Upon launching a ballistic missile, it is included in a complex interaction governed by physics, and while most people imagine that the missiles fly in a simple equivalent arc from the point of launch to the target, the reality is much more complicated, as the rotation of the Earth is one of the most important factors affecting the rocket’s path, especially for long distances.
This rotation provides many physical effects that the missile designers and military planners must carefully observe, and may even ignore them to severe targeting errors, ranging from hundreds of meters to several kilometers.
Earth .. a rotating reference frame
To understand how the Earth’s rotation affects the missiles, we must realize that the Earth is not fixed, but rather revolves around its axis from west to east, to complete one cycle every 24 hours.
At the equator, the Earth’s surface moves east at a speed of about 1670 km per hour, and this speed decreases as we approach the two poles, to become completely zero in the northern and southern poles.
With the launch of a missile, it does not leave the ground only, but keeps the speed of its rotation at its starting point, and it is similar to that you throw a small rock up while you are in a car, so you will find that it takes the speed of this vehicle, and if you drop something from a plane, it will take the speed of the plane while it crashed.
Coriolis effect
It extends to what is deeper than that, as it is prepared Coriolis effect One of the most important and famous consequences of the Earth’s rotation, is defined as a phenomenon that arises from the rotation of the earth, and causes the deviation of moving bodies from its straight path for an observer on the surface of the earth.
And imagine, for example, that you and your friend are playing in the game “vortex” that rotates quickly in the cabarets and children sit in a circular way, sit on two opposite seats, and the game began to rotate quickly. In this context, you decided to throw a ball to your friend directly, and although you threw it “in a” straight way “towards him, she will deviate and go to another side.
The same talk applies to the surface of the rotating land. If a missile sets north or south, it moves between areas of the earth at different rotational speeds, and therefore the missile launched north (the top of the equator) will seem like it bend to the right. In the southern hemisphere, the opposite occurs, where it bends to the left.
This is not because of the actual force that pushes the missile, but rather because the ground below it moves differently from the speed of its launch.
As for short -range missiles (less than 100 km), Coriolis effect is minimal but measurable, but for intercontinental ballistic missiles -which can travel between 5 thousand and 15 thousand km, the deviation resulting from the effect of Coriolis can range between tens and hundreds of kilometers.
Etoos effect
There is also what is called Etoos effect On the movement of the missiles, this name was named after the Hungarian physicist Larand Itfos, a small change in the sense of gravity when the body moves quickly or west on the surface of the earth, due to the rotation of the Earth.
Because of this effect, the move east (with the Earth’s rotation) makes you feel like you are slightly lighter, and when you move west (the opposite of the Earth’s rotation) you feel like you are a little heavier.
And imagine, for example, that you are standing inside a very fast train, walking east, and you jump vertically, and here you may notice as if you were a little “bleeding” in the air, and you got on the floor late from your expectation, and the reason is that the train gives you an additional speed with your jump, so you feel lighter.
And if the train was walking west, you feel that you are jumping faster, because the movement of the train reduces the speed that helps you in the “bottom”, you feel that you are heavier.
In the case of ballistic missiles, the east heading missile will be subjected to a slightly less attracted force, which makes it stay at the top for a longer period, and may exceed its target vertically, and on the contrary the missile heading will fall to the west slightly quickly.
Although the difference in the strength of gravity is small (with the limits of parts of the hundred), it may be translated into meters or dozens of meters in height, which is a sufficient difference to influence significantly on the accuracy of targeting if it is not correct.
Fueling direction and fuel efficiency
It is interesting that the Earth’s rotation can also be an advantage if it is used properly. Because the Earth rotates east, and therefore the launch of an oriental missile gives it a boost in the speed of the Earth’s rotation, and this means the need for less fuel to reach a certain speed, or it can be a heavier load in the same amount of fuel.
For this reason, most space missiles are launched east, including that launched from NASA’s Kennedy’s Kennedy Space Center in Florida, and the fact is that there is a reason to choose this place, the closer launch of the missile, the greater the Earth’s speed as we mentioned earlier, and then the missile needs less fuel. On the other hand, the launch requires more (the opposite of the Earth’s rotation) more fuel.
Visings Modern missile systems Self -deficiency navigation systems and global positioning systems to deal with these simple deviations, where pre -launch accounts are mixed with a full 3D journey using physical equations, including Earth curvature, gravity variation, air clouds, korelis power, display line, and thickness for launch during flying, gyroscopes, acceleration standards and computers are modified. Correct path. In some advanced missiles, the final guidance is guaranteed using radar or satellites accuracy in the last seconds of the flight.
But even before the rockets appeared, the effect of Coriolis was known to the long -range artillery. For example, in the First World War, the German “Paris” cannon fired shells of 120 km. And it was necessary to correct the deviation of Coriolis by hundreds of meters. In the maritime war, long -range shells required an angle correction based on the hemisphere and the direction of launch. These early lessons paved the way for modern missile paths.