Kronos by Aurum Copyright © 2020 Aurum All Rights Reserved.

Authors Note: This document is totally unnecessary to the story, however, if you'd like some extra explanation of some of the concepts mentioned then this may be for you. If you enjoy thinking about these kinds of objects, then you may love Isaac Arthur's YouTube channel, I know I do. This is a living document so I'll add more as it becomes relevant or I think it'll be added in the future. This is just a moderately edited glossary for now, but I may add a lore section as the world becomes fleshed out or I think it's relevant.

• Active Support - imagine a piece of paper floating over an air vent. Active support involves shooting particles to keep an object held up. The advantage of active support is that it allows you to build towers and rails much taller and longer than would otherwise be possible. Every material has a compressive force that limits how high it can be stacked and a tensile force that limits how long it can be stretched without breaking, but active support can exceed this by an order of magnitude.
• Atlas Pillar - these are massive towers that stretch 100km high. At this height they reach just beyond the Karman Line, which is where space begins. Technically this would count as a marginally useful space elevator. Each tower is made of graphene and uses active support to keep from collapsing. The support is powered by a molten-salt fission reactor and a helium-3 fusion generator powers the lift. For safety reasons, the tower can be broken with small explosives into 10km segments with massive parachutes capable of reducing its fall rate to safe crash speeds.
• Atlas Launch System (ALS) - this is a massive structure stretching 1,300km (808mi). It is comprised of seven Atlas Pillars separated by 185km (115mi) each. While not powering the lift the helium-3 fusion generators store energy is massive supercapacitor banks that allow the rail to accelerate a 50 metric-ton payload to orbital speeds. The max acceleration rate of the rail is 2.5g for 318 seconds. This allows the shuttle to reach a max speed of 7.79km/s (17,425mph). Although it is mildly uncomfortable, even an untrained person can handle it without issue. During the last 70km the sled undergoes 50g deceleration to come back to a stop, obviously no human could withstand the massive deceleration. For those wondering, the sled is powered via magnetic levitation like the bullet trains of the 21st century. Currently there is only one in existence, which starts in Atlas, AZ (50mi SE of Phoenix) and ends in Weatherford, TX (60mi west of Dallas).
• Centripetal Force - this is a simulation of gravity that occurs from spinning an object. This is not gravity creation like is seen in most space operas, but a real force like the fair ride that pulls you against the walls as it spins around. Although there are some differences between it and gravity, it is sufficiently similar in most activities. Differences include the path of a falling object relative to the ground and the rate at which “gravity” changes as you move from the floor. Past that, the main consideration is that while gravity pulls you in, for example you’re being pulled towards the center of the Earth, centripetal force (spin gravity) pulls you out. While experiencing centripetal force, you are actually being pulled towards the outermost wall relative to the center of spin.
• Delta-V - a measure of how much a spacecraft can change its velocity. A higher delta-v generally allows a rocket to burn longer and achieve a higher final velocity. Note that on many voyages nearly half of the delta-v is required for slowing down, although sometimes it is possible to save fuel by using orbital slingshots to accelerate and decelerate. Another consideration for scientists is how the weight affects delta-v, including the weight of the fuel burned during the earlier maneuvers.
• Direct Fusion Drive - the direct fusion drive is a real theoretical drive that funnels the emissions from a fusion reactor through an exhaust nozzle. It does not depend on heating a propellant like ion drives or hybrid designs, however it still consumes fuel in the fusion reaction. Most designs use a combination of Helium-3 and Deuterium and can achieve up to 10 Newtons of thrust per MW of power. Within Kronos, the KATS shuttle uses the same fusion fuel, but can achieve 25 Newtons of thrust and produce 500 MW of power. I’m assuming the designs within this universe have improved dramatically without reaching physics breaking levels. If I’m wrong let me know, I’m not a physicist, but am doing my best to respect science.
• Fission - this is the act of taking a heavy particle, specifically uranium for the ones used at the Atlas Pillar, and starting a chain reaction that turns it into lighter particles. The reaction releases massive amounts of energy compared to conventional power plants. The advantage of fission over fusion is that it is easier to sustain a reaction for years, preventing downtime.
• Fusion - this is the act of taking a light particle and turning it into heavier particles. Although this is the ideal form of power generation, there are inevitable downtimes when the reaction simply cannot be sustained. Fusion is how the sun produces light and energy, but the methods humans use reach significantly higher temperatures since they don’t have all that mass to help. Fusion generators are broadly broken into two methods via the fuel they use. On the ground large deuterium generators are preferred since deuterium is relatively abundant in Earth's oceans. On space stations and spaceships helium-3 generators are preferred since it allows for direct fusion drives to accelerate the ship. Higher class models can produce 25 Newtons of thrust for every MW of power. Commercial fusion generators typically use the magnetized target fusion (MTF) approach, although some older models still operate with an inertial electrostatic confinement (IEC) system.
• Fusion Fuel - the fuel used in fusion generators. Although people are still working on building a viable fusion generator that runs on plain hydrogen, the most abundant element in the universe, it still has yet to be done. Currently the two main methods are helium-3, which is a stable isotope of helium with only one neutron. It is relatively abundant on Earth and very abundant on the moon and gas giants. Deuterium is a stable hydrogen isotope with a neutron, whereas plain hydrogen only has a proton and an electron. It is also reasonably abundant on Earth, accounting for 0.02% of the naturally occurring hydrogen in the oceans.
• Gravity in Space - there are only two known ways to produce gravity in space. As mentioned above, centripetal force can closely approximate gravity through the spinning of an object. The other alternative is a gravitational force caused by acceleration. Note, going very quickly does not generate any gravitational effects whatsoever. However, accelerating or decelerating produces the apparent affects of gravity. If a ship were to accelerate at 9.81m/s², then everything inside would experience Earth normal gravity, accelerating at 1.62m/s² would produce Moon normal gravity. This affect would only remain as long as the ship continued accelerating or decelerating, the moment it starts coasting this apparent gravity would disappear.
• Matrioshka Brain - this is a massive superstructure that fully encompasses a star. The design typically incorporates trillions of orbital structures that form a swarm around the star, absorbing all its light to have unfathomable amounts of computing power. What’s more, since this first shell of orbital supercomputers will emit waste heat, another swarm can be built around them, absorbing their heat to run calculations more efficiently. As more and more shells of supercomputers are built, each running on less energy, but processing information more efficiently the calculations the Matioshka Brain can run grows exponentially. In theory, these shells could be built thousands of levels thick until the outermost shell is absorbing energy only slightly above the background temperature of the universe. Note: this is not reversible computing, energy is used at each level to flip the bits, but it is extremely efficient recycling of the waste heat produced from that process.
• O’Neill Cylinder - this is a large cylinder the spins to produce centripetal force (spin gravity). Unlike in fiction, a couple important considerations are that the walls towards the edges would not be capped with flat disks but cones since they provide greater structural integrity. In most cases, these caps would be decorated to appear as large mountains on the inside. What’s interesting about these mountains are that as you climbed it, the apparent gravity would decrease while the air pressure would remain constant; that’s basically the complete opposite of mountains on Earth, where gravity remains constant while air pressure decreases. Another big difference between O’Neill cylinders and what you often see in fiction is that the outermost wall would probably be inside a rocky body like an asteroid. This would greatly enhance protection from small micro-meteors and radiation. Although this isn’t a requirement, you can assume all of the ones in this universe are built like such unless stated otherwise. Something else to note is that if steps were not taken, you’d be able to see the ground above you instead of the sky. People didn’t like that so inside most O’Neill cylinders there is a second cylinder that spins in the opposite direction. This does two things, one it helps the O’Neill cylinder be more stable in space, preventing it from turning end over end, second it allows large screens to simulate the sky and clouds preventing anxiety. O’Neill cylinders range from 500m (1,600ft) in diameter to 10km (6.2mi) depending on it’s needs. The length of an O’Neill Cylinder can be however long is desired (within reason), but most range from 1km (0.62mi) to 50km (31mi). The only entrances into an O’Neill cylinder are at both cone caps, which also happens to experience almost no centripetal force (spin gravity).
• Quantum Thermal Fluctuations - at absolute zero all classical temperature fluctuations stop, but due to the Heisenberg Uncertainty Principle, quantum fluctuations will continue to occur. Therefore, even at absolute zero, and definitely at a microKelvin above that, quantum particles will continue to behave randomly. Thus, even with a perfect measuring device, it is impossible to know the complete, precise information about quantum particles no matter how cold it is.
• Solar Sail - a method of space propulsion that requires no propellant. By having a large foil absorb or reflect light emitted by stars the spacecraft can travel away from a star. Most foils reflect light since that provides more momentum for the same surface area. Limitations of this propulsion method are that it becomes less effective the further it is from the sun. Anything further than Jupiter requires massive sails to produce even small amounts of thrust. By pitching the foil it can travel at various angles, it can even approach the sun by angling the sail so it’s accelerating against it’s orbital direction.
• Supercapacitor - this is the holy grail of energy storage. A capacitor is cable of storing massive amounts of energy and even charging quickly, but it must also discharge quickly. A battery is capable of storing less electricity and charges much more slowly than a capacitor, but is capable of releasing its charge as slow as needed. A supercapacitor combines the best aspects of each and even deteriorates more slowly. Current supercapacitors are built with carbon fiber and metal oxides including titanium dioxide and polyaniline.
• Torchdrive - is a powerful rocket with a high delta-v. Most rocket engines of the 21st century fall into one of two camps. Either they have low thrust but a high delta-v since they're very fuel efficient, or they provide high thrust but have a low delta-v since they burn fuel so quickly. Currently, the direct fusion drives are the closest thing. On KATS 50 metric-ton shuttles, the reactor can produce 500Mw of power and accelerate at 0.25 m/s² or 0.025g.