How difficult is it to go deep into the universe?

People on earth had the idea of exploring the depths of the universe at a very early age, and it was also a long-time idea to move to other planets, and Mars has always been regarded as the first choice for people to move. Specifically, there are three routes to choose from from the Earth to Mars. The first route is called Hohmann transfer orbit, which was discovered by mathematician Walter Hohmann.

People on earth had the idea of exploring the depths of the universe at a very early age, and it was also a long-time idea to move to other planets, and Mars has always been regarded as the first choice for people to move. Many people imagine that Mars is close to the earth, but it is not.

So, how difficult is it to reach the depths of the universe? We might as well take Mars as an example to explore. Both the Earth and Mars revolve around the sun, but their speeds are different, and their paths (ellipses) and lengths around the sun are different, so their relative positions are always changing. When Mars and the Earth are on the same side of the sun and basically in a straight line, and Mars is at perihelion and the Earth is at apohelion, the distance between Mars and the Earth is the closest (called "Chong" by ancient astrologers), about 56 million kilometers; When Mars and the Earth are on both sides of the sun and basically in a straight line, and both Mars and the Earth are at apohelion, Mars is the farthest from the Earth (called "conjunction" by ancient astrologers), about 400 million kilometers. But the distances mentioned here are all linear distances, and the route from the earth to Mars can't be a straight line, only an arc or an elliptical route. Obviously, when the fire hits the ground, the route to Mars is also different.

Specifically, there are three routes to choose from from the Earth to Mars. The first route is called Hohmann transfer orbit, which was discovered by mathematician Walter Hohmann. This route is a huge ellipse, with one end tangent to the earth at the starting point and one end tangent to Mars at the ending point. When the fire meets the earth, the spacecraft sets out, because the direction of the spacecraft is consistent with the direction of the earth at this time, and the speed of the earth can be about 30 km/s, so it is the most fuel-efficient and least difficult route. The only problem is that it takes a long time.

The second route is called the rush point route. If we imagine the solar system as a dynamic plane with the sun as the center and eight planets revolving around it, then this route will be easier to understand. The spacecraft set out when the fire collided with the earth, but instead of going straight to Mars, it flew inward to the sun, flew over the orbits of Venus and Mercury, and bypassed the sun at an extremely fast speed. At this time, the sun will exert a huge afterburner on the spacecraft, forming a "gravitational slingshot" effect, just like the sun "throwing" the spacecraft out, and its speed far exceeds the power that the engine can provide. Then with a little adjustment, the spacecraft will reverse the orbits of Mercury, Venus and the Earth and reach the end of the route, namely Mars. This route is the longest, the most complicated and the most dangerous of all routes, but it is also the fastest and the shortest time-consuming.

The third route is called the rapid rendezvous route, which is an improved route of Homan transfer orbit. Compared with Hohmann's transfer orbit, fast rendezvous navigation requires the spacecraft to change course with the engine in the middle, which is equivalent to using more fuel to "cut corners". This route is closer, less time consuming and safer than the second one. No matter which route, using the existing rocket technology, it will take more than 180 days. Moreover, the road to Mars is not only long, but also full of accidents and dangers. The Soviet Union sent more than 20 unmanned probes to Mars, all of which ended in failure. Americans are much luckier, but the success rate is less than 50%. That's why we landed on the moon in 1969, but we haven't landed on Mars yet. Think about it, it's so difficult to go to Mars. How difficult is it to go to other planets in the solar system, even outside the solar system, outside the milky way and outside the local galaxy group?