The uncertainity of future
Our solar neighborhood is constantly changing, its stars traveling hundreds of kilometers every second. Only the very large distances between these objects protect us from all these dangers. But we may well be unlucky in the future. At some point, we might face a star turning into a supernova or a massive object passing close to Earth and causing a bombardment of asteroids. If this were to happen, we would know thousands, if not millions of years in advance. But we could not, in spite of everything, change much about it. Unless we move our entire solar system out of its way. |
| Photo by David Becker on Unsplash |
Moving the solar system:
To move the solar system, we would need a stellar motor, a megastructure capable of moving a star in the galaxy. This is the kind of work that could be done by a civilization technologically advanced enough to build a Dyson sphere, to secure their future millions of years in advance. But how could we move the hundreds of thousands of space objects from our solar system? The good news is that we can ignore all of these. We just have to move the Sun, the rest of the objects being linked to it by gravity and will follow him no matter where he goes. There are many ideas on how a stellar motor might look and how it works.Models that will suffice
We selected two models based on our current understanding of physics, which could theoretically be constructed. The simplest stellar engine would be the Shikadov propellant, a giant mirror. It works on the same principle as a rocket. Like the fuel in a rocket, photons released by solar radiation generate a thrust. Not very powerful but sufficient. For example, if an astronaut lit a torch in space, its light would push it very, very slowly. A stellar motor would be much more efficient than a flashlight because the Sun produces a large number of photons.The basic idea of the Shikadov propellant is to think up to half the solar radiation to generate a thrust and thus slowly push the Sun in the desired direction. In order for the Shikadov thruster to operate, it must be kept fixed and not in orbit around the Sun. Although solar gravity will try to attract it, it will be kept at a distance by the radiation forces, which will lift it. That means the mirror will have to be very light, in the form of a reflective sheet of one micron thick made of a material such as an aluminum alloy. The shape of the mirror is also important. Wrapping the Sun in a huge spherical shell would not work because it would focus light towards the Sun, causing it to overheat and creating all sorts of unpleasant problems. Instead, we would use a dish, which would return the photons around the Sun and in the same direction, which would maximize the thrust.
What wil be the direction?
To avoid burning or freezing the Earth by excess or absence of sunlight the only place to position the Shikadov propellant would be above the poles of the Sun. That means we couldn't move the Sun vertically with respect to the system plane. and in only one direction within the Milky Way, which somewhat limits our route options. But that's basically it. For a civilization capable of building a Dyson sphere, this is a smaller project. Not complicated, but difficult to build. At full power, the solar system could move a hundred light years in 230 million years. Over several billion years, that would give us almost total control of the Sun’s orbit within our galaxy. But in the short term, it might not be enough to avoid the explosion of a nearby star. That's why we think we can do better. So we asked our astrophysicist friend if he could design a faster stellar thruster.We are going to call our new star engine: "The Caplan propellant"! It works on paper like a traditional rocket, by pulling material in one direction to propel itself opposite. It would be a huge space station, powered by a Dyson sphere, which would collect matter from the Sun to make nuclear fusion The station would reject a powerful beam of particles, at about 1% of the speed of light outside the solar system. A second beam would in turn push the Sun like a tug.
The working mechanism:
The Caplan thruster would require a lot of fuel, or millions of tonnes per second. In order to recover this fuel, our propellant would use very strong magnetic fields so as to channel hydrogen and helium from solar winds within the reactor. Solar winds, however, would not be enough to provide enough fuel. And that's where the Dyson sphere comes in. By harnessing its power, sunlight could be locally focused on the surface of the Sun. This would heat a small region of the star, wringing billions of tons of matter from the star. This mass could then be collected and separated between hydrogen and helium. The helium would then be explosively burned in a thermonuclear fusion reactor.A beam of radioactive oxygen at a temperature of about a billion degrees would then be rejected, forming the main source of propulsion for the stellar motor. In order to prevent the station from crashing into the Sun, it needs to compensate for this push. For this purpose, we could accelerate the hydrogen collected using electromagnetic fields using a particle accelerator and thus draw a second beam towards the Sun. This would balance the station and transfer its thrust to the Sun. In just a million years, this engine could move the Sun by 50 light years. More than enough to avoid a supernova.
At full power, the solar system could reach a new galactic orbit in 10 million years. But doesn't that risk reducing the life expectancy of our Sun? Fortunately, the Sun is so massive that even billions of tonnes of matter represent only a tiny part. In reality, this megastructure could even extend its life expectancy, because less massive stars burn less quickly, thus making the solar system habitable for several billion more years. With a Caplan propellant, we could transform our solar system into a spaceship. For example, orbiting backwards in the galaxy and colonizing hundreds or thousands of stars by crossing them. It would also allow us to escape from our galaxy and to extend our influence beyond the Milky Way.
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