The gravitational slingshot is a way that scientists have truly harnessed the gravitational pull of a planet by using it to launch satellites and other useful projectiles towards their desired locations. This method was developed through the use of Newton's Laws of Gravity and Kepler's Laws of Planetary Motion. When these ideas of gravity and the shape of a planet's orbit were brought together piece by piece, this new theory changed how a projectile traveling through space could simply cross an orbital pattern, which would in turn change the path of the moving object. The change in the path accelerates the object at a higher rate and sends it speeding off in its proper direction. The gravitational slingshot doesn't guarantee perfect results every time, but it has shown to be an extremely helpful technique in the world of space travel, which when studied and tested can be further improved to ensure safe and accurate results every time.[1]
The Men Behind the Idea
Newton
isaac_newton.jpg Newton, while sitting out in a field one day, was hit on the head by an apple that fell from a tree.
Most people would think nothing of this event, but Newton brought into perspective that some force had to draw that apple to ground once it was released from the branches of the tree. Through much observation and testing, Newton came up with a name for this force. He called it gravity. Newton created three laws to use as guidelines for gravity. Law one states that an object in motion stays in motion and that an object at rest stays at rest. The second Law states that force equals the product of mass and acceleration. The final Law simply states that for every action, there is an opposite and equal reaction. These theories originated from something as simple as Newton observing how one object reacts to another with the presence of gravity. Using these laws, scientists have been able to formulate ways to make travel in space more successful and efficient. [2]
Kepler
johannes_kepler_1610.jpgKepler established the Laws of Planetary Motion. The first Law states that the orbit of every planet is an ellipse with the Sun at one of the two foci. The second law states that a line joining a planet and the Sun sweeps out equal areas during equal intervals of time. And the final Law tells that the square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit. Kepler's Laws also come into play with the use of the gravitational slingshot, because Kepler believed that the orbit that a planet takes around another body follows an elliptical pattern, instead of traveling in a perfect circle. Of course each planet has a specific elliptical orbit, just as humans have different fingerprints to identify them. Before launching their equipment into space, each planet must have its pattern identified to ensure accurate results for the launch. This knowledge helps scientists identify where the ellipses are in relation to the paths of orbit so that they can launch satellites in the proper direct, at the proper time, with the proper velocity. Combining both of these sets of theories together has lead the way to the effect we know as the gravitational slingshot effect. [3]
Today's UseSlingshot4.GIFToday, the gravity assist effect is used extremely often by NASA and the Air Force. It is the most fuel efficient, naturally occurring “booster” in the universe. The gravitational force of a planet, even one as small as Mars, cause exponentially increase the velocity of an object. Using the Conservation of Kinetic Energy equation, which was developed by Newton, we see that no kinetic energy, or displacement energy is being lost as Gravitational Potential Energy. GPE is just that, potential energy that is not put into motion quite yet. In addition to Kinetic Energy, Linear Momentum is conserved also. The Conservation of Linear Momentum Equation proves that no speed is lost in the use of a gravity assist. In fact, it is greatly increased. Both of those equations, when combined, lead back to Newton’s Law of Collisions, proving that this method of acceleration is accurately accredited to Sir Isaac Newton himself.
When the probe or satellite, or even the space ship is slung around the planet, it not only keeps its own speed, proved above, but it also inherits twice the velocity of the planet itself. As the planet rotates, it also revolves around the Sun. If the rotating field is hit at the right time and at the right angle, all of the velocities of all parties involved are summed up in one final velocity of the probe that is massively superior to its initial speed. The probe’s velocity is perpendicular to the planet’s gravitational field and ends up facing in the exact opposite direction it started in, but infinitely faster. Infinitely because theoretically, it can be used with any spectral body of any size. All of this is accomplished with a tedious calculation and just enough fu