Lightship

by Stephan Besik

  Spinal column might have been a better term because virtually all of the ship’s electrical cabling, the nervous system of the ship, ran along the center of a keel section. Where the keel split to go around a cargo pod, the electrical cabling split too. The team thought that calling the ship’s backbone a spinal column was a little too long and too anatomical, though. So the lightship had a keel.

  The keel was attached to the inner ring of the sail gimbals, the other foundation structure of the lightship. Four sturdy struts connected the keel to the ring. The keel and the gimbals would take a lot of stress during ship maneuvers, as the mass of everything in the ship’s hull changed direction compared to the sails. The strength of the ship was based on those two components.

  Once the lightship was fully assembled, the keel would run from just forward of the four cone-shaped engine exhausts to slightly aft of the nose of the ship. The nose housed the ship’s primary sensors, forward-looking radar and lidar units and cameras. Those were the critical sources of data for navigation of the ship.

  The drive module looked very rocket-like, with four thrust nozzles at the back and cooling fins on the sides. The fins looked a little like the stabilizing fins on an old unguided rocket, but served the entirely different purpose of keeping the plasma thrusters cool. The drive module contained four plasma engines, the cooling system for the engines, and pumps that brought fuel from the fuel tanks to the plasma motors.

  Similar to the keel space in front of the gimbals where a cargo pod would sit, there was nearly empty space behind the gimbals as well. Between the drive module and the gimbals there was only a series of pipes and the keel. The pipes would connect to the ship’s fuel tanks. The fuel tanks were a set of four cylinders that fit along the empty keel section behind the gimbals. Both cargo and fuel tanks could be quickly removed and replaced by the ship’s drone crew, for quick turnaround. Time in dock was time not earning money.

  The electrical connections for the control system ran down the center of the keel, in a hollow space at the center. Two separate conduits on opposite sides of the keel brought power back to the engines from the sails, with one conduit feeding power to each of two drive units. Cables running in the conduits also attached to a bank of batteries that sat between the sail ring and the control module. When a ship was docked, it would look like a long, skinny thing with a bulky tail (the drives), a bulge forward of the gimbals for batteries and control module (like a stomach?) and a tiny head (the forward control and sensor module) with separations of near-empty space for modular fuel tanks and the pill-shaped frame for the cargo pod.

  The fuel tanks would be attached to an empty section of keel just ahead of the drive module. Just behind the gimbals, connected to the inner ring, there was a lightweight skeletal frame attached to the keel that provided attachment points for four fuel tanks. Immediately in front of the drive module, the fuel tanks would be fastened around the keel and connected to the fuel lines into the engines. Like the cargo frame in front of the sails, the keel in front of the drive module was configured to enable quick and easy exchanges.

  With the exception of the drive module, the permanent sections of the lightship were relatively short cylinders that would be slid onto the forward end of the keel after the keel’s connection to the sail ring. Once the ship was fully assembled, the battery pack would sit just ahead of the sail ring and the primary control module would sit at the front of the battery system. The cargo frame was just ahead of the primary control module, and the nose of the ship was the backup control module and primary sensor bank.

  The batteries would drive the ship for a limited period if the sails were not exposed to the sun, but their primary purpose was to keep the ship operating when there was no power from the sails. The battery pack was not intended to be used as a long-term source of power for the plasma engines. It could be used that way in a pinch, of course, but the batteries didn’t have enough capacity to run the engines for very long. Powering the engines on batteries was for emergencies only.

  The two control modules were both adequately equipped to run the entire ship in case a unit failed. Like the battery pack, the body of a control module was only a few meters long. Each control module housed computers, sensors, environmental controls, and masses of wiring connected to the cable harness that ran down the center of the keel back to the drive module. The control modules had their own ammonia-based cooling systems, separate from the fuel tanks and the cooling system of the drive module. Each had its own environmental conditioning system, using a small tank of ammonia as its working fluid. The idea was to preserve controls even in the event of a significant accident that affected fuel tanks, the drive, or the other control module. In a real pinch the control system coolant could be diverted into the fuel tanks, but it wasn’t recommended. The extra wouldn’t last very long, and neither would the plasma drive if ammonia from the control module had to be diverted. Again, diversion of the control module cooling system was for emergencies only.

  The control modules had priority on power from the batteries. The ship could operate in driveless mode for quite a long time, but without control there would be no ship.

  The split keel that was the attachment area for cargo made space for larger payloads. Otherwise payloads would have to be organized or designed to work around the central keel. While that was possible for an array of fuel tanks near the drive module, having to work around a central cylinder in the cargo area would be a problem. The central keel would have been a serious limitation in the ship’s cargo space, especially since many if not most of the trips to the Moon would require a fairly large lander to put cargo on the surface.

  The initial designs called for three pod types that could be swapped out as needed- one for material cargo with its own power source for soft landings on the surface, one for human beings who would stay with the ship, and another for people who would be descending to the surface in a lander. The basic concept was still one of modularity- cargo and manned pods could be inserted into the ship or removed in a just a few minutes by disconnecting them from the cargo frame.

  At the front end of the cargo frame, in the most forward part of the ship, the keel came back together into a single central core. This was the nose of the ship, supporting the secondary control module. The secondary module contained a complete duplicate of the primary control module along with an array of more sensitive cameras, radar, lidar, and radio and laser transceivers. The bow of the ship housed most of the forward-looking sensors of the control systems. While the ship could be operated with one control module down, it was best if the ship used data from the big sensors in the forward module while operations were conducted from the central module. This combined the best of both control worlds- large computing capability hidden safely in the rear control module with well-positioned and highly sensitive sensors in the forward module.

  The module at the ship’s bow was in a somewhat hazardous location; the likelihood was that the bow would be the first thing to hit a hazard. Virtually all of the equipment in the bow was duplicated in the control module, an area that was much less exposed to hazard as the ship traveled. The “view” wasn’t as good from the central control module since the cargo frame sat between the control module and the bow, and the sensors were somewhat more limited than those in the nose. That wasn’t much of a loss, though. If there was something so close to the bow that it couldn’t be seen from the control module, it was probably too late to avoid a collision, anyhow.

  Building the Ship

  It was time to put the ship together.

  The keel and sail ring would be assembled as the backbone of the lightship. This was the first time that two major parts of the ship would be joined together. The task had been done in simulation, but now the drone drivers were playing with real money.

  “Okay, Art. We’re in position. Drones are lined up and tethers are both attached.” Rob was leading the drone people who were involved in what they were all calling The Shove. Rob and Lucy were the drive
rs of the drones that would push the keel of the ship into position within the interior gimbal ring. Their partner handlers, a woman named Kelly on Rob’s drone and Aman on Lucy’s, had already adjusted the manipulators to sit flat against a collar on the keel that would match up with a similar collar at its final resting position inside the gimbal assembly. A portion of the keel would be pushed through the gimbal, providing attachment space for the battery pack and primary control module in front of the ring.

  The other drone drivers and handlers were clustered around the supervisory station that Arturo was using. The Shove was a big deal; fastening the keel to the sail ring was the first of a number of push projects that would be the major efforts in assembling the ship. Soon all of the drone staff would be doing push jobs, adding modules along the keel or building the sail assemblies.

  Before the Shove could start, the drones had to align the keel with the open center of the interior gimbal ring. The drones on the keel first got a key matched to a slot in the big metal ring. It was a delicate process; the alignment had to be perfect so that the keel would slide straight into place. If the keel was at an angle to the center ring, it would push the sail ring away instead of sliding in properly. If the alignment was bad enough, the sail ring would start to slip away from the space dock. Or worse, it might take the space dock with it.

  Once the keel and interior gimbal ring were lined up, the two big pieces of the ship were ready for the Shove.

  The two drones on the keel had their manipulators flat against the collar that would be fastened to the sail ring itself. There were two drones in place against the front of the sail ring, ready to push against the ring in case there was enough friction between the keel and the ring to start both keel and ring moving in the same direction. That would make the entire push harder, and perhaps cause it to fail.

  The intent was to ensure that the ship assembly would not drift forward as the drones pushed the keel into the center of the inner gimbal ring. In the supervisory station, Arturo would watch the overall motion of the two big parts and control any counterbalancing thrust that would be necessary if the sail ring began to float away.

  “Rob, Lucy, tension up your tethers now.”

  “Aye, Cap’n, rolling up the slack now.”

  The two push drones were attached to the sail ring collar by their safety tethers, both to help keep the push properly aligned and ensure that the drones couldn’t fly off into space in the event of a problem.

  “Okay. Execute jet burst at zero point one meters per second-second for one second. Begin tether reel-in immediately after initial acceleration. Execute burst on my mark.”

  Lucy repeated the command back. “Accelerate zero point one meters per second-second for one second. Reel in as we go. Ready and waiting.”

  Rob chimed in. “Point one meters per second-second, duration one second. Take up tether slack as we go. Ready here.”

  “Mark.”

  The drones gave the unit a push, starting the keel moving through the sail ring. The push was short, just enough to get the keel moving at constant speed through the center of the interior gimbal ring.

  With one drone on each side of the keel and one behind each side of the gimbal, the collar of the keel moved closer to its stopping point against the mating collar on the gimbal ring.

  “Keep your tethers reeling in slowly. Confirm and brake your drones on my mark.”

  The drivers on the tethered drones responded, affirming their instructions.

  “Mark.”

  The drones fired their braking jets to slow the momentum of the keel. While there had been a little friction between the keel and the sail ring, there was still a lot of moving inertia in the keel. The idea was to bring the keel collar as close to a full stop at the terminal point of the push, leaving just a little bit of momentum to ensure that the collar didn’t stop short. No one wanted to jocky the collar a few extra inches toward the mating collar on the sail ring if they could avoid it.

  In the supervisor station, Arturo was watching the movement of the sail ring as the keel slid into position. He was the one who would fire the jets on the drones that were supposed to hold the sail ring in place.

  As the keel slid through the sail ring, there was just enough friction to move the ring a few inches. Arturo watched the position gauge carefully. He also watched a calculation on his display that converted the movement speed of the two pieces into an estimate of the force that his drones would have to exert to stop the motion of the assembly once the collars on the keel and sail ring were in position next to each other.

  There was tension in the drone room as The Shove neared its end. “Almost in position,” announced Arturo. When the collars touched, he would push the button that would cause the drones on the sail ring to fire their jets, stopping the momentum of the new assembly. Once the keel pressed against the mating collar on the sail ring, it would share its inertia and its momentum with the ring. Unless that extra momentum was counteracted, the whole assembly would begin to drift away.

  The force estimator jumped and the view from the drones wiggled a little as the two collars came together. Arturo hit the button, and his two drones fired their jets. The new assembly slowly moved a few more inches and then stopped.

  The whole room took a deep breath, and there were some applause. Arturo grinned and wiped some sweat from his face. “Good show, people. One shove completed. A bunch more to go. But we know it will work. Kelly, Aman, get the collars fastened together. Rob, Lucy, let’s take a break. Then we can start planning the next push.”

  Publicity

  The people in the conference room represented the twenty nations that were signatories to the Lunar Compact. Danny thought of them as “non aligned” because none of them were clients of any of the current major power space agencies. There were also about a dozen journalists in attendance, half from technical websites and half from moderately prominent news sites.

  Charity and Stanley, her assistant, stood at the back of the room. Charity welcomed people into the conference room, while Stanley handed out a hard copy of their announcement and pointed people to coffee, tea, and donuts. Danny was a little chagrined about the donuts; it had gotten to be a thing with the press when he retired from basketball and was committing all of his resources to his acquisitions. Now they stuck with him, even though he would have preferred some decent croissants, with maybe some fruit as well. Hard to complain, though- Stanley had a secret place with donuts that he couldn’t pass up. Neither could the journalists. The coffee was good, too.

  A mixture of scientists, politicians, and journalists, it made a strange group. The media were there because a well-known and quite wealthy retired pro basketball player had spent a ton of money on a spaceship. Perhaps more consequential to some of their readers, Danny was a wealthy African American contributing to scientific progress in a very public way. As for the others in attendance, the scientists and the politicians were there to represent their countries and see what their countrymen had bought for their signatures on some rather obscure paperwork.

  Danny went to the podium to make his announcement.

  “Ladies and gentlemen, a bit later today the solar lightship Edison will make its maiden voyage to the Moon. On its first voyage Edison will equal the speed of the early Apollo runs from Earth orbit to Luna. The trip will be made at a quarter the speed we will come to expect from solar ships like Edison, at far less cost in equipment and fuel than the Apollo missions. Assuming this first trip is successful, our next step will be to make a series of runs to carry cargo to the Moon. The first of these trips will drop a variety of probes to conduct in-depth research on possible habitat sites. Subsequent runs will focus on a small number of potential sites for establishment of permanent stations. Once we know more about the Moon and have selected sites for the new stations, we will send up robots and other machines, with some humans included, that will build facilities to house human researchers for limited periods. Assuming all goes well, we will return manki
nd to the Moon to stay.”

  The last line caused a little conversation among the politicians and scientists. They now knew what their countries had signed on to but they were still a little unsure about what it all meant.

  The journalists had questions. One of them rose to ask his.

  “Uh, Mr. Smith, uh, I just got this assignment. I guess the rep that knows this story is out sick. I apologize if my questions are silly. You mentioned ‘solar lightship’ and ‘solar ship’. Does that mean your spaceship is powered by the Sun?”

  “I didn’t catch your name, sir.”

  “Oh, sorry, I’m James Moreno. I’m from Science and Politics.” He smiled ruefully. “Some of our people think of us as the technology oxymoron.”

  There was a bit of laughter before Danny responded.

  “Well, Mr. Moreno, I hope your friend recovers soon.

  “Concerning your question, you’re right. Edison is the first of what I hope will be a series of solar powered spaceships capable of transporting large cargoes, and soon people, to the Moon. In addition to Edison we have one more ship in final assembly at the Smith Systems space dock in Earth orbit, and another in parts at our facilities in Taiwan, Costa Rica, and Puerto Rico.”

  A young lady rose immediately and asked the next question. “Cynthia Camallo of Science International, sir. I understand your ship uses ammonia fuel. Did you consider any other options, and if so what were they?”

  The first reporter looked confused and interrupted. “Wait, I thought the ship was solar powered?”

  Danny responded, “It does use ammonia fuel. I understand that other fuels were considered but there were strong arguments for ammonia. As for your confusion, Mr. Moreno, you have to remember Newton’s Third Law. You know, action requires equal and opposite reaction? Edison uses electricity provided by its solar panel sails to accelerate ammonia ions, which provide thrust to propel the ship. The electricity has to have something to push in order to make the ship move.” He grimaced ironically. “And I am afraid you have exhausted my technical knowledge concerning the ship’s propulsion. I will have to refer any more technical questions to the head of the Smith Space Division, Dr. Chaz Delsun, who can also put you in touch with my technical staff for anything really complicated.”