Some science and science fiction
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Why we are using an octagonal shape sail instead of a circular one. The main reason is that we are using solar panels as a sail, and we are not making curved panels. Curved panels are very hard to manufacture and also difficult to replace if something gets damaged. An octagonal shape has straight edges, so it is easier to build and maintain. At the same time, it still fills space quite well, almost like a circle, because it has enough parallel sides.
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Why we are using light-colored or orange solar panels instead of dark or blue ones. Since the sail also works for propulsion, we want it to reflect light more than absorb it. Dark colors absorb radiation, but for a solar sail, reflection is more useful. That is why we are choosing lighter colors for better performance.
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Using two counter-rotating centrifugal sections in the spaceship. One rotates clockwise and the other rotates counterclockwise, so their angular momentum cancels out and keeps the system stable. One of them is smaller because there are already one or two more smaller centrifuge systems inside the main body. These are used in the environmental control unit to separate gases from liquids, like removing gas bubbles from water using rotation.
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Solar panel sails are the primary method of travel. As long as we are close to the Sun or still inside the solar system, this works well and saves a lot of fuel. But as we move farther away, solar radiation becomes weaker due to the inverse square law. At that point, we switch to NTR - hydrogen thrust engines to continue propulsion.
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Use of inertial control gyroscopes. These are used to change the orientation of the spaceship without using fuel. They work like heavy rotating discs or flywheels. By controlling their motion in specific ways, we can rotate or stabilize the ship without wasting any propellant.
FICTIONAL POINTS
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There is also a concept of using charged particles in space as fuel or to generate hydrogen by recombination, but this is not practical. The density of particles in space is extremely low, around a few particles per cubic centimeter, while on Earth it is extremely high. Because of this, collecting enough material from space is not efficient, so this idea is not very useful.
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There is a concept of moving from asteroid to asteroid for refueling or material extraction. Instead of going directly to the destination, the spaceship can stop at asteroids along the way. But this requires a lot of planning, and there must already be probes placed in advance to prepare those asteroids. Also, space is mostly empty, so asteroids are not always available in the path. Because of that, this method is possible but not always reliable.
I hope you love it. Have a nice day 
