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How to change orbit and rotation

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Many planets and moons, from Solar System and beyond, have long rotation periods or elliptical orbits. Changing orbit and rotation data will help terraforming process. Such a modification will require mega engineering processes, beyond current technology. It is possible that some planets will not survive the changes.

Technology Edit

Many people have proposed from time to time methods to change orbit and rotation. Current technologies are limited, but far future engineers might come with a solution.

Current technology Edit

Chemical engines, currently used for spaceships, have limited power. They might divert a comet or an asteroid, but for sure not a planet. It will require huge amounts of materials and energy.

Ion propulsion engines might be used for pushing asteroids and small satellites, but for sure not large bodies. If a planet has atmosphere, the jets will only push the gasses, without any effect on the planet.

Atomic engines could be used. Fission or fusion engines are able to generate much more energy. However, this has never been tested on a spacecraft. The main problem is the residual radiation left on the planet.

Solar wind can be focused by a gigantic mirror. It might prove useful for moving an asteroid, but never for a planet.

Gravity influence is a way to do this. By placing a spaceship near an asteroid and keeping it in position, its tiny gravity can attract the asteroid in time, pushing it away from its trajectory. By keeping a large enough asteroid in a fixed point relative to a planet, we can slowly divert that planet into other orbits. By placing an asteroid on orbit around a planet, depending on planet's rotation period, some momentum can be transferred from the new satellite to the planet (or from the planet to the moon), gradually changing rotation speed. The process takes a long time.

Impacts with diverted asteroids and comets can prove useful in changing rotation or a celestial body, but will not do much in changing the orbit. A single impact will do nothing. For example, Mercury is 50 billion times more massive then a comet with diameter of 3 km. In a collision, if the comet is moving with 10 km/s faster, Mercury will increase its speed by only 0.0002 mm/s. If all comet's energy is transferred to rotation, a day on Mercury will last a few seconds shorter. So, we will need a huge amount of impacts for a visible results.

Space elevators are a simple way to slow down and eject matter from a celestial body. A space elevator is a long nanotube (or made by other materials), with its gravity center placed beyond the geostationary orbit. The elevator moves once with the planet. If we use a very long elevator, twice above geostationary orbit, it can be used to remove fluids. At, a huge pumping station will push water from the surface to geostationary orbit. Then, water will flow to the end of the wire, powering a turbine that will allow the pump to force more water. This process can be used to remove water from a planet whose ocean covers all land. The energy used for the process comes from rotation energy, so the rotation speed will gradually decrease.

Future technologies Edit

We don't know what the future will bring to us. From the world of today, two methods are more promising:

Curved space generated by a machine from year 300 000 will change space shape and will force a celestial body to change its movement.

Artificial gravity can be used to attract and divert a planet or a moon. The process will require far more gravity then what a spaceship needs to keep people walking on their feet. Special caution should be take in not diverting other celestial bodies.

Challenges Edit

A massive project like changing orbit or rotation of a celestial body will be a hard task.

Surface - volume problem Edit

By increasing the radius of a sphere, the surface is increasing by the square and the volume by the cube. This creates a major problem, exposed in the following scheme:

R = radius, S = surface, V = volume, E = volume/surface (all data shown in km)

  • R = 1, S = 3.14, V = 4.19, E = 1.33
  • R = 10, S = 314, V = 4 190, E = 13.3
  • R = 100, S = 31 400, V = 4 190 000, E = 133
  • R = 1 000, S = 3 140 000, V = 4 190 000 000, E = 1 330
  • R = 10 000, S = 314 000 000, V = 4 190 000 000 000, E = 13 300.

The E comes from engine surface. Suppose that on every square meter of the surface, there is an engine pushing the body away, we can see this: On an asteroid with radius of 100 km, each engine will push 133 cubic meters or rock. For a planet with a 50 times greater radius, there will be 50 times more rock to be pushed by each engine. Moving a greater body will be harder because there will be no empty place for extra engines on the surface. By using too much force, the engine can get buried by its own power.

Forcing the crust Edit

By applying a too strong impulse on the surface, it might break. Even a tiny but global push will be enough to power-up volcanic activity. At the same time, by pushing the body out of its orbit, out of its initial tidal stress, strong volcanism might appear.

Changing the rotation will also affect volcanism. If force is applied only on the crust, the molten core will spin with the same speed. The crust might break into pieces or if it will not, volcanoes will erupt. Also, the process will generate strong friction, powering volcanism, tectonic and seismic activity.

Even for a solid body, there will be earthquakes. Each planet or moon is more or less deformed from a sphere, to accommodate to its rotation (centrifugal force) and gravity from its hosting body. By changing rotation speed and gravity on a large body, some geological activity might be seen.

Secondary effects Edit

The process can leave unexpected effects. Many asteroids are in an orbital resonance with larger planets and also many moons are in a resonance one with the other. By moving a large body from a place to another, orbits will be perturbed. By extracting a moon from a planet, it will be a change of mass, affecting also other planets.

Colliding small bodies Edit

sometimes, by changing orbits, smaller bodies can collide, creating a larger object. It is possible to create a planet from asteroids or a larger moon from smaller ones. It is to be discussed if that new body will be suitable for terraforming and colonization or if it will be too hot.

Colliding small bodies could be useful in case of the moons of Uranus. The resulting body will be large enough to hold an atmosphere. The moons have large amounts of ice. After a collision, ice should melt and help the new moon to cool down. Strong convection currents will bring heat water up to the extreme cold surrounding environment. For a long time, the new moon will have an atmosphere of water vapors. Then, when ocean temperature will drop below boiling point, it will be a strange ocean, with extreme humidity. Later, when temperatures will decrease even more, it is possible that ice will cover small areas. By this point, the equilibrium will change, because ice will provide good heat insulation. Atmosphere will cool down and the ocean will keep heat trapped.

The same method proposed for Uranus can be used for rocky moons of Saturn or for Kuiper Belt objects.

In the main Asteroid Belt there is not enough matter to create a planet able to sustain an atmosphere. However, other stars might have larger asteroid fields.

By colliding two brown dwarfs, we could create a star. Also, two dim stars can be merged to create a lighter star, if they survive a supernova.

Costs Edit

Does it worth to change the orbit or rotation of a planet? As long as spaceships will not pass the speed of light, we will be stocked around Solar System and other nearby stars. First settlers will come in small numbers and will create little settlements. then, the towns will grow. Massive transformation processes, like changing orbits and rotations, are risky and might change a planet into a ball of lava. Settlers will consider it too risky.

Still, it is possible that at some point a megacorporation will try to try massive engineering transformations on an uninhabited environment, like some interstellar planets. Orbit and rotation transformations might be achieved there.

When humans will pass the speed of light, a bloom colonization era might start. Settlers will have many planets to choose. At that point, it will be more easy to find a planet more similar to Earth then to try extreme terraforming models on different planets.

Yet, when human civilization will colonize many galaxies, it is possible to see very rich people, having private land covering thousands of light years. Just like hunting today, the very rich will find it relaxing to collide and blow planets or even stars.

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