<h1>Why did humans land on Mars? </h1>
Mars and Venus are the two most explored planets. The maximum temperature on the surface of Venus can reach more than 450 degrees Celsius, and the environment on Venus can be described as "hell" compared to the environment of Earth. The environment on Mars is much gentler than that of Venus. Humans have successfully landed on the moon, and a manned landing on Venus is obviously not a wise move, so people have set their sights on Mars farther away.
Eggs cannot be placed in the same basket, and for the long-term development of mankind, we cannot live only on the earth. One day, the resources on Earth will not meet the development needs of human beings, and then we will need to implement interstellar migration. Venus is the closest planet to Earth, but the environment is very harsh and not suitable for colonization at all, and it is clear that Mars is the best choice. Although Mars is smaller than Earth, it is very similar to Earth in many ways, such as Mars rotating for about 24 hours a week. Mars is the outpost of human exploration of the universe.
So how long will it take for humans to reach Mars under existing technology conditions?
<h1>Take a look at the current level of human space technology development</h1>
To enter the vast expanse of space, you first need to get rid of the gravitational pull of the earth, and the size of the rocket thrust determines what you can achieve.
Tsiolkovsky of the former Soviet Union was the first person in human history to put forward a perfect theory of space navigation, and is known as the father of space navigation. He first demonstrated the feasibility of interstellar voyages with rockets, satellites, and space stations, and designed a series of solutions for the structure of liquid rocket engines.
In 1926, the American engineer Goddard invented the first liquid rocket, and the rocket really entered the practical stage at the end of World War II, when Germany used a V2 rocket carrying explosives to bomb London, which was also the world's earliest missile. Much of the original rocket propulsion technology of the former Soviet Union and the United States originated in Nazi Germany.
In the 1970s, the United States carried out a series of Apollo moon landing programs and successfully sent 12 astronauts to the lunar surface in 6 times, and a large part of the american success was because they had large-thrust launch vehicles. At that time, the United States used the Saturn 5 carrier rocket, and the low-Earth orbit carrying capacity of the Saturn 5 carrier rocket could reach 130 tons, second only to the former Soviet Union's Energy carrier rocket. The chief designer of the rocket is the chief designer of the famous V2 rocket von Braun, which is still the largest launch vehicle in the world to this day. China's Long March rocket is still a little bit of fire to send astronauts to the moon, and the maximum carrying capacity of low-Earth orbit has reached tens of tons, which is the same level as Russia.
Pictured above is the Saturn 5 launch vehicle
In the 1990s, the United States had the ability to launch landing probes and rovers to Mars, and has since successfully launched several probes to Mars, such as the famous Curiosity rover. A lot of the current data on Mars comes from NASA.
The maximum carrying capacity of the space launch system currently being developed by the United States will exceed that of the Saturn 5 launch vehicle, and it is likely that the Americans will land on Mars first, but this may not wait until after 2030, because the United States now plans to return to the moon before 2024.
In addition to carrying capacity, speed is also important. To break free from the constraints of Earth's gravity, it is necessary to reach a second cosmic speed of 11.2 kilometers per second. To escape from earth's orbit from the sun's gravitational pull, a third cosmic velocity would need to be reached.
At present, the fastest speed of probes launched by humans has reached the third cosmic speed, that is, 16.7 kilometers per second. In the last century, to achieve this speed, it was also necessary to rely on the gravitational pull of the planets to accelerate, that is, to use the gravitational slingshot effect to accelerate. To achieve faster speeds, new propulsion technologies, such as the use of nuclear energy, are needed.
The initial velocity of the New Horizons probe launched by NASA in 2006 reached 16.26 kilometers per second, the fastest initial speed spacecraft ever launched in human history. The Parker Solar Probe is the fastest spacecraft in human history, with perihelion reaching a maximum velocity of more than 100 kilometers per second, but this is the effect of the sun's gravity.
Pictured above is the New Horizons probe
Although many new space propulsion technologies have emerged, such as ion thrusters that have entered the practical stage, chemical fuel rockets are still mainstream. Under the influence of many factors, in the future, human beings will still rely on chemical fuel rockets for space exploration for a long time.
<h1>How far is Mars from Earth? </h1>
The distance between Mars and Earth is not fixed, but changes over time, with a closest and farthest distance. It is well known that both Earth and Mars orbit the Sun in an elliptical orbit, with aphelion and perihelion. Taking the Earth as an example, the Earth is 147 million kilometers away from the Sun at perihelion, 152 million kilometers away from the Sun at the aphelion, and the average distance between the Sun and the Earth is 150 million kilometers.
The average distance between Mars and the Sun is 230 million kilometers. Although mars and earth both orbit the sun, Mars has an orbital period of about 687 days, while Earth's orbital period is about 365 days. Mars is 400 million kilometers away from Earth at its farthest and only 55 million kilometers apart at its closest. When the Tropics are closest, the Sun, Earth, and Mars are in almost the same straight line, which is called the Martian opposition, which occurs about every 780 days.
<h1>Under existing technical conditions, how long will it take for humans to reach Mars? </h1>
The Moon is 380,000 kilometers from Earth, and it took four days for the Apollo 11 spacecraft to send humans to the Moon in 1969. Mars is 55 million kilometers away from Earth, so how long does it take for a manned landing on Mars?
At present, we all choose to launch probes when Earth and Mars are closest, which saves both time and fuel under existing technical conditions. Let's take the United States InSight Mars rover as an example to illustrate. On May 5, 2018, the InSight Mars rover was launched, and on November 26, 2018, the InSight Mars rover successfully landed on Mars, which took more than 6 months. That is to say, it will take about half a year for us to land on Mars, but it will take more than two years to make a round trip.
Although the landing time on Mars is not too long, surviving on Mars requires very large supplies, and we need to transport these things to Mars in advance. The key is that astronauts need to live on Mars for two years before they can return to Earth. In addition, astronauts also need a lot of supplies during the six-month journey to Mars. Under existing technical conditions, it is not possible to send so many supplies into space at once, but we can send these materials to Earth orbit in batches and then transport them to Mars.
The straight line between the two points is the shortest, but the current power of the human spacecraft is not enough to walk in a straight line, in order to save fuel, we are all walking curves.
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