A rocket is an independent aeronautical system whose mechanics of motion obey the classical laws of mechanics formulated by Isaac Newton. A rocket is a transport system that is used to transport an object from one place to another. It has two main applications, one is a military use and the other is an application in the research of the outer space. In the military use of rockets, it is used to transport all kinds of explosives from conventional warheads such as TNT and TNP to the transport of chemical weapons such as nerve gases. This is in addition to the transport of nuclear warheads and bacteriological weapons.
In the use of rockets for the exploration of space and research performance in the outer atmosphere, rockets can be used to transport heavy systems such as the US shuttles and the Russian spaceship Soyouz. The mechanics that govern the motion of rockets within the atmosphere of the earth is completely different than that used in outer space. In order to send a rocket to outer space outside the earth's atmosphere, one needs to overcome the gravitational force of the earth. In addition, the mechanics in the outer atmosphere are completely different because of the lack of the gravitational field usually experienced by flying objects within the atmosphere of the earth.
According to the law of energy conservation, an object on the earth surface requires a specific amount of velocity in order to be able to escape the gravitational field of the planet. This is also applicable to rockets that intend to leave the earth's atmosphere in space exploration missions. Nowadays, technology shows that it is not a problem to achieve such as velocity even for a rocket bearing heavy weights such as the American space shuttle. This is usually achieved through the choice of fuel that has a remarkable propelling capability.
A shuttle in outer space that is revolving around the earth is all the time in a state of free falling. Namely, it feels as if it is freely falling to the earth surface. After reaching the escape velocity rockets that are sent to another planet usually use nuclear fuel due to the long period of time that is required for the rocket to achieve its destination.
The mechanics of rocket propulsion in outer space is governed by the law of conservation of momentum due to the lack of any force that can act on the rocket. Therefore, once the rocket achieved a certain required velocity outside the earth's gravity, it can turn off the engines and still have the same velocity. This is due to the law of conservation of momentum that says that an object that is traveling at a constant speed will remain traveling in that speed as long as there is no other force acting on it. This is exactly the condition of a rocket traveling in outer space. The engines of the rocket work only when there is a need to increase the speed or lower it or when there is a need to rotate the spaceship.
The manner of function of the rocket in outer space is also completely different than that operated within the earth's atmosphere. The combustion process of the fuel in rockets can be either oxygen dependent or oxygen independent. In outer space, there is no oxygen available to participate in the combustion process of the rocket fuel. This is not the case within the earth's atmosphere which abounds with oxygen. However, today rocket propulsion uses other sources of oxidizing agents that can be mixed with the fuel so that a more efficient combustion process occurs.
The mechanics of rocket motion within the earth's atmosphere is governed mainly by the force of gravity and the frictional force that the air exerts on the rocket. The force that propels the rocket is obtained according to the third law of Newton which states that for every action there is a reaction that is opposite to it in direction and equal in value. This force is obtained by the combustion process of the rocket fuel. The fuel itself can be in any possible phase such as liquid and solid and gaseous forms. An example is the fuel hydrazine.
The speed of the rocket will be determined based on the force that is generated from the combustion of the fuel. Different fuels will combust at different rates based on their quality. Therefore the velocity of the rocket will largely be dependent on the type of fuel that is used. The force that propels the rocket serves two purposes. One is to propel the rocket horizontally and forward and the other function is to balance the gravitational force so that the rocket does not fall to the ground.