Any object, being thrown up, sooner or later appears on the earth's surface, whether it is a stone, a sheet of paper or a simple feather. At the same time, a satellite launched into space half a century ago, a space station or the Moon continues to rotate in its orbits, as if they were not affected by the gravity of our planet. Why it happens? Why does the moon not threaten to fall to the earth, and the earth does not move towards the sun? Can it really be that gravity is not affecting them?
From the school physics course, we know that gravity affects any material body. Then it would be logical to assume that there is a certain force that neutralizes the effect of gravity. This force is called centrifugal. Its effect is easily felt by tying a small load at one end of the thread and spinning it around the circumference. Moreover, the higher the rotation speed, the stronger the tension of the thread, and the slower we rotate the load, the greater the likelihood that it will fall down.
Thus, we came close to the concept of "cosmic velocity." In a nutshell, it can be described as a speed that allows any object to overcome the gravity of a celestial body. The planet, its satellite, the Solar or other system can act as a celestial body . Every object that moves in orbit has cosmic speed. By the way, the size and shape of the orbit of a space object depends on the magnitude and direction of the speed that the object received at the time the engines were turned off, and the height at which the event occurred.
Space velocity is of four kinds. The smallest of them is the first. This is the lowest speed that a spacecraft must have in order for it to enter a circular orbit. Its value can be determined by the following formula:
V1 = õ / r, where
µ - geocentric gravitational constant (µ = 398603 * 10 (9) m3 / s2);
r is the distance from the launch point to the center of the earth.
Due to the fact that the shape of our planet is not an ideal ball (it’s a little flattened at the poles), the distance from the center to the surface is most at the equator - 6378.1 • 10 (3) m, and least at the poles - 6356.8 • 10 (3) m. If we take the average value - 6371 • 10 (3) m, we get V1 equal to 7.91 km / s.
The more cosmic velocity exceeds this value, the more elongated the shape of the orbit will take, moving farther away from the Earth. At some point, this orbit will burst, take the form of a parabola, and the spacecraft will go to plow the space. In order to leave the planet, the ship must have a second cosmic speed. It can be calculated by the formula V2 = √2µ / r. For our planet, this value is 11.2 km / s.
Astronomers have long determined what cosmic velocity equals, both the first and second, for each planet of our native system. They can be easily calculated using the above formulas if we replace the constant µ with the product fM, in which M is the mass of the celestial body of interest and f is the gravitational constant (f = 6.673 x 10 (-11) m3 / (kg x s2).
The third space velocity will allow any
spaceship to overcome the gravity of the Sun and leave its native solar system. If we calculate it relative to the Sun, we get the value of 42.1 km / s. And in order to enter the circumsolar orbit from the Earth, it will be necessary to accelerate to 16.6 km / s.
And finally, the fourth cosmic velocity. With its help, one can overcome the attraction of the galaxy itself. Its value varies depending on the coordinates of the galaxy. For our Milky Way, this value is approximately 550 km / s (if calculated relative to the Sun).