The problem with interstellar travel is where we would go?

The problem with interstellar travel is where we would go?

What type of star would be a target for our first interstellar probe? The journey to that star would take hundreds of years. If we would select the wrong star, the best thing that we can imagine is that there is no planet at all.  But if we would want to make space colony the young stars would be the best targets, because there are no advanced lifeforms in that kind of planets.

And if we are thinking about the situation, that the entire human civilization would start to travel to the other solar system when the sun has turned to the red giant, that means that the young stars would be more attractive than old, The lifetime of the young stars is longer, and that means that we have time to benefit that solar system. If the solar system, where our descendants would travel in the distant future is mature, there is a possibility that something goes wrong, and in the worst case, we could meet another civilization, which turns the conflict. The possibility of that kind of conflict is very small.

So if we would want to create the interstellar spacecraft, we would have one problem, where we would send that thing. If we are thinking about the journey, what takes about hundreds of years, there must be something to see, and what we would want to take the close look.

And that thing means deciding on the targeted solar system is extremely important because that kind of journey takes time and sophisticated technology, what is existed only at the theoretical level. The most important parameter in the long-distance space traveling is the time, launching the space probe must be happening in the right moment.

That moment is called a "launching window". The moment of this thing is important, because of the gravity of the sun is so powerful, that resisting that thing needs so huge rocket, that it cannot rise from the ground. That's why the researchers need the use the other planets as the gravity sling and another thing is that the probe must reach the targeted planet at the moment, that the planet is visible from Earth. So we cannot shoot the probe freely even to Mars, because the planet must not be at another side of the Sun.

But sending a probe to more distant planets and moons is more complicated, because of other planets on the journey must be in the right direction and location, that the use of the gravity sling is possible. The gravity sling means that when the probe reaches the planet in the absolute right angle, that thing would turn the trajectory of the probe, and give it more punch. This might seem very easy, but the angle, what the probe uses must be an absolute right. The most used object in the solar system for gravity sling is Jupiter.

The gas giants are a complicated thing because their moons are also massive objects and the big moons like Ganymede give their effect to the trajectory. Gas planets are forming the entirety with their moons and the position of those sub-particles causes the asymmetries to the gravity field, and even the smallest errors in the trajectory can be fatal for the mission because, in the huge distances, that thing would be multiplied.

But if we are sending spacecraft to another star the problems are not smaller. They are bigger. When the spacecraft will send outside the solar system, the gravity that pulls the craft back would be more powerful, because every single object in the solar system is taking part in that gravitational pull. And that requires extremely powerful engines.

The antimatter engines and other exotic motor systems like a photon or laser-photon engines have a couple of problems. The antimatter engine uses the annihilation reaction as the energy source. If the antimatter touches the wall of the tank, that thing causes the huge explosion, and that's why the system must build far away from earth. The energy level of the gram of the antimatter is so huge, that it can turn the Earth-size planet to the molecular nebula. And if that explosion happens too close to that planet, the thing is causing, that the entire planet would turn the planet away from its trajectory.

The only thing, that can reach the speed of the light is a photon. But the photon rocket requires also the use of antimatter engines because the thrust of the photon rocket is so weak. This means that the acceleration to the speed, what is close to the speed of light must be made by using another type of engine. And even if we would reach the speed, what is near the speed of the light, that means that the journey to the nearest star system Alpha Centauri would take many years.

In real life, the journey to Alpha Centauri takes more than four years, because the spacecraft must accelerate to the top speed. And then it must start to slow speed. That should also happen gently because of the structures of the spacecraft must stand the punch. So the slowing the spacecraft takes years. And here we are talking about the journey to Alpha Centauri, what is the star system at the distance of 4,5 light-years.

Image: https://www.wired.com/2008/08/space-limits/