The first cosmic speed

On the body that moves around the Earth, only one force acts: it is the gravitational force of our planet. The object will move unevenly and unevenly. This is because acceleration and speed in this case will not satisfy the conditions of uniform / uniformly accelerated motion with constant velocity and acceleration in direction and magnitude. These two vectors (velocities and accelerations) will change their direction as they move along the orbit. Therefore, this motion is sometimes called a motion with a constant velocity along a circular orbit

The first cosmic - the speed that you need to give the body to bring it into a circular orbit. In this case it will become like an artificial satellite of the Earth. In other words, the first cosmic - the speed, reaching which the body moving over the surface of the Earth, will not fall on it, but will continue to move in orbit.

For the convenience of calculations, we can consider this motion as occurring in a non-inertial frame of reference. Then the body in orbit can be considered to be in a state of rest, since two forces will act on it : centrifugal and gravitational. Consequently, the first cosmic velocity will be calculated based on the consideration of the equality of these two forces.

It is calculated by a certain formula, which takes into account the mass of the planet, the mass of the body, the gravitational constant. Substituting the known values in a certain formula, get: the first space velocity - 7.9 kilometers per second.

In addition to the first space, there are second and third speeds. Each of the cosmic velocities is calculated according to certain formulas and interpreted physically as the speed at which any body launched from the surface of the planet Earth becomes either an artificial satellite (this will happen upon reaching the first cosmic velocity) or exits the gravitational field of the Earth (this occurs when the Second cosmic speed), or leave the solar system, overcoming the attraction of the Sun (this occurs at the third cosmic speed).

The spacecraft, gaining a speed equal to 11.18 kilometers per second (the second space flight), can fly toward the planets in the solar system: Venus, Mars, Mercury, Saturn, Jupiter, Neptune, Uranus. But in order to achieve any of them, one must take into account their movement.

Previously, scientists believed that the motion of the planets is uniform and occurs along the circumference. And only Kepler established the present form of their orbits and the regularity by which the velocities of the motion of celestial bodies change as they rotate around the Sun.

The concept of cosmic speed (first, second or third) is used in calculating the motion of an artificial body in the gravitational field of any planet or its natural satellite, as well as the Sun. So you can determine the cosmic speed, for example, for the Moon, Venus, Mercury and other celestial bodies. These velocities should be calculated by formulas in which the mass of the celestial body is taken into account, the gravitational force of which must be overcome

The third cosmic one can be determined on the basis that the spacecraft must have a parabolic trajectory of motion relative to the Sun. For this, during the launch at the surface of the Earth and at an altitude of about two hundred kilometers its speed should be about 16.6 kilometers per second.

Accordingly, cosmic velocities can be calculated also for the surfaces of other planets and their satellites. For example, for the Moon, the first spacecraft will be 1.68 kilometers per second, the second - 2.38 kilometers per second. The second space velocity for Mars and Venus, respectively, is 5.0 kilometers per second and 10.4 kilometers per second.