Styx is the smallest known moon of Pluto and the second moon from inside out, after Charon. It orbits Pluto - Charon barycenter in 20.16 Earth days or 3.16 Plutonian days, at a distance of 42700 km. Styx is irregular, being 16X9X8 km. It has a chaotic rotation, meaning that its rotation axis and period varies over time.
Styx was imaged by the New Horizons probe in limited detail. Not much is known about its internal composition, but based on its albedo, it appears to be made of water ice. Because of the high distance to the Sun, the Solar Constant is very low. Temperatures are below -200 C and luminosity is dim, making plant life hard.
Importance
Among all Kuiper belt objects, Pluto is the most studied and the most interesting. Until recently, it was considered a planet and many people still consider Pluto to be a planet. This is why Pluto is expected to receive the highest number of settlers in the Kuiper Belt.
It must be noted that Pluto has a very interesting chemistry, with nitrogen, methane and tholins on its surface. In addition, Charon has its own deposit of organics close to the poles, created from runaway gasses escaped from Pluto. When humans will exhaust fossil fuel reserves on Earth, organic compounds will still be needed to make plastic and rubber. There will be two options: to produce organics from algae in closed ecosystems or to harvest them where they still exist. Even if other distant celestial bodies, like Eris and Sedna have methane on their surface, they are either too far away or lack the chemical complexity found on Pluto.
There are models for terraforming Pluto and even Charon, which will be very costly.
So, there are both historical - spiritual and economic reasons to colonize Pluto and Charon. However, because of the high costs and rare flight windows that occur along the Trade Routes, both passengers and cargo will be shipped to and from Pluto with the help of large interplanetary ships. Such ships will be huge, over 2 km long and will connect Pluto with other planets when flight windows allow. Big ships will find impractical to land on large celestial bodies and they will need a space station. Luckily, Pluto has four small moons, which are suitable for this: Styx, Nix, Kerberos and Hydra. From all of them, Styx is the closest to both Pluto and Charon.
Styx will be the space station serving Pluto system. All passenger and cargo ships will stop here. From here, smaller ships will carry all the goods and people within the Pluto system.
Challenges
Styx is a small moon with very little gravity. Ships will need to dock carefully here. Also, during cargo transshipment, everything needs to be manipulated with care. A single unwanted move can send a cargo container into orbit around Pluto.
Styx is made of water ice, with an unknown amount of impurities. We can use the ice for building, but many materials will need to be imported.
It appears that Pluto lacks a magnetosphere. Because of this, there is no radiation belt surrounding the planet. A small part of the atmosphere exits into space, but that should not harm electronics. The solar wind was confirmed to exist even at that distance, but it is far weaker then at Earth's orbit. However, cosmic rays are far more frequent.
The Sun barely heats Pluto. The base will need to have a very good insulation, to keep the inside warm enough for people. In addition, solar panels are useless. Energy will need to be produced by a nuclear generator.
The Base
Because the Pluto - Charon system is far smaller, space traffic will be far lower then for all planets. Still, the base will need to provide many basic services.
Thermal insulation. First of all, the base needs to be well insulated. Water ice, mainly if it has some porosity, is a good thermal insulator. So, the base, at least the part that is habitable, needs to be covered with a thick layer of ice. Building the base inside the moon will be a good idea. On the interior, the ice walls could be covered with natural tholins and organic compounds refined or produced on Pluto.
Construction materials. New Horizons probe detected no metals nor rocky compounds on Pluto, Charon and other moons. Water ice plays the roll of rocks here, while other ices and tholins play the role of soft ground. In order to limit the imports of metals, technicians might look for plastic, which can be created here from organics. It is a radically different approach. Metals will be used only when no other solution is possible. Inside the base, all walls and furniture will be made of plastic. It is possible to build from plastic many accessories used for cargo shipping.
Energy source. There is no way we can use solar light as a significant source of energy. Solar panels will be useless. A nuclear generator will be mandatory. If anything goes bad with the generator, the station is doomed and everyone will freeze to death. A better approach will be to have three reactors. Reactors 1 and 2 will produce energy alternatively. When one reactor is working, the other one will be repaired and prepared to start working. Reactor 3 will always be ready and will start working in emergency situations. These reactors will produce electricity and heat for the station. At Pluto's orbit, solar light is enough for a human to see, but it is too dim for plants to grow properly. Also, most of the base will be underground, shielded from cold and from cosmic rays. Artificial light is mandatory.
Ecosystem. There are two scenarios. In the first model, the base will produce all oxygen and food needed for passengers and working personnel. In order to do this, we will need underground domes, well insulated, heated and illuminated, to grow plants. Then, we will also need tanks filled with bacteria, to decompose human dejections and sediments in residual water to minerals needed for plants. There is also a possibility that food and oxygen will be shipped from Pluto or another moon with maintenance ships, while carbon dioxide and human dejections will be transported back. In this case, the base still needs technology to recycle water and to extract carbon dioxide.
Inhabited area. The place where people will stay needs to be heated to a temperature acceptable for humans (for example, +20 C). This will be the central part of the station. To reduce heat losses, the inhabited area will be composed of many parallel levels. Workers will have their apartments, while passengers will have a central dome, a mall, a recreation area and a place to sleep. There will also be places to eat and toilettes.
Spaceport
The station will have at the surface platforms for spaceships. On Styx, there will be a few different types of ships:
- Large interplanetary ships will travel probably between Pluto and a few powerful economies of the Solar System. These ships have over 2 km long and will require special docking platforms.
- Intermediate size interplanetary ships will travel towards smaller economies, like Mercury, Uranus, Neptune or Ceres. They can be docked on large platforms, but some might suggest the use of average-sized landing pads.
- Small size ships will travel between Pluto and other Kuiper Belt Objects that happen to be close enough. They will require small pads, like local ships.
- Local ships will link the station with Pluto and its moons. They will be frequent and will require small pads.
Because of the high distance, it is more plausible that interplanetary ships will be made for both passengers and cargo.
For space stations located closer to the Sun, the use of underground or surface corridors is feasible, since they don't require so much heat. In case of Pluto, it is more feasible to use small ships that will dock themselves to each ship to ferry passengers from and towards the base. A long corridor will require much energy to be heated. Also, changings in temperature between -230 and +20 C will cause cracks to occur in the walls.
When a ship arrives, first will be deployed people, then cargo. Also, when a ship departs, first will be uploaded cargo, then people.
Freight can be shipped as containers, just as it happens on Earth. Standard containers will have the same size and will be lifted and moved with automated cranes. Many products (like foods, textiles, minerals and machinery) can be transported at local temperatures, which are below -200 C. Others will require a certain temperatures and will need to be transported in special rooms, with access to electricity.
Still, there will be items that don't fit into regular sizes, like large chunks of rock, grinded rock and large pieces of equipment. They will be handled with special robotic arms, flying cars and with much care.
A major problem comes when Styx base will deal with fluids. Most fluids will be frozen at this temperature, even if they were liquids or gasses where they came from. In this case, tanks used to store fluids need to be heated. Then, fluids need to be pumped fast into other tanks inside the base. When filling the tanks of a ship, fluids need to be heated, so that they can be pumped in.
Flight Windows
Trade routes are dependent of flight windows, which occur when planets are properly aligned. However, no spaceship has traveled this far without at least one gravity assist.
Between the Plutonian system, the following flight routes exist:
Pluto - Styx: 9.35 Earth days Charon - Styx: 9.35 Earth days Styx - Nix: 93.63 Earth days Styx - Kerberos: 55.51 Earth days Styx - Hydra: 42.62 Earth days
Towards the inner planets:
- At every 12 Earth years, Jupiter is in place for a gravity assist.
- At every 30 Earth years, Saturn is in place for a gravity assist.
- At every 59 Earth years, both Jupiter and Saturn are aligned for a gravity assist.
Without a gravity assist, the following flight windows exist:
Mercury - Pluto: 88 Earth days Venus - Pluto: 225 Earth days Earth - Pluto: 1.01 Earth years or 367 Earth days Mars - Pluto: 1.90 Earth years or 690 Earth days Ceres - Pluto: 4.67 Earth years or 1712 Earth days
When a ship is going to the Kuiper Belt (for example, a Mars - Pluto voyage), Jupiter or Saturn will boost the speed. By opposite, when a ship is traveling from the Kuiper Belt, Jupiter or Saturn can be used to decelerate.
Towards giant planets:
There are flight windows to and from Jupiter at every 12 Earth years. However, for all other giant planets, flight windows are far more rare. Because of this, ships will take not the ideal routes, at the expense of fuel.
Without gravity assists, the following flight windows exist:
Jupiter - Pluto: 12.47 Earth years or 4550 Earth days Saturn - Pluto: 33.43 Earth years or 12210 Earth days Uranus - Pluto: 127.0 Earth years or 47410 Earth days Neptune - Pluto: 483 Earth years or 176400 Earth days
Inside Kuiper Belt:
Objects in the Kuiper Belt orbit the Sun very slow (with speeds up to 4 km/s). So, it is very easy to make a ship go in whatever direction you want. However, given the vast distances between Kuiper Belt Objects, each ship will need a lot of time to travel. Ideal flight windows are rare, one in a few hundred or thousand Earth years.
Major challenges:
The major problem is that flights towards, from or inside the Kuiper Belt require much time, sometimes up to decades. Passengers will not be happy with this, while cargo transport companies will see their profits diminishing. Because of this, ships will not follow the cheapest flight windows, which require much time. The New Horizons probe could have reached Pluto with less energy consumption, using an alternative trajectory and multiple flybys. However, they decided a much faster trajectory with a single flyby, at the expense of fuel. As a direct result, New Horizons arrived faster, but passed very fast past Pluto, limiting its available time for observations. If we want to reach a celestial body in the Kuiper Belt and land there, we have to dramatically increase flight time or use fuel to slow down the ship.
When not the cheapest routes are selected, many more additional flight windows can be considered.
Schedule:
For other space stations, using mainly ideal flight windows, there are about 15 ship launches during an Earth year. Also, as discussed for Jovian station Himalia, for Saturnian station Helene, for Uranian station Perdita and for Neptunian station Halimede, when flight windows are too rare, a ship will travel at every 1000 Earth days. For Pluto, let's suppose that only towards Earth, there will be a ship departing at every flight window (which occurs about once every 366 Earth days). For other destinations, like Mercury, Venus, Mars, Ceres, Jupiter, Saturn, Uranus and Neptune, there will be a ship every 1000 Earth days. This will imply for an average of 3.92 launches during an Earth year or one launch at every 93 Earth days. One ship will launch or land at roughly 46 Earth days.
Between Styx and both Pluto or Charon, flight windows occur at every 10.129 Earth days or 1.5 Pluto days. There will be many local flights, connecting the planet and all moons.
If any inhabited Kuiper Belt Object is close enough to Pluto (at maximum 20 AU), a scheduled service could exist. However, if the distance is larger, it becomes more feasible to use other space stations.
Delta-v
The Delta-v shows the energy required for a ship to travel. for Styx base, values are listed below:
Mercury Space Station – Pluto Styx 23.921 Venus Space Station – Pluto Styx 19.361 Earth Space Station – Pluto Styx 17.565 Mars Phobos – Pluto Styx 13.922 Ceres Space Station – Pluto Styx 9.662 Jupiter Himalia – Pluto Styx 8.637 Saturn Helene – Pluto Styx 9.154 Uranus Perdita – Pluto Styx 5.918 Neptune Halimede – Pluto Styx 1.114 Pluto Styx – Eris low orbit 1.540 Pluto Styx – Sedna low orbit 2.780
Pluto – Styx 1.334 Charon – Styx 0.762 Styx – Nix 0.046 Styx – Kerberos 0.058 Styx – Hydra 0.061
For comparison, an Earth surface - Moon surface flight will require a delta-v of 14.466 km/s.
One can see that flights to the rocky planets require high delta-v values, which can be lowered with the help of flybys, which occur often. Flights to the gas giants appear to require less fuel, however, they will last at least a century. Because of this, ships will sacrifice fuel to get faster to their destinations.
Flying inside the Pluto system requires only little fuel consumption. Because of this, if Pluto will become a free state, its moons will be so tightly connected that they will be part of that state.
Strategic Importance
The Styx station will be very important for Pluto, giving it a planet-like status. Also, the station will be very important, as the first trading center in the Kuiper Belt. Giving the vastness of the belt, it will be impossible for Styx station to serve more then 20% of all Kuiper Belt Objects that will be inhabited.
After Styx station will be operational, it is highly possible that other stations will be built around Eris, Sedna, Haumea and other dwarf planets.
The Main Asteroid Belt has a significant chance to become a state or a federation... or at least there is a significant chance that most of it will be. However, the Kuiper Belt is too large for strong economic ties to form between all colonies. Most probably, there will be a multitude of states, federations, unassociated territories and possessions of inner Solar System states.
