The Enceladus Mission: Hard Science Fiction

by Brandon Q Morris

  On this diagram, the plasma chamber in which a fusion reaction turned helium-3 and deuterium into helium-4 and hydrogen, the actual drive took up the smallest part. Around it, there were all kinds of systems that started, cooled, or shielded the drive. At the bottom right there was a flashing red field labeled ‘gas turbine.’

  “You are looking at the status of drive 4,” Watson explained. “The gas turbine of this DFD has failed. Currently, a root cause analysis is not possible. The effect of this failure is that the coolant liquid of the fusion reactor no longer can give off its heat. After the drive heated by more than ten percent above normal range, I deactivated it. An immediate intervention by the crew is necessary, and for that reason I turned off the other DFDs as well.”

  “Can’t we just fly on with five drives?” Marchenko asked. Martin considered that a naive question, but then Marchenko was a doctor, not a physicist.

  The AI replied, “Of course. I calculated that the ensuing trajectory would take us out of the solar system in 4.3 years.” Watson appeared to have a sense of humor. “Our ship has been decelerating for a while to get below the capture velocity of Saturn. With our power output reduced by one-sixth, that would be impossible.”

  “And what if the repair was successful?” Amy asked.

  Watson remained patient. “Commander, it is no longer possible to maintain the planned trajectory. However, I can calculate an alternative course that makes it possible to reach all research goals. For this, we would have to use the decelerating effect of Saturn’s gravitational field more than originally planned.”

  Martin saw Amy pondering. Her eyes were closed. Then she said, “Specify necessary repair options.”

  “It is necessary to connect the helium pipes carrying the coolant of DVD 4 with the gas turbine of one of the other five drives. Due to its proximity, I would recommend drive 3.”

  The commander asked, “Will the doubled gas flow be within the parameters for the turbine?”

  “Almost. Temperatures will be within the specified range. The mean life expectancy of turbine 3 will be cut in half, though, from ten years, as planned, to five years,” Watson reported.

  “It has been running for one year. This means we have a 1 in 4 probability that we will encounter another problem with it during the return flight,” Martin said out loud. “Good thing we have no other issues.”

  The AI said, “That estimate is correct. Without the suggested repair, though, the probability of a return flight is zero percent.”

  “It’s obvious,” Amy said. “We have to go outside. How much time do we have, Watson?”

  “The available time frame cannot be calculated.”

  “What is that supposed to mean?”

  “Battery capacity at 80 percent,” Siri reported. It was against protocol for one AI to interrupt the other, so this must be an urgent message.

  “Before the repair, the drive must be almost completely cooled off,” Watson said. The drives were Watson’s area of expertise. “As the vacuum insulates well, the coolant has to keep flowing during this time. The pumps need electricity, which is provided by the batteries. Within 30 minutes, the charge has decreased by 20 percent. If the energy consumption remains constant, the capacity will reach zero in two hours.”

  No one said a word, as they immediately realized the consequences. Out here, the solar sails were useless. Without energy, neither life support systems nor communication would work. We will suffocate in this tin can without being able to alert Earth, Martin thought.

  “When will the drive be sufficiently cooled off so that we can send someone out?” Amy always managed to ask the crucial questions.

  “According to my calculations, no sooner than ninety minutes,” Watson said.

  “Well, you heard what Watson said.” Amy turned toward the entire crew. She exuded a convincing sense of calm while she spoke. Even Jiaying, who had nervously bounced her knee the whole time, listened attentively.

  “We have an hour and a half to prepare. That's tight, but it can be done. The two people who perform the repair will then have half an hour to do it. Rerouting a pipe, that doesn’t sound too complicated. Are there any volunteers?”

  Hayato immediately raised his hand. Marchenko and Francesca did the same right afterward. Even Martin raised a finger.

  “Martin and Hayato, you will be doing it.”

  Martin nodded. The decision is correct. No matter how the mission ends, we will need the doctor and the pilot on board. Both Martin and the Japanese man, though, would not be required until the ship reached Enceladus. Martin was still impressed by the fact, though, that the commander would send the father of her child on a spacewalk. Afterward, Amy ordered complete radio silence toward Earth. The antenna of the Deep Space Network used energy they needed more urgently for survival. Mission Control would have to deal with not hearing from them for a couple of hours.

  “We have to try to lower the energy consumption on board. Everyone should try to come up with some way to do this. Five minutes,” the commander said.

  Martin heard somebody’s feet scratching against the floor. It must be Jiaying. He pondered, How can we generate energy in a spacecraft flying through the void? He visualized the layout of the ship, with its random conglomeration of modules. Usable energy can be found where potential differences exist—heat, radiation, fields, motion. The spaceship moved silently through his head. The spokes of the ring rotated slowly.

  He had found it—motion.

  As a child, he’d had an old bicycle without an electric motor, so he had to pedal it himself. To turn on the headlight he’d needed to clamp a dynamo against the sidewall of the front wheel. What if we give the habitat ring a dynamo that would generate electricity—like on my bicycle? Martin thought of arguments against it. The removed energy will slow the ring, but we could compensate with the solid-propellant engines. They should still contain more than enough propellant. He calculated the potential in his head, using a simplified model. For the rotational energy he would need the inertial torque, which included the mass and the square of the radius of the ring, and the square of the angular velocity. The ring weighed several tons, the radius was 6 meters, and the angular velocity 0.6 per second. Damn. The dynamo would not be able to generate more than a couple hundred watts. It would be enough for a few lamps, but not for the life support system. I can't do anything about the mass of the ring or the radius, but I can change the rotational speed. Since it is squared, doubling it would generate four times the energy.

  Martin asked the AI, “Watson, up to what rotational speed is the habitat ring specified?”

  “The ring is turning at its specified speed.”

  “Then let me rephrase the question. What maximal speed does the mechanical construction of the ring permit?”

  The others listened up. Their expressions told Martin they did not understand what he was trying to do.

  “The spacecraft will remain in a stable configuration as long as the ring does not move faster than two revolutions per second,” the AI replied.

  This gives me a lot of leeway. Not only can I double the angular velocity, but increase it twentyfold. 10 kilowatts instead of 500 watts. That sounds quite different.

  “Watson, extrapolate the status of the ship if a total energy supply of 10 kilowatts is available,” Martin instructed.

  “To do this, I would need to have the priorities for all systems defined.”

  “Life support 100 percent priority, all other systems zero percent.”

  “Under those circumstances, the life support system can reliably provide for the command module. Other modules must be shut down.”

  It was time for Martin to explain his idea to the others. He described the task at hand. “We have to build a dynamo.”

  Jiaying immediately said, “I can do that.”

  That's unusual. She is not an engineer, Martin thought.

  “I used to refurbish old dynamos together with my father. Put in new carbon brushes and such. Our family w
as poor,” she finished quietly. Because of her childhood experience, Jiaying was convinced she could build one.

  Afterward, they would attach the device outside and connect it to the current supply. They had a total of two hours for the task, but there was a problem.

  “We only have three EMUs on board,” Amy explained, referring to the Extravehicular Mobility Units. The repair of the DFD could not be performed by one person. And a third one would have to get into the remaining spacesuit and attach the dynamo, alone. This was against all protocol, because during EVAs, astronauts were always supposed to work in teams. Yet they had no alternative.

  Francesca volunteered, but Jiaying objected.

  “If I build the thing, then I will know how best to attach it.”

  “Are you sure?” Amy’s voice sounded concerned. I know why Amy is worried, Martin realized. “You will have little time for decompression procedures. Less than would be healthy.”

  “I’m well aware of that. I just have to hurry when I construct the dynamo,” Jiaying said.

  “As far as that is concerned, you could already start breathing pure oxygen through the mask. Francesca, please help her with her work. Hayato and Martin, start preparing for the spacewalk immediately.”

  “Battery capacity at 40 percent.” Siri conveyed these depressing messages every 30 minutes. Martin and Hayato were already in the airlock, where the air pressure had been reduced, and they breathed pure oxygen. At their feet was a tube, about three meters long, with a metallic sheen. It looked like a snake that had gorged itself and was now resting. Martin lifted one end of it. He could have easily placed his leg inside it, including the spacesuit. They had said goodbye to the others outside the airlock, as if their journey was coming to an end. Martin had really felt this might be the last time he would see them. His heart was beating faster. He wanted to flee, to float off into space. What he was feeling must be pure panic. He tried to breathe deeply.

  He looked at Hayato, who was busy with the metal segments of the snake. It is hard to imagine hot gas can stream through its inside for months without causing any problems... although it will be helium, he thought, which is an inert gas and does not cause chemical reactions.

  Martin's brain continued to analyze the details. This special material was also able to withstand the heat. The metal rings that surrounded it served both to radiate heat into space and to protect against meteorite strikes. Nevertheless, the rerouted pipe would represent a weak spot compared to the rest of the hull. The risk of a hit was reduced as long as the drives were not pointed in the direction of flight. This, however, was the case now when the DFDs were supposed to be decelerating them during the final approach to Saturn.

  On his arm display, Martin had Watson show him once again how Jiaying wanted to install the dynamo. He was satisfied. She had come up with a design that was both clever and safe. The AI reported Jiaying was making good progress. It even looked as if the two of them would have to hurry with exiting the spacecraft. If Jiaying finished early, she had to get outside as quickly as possible, and in this case, Martin and Hayato shouldn’t be blocking the airlock anymore.

  He gave his fellow astronaut a signal. Hayato obviously had similar ideas, as he immediately understood what Martin was trying to say.

  “EVA crew to Commander, we are preparing to exit.”

  “I understand.” Amy neither criticized them, nor did she point out the increased danger of getting the bends by exiting the ship earlier than planned.

  Martin opened the hatch to the outside, remembering to secure himself. Hayato followed him. After they were outside, both stopped for a moment. The spoked wheel of the habitat ring was turning noticeably faster than last time. Martin believed he could see the four jets that were accelerating the giant wheel, with the goal of reaching two revolutions per second. Previously, it had taken six seconds to complete a single rotation. Martin hoped the construction was really as sturdy as Watson maintained. He suddenly remembered he had not cleaned up his cabin this morning. Anything he'd left lying around would be thrown about. The simulated gravity should be above that on Earth by now. He wondered whether the equipment inside the spaceship could handle it. The shower, the whole WHC? It didn’t matter. Without the electricity provided by the dynamo, he would never have to take a shower again.

  He looked toward the stern. They had to go further than ever before, and enter an area prohibited to astronauts. And they needed to be careful not to stumble over the small plungers sitting above the repaired spots on the hull. The danger of misaligning a part of the DFD by a clumsy step was considerable. Watson had explained to them that, near the drives, all areas they were allowed to enter were marked. Anything not marked was off limits. Martin went ahead and Hayato followed him with the weightless tube he had secured to his belt. It was a fascinating walk, even in the face of looming death. The universe around him seemed to stand still, even though they were moving dozens of times faster than a racecar. There was a little bit of metal at his feet, but otherwise he felt alone. The limitless cosmos extended in all directions. The stars, even the sun, were far away. By now, Saturn had become a tiny disc rather than a dot, though its rings were not yet visible to the naked eye. He made a decision. If the repair fails, I will latch my spacesuit to the ship and wait for death. That is a hundred times better than to fall asleep forever in my bed at some point. I am glad I came on this journey.

  Nevertheless, the repair must not fail. The two of us owe that to the others.

  Martin looked around to Hayato, who was just attaching a carabiner to a protruding strut. He waved, and the Japanese man waved back. They had reached the last module, but were still about 20 meters away from the drives. From this perspective, the six DFDs, arranged in a circle, seemed much more massive than in a schematic diagram. They looked like giant gasifier tubes, surrounded by cube-shaped modules. One of these modules, the one next to drive 4, had stopped working. The DFDs would have been indistinguishable from each other if their numbers had not been printed on metal plates that could be clearly seen from the spaceship. Martin had only to aim his flashlight to find the culprit.

  Between him and drive 4 was an abyss, an infinite chasm bridged by a structure made of metal girders. Martin took a step forward, but then quickly jerked back. The depth seems to hit me in the face. It's maddening. It is easy for me to look up into infinity, but my vertigo is triggered when the same limitless expanse is below me.

  Hayato came toward him from behind and placed a hand on his shoulder. Since he was wearing the HUT, Martin did not feel the touch directly, but he noticed the pressure it exerted. He turned toward Hayato and searched for his face behind the round glass of his helmet. The Japanese engineer smiled at him. It was a smile that exuded confidence. During Martin’s childhood, he had always lacked confidence. This is the reason why I both like this feeling, but also distrust it, because in the end I fear it will disappoint me.

  He had to outsmart his vertigo. There was no easier place to do this than on a spaceship. Above and below are not fixed concepts in space. Martin first sat down, and then he lay on his back. He did not want to know what Hayato thought about him at that moment. Well, my friend, do you still trust me? he thought. Then he used his safety line to pull himself toward the abyss, but in such a way that the metal structure was to his right. When he now looked through it, he did not see a chasm, but a far-away plane.

  Hayato arrived on the other side at the same moment as Martin. Martin got up again and signaled he was okay. The engineers who had designed the spaceship had been clever. They had expected one of the modules to fail and had planned for alternate paths. At the spot where the coolant flowed into the gas turbine, there was a valve that fit the mouth of their metal snake. At the other turbine—the working one—they found its counterpart. Each of them had to attach one end of the snake, and then they had to redirect the flow as simultaneously as possible. A time difference of one or two seconds wouldn’t matter, but it shouldn’t be more than that. Otherwise, irrepla
ceable helium would be lost.

  Martin crouched in front of the port for turbine 4 and installed his end of the alternate tube. He had to push the ‘mouth’ over the port and turn it several times before the special threads engaged. Hayato did the same at drive 3. Then Watson gave a signal via the helmet loudspeaker. Martin and Hayato each lifted a cover next to 'his' adapter and turned the lever hidden below it.

  “Coolant circuit for drive 4 has been reestablished,” Watson reported.

  “Congratulations. Fifteen minutes before the deadline. Come back inside, the both of you,” Amy’s voice said. She sounded relieved, even though the danger was not completely over.

  “Jiaying, are you moving along? Do you need help?”

  “I have reached the hub of the habitat ring. I am starting the installation,” Jiaying reported.

  “Commander, requesting permission to help Jiaying,” Martin said. Without waiting for Amy’s approval, he repeated his maneuver for crossing the infinite abyss and moved quickly but carefully toward the ring—which, from his perspective, was rotating behind the exit hatch.

  “Uiiii.” He heard the voice of the Chinese astronaut in his headphones. She was breathing heavily. After a few more steps, Martin recognized the reason for it. The ring is turning very quickly now. The dynamo consisted of a magnetic coil, in which the rapid movement of the metal ring generated electricity through induction. To work efficiently, it must be as close as possible to the metal of the habitat. However, the ring was not a perfect circle. The rigid living module alternated with softer transition modules that had a smaller circumference. If Jiaying moved the dynamo too close, it would be destroyed by the enormous rotational energy. And it would probably kill the person in its immediate vicinity. If the dynamo was too far away, though, its power output would decrease dramatically.

  Martin stopped. He wondered how he could help Jiaying. They would need a dummy object, something they could move closer and closer, but it shouldn’t matter if that object got destroyed. He looked around but did not find anything. From the corner of his eye he noticed the SAFER, the rocket backpack he had strapped on. There was a second SAFER on board, so this one was expendable. With one hand, Martin signaled Hayato to come over and help him take the SAFER off. Then he radioed Jiaying and explained what he was trying to do. He would kneel down at the spot where she needed to attach the dynamo. Then he would move the SAFER forward, millimeter by millimeter, and mark the front edge on the hull each time. On his tool belt he had a pen that could write in space. Jiaying lifted the dynamo and made room for him. Martin put the SAFER in its place. The habitat modules were zooming past them closer and closer. It was an eerie feeling, as everything was noiseless, and there was also no airflow such as one might expect from such a mighty carousel.