In general term, velocity can be viewed as speed. Speed is a measure of the distance traveled by a body with respect to the time taken to cover the said distance. Precisely, velocity is not exactly the same as speed in the sense that whereas speed is a measure of distance with time, velocity is the measure of displacement with time. This makes velocity a vector quantity.
Vector quantity are quantities that posses not only magnitude but also direction as opposed to scalar quantity which have only magnitude. Escape velocity is the least amount of speed needed by a body to escape the gravitational grips of a massive body, example a planet.
The escape velocities of the first eight planets are pictured right. When we throw an object upwards, i.e, against the gravity, that object returns back to its initial position as a result of gravitational pull. The higher we throw this same object, the more time it spends in the air before returning. If the object is thrown upwards in such a way that the work done on the earth's gravitational pull from the point of throwing the object up to infinity is equal to the object's kinetic energy, the said object will never return to earth's surface. The speed offered by the said upward force is the escape velocity.))
Mathematically, the earth's escape velocity is given as
sqr(2gR)
where g is the acceleration due to earth's gravity and is equal to 9.8 meters per second square
and R is the radius of the earth and is equal to 6,371 kilometer with a meter equivalent of 6.37 10^6.
this implies that earth's escape velocity has the value of
sqr (29.86.37107)=11.22*103 meters or 11.2 kilometers as shown in the picture above.
One of the major application of escape velocity is launching satellites in the earth's orbit. Satellites are large bodies (even planets are satellite) that orbits a star or a planet. Earth is a natural planet so also is moon but our focus today is on the artificial satellite and the process of launching it in the space. Satellites are important to us because it improved our standards of living. It took communication, security, entertainment to a whole new level.
In order to for satellites to attain this escape velocity using the least amount of resources, the satellite is placed perpendicular to the earth's surface. By so doing, the densest part of the earth's atmosphere is easily penetrated.
Modern Satellites are launched riding on a rocket's nose cone (the pointy end of the rocket). As the rocket approaches altitude close to the predestined orbit for the satellite, it is then ejected and the newton's third law of motion (action and reaction is equal and opposite) is utilized in pushing the rocket back to the earth.))
Before the rocket is launched, a flight plan is mapped out for the rocket and this is specification of the movement pattern of the rocket. For this plan to be accurately executed by the rocket, a control mechanism which controls the rocket's nozzle movement by executing some calculations. Most flight plans specify that the satellite launching rocket should move in the same direction as the earth (east) to ease the movement and sometimes even give the rocket a boost.
As the rockets moves vertically, at the altitude of about 193 kilometer, smaller rockets are fired off to aid the horizontal positioning of the rocket. At the desired orbit, the rest of the rockets are fired to separate the satellite from the rocket. The venue of the rockets launch has effects on the overall movement of the rocket during the launch but the best position for launching a rocket that pushes satellite to orbit is at the fastest rotation point of the earth; the equator.
What happens when satellite are launched wrongly?
Many satellites were lost in the space due to many reasons. Mostly because the velocity used in launching the satellite. When the launch velocity is a bit less than the escape velocity, the satellite with time will find itself back to earth and when the speed is far beyond the escape velocity, the satellite with time, be lost in space. In the 2017 movie by Warner Bros, Geostorm, the weather control satellites lost its control and the effect was an irreversible catastrophe which caused the controlling satellites to move back into space.
Watch the video below for a visual understanding of the above theory.
video credit: Shaun O'keefe
SUMMARY
The escape velocity is the minimum speed required for a body to escape the grip of the gravitational pull of a massive body, like a planet. The larger the body exerting the pull, the higher the speed required to escape its gravitational pull. Satellites which has improved our leaving standards must poses this minimum speed before it could reach its orbit. The Inertial navigation system (INS) is used to guide the movement of the launching rocket to accurately deliver the satellite to a desired orbit. The location of the launch affects the overall speed of the rocket. Smaller rockets are fired to help in the direction the movement of the rocket.
REFERENCES
- Inertial navigation system -wikipedia
- Satellite orbit -globalcomsatphone
- How satellite works -howstuffworks
- what is satellite -Nasa
