleasurable. Nicole and Elizabeth danced the slower numbers together, using the opportunity to recycle anecdotes from the pre-Shroud days. Life was good.

  And then, in May of Year Eight, seven months after the successful diesel test, one of the leaves of the avocado tree turned blue.

  CHAPTER TWENTY-SEVEN

  Blight

  It was Elizabeth, in the midst of her chores on May 22 of Year Eight, who saw it first. The avocado tree, a dwarf variety, sat next to a makeshift kitchen counter they had rigged up near the stove. Elizabeth had enjoyed being able to just reach out and pick the ripe fruit before they sat down for their meals and, on that day, had already plucked one. As she examined the tree to see if she could find another, she noticed a bluish stain on one of the leaves. It looked like a splash of paint, but she knew there was no paint in the Shell—or indeed, any other volatile chemical except a can or two for emergencies. She was puzzled but forgot about it as she busied herself getting their lunch ready. It was only at the end of the meal that she said casually: “Anna, did you see the avocado tree today? One of its leaves is blue.”

  Anna’s silence caused the others to put down their forks. “A blue leaf?” she said eventually. Her face had gone pale. Without waiting for a response, she got up and ran over to the tree. When she came back to the table, she was so ashen that the others exchanged looks of puzzlement and alarm. What was all this fuss about a blue leaf?